*Review* **Date (***Phoenix dactylifera* **L.) by-Products: Chemical Composition, Nutritive Value and Applications in Poultry Nutrition, an Updating Review**

**Adel I. Attia <sup>1</sup> , Fayiz M. Reda <sup>1</sup> , Amlan K. Patra <sup>2</sup> , Shaaban S. Elnesr <sup>3</sup> , Youssef A. Attia 4,5,6,\* and Mahmoud Alagawany 1,\***


**Simple Summary:** The demand and price of feed/feed stuffs was greatly altered after the COVID-19 crisis, showing great interest on depends on local feed stuffs and a decrease in the imported ones. Date palm (*Phoenix dactylifera* L.) is a common crop in arid and semiarid regions for production of date fruits. This updating review provides the recent knowledge on the use of date palm by-products and improving their utilization in poultry rations. This article focuses on the chemical composition, amino and fatty acids, mineral content, growth performance, economic aspects and nutritional potential in comparison with widely used corn and barley grains in poultry.

**Abstract:** Several by-products, such as whole cull dates, date stones (also called pits, seeds, kernels), sugar-extracted date pulp, are produced from date fruit processing industries. These by-products, particularly date stone meal represent 10 to 20% of the whole dates are wasted, causing environmental issues. However, the date stone is rich in various nutrients, such as nitrogen-free extract, fiber, fat, and minerals, which could be used as an alternative feed source in poultry nutrition. However, the high fiber content in date stone meal restricts its use in poultry diets. Whole date wastes and date pulp have lower protein, fiber and fat content than those in date stone meal. Several studies have investigated the use of date stone meal and other by-products as a replacement of dietary corn and barley on feed intake, growth, feed efficiency, and nutrient utilization in poultry. The compilation of results obtained from different studies indicates that date fruit by-products, particularly date stone meal, could be incorporated up to 10% levels, replacing corn or barley grains without hampering production performance, and this could reduce the production cost. Moreover, the use of date stone meal at lower levels (5–10%) sometimes shows better growth performance, probably due to the presence of bioactive principles such as antioxidants and phenolic compounds. The use of date stone meal in poultry diets may be practically important under certain circumstances not only under the COVID-19 crisis due to the lockdown of airports, dry ports, ports and traffic restrictions, but also in countries with a limited supply of classical feed resources and which depend on imported ones. Finally, it can recommend that using date stone meal (DSM) up to 5–10% in poultry diets positively affect the productive performance. Due to the variability in the nutritive value of the DSM, developing a formula for metabolizable energy (ME) of DSM = a (intercept) − b (slope) × crude fiber (CF) content should be considered to improve the precision of feed formula for poultry. However, the nutritional value of DSM might not only depend on crude fiber but also on other compounds.

**Citation:** Attia, A.I.; Reda, F.M.; Patra, A.K.; Elnesr, S.S.; Attia, Y.A.; Alagawany, M. Date (*Phoenix dactylifera* L.) by-Products: Chemical Composition, Nutritive Value and Applications in Poultry Nutrition, an Updating Review. *Animals* **2021**, *11*, 1133. https://doi.org/10.3390/ ani11041133

Academic Editors: Ilias Giannenas and Jan Jankowski

Received: 3 March 2021 Accepted: 12 April 2021 Published: 15 April 2021

**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

**Keywords:** date by-product; date stone; poultry; nutritive value; production performance

#### **1. Introduction**

Several agricultural and agro-industrial by-products are produced during the production or processing of fruits and vegetable crops, which may cause environmental pollution. These by-products were of great interest during the COVID-19 crisis due to lockdown, close of dry borders and ports and traffic restrictions [1,2]. The use of alternative feedstuffs and locally available feed ingredients would improve a possible solution. Date by-products are the best-known by-products that are produced from the arid and desert regions, which are sometimes used in livestock and poultry diets.

In arid and semiarid regions of the world, date palm (*Phoenix dactylifera* L.) constitutes one of the main crops. In countries of the Middle East, date cultivation is common, as it is where about 70% of the world date production occurs [3]. The world date production has been reported to have increased from 1.8 million tons in 1961 to 2.8 million tons in 1985 and to 5.4 million tons in 2001 [4]. The fruit of date palm is comprised of a fleshy pericarp and an inedible seed. A number of date by-products, such as whole cull dates, date stones (also called date pits, seeds, kernels or pips), sugar-extracted fruit date pulp and pressed cakes from date processing are available for date industries [5]. The date stone is a hard oblong body, ventrally grooved and present in the midst of the date fruit, and its length ranges from 12 to 36 mm, while the width ranges from 6 to 14 mm. The weight of the seeds represents 10–20% of the date fruit [6]. The size and weight of the seeds depend upon the variety, maturity and growing conditions. At the back of the seeds, there is a micropyle, where the embryo is located. The embryo is a small oblong body surrounded by the endosperm. The latter is a group of cells inside their walls. The hemicellulose is accumulated, giving it thickness and hardness. Date stone meal (DSM) is rich in carbohydrates and fat along with crude protein content compared to barley and corn grains depending upon the varieties of date palm, which is used as a feed ingredient for livestock feeding. However, DSM contains high amounts of crude fiber, which is the constraint for its use in the diets of monogastric animals, especially for poultry [7]. Tabook et al. [8] pointed out that date fiber can be included at a level of 5% in a broiler diet without affecting the performance of broiler chickens. On the other hand, Slominski [9] reported that enzyme supplementation improved nutrient digestibility and nutrient utilization and allowed use of the agro-industry by-product in poultry nutrition. Moreover, DSM also has functional properties due to the presence of mannans, phenolic compounds and antioxidant activity [5]. A number of studies have been conducted to utilize date fruit by-products as a feed ingredient of poultry diets. The DSM can give a potential alternative for energy source in diet ingredients of poultry. Dietary inclusion of DSM significantly improved the performance and feed utilization of poultry [3,10]. These low-cost feed ingredients have emerged as potential alternatives in poultry that can reduce the cost of rations, but the effects of these by-products on production performance varied among the studies. Therefore, this review was undertaken to compile the findings of the experiments on date fruit by-products for the chemical composition, nutritive values, growth performance, carcass traits and economic aspects in comparison with widely used corn and barley grains in poultry.

#### **2. Chemical Composition and Feeding Values of Date Waste**

#### *2.1. Proximate Analysis*

The proximate analysis of DSM was studied by several investigators and is shown in Table 1. The chemical composition (%) ranges widely between 88.2 and 92.0, 5.27 and 10.5, 2.89 and 9.43, 8.22 and 28.9, 58.0 and 72.4 and 0.98 and 9.08 for dry matter (DM), crude protein (CP), ether extract (EE), crude fiber (CF), nitrogen free extract (NFE) and ash, respectively. Additionally, the DSM contains 3.3 MJ/kg DM true metabolizable energy (TME) for poultry. Based on the chemical composition of DM, the nutritional value is very

low for TME, due to the very high fiber content and the low protein content, resulting in metabolizable energy levels as low as 2.9 MJ/kg. It can be used in poultry diets provided that this low energy level is taken into account in diet formulation and compensated by supplementation of oil or fat [11].

The chemical composition of dried date press cake (excluding the pits) varies, particularly for CF, CP and NFE depending upon the sources and varieties of dates but are within the range of 87.7 to 95.2 for DM, 4.4 to 8.1 for CP, 9.1 to 21.8 for CF, 1.8 to 2.7 for EE, 2 to 3.5 for ash and 55.3 to 72.7 for NFE on a dry matter basis [5]. The chemical composition of date wastes is usually close to the chemical composition of corn and barley, except for CF values which are higher than those of corn and barley (8.22–16.6 vs. 2.3 and 5.0%, respectively). Higher fiber content is present in DSM or whole date fruit due to the presence of greater fiber content in the outer layer of the date seeds. The pulp of the dates has less fiber, low CP and higher NFE. The sugar extracted date fruit pulp was reported to contain 5.5% CP, 11.8% CF, 0.4% EE, 79.6% NFE and 2.7% ash [12]. Thus, pulp can be added to broiler diets at levels up to 20%. As date pulp contains less CP, whole date wastes have a low CP (2.9%), which is much lower than for DSM, maize and barley [13]. The fruit flesh is rich in NFE (76.2%), which is closer to values of barley (79.0%) but greater than that of DSM. The amino acid in flesh, mainly methionine (0.06%) and lysine (0.10%) are lower than those in the DSM, maize and barley due to lower CP concentration in the flesh [14].

Date is found to be low in protein and fat but highly rich in sugars, especially glucose and fructose [15]. Date is a good source of energy, where 100 g of date can provide about 1.31 MJ. In addition, minerals were reported, such as selenium, potassium, copper, and magnesium. The daily consumption of 100 g can cover about 15% of the recommended requirement of these minerals. Date contains about 8.0 g/100 g date, but insoluble dietary fiber is the major part of dietary fiber in this fruit. Regarding the vitamin content, vitamins C and B-complex are the major vitamins in dates. It is also a good source of antioxidants, mainly phenolic compounds and carotenoids. The seeds of date contain considerable concentrations of fat (9.0 g/100 g) and protein (5.1 g/100 g) when compared to the flesh. Additionally, seeds are high in phenolics (3942 mg/100 g), dietary fiber (73.1 g/100 g), and antioxidants (80,400 mmol/100 g) [16].

Shaba et al. [17] reported that date palm fruits contain low amounts of anti-nutritional factors, such as oxalate, tannin, saponin, alkaloid and cyanide. This indicates that the date seeds can be used effectively as the anti-nutritional composition is low and there would be no interference with the nutrient-like minerals and protein in the body. Depending on different varieties of date by-products, date pits contain significant amounts of micronutrients and macronutrients, but all varieties are excellent sources of fiber and maybe used as important sources of functional foods [18–20].


**Table 1.** Chemical composition (%) of different varieties of date stone meal compared with yellow corn and barley.

\* Central laboratory of food and feed, CLFF; ND: not defined or not determined; DM = dry matter; CP = crude protein; EE = ether extract; CF = crude fiber; NFE = nitrogen free extract, TME = true metabolizable energy.

#### *2.2. Digestion Coefficients and Feeding Values of Date Waste*

The digestibility values of CP, CF and NFE, in general, were lower than those of barley and corn, while the digestion coefficient of EE was better than those of barley and corn (Table 2). Metabolic energy values of DSM were lower than that of corn (14.14 MJ/kg). More studies in this regard revealed the nutritional value of DSM. For example, Sawaya et al. [23]

reported that the protein digestibility and calculated protein efficiency ratios were 64.1, 1.67 for Ruzeiz, 62.9, 1.65 for Sifri date, respectively, with an average of 63.5, and 1.65 for Ruzeiz and Sifri compared to 90.0 and 2.50% for casein. Attia and Al-Harthi [12] evaluated date waste in broiler chickens fed at 0 to 200 g/kg diet replacing wheat bran containing similar energy and protein concentration and observed that digestibility of nutrients was not affected except decreased CP digestibility at 200 g/kg. In addition, El-Deek et al. [24] reported that inclusion (0 to 150 g/kg diet at 6 levels) of inedible date waste (85% fruit and 15% pits) in broiler chickens did not affect nutrient digestibility. Al-Homidan [3] reported ME values of 7.23 and 4.71 MJ/kg, respectively, for broiler chickens. In future, developing a formula for ME of DSM = a − b × CF seems essential due to variability in the nutritive value of DSM to improve the accuracy of feed formula for poultry. Nonetheless, the nutritional value might not only depend on crude fiber but also on other compounds.

**Table 2.** Digestion coefficients (%) and metabolizable energy (ME, MJ/kg) of different varieties of date stone meal compared with yellow corn and barley.


DM = dry matter; OM = organic matter; CP = crude protein; EE = ether extract; CF = crude fiber; NFE = nitrogen free extract; ME = metabolizable energy.

#### *2.3. Fiber Fractions*

Fiber fractions of DSM as reported by several workers, compared with yellow corn and barley, are shown in Table 3. The values ranged from 39.6 to 57.5, 51.6 to 75.0, 12.0 to 17.5, 26.1 to 42.5 and 7.21 to 11.0 for acid detergent fiber (ADF), neutral detergent fiber (NDF), hemicellulose, cellulose, and lignin, respectively, which were higher than those of both corn and barley. Fiber fractions of DSM were reported to be 57.6, 46.4 and 13.7 for NDF, ADF and ADL, respectively [25]. These results indicated that the low-energy values of DSM compared with corn and barley could be due to higher fiber fractions [11].

**Table 3.** Fiber fractions (% of dry matter) of date stone meal compared with yellow corn and barley.


\* Acid detergent fiber (cellulose + lignin); \*\* Neutral detergent fiber (hemicellulose + cellulose + lignin); \*\*\* Central Laboratory of food, CLFF [22]; ND: Not defined or not determined.

#### *2.4. Fatty Acid Content*

Oil extracted from date seeds is a pale yellowish–green in color and has a pleasant odor [5,26,27]. Abdel-Nabey [19] reported that the crude oil extracted from date pits has a pale-yellow color and is semi-solid at refrigerated temperature (−40 ◦C). The main median characteristics are as follows: an acidity value of 1.11, 0.96% unsaponifiable matter, a refracted index of 1.46, an iodine value of 49.7 and a saponification value of 219.6. The date seed oil is a natural source of medium-chain fatty acids (MCFAs) such as lauric acid (10.36–35.31%) and capric acid (0.2–0.8%). These MCFAs are effective against a wide range of microorganisms in chicken intestines and can improve the growth performance and immunity of poultry [28].

The values (% of fat) ranged between 12.20 and 23.06, 9.70 and 11.30, 10.11 and 12.70, 1.56 and 3.56, 35.1 and 45.80, 8.10 and 11.00, and 0.37 and 0.80 for lauric, myristic, palmitic, stearic, oleic, linoleic and linolenic acids, respectively. The values were close to the corn, except for myristic and oleic fatty acids, which were higher than those of corn were. Corn contained higher linoleic and linolenic than DSM (51.5 and 1.7% vs. 8.10 to 11.0% and

0.08 to 0.37%, respectively). Abdel-Nabey [19] reported that date pit oil has a very low content of linolenic acid (0.37) in comparison with many vegetable oils, i.e., cottonseed, sunflower and maize oils. The ratio of unsaturated to saturated fatty acids varies from 1.10 to 1.20 with an average of 1.17 because the total amount of unsaturated fatty acids is slightly higher than those of saturated fatty acids. This ratio, however, is lower than those of the common edible vegetable oils in which their degree of unsaturation is quite high.

#### *2.5. Amino Acid Content*

Amino acid content of DSM as indicated by several studies, compared to corn and barley, are shown in Table 4. The highest amino acid contents of DSM are almost close to those of corn grain, while they are lower than those of barley, except for arginine which is higher than that of corn and close to that of barley (0.36–0.60 vs. 0.17 and 0.52%).


**Table 4.** Amino acid content (% of dry matter) of date stone meal compared with yellow corn and barley.

ND: not determined.

#### *2.6. Mineral Content*

Studies showing both major and trace elements of DSM in comparison to corn and barley are presented in Tables 5 and 6. Date stone meal contents of Mg, K and Na are close to those of both corn and barley. The level of P is close to that of corn, but lower than that of barley, while the content of Ca is higher than those of both corn and barley. The trace elements (Zn, Cu, Mn and Fe) of DSM are in general higher than those of corn but close to those of barley. Calcium and phosphorus levels (0.76 and 0.52%, respectively) are present in higher amounts than in maize and barley. The protein content (8.1%) in DSM is higher than that of whole date but is nearly close to that of maize grains (8.6%) [14].

**Table 5.** The major mineral element content (% of dry matter) in different varieties date stone meal compared with yellow corn and barley.



**Table 6.** The trace element content (mg/kg of dry matter) of different varieties of date stone meal compared with yellow corn and barley.

#### **3. Effect of Date Waste on Poultry**

#### *3.1. Effect of Date Waste on Growth Performance*

Several studies recommended that DSM up to 10% in broiler diets can be incorporated without negative effects on growth performance [1,4]. El-Deek et al. [24] tested six levels (0 to 150 g/kg diet) of inedible date waste (85% fruit and 15% pits) in broiler chickens and noted that body weight, feed intake and feed efficiency were similar at all levels of date waste. Date palm pollen is used to improve fertility and ovulation in men and women due to it contains fatty acids, amino acids, saponins, flavonoids and sterols. Egg mass, egg weight and egg production of laying hens treated with different levels of date palm pollen were increased when compared to the control [32]. Jaffer and Jassim [33] used 0, 5, 10 and 15 of % date by-product with or without enzyme instead of maize and they found body weight, feed intake, and feed conversion as well as economic feasibility were not affected by this by-product.

As DSM contains high fiber content, which limits its use in poultry diets, some processing of DSM has been performed to improve feed utilization efficiency and performance of chickens. For example, Al-Saffar et al. [34] conducted two experiments to investigate the effect of phytase and/or multienzymes (xylanase, β-glucanase, cellulase, hemicellulose, protease and amyloglucosidase) on improving the utilization of DSM in laying hens. In experiment 1, DSM completely replaced corn in isocaloric and isonitrogenous diets, but with added phytase (500, units of phytase (FTU)/kg) and/or multienzymes (0.1%). In experiment 2, DSM was added at 0, 15, and 30% in isocaloric and isonitrogenous diets, and diets containing DSM were fed without or with phytase and/or 0.1% multienzymes. In experiment 1, laying performance and eggshell quality of hens reduced significantly due to complete substitution of corn, but hatchability and fertility were not influenced. Supplementation of phytase and multienzymes did not restore the laying performance compared to the control level. In experiment 2, the results showed that DSM could be included in diets up to 30% when supplemented with multienzymes without affecting the laying performance of hens.

Hussein and Alhadrami [35] used date pits at 0, 10, 15, and 20% with or without enzyme supplementation (Avizyme 1500) to the starter and finisher diets, while grower diets contained 10% uncooked or cooked date pits. The results showed that adding date pits with or without enzyme to the starter and finisher broiler diet had no effect on broiler performance. Body weight gain of birds who received 10% uncooked date pits were significantly higher compared to the control group birds. Groups fed a diet containing 10% date pits had no effects on feed intake or feed conversion ratio. Barreveld [5] reported that date stone could successfully replace 10% barley in chick diets. The increased live gain over the control is related to more feed intake and may be due to the existence of a growth promoting substance in date stone. Similarly, date waste (0 to 200 g/kg diet replacing wheat bran containing similar energy and protein concentration) fed to broiler chickens did not affect body weight gain up to 200 g/kg diet [36].

Al-Homidan [3] determined the effect of adding date waste (whole date waste meal and date pits meal) in starter and finisher broiler diets. Seven levels of date waste representing 0, 8, 16, 24% date waste meal and 5, 10, and 15% date pits meal were used in the starting period, while 0, 8, 16, 24% date waste meal and 6, 12 and 18% date pits meal were used during the finishing period. Results indicated that body weight and daily gain were

improved when chicks were fed diets containing 8% date waste meal or 10% date pits meal during the starting period (0–4 weeks). During the finishing period (5–7 weeks), chicks fed a diet containing 8% and 16 date waste meal or 18% date pits meal had better body weight and daily gain than the control. Feed conversion improved significantly when the level of date pits meal was 10% during the growing period. During the finishing period, feed conversion was better when diets included 18% date pits meal compared with the control.

In broiler chickens, date waste (0 to 200 g/kg diet replacing wheat bran) reduced feed intake and improved feed efficiency and European feed production efficiency at 50 g/kg, whereas these variables in other date waste levels were similar to the control [12]. Kamel et al. [14] fed diets containing date pits at 5, 10 and 15%, and whole zahdi dates at 5, 10, 30 and 47.7% to broiler chicks. They found that the incorporation of 47.7% whole date as a total replacement of corn resulted in a slight decrease in feed conversion of chicks.

In some studies, the use of DSM improved production performance when used at low levels compared with the corn or barley grains, which is attributed to the presence of bioactive compounds present in it [34–37]. In addition, DSM may be effective against the aflatoxicosis. Abdel-Sattar et al. [36] reported that the inclusion of DSM (2 and 4%) in diets of broiler chickens ameliorated the negative effects of aflatoxins and provided a partial protective effect against aflatoxicosis, which was dose-related as 2% supplementation provided better protection than 4% supplementation. Moreover, supplementation of DPS in the diets reduced malondialdehyde content in muscle.

El-Far et al. [37] conducted a study on broiler chickens fed diets containing 2, 4 and 6% DSM. Results indicated that DSM significantly increased serum reduced glutathione content for all DSM, and interferon-gamma and interleukin-2 levels were significantly higher in chicks fed 2% DSM. Therefore, the authors concluded that increase growth performance, immunity, and antioxidant status of chickens due to DSM supplementation might be related to the antioxidant and immune-stimulant constituents in DSM.

The productivity and qualitative traits of eggs of laying hens were not adversely affected by the inclusion of date pits in the diets [38]. Hermes and Al-Homidan [39] clarified that the best performance was seen when 16% date waste meal or 10% date pits meal could be replaced by yellow corn without any adverse effect on productive performance, egg quality. Up to 20% date seeds was tested without an adverse effect on egg production and feed efficiency, but it decreased egg quality [40]. Al-Harthi et al. [41] recommended that using date pits as alternative feedstuff enhanced maturity of Lohmann pullets and reproduction performance of layers. Ghasemi et al. [42] stated that date pits at the level of 10% could be partly used as alternative feedstuffs in laying hens' diets, without negatively affecting the productive and health parameters but more than 10% feed intake was reduced due to the presence of non-starch polysaccharides which increase the viscosity of gut contents.

Generally, the age of the bird affects the benefit from adding dates to the diets, as old birds benefit from the fibers more than young birds. Due to the high percentage of fiber in date wastes, it should be added to finisher diets with a higher percentage than the starter diets. Additionally, ducks and laying hens benefit from the diets containing date waste more than broiler chickens. Finally, from the previous studies that were reviewed, it can be concluded that using DSM up to 5–10% in diets of poultry (broiler, laying hen, ducks, quail or turkey) positively affects the productive performance. We summarized effects of date by-products on performance of poultry in Table 7.


**Table 7.** Effects of Date by-products on performance of poultry.

DW = date waste; DWM = date waste meal; DPM = date pits meal; BW = body weight; BWG = body weight gain; FCR = feed conversion ratio; FI = feed intake.

#### *3.2. Effect of Date Waste on Carcass Traits*

Kamel et al. [14] fed broiler chicks with diets containing date pits at 0, 5, 10 and 15% or whole Zahdi dates at 0, 5, 10, 30 and 47.7%. The gross examination of various internal organs (liver, heart, spleen, pancreas and intestines) in both date by-products revealed abnormalities. The weight of inedible parts (including feather) of carcass as well as their proportional weight showed an insignificant response to the effect of date seeds levels [4]. The absolute and percentage weights of total edible meat differed significantly between 5% date seeds (1188 g) and the control group (1347 g). Differences for carcass weight between the 5% group (1077 g) and the control group (1229 g) were also significant, while differences between 5% and other groups were not significant. Percentage of carcass weights of the control group (66.4%) was higher than the other groups except 10% (67.2%). In addition, giblet weights were not significant for all groups.

Osman et al. [44] studied the extent of using DSM in starter and grower Pekin duckling diets. The results indicated that dressing percentage was not significantly affected by the level of DSM in the diets, but gizzard percentage increased when increasing the level of DSM in the diets. Moreover, there were pronounced trends for increased absolute and relative digestive tract weight and length of digestive tract and caecum when increasing level of DSM in the diets. This could be attributed to the gritty nature and to the high fiber content of DSM. Such increase in gizzard percentages may be an adaptation of the birds to digest the gritty and fibrous feed at the high levels of DSM. In addition, both small intestine and caecum length increased gradually with the increasing of DSM, but fasting body weight, carcass, liver and heart percentages were not affected by the level of DSM in the broiler diets.

Al-Homidan [3] determined the effect of addition of date wastes (whole date waste meal, and date pits meal) to starter and finisher broiler diets containing 0, 8, 16 and 24% whole date waste meal, or 5, 10 and 15% date pit meal in the starting period and 0, 8, 16 and 24% whole date waste meal and 6, 12 and 18% date pit meal during finishing period. Results indicated that the corresponding values for dressing percentage ranged between 68.7 and 70.5%, while ready to cook (hot carcass weight and giblets weight) percentages ranged between 73.3 and 75.6%, without significant differences among the levels.

Attia and Al-Harthi [12] reported that date waste in broiler chickens fed at 0 to 200 g/kg diet did not affect dressing percentage, weight (%) of liver, gizzard, but altered many other carcass traits such as weight (%) of heart, spleen, pancreas and intestine. Similarly, inedible date waste up to 150 g/kg diet of broiler chickens did not affect dressing percentage, chemical composition of meat along with water holding capacity, pH, tenderness, and color, but weight (%) of heart, pancreas and spleen differed among the inclusion levels [37].

#### *3.3. Effect of Date Waste on Mortality*

Regarding mortality, Kamel et al. [14] found no effect due to DSM levels on broiler mortality. They reported that there was no link between chick mortality and the use of date pits in the diets. The effect of using DSM as a substitute for yellow corn in chickens quail diets up to 24% levels on the mortality rate of Japanese quails was studied [36]. These studies reported that up to 10% DSM can be fed to chickens without affecting growth performance. Al-Homidan [3] found no significant effect on broiler mortality rate (the mortality rate was 2.2% during total experimental period of 0 to 7 weeks) due to using date waste (0, 8, 16, 24% whole date waste meal) or (5, 10, and 15% DSM) during the starter period, or (0, 8, 16, and 24% whole date waste meal) and (6, 12 and 18% DSM) during the finishing period. Date waste up to 200 g/kg diet replacing wheat bran did not affect mortality of chickens [37].

#### *3.4. Effect of Date Waste on Feed Cost and Economic Efficiency*

The net profits in broilers fed 0%, 1%, 2%, 3% and 4% of date palm kernel were 27.01, 32.77, 36.78, 43.47 and 44.51 (Rs.) per broiler, respectively. It was reported that the maximum net profit (44.51/bird) was recorded from the birds fed 4.0% date palm kernel, closely followed by those birds fed 3.0% date palm kernel (43.47/bird) [45]. Furthermore, in broilers, the feed cost per kg live weight gain was statistically less in birds fed date palm kernel with or without enzymes compared to the basal diet [46].

Al-Homidan [3] found that using date wastes (whole date waste meal and DSM) at 5, 10 and 15% in broiler diets reduced the cost of the diet compared with the control group. Application and beneficial uses of date by-product and wastes in poultry nutrition are illustrated in Figure 1. *Animals* **2021**, *11*, x 10 of 14

**Figure 1.** Application and beneficial uses of date by-products and wastes in poultry nutrition. **Figure 1.** Application and beneficial uses of date by-products and wastes in poultry nutrition.

#### **4. Recent Knowledge and Future Direction 4. Recent Knowledge and Future Direction**

Recently, there have been trends to utilize the phytochemical properties of industrial fruit or herbs wastes in animal feeding, which will not only reduce environmental burdens, but also improve animal production and health [47,48]. Similarly, phytochemical or nutraceutical prosperities of date pit or waste have been explored or attempts have been Recently, there have been trends to utilize the phytochemical properties of industrial fruit or herbs wastes in animal feeding, which will not only reduce environmental burdens, but also improve animal production and health [47,48]. Similarly, phytochemical

made to improve them using solid state degradation by *Trichoderma reesei* L. and their utilization in animal feeds [49–53]. Alyileili et al. [49] reported that solid state degradation

equivalent/kg) and flavonoid (117 g rutin equivalent/kg) content of degraded date pits and antioxidant activities. Due to the presence of probiotic, phenolics and flavonoids along with high antioxidant activities, the degraded date pits might provide beneficial impacts on gut health and barrier function [54,55]. Therefore, extra-nutritional effects of *T. reesei*-mediated solid state degraded date pit were explored in poultry [56,57]. The inclusion of 10% degraded date pits (phenolics, flavonoids and mannan–oligosaccharide) in the diets of broiler chickens increased catalase, superoxide dismutase and glutathione peroxidase activities in the serum, liver, and intestine, and decreased malondialdehyde content compared to the control group [50]. It also increased pancreatic enzyme activities, the villus length, and the villus/crypt ratio, and decreased the crypt depth of the intestine [51]. The number of pathogenic bacteria such as *Escherichia coli, Enterobacteriacea, Salmonella*, and *Shigella* were reduced, but beneficial *bacteria such as Bifidobacterium* and *Lactobacillus*  were increased in the gut of poultry by 10% degraded date pits [52]. Additionally, immunoglobulin A and G content in serum and intestinal tissue, gene expressions of mucin-2, cathelicidin-1, beta defensins, and liver expressed antimicrobial peptide-2 (which prevents the attachment of invading pathogens in intestinal epithelia) in jejunum of chickens fed degraded date pits were increased [52]. However, body weight, feed intake, and feed conversion ratio were not influenced by 10% degraded date pits compared with the control [52]. Alyileili et al. [53] compared 5 and 10% non-degraded date pits vs. degraded date pits in chickens. The populations of *Escherichia coli, Salmonella*, *Campylobacter* and *Shigella*  spp. were reduced in both degraded and non-degraded date pit-diets compared with the control, but degraded date pit diets had a stronger effect than the non-degraded date pit diets. Body weight gains were not affected, but feed conversion ratio was higher for nondegraded date pits diets than control and degraded date pit diets. European production efficiency index was greater with 5% and 10% degraded date pits than non-degraded date

or nutraceutical prosperities of date pit or waste have been explored or attempts have been made to improve them using solid state degradation by *Trichoderma reesei* L. and their utilization in animal feeds [49–53]. Alyileili et al. [49] reported that solid state degradation of date pit with *T. reesei* enhanced mannan oligosaccharide content, phenolic (142 g gallic equivalent/kg) and flavonoid (117 g rutin equivalent/kg) content of degraded date pits and antioxidant activities. Due to the presence of probiotic, phenolics and flavonoids along with high antioxidant activities, the degraded date pits might provide beneficial impacts on gut health and barrier function [54,55]. Therefore, extra-nutritional effects of *T. reesei*mediated solid state degraded date pit were explored in poultry [56,57]. The inclusion of 10% degraded date pits (phenolics, flavonoids and mannan–oligosaccharide) in the diets of broiler chickens increased catalase, superoxide dismutase and glutathione peroxidase activities in the serum, liver, and intestine, and decreased malondialdehyde content compared to the control group [50]. It also increased pancreatic enzyme activities, the villus length, and the villus/crypt ratio, and decreased the crypt depth of the intestine [51]. The number of pathogenic bacteria such as *Escherichia coli, Enterobacteriacea, Salmonella*, and *Shigella* were reduced, but beneficial *bacteria such as Bifidobacterium* and *Lactobacillus* were increased in the gut of poultry by 10% degraded date pits [52]. Additionally, immunoglobulin A and G content in serum and intestinal tissue, gene expressions of mucin-2, cathelicidin-1, beta defensins, and liver expressed antimicrobial peptide-2 (which prevents the attachment of invading pathogens in intestinal epithelia) in jejunum of chickens fed degraded date pits were increased [52]. However, body weight, feed intake, and feed conversion ratio were not influenced by 10% degraded date pits compared with the control [52]. Alyileili et al. [53] compared 5 and 10% non-degraded date pits vs. degraded date pits in chickens. The populations of *Escherichia coli, Salmonella*, *Campylobacter* and *Shigella* spp. were reduced in both degraded and non-degraded date pit-diets compared with the control, but degraded date pit diets had a stronger effect than the non-degraded date pit diets. Body weight gains were not affected, but feed conversion ratio was higher for non-degraded date pits diets than control and degraded date pit diets. European production efficiency index was greater with 5% and 10% degraded date pits than non-degraded date pits and the control [53]. Overall, these results suggested that date pits can improve gut health by reducing pathogenic bacteria, enhancing beneficial bacteria, gene expressions of antimicrobial peptides in the jejunum, and immunoglobulin concentrations in the intestine and serum while degraded date pits likely have greater effects than the non-degraded date pits. Future studies may also investigate the gut barrier and electrophysiological functions such as mRNA expressions of tight junction proteins, permeability, especially during a pathogenic microbial challenge models due to the presence of plant bioactive principles (such as phenolics and flavonoids) in non-degraded or degraded date pits because these plants bioactive have been shown to improve the gut barrier function in animals including in poultry [56,57].

Dates by-products are currently used in the feeding of animals, poultry and fish industries. Due to the presence of a large amount of total fiber, they are considered to have potential health benefits for human as prebiotics [58]. The dietary fiber concentrate of date seeds/kernels presented the potential to be used as a novel source of prebiotic feed additives, by increasing the numbers of *Lactobacillus paracasei* as probiotics [58]. Fiber concentrate of date fruit has been converted into another product rich in antioxidant soluble fiber by enzymatic hydrolysis [59].

Based on the nutritional values and chemical composition of the protein, carbohydrate, fat and minerals content in the date kernels, it has been reported that they could be used as a novel source of functional products with interesting technological functionalities that could also be applied as an excellent source of prebiotic due to the high content of dietary fiber [16,60]. All the above information will enhance the value of date by-products, fruits, seeds, etc. as excellent and cheap sources of a natural diet that can act as bioactive and nutritive ingredients in the pharmaceutical industries, food sector, and for other aspects [61,62].

#### **5. Conclusions**

Date fruit by-products, particularly DSM, have good nutritional values in poultry diets. The date has high concentrations of oleic acid and lysine and methionine content which are comparable to the corn and barley grains. Considering variability in the nutritive value of the DSM, developing a formula for ME of DSM = a (intercept) − b (slope) × crude fiber content should be considered to improve the feed formula accuracy. However, the nutritional value might not only depend on crude fiber but also on other compounds.

The results obtained from different studies indicate that date fruit by-products, particularly DSM, could be incorporated up to 5–10% levels, replacing corn or barley grains without hampering feed intake, growth, feed efficiency and nutrient utilization in poultry (broiler, laying hen, ducks, quail and turkey), and this could reduce the production cost. Maximum levels of DMS should be 5% in young birds and 10% in grower–finishers. Higher levels could be acceptable in slow-growing birds due to low-nutritional requirements. It also seems that young birds are less tolerant of DSM than older birds. In layers, up to 20% DMS was evaluated without any adverse effect on feed efficiency and egg production, but it decreased egg quality. The balance of protein and energy in the diet should always be established carefully. These agriculture-by-products become important if circularity becomes more important, not only in the Covid-19 crisis, but also in countries with a limited supply of classical feed resources and dependence on imported ones.

**Author Contributions:** All authors contributed equally to this review, and have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Data Availability Statement:** All data are published in the cited literature and reported in the text of this manuscript.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**


### *Article* **Research on the Effects of Gender and Feeding Geese Oats and Hybrid Rye on Their Slaughter Traits and Meat Quality**

**Dariusz Lisiak <sup>1</sup> , Piotr Janiszewski 1,\*, Eugenia Grze´skowiak <sup>1</sup> , Karol Borzuta <sup>1</sup> , Beata Lisiak <sup>1</sup> , Łukasz Samardakiewicz <sup>1</sup> , Tomasz Schwarz <sup>2</sup> , Krzysztof Powałowski <sup>1</sup> and Krzysztof Andres <sup>2</sup>**


**Simple Summary:** The research showed the influence of the gender of geese on some slaughter value traits and meat quality of geese slaughtered at the age of 17 weeks. It was found that ganders had a greater body and carcass weight than females but no significant differences in slaughter yield nor in carcass element share were observed. Gender did not have an effect on the majority of the studied breast meat quality traits. The studied feeding model did not have a significant influence on goslings' body weight; however, the birds fed hybrid rye had a lower slaughter yield as compared with those fed oats, but their meat had better physical and chemical characteristics (lower fat content, lower drip loss, higher protein content and, in the female goslings, also better sensory quality). Hybrid rye may be used in geese feed because it does not have a negative effect on pre-slaughter body weight and has a positive effect on some meat quality traits as compared with feeding geese oats.

**Abstract:** The aim of the study was to determine the effect of feeding Zatorska variety geese hybrid rye, oats, or a mixture of both grains (1:1) on slaughter value and meat quality. At 14 weeks old, the birds were separated into three feeding groups (*n* = 12) and were fed between 15 and 17 weeks of age with hybrid rye, oats, or a mixture of these two grains. The research proved the effect of gender and feeding on some slaughter value traits and meat quality of the goslings' breast meat. It was found that the ganders had a 10% to 15% higher body and carcass weight than the females. No significant differences were observed between the genders within the majority of the physical and chemical characteristics as well as the sensory traits. The feeding type did not have a significant effect on the goslings' body weight and carcass element share. The birds fed hybrid rye had a 2 percentage points lower slaughter yield than those birds fed oats which was combined with a lower share of subcutaneous fat (measured as the weight of the tissue coming from dissection) in birds fed hybrid rye. The meat of the birds fed hybrid rye had some better physical, chemical characteristics and, in the female goslings, also better sensory quality. The results indicated that hybrid rye may be used in feeding goslings at the end of the growing period, because it did not cause any negative effects on the pre-slaughter body weight and had a positive effect on some meat quality traits, such as better sensory estimation results, higher protein content, and lower drip losses.

**Keywords:** geese; feeding; rye; oats; slaughter value; quality traits

#### **1. Introduction**

The share of geese in the poultry production sector in Poland is at a low level, amounting to just 1.5%. Approximately 95% of the geese population in mass production are the White Kołudzka geese bred in the Experimental Center of the National Research Institute of Animal Production in Kołuda Wielka [1–4], originating from the white Italian geese.

**Citation:** Lisiak, D.; Janiszewski, P.; Grze´skowiak, E.; Borzuta, K.; Lisiak, B.; Samardakiewicz, Ł.; Schwarz, T.; Powałowski, K.; Andres, K. Research on the Effects of Gender and Feeding Geese Oats and Hybrid Rye on Their Slaughter Traits and Meat Quality. *Animals* **2021**, *11*, 672. https:// doi.org/10.3390/ani11030672

Academic Editor: Ilias Giannenas

Received: 9 December 2020 Accepted: 25 February 2021 Published: 3 March 2021

**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

Purebred animals may still be found on some breeding farms especially in the flocks under the protection program.

The results of many studies have proven that genotype has a significant influence on tissue content of carcass and chemical content of meat, as well as the muscle structure [3,5]. For instance, geese from rare breed flocks have a lower body weight, better musculature, and a lower fat content as compared with the popular white Kołudzka geese [2,3,5,6].

The Zatorska variety geese, kept in the Experimental Center of the Agricultural Academy in Cracow, belong to the Southern varieties which are used in the protection program.

In a study by Kapkowska et al. [7], the results of fattening the Zatorska and white Kołudzka geese by feeding oats between 14 and 17 weeks were compared, proving that the Zatorska geese body weight (both sexes) in the 17th week of age (5648 g) was significantly lower than the white Kołudzka geese body weight (6814 g). Moreover, the Zatorska geese had a lower slaughter yield and higher thigh and shank muscle share. Gomułka et al. [8] estimated the microstructure of the pectoralis superficalis and biceps femoris muscles and determined the technological parameters of the birds' meat at the age of 17 weeks after fattening by feeding oats. The muscle microstructure seemed to be similar in the Zatorska and white Kołudzka geese apart from the higher content of type I muscle fibres in the M. pectoralis superficialis in the Zatorska geese. Similar values for the majority of the physical traits for the muscles of both groups of geese were observed [8].

Geese fed oats have been the subject of many studies and publications [9–12]. Rye is traditionally regarded as a grain of limited suitability in poultry feeding especially in young slaughter birds. The reason for these limitations is the negative impact on the digestive system because of higher food content viscosity, the lower speed rate of the movement of intestinal digestion, and the lower digestibility of nutrients. Such observations may lead to negative effects in terms of poultry production and welfare factors [11]. In recent years hybrid varieties of rye have appeared on the market such as Brasetto which has better agrotechnical features. Furthermore, hybrid rye has a lower anti-nutritional substance content especially with low starch polysaccharides (NPS). NPS present in grains are among others pentosans (xylans and arabinians) as well as beta glucan. Rye grain is especially rich in arabinoxylans (AX) that are not digested by monogastric animals due to the lack of suitable enzymes [13,14]. The AX structure varies because of many factors, i.e., the grain type and variety. The various AX structures have an impact on the functional features and anti-nutritional effect level [13,14].

The research of Swi ˛atkiewicz and Arczewska-Włosek [ ´ 14] showed that the Brasetto hybrid rye grain can be used in the feeding of young chickens, since it is a useful energy and protein source. Introducing 15–20% rye into the feeding mixture for older birds (from 22 days of age) contributed to obtaining the desired production results, while introducing Brasetto rye added to the feed mixture for smallest chickens (1–21 days) had a negative effect on daily gain [13].

The aim of this study was to determine the effect of gender and feed mixture on slaughter value and physical, chemical, and sensory traits of the meat of birds fed hybrid rye, oats, or a mixture of these two grains.

#### **2. Material and Methods**

#### *2.1. Experimental Material*

The experiment was performed according to the guidelines issued by the Ethics Commission (Regulation 22/2016 of 20 January 2016r ILKE in Cracow). The experiment was performed on the Zatorska variety geese. This is a Polish rare breed meat type that is under the genetic resource protection program.

The geese were hatched from hatching eggs (Brinsea Ova-Easy 380) that belonged to the Experimental and Education Centre of WHBiZ UR (Faculty of the Animal Science University of Agriculture, Cracow, Poland). The experimental flock was made up of 300 young geese that were reared according to the slaughter geese rearing regulations in

Poland. Geese reared in Poland in the last 3 weeks of fattening are fed only oats and water. Oats, due the specific chemical composition, characterized by a high fat content and the profile of fatty acids profitable for human health, increase the value of goose meat and fat [2].

After hatching on 18 July 2017 and after gendering, the young geese were moved to a nursery where they were kept on straw bedding with natural light and with additional artificial lighting for 24 h in the first week of life.

For the first 3 weeks, the geese did not have access to pasture and the density was 7 geese per m<sup>2</sup> . The temperature in the nursery was lowered from 28 ◦C to 22 ◦C within this period and the relative humidity ranged between 65–70%.

#### *2.2. Feeding*

The plan of the experiment is presented in Table 1 below.

**Table 1.** The experimental plan of the Zatorska geese breed fed different kinds of cereals.


**Table 2.** Composition of concentrates and chemical composition of feed used in geese feeding (%).


For the first 3 weeks, the geese had access to feed and water through the adjusted to their age troughs and semi-automatic drinking bowls. The geese were fed dry complete feed of the proper content and nutrients which are presented in Table 2.

Between the 4th and 14th week of age, the geese were kept on straw bedding with 3.6 goslings/m<sup>2</sup> stocking density in a building with windows. The geese had access to pasture, with 12.5 m<sup>2</sup> space for each bird, and they stayed on the pasture for at least 8 h a day. The temperature in the nursery building was 20–22 ◦C and the relative humidity ranged between 65–70%. Between the 4th and 14th week of age, the geese were fed a mixture similar to the feed provided to geese between 0–3 weeks of life but additionally enriched with sunflower meal and wheat bran (Table 2).

After reaching 14 weeks, the birds were weighed and divided into groups according to gender and randomly divided into 3 feeding groups for each sex (*n* = 12). The birds of each group were fed ad libitum with grains according to the following schemes:

**Group A**: Brasetto hybrid rye with the chemical composition according to Swi ˛atkiewicz ´ and Arczewska Włosek [13];

**Group B**: Oats, according to the composition and nutritional recommendations for geese [14,15];

**Group C**: A mixture of the Brasetto hybrid rye and oats (1:1 by weight).

The fattening was performed in pens of 1 bird/m<sup>2</sup> density on the floor system, in a building with windows, on straw bedding, with 8 h access to straw pasture (stocking density 1.2 m2/bird). The temperature in the building was 12–18 ◦C. and the relative humidity ranged between 65–70%.

In the 17th week of life after being fattened by feeding grain, the birds were marked and not fed for 10 h because emptying the intestines has an impact on the quality and shelf life of carcasses during storage. After no food for 10 h, each bird was weighed individually, and then slaughtered in the commercial slaughter plant. The carcasses, after gutting, were chilled using the blowing and spraying method. Then, each carcass was weighed individually. The slaughter yield was calculated according to the following formula: MT/MC × 100%, where MT is a weight of chilled carcass and MC body weight before being slaughtered.

#### *2.3. Dissection*

The cut-up of the carcasses was performed according to the Ziołecki and Doruchowski [16] method for determining yield of the following parts: breast muscles, leg muscles, skin with fat, abdominal fat (from the bottom part of the abdomen), neck with fat (cut between the last cervical vertebrae and the first thoracic vertebrae), and wings (cut at the shoulder joint). Each carcass part was weighed and its share in the total chilled carcass was calculated.

#### *2.4. Physical and Chemical Characteristics of Breast Muscles*

Twenty-four hours after slaughter, the pH was measured using a Mettler Toledo 1140 type pH meter with a Mettler Toledo electrode (Mettler Toledo, OH 43240, D.C., US). The meat colour was determined on the muscle cross-section using a Konica Minolta Chroma CR 400 tool (Konica Minolta, Tokyo, Japan). Colour was classified according to the CiE lab determining L\* (lightness), a\* (redness), and b\* (yellowness), with the following measurement parameters: light source D65; observer 2◦ ; measuring head slot 8 mm; and calibration on the white tile L\* = 97.83, a\* = 0.45, and b\* = 1.88.

The samples of the final products were taken for lab analysis. The water content was measured according to the ISO 1442 (2000) [17]. Approximately 3 g of the minced meat was put on a weighing dish, weighed, and dried at a temperature of 105 ◦C up to the moment when the stable mass was reached. The water content expressed in % was calculated as a difference between the sample weight before and after drying.

The intramuscular fat content was established according to the ISO 1444 (2000) procedure [18]. The dried and weighed sample was placed in an extraction tube and the fat

substances were extracted with paraffin oil in a Soxtherm device produced by the Gerhardt Laboratory System (Gerhard GmbH & Co, Konigswinter, Germany). The fat content was calculated as the difference between the sample weight before and after extraction. The protein content was established according to the Polish norm PN/A-04018 [19] with a Kjeltec System 1002 Distilling Unit (Foss, Hilleroed, Denmark), according to the manufacturer's instructions. The sodium chloride in the final products was established according to the ISO 1841-2 (2002) procedure.

Apart from measuring the colour with a device it was also determined visually using a pattern with a 1 to 5 scale (1, light pink colour to 5, dark red colour) [20].

Similarly, meat marbling was estimated on the muscle cross-section according to a pattern with a 1 to 5 scale (1, slight fat content to 5, high fat content [20].

Drip loss was determined as follows: A muscle sample of approximately 100 g was weighed, placed in a plastic bag, and left in a refrigerator at a temperature of 4 ◦C for 48 h. The drip loss was calculated and based on the weight difference before and after storage.

Cooking loss was determined as follows: A muscle sample of approximately 150 g was weighed. Next, it was heated in water up to a temperature of 75 ◦C in the geometric sample centre. After cooling, the sample was weighed, and the weight loss was calculated based on the difference between the weights before and after cooking [21].

#### *2.5. Sensory Test*

A sensory test of cooked meat was performed by a team of 5 people trained in terms of sensory sensitivity with the Baryłko-Pikielna and Matuszewska method [21]. The estimation was performed in daylight at room temperature. Meat flavour, juiciness, tenderness, and palatability were determined using a 5-point scale [22]. In the cooked meat samples, meat tenderness was measured by using the Warner–Bratzler shear force method in a Zwick Roell Z 0.5 device (Zwick Roell, Ulm, Germany) with 500 (Kilonewton—kN) force and 100 mm/min of head movement.

#### *2.6. Statistical Analyse*

The results were statistically developed by calculating mean values (x) and standard error of the arithmetic mean (SEM). The statistical significance of the differences between the mean values of groups was verified by using a two factors variance analysis according to Anova procedure using the Statistica program Version 13 (StatSoft Hamburg, Germany).

#### **3. Results**

The geese body weight before slaughter in all of the feeding groups was at a similar level (Table 3). Clear differences were found between the genders (*p* ≤ 0.01). The ganders reached a higher body weight than the young female geese (by approximately 10–15%). A similar effect was observed for carcass weight, but the effects of feeding was confirmed here in the group of young female geese that were heavier in the group fed oats than in the group fed hybrid rye (*p* ≤ 0.05). A significantly lower slaughter yield was observed in both genders fed hybrid rye than those fed oats and the difference between the groups was over 2 percentage points (pp). The slaughter yield of those geese fed a mixture of both grains did not differ significantly as compared with the birds that were fed hybrid rye or oats only.

The weight and the percentage share of the basic carcass parts are presented below in Table 4. The weight of these parts was significantly different between the sexes (*p* ≤ 0.01), except for body frame weight in the oats group. The higher weight of the other parts was observed in the ganders due to their higher carcass weight. The feeding method had a significant impact on the leg weights of the young female geese which were heavier in the group fed oats than those fed hybrid rye and a mixture of both grains (*p* ≤ 0.01). The carcass parts yield did not depend on the gender and the feeding method, except for the higher share of wings in the ganders fed hybrid rye.


**Table 3.** Mean of the slaughter traits of geese fattened by feeding hybrid rye or oats.

N = 12 in every experimental group males and females; the letters A, B, C mean the fattening groups, i.e., (A) birds fed hybrid rye, (B) birds fed oats, (C) birds fed a mixture of hybrid rye/oats (1:1); SEM, standard error of the means; means marked with a letter (A, B, C or a, b, c) represents the fattening group with which it differs statistically, means marked by lowercase (a, b, c) are significant at *p* ≤ 0.05 and means marked by uppercase (A, B, C) are significant at *p* ≤ 0.01, the lack of a letter means that the mean does not statistically differ with any other fattening group.


**Table 4.** Weight and the proportion of parts in geese carcasses.


**Table 4.** *Cont*.

N = 12 in every experimental group males and females; the letters A, B, C mean the fattening groups, i.e., (A) birds fed hybrid rye, (B) birds fed oats, (C) birds fed a mixture of hybrid rye/oats (1:1); SEM, standard error of the means; means marked with a letter (A, B, C or a, b, c) represents the fattening group with which it differs statistically, means marked by lowercase (a, b, c) are significant at *p* ≤ 0.05 and means marked by uppercase (A,B,C) are significant at *p* ≤ 0.01, the lack of a letter means that the mean does not statistically differ with any other fattening group. Additionally, if the mean is signed by two letters "ac", that means significant difference as compared with means of both signed fattening groups a and c.

> The average weight and share of the chosen muscles and fat is presented below in Table 5. No significant differences between the dissection elements were found in terms of sex and feeding method, except for leg muscle weight and skin with fat weight. The muscle weight from the ganders' legs was approximately 17% higher than in the young female geese (*p* ≤ 0.01). The weight of the meat from the legs was significantly higher in the female geese fed oats (*p* ≤ 0.05) than those fed hybrid rye or a grain mixture. The weight of skin with the fat of females was lower in those birds fed hybrid rye only, but the share of this element was the same in all groups. A no gender not feeding method effect was confirmed on the weight and percentage share of breast muscles and abdominal fat. The only exception was the group of birds fed a mixture of both grains in which the breast muscle weight of the ganders occurred to be higher than in the female geese (*p* ≤ 0.05) and the abdominal fat share was higher than in the female geese (2.04% and 2.94%, respectively).

> The results of the breast muscle physical parameters measurements are presented below in Table 6. Lower average pH<sup>24</sup> values were reported only in the muscles of geese fed oats (5.88). No significant effect of sex and feeding method on colour lightness L\* and colour parameters (a\* and b\*) was observed. These parameter values were similar with the following ranges: L\* from 35.60 to 36.52, a\* from 18.39 to 20.15, and b\* from −1.76 to −0.95. Generally, these measurements were confirmed by a visual colour estimation of the muscles of the birds, both genders, fed hybrid rye or oats (3.12 to 3.38 points). However, the muscles of the female geese fed a mixture of both grains were lighter (2.97 points) than those fed hybrid rye (3.28 points).

> The meat marbling of both sexes was significantly influenced by the feeding method (*p* ≤ 0.01). Greater marbling was observed in the muscles of birds in both sexes fed oats (1.6 points) than those fed hybrid rye (1.32 points). In addition, birds fed a mixture of both grains had greater marbling than those fed hybrid rye (*p* ≤ 0.05) but only in the case of female geese (1.53 points). The drip losses in both sexes were influenced by the feeding method (*p* ≤ 0.01). No drip losses were observed in the muscles of both sexes fed hybrid rye, which may have been associated with the higher pH<sup>24</sup> value, which was above 6.0.


**Table 5.** Mean of weight and percentage of chosen muscles and fat obtained from the dissection of geese carcasses.

N = 12 in every experimental group males and females; the letters A, B, C mean the fattening groups, i.e., (A) birds fed hybrid rye, (B) birds fed oats, (C) birds fed a mixture of hybrid rye/oats (1:1); SEM, standard error of the means; means marked with a letter (A, B, C or a, b, c) represents the fattening group with which it differs statistically, means marked by lowercase (a, b, c) are significant at *p* ≤ 0.05 and means marked by uppercase (A,B,C) are significant at *p* ≤ 0.01, the lack of a letter means that the mean does not statistically differ with any other fattening group. Additionally, if the mean is signed by two letters e.g., "ac", that means significant difference as compared with means of both signed fattening groups a and c.



N = 12 in every experimental group males and females; the letters A, B, C mean the fattening groups, i.e., (A) birds fed hybrid rye, (B) birds fed oats, (C) birds fed a mixture of hybrid rye/oats (1:1); SEM, standard error of the means; means marked with a letter (A, B, C or a, b, c) represents the fattening group with which it differs statistically, means marked by lowercase (a, b, c) are significant at *p* ≤ 0.05 and means marked by uppercase (A,B,C) are significant at *p* ≤ 0.01, the lack of a letter means that the mean does not statistically differ with any other fattening group. Additionally, if the mean is signed by two letters e.g., "ac", that means significant difference as compared with means of both signed fattening groups a and c.

> Muscle loss in cooking was significantly influenced by the sex–feed type interaction (*p* ≤ 0.01). Clearly higher loss was observed in the muscles of female geese fed with oats (38.3%) than those fed hybrid rye or a mixture of both grains. Whereas in the ganders' group this dependence was the opposite, ganders fed oats had a significantly lower loss rate in cooking than the ganders of the other feeding groups.

> The results of the basic chemical composition (Table 7) showed a significant effect of feeding on the fat and protein level (*p* ≤ 0.01). Clearly a higher fat content was observed in the muscles of ganders and female geese fed a mixture of both grains (5.10% and 4.83%, respectively) as compared with birds fed hybrid rye only or oats only (3.6% on average).

The higher protein content was confirmed in the muscles of both sexes of birds fed hybrid rye than those fed oats (by approximately 0.9 pp) or the grain mixture (by approximately 1.8 pp).


**Table 7.** Basic chemical composition of the breast muscles.

N = 12 in every experimental group males and females; the letters A, B, C mean the fattening groups, i.e., (A) birds fed hybrid rye, (B) birds fed oats, (C) birds fed a mixture of hybrid rye/oats (1:1); SEM, standard error of the means; means marked with a letter (A, B, C or a, b, c) represents the fattening group with which it differs statistically, means marked by lowercase (a, b, c) are significant at *p* ≤ 0.05 and means marked by uppercase (A,B,C) are significant at *p* ≤ 0.01, the lack of a letter means that the mean does not statistically differ with any other fattening group. Additionally, if the mean is signed by two letters e.g., "ac", that means significant difference as compared with means of both signed fattening groups a and c.

> The sensory test results of the cooked breast muscles are presented in Table 8. A statistically significant sex–feed type interaction was observed in the flavour test which indicated that the muscle flavour of geese fed the hybrid rye and oat mixture was less intense (4.05 points) than that of both sexes fed either hybrid rye only or oats only (on average approximately 4.35 points). Feeding had an impact on the remaining organoleptic features, i.e., juiciness, tenderness, and palatability but only in the young female geese. The lowest values for these traits were in the group fed the grain mixture. The sheer force measurements using device did not confirm the differences in the meat tenderness sensory tests results because they ranged between 15.32 and 17.49 N in all of the tested groups. An interesting fact was observed in terms of gender effect on the sensory test results. Feeding the geese hybrid rye or oats showed no differences between the genders in terms of sensory traits but, in the group fed a mixture of these two grains, female geese muscles obtained lower scores than ganders' muscles in the meat flavour, taste, juiciness, and tenderness tests.


**Table 8.** Sensory evaluation results (points) and shear force measurements of cooked breast.

N = 12 in every experimental group males and females; the letters A, B, C mean the fattening groups, i.e., (A) birds fed hybrid rye, (B) birds fed oats, (C) birds fed a mixture of hybrid rye/oats (1:1); SEM, standard error of the means; means marked with a letter (A, B, C or a, b, c) represents the fattening group with which it differs statistically, means marked by lowercase (a, b, c) are significant at *p* ≤ 0.05 and means marked by uppercase (A,B,C) are significant at *p* ≤ 0.01, the lack of a letter means that the mean does not statistically differ with any other fattening group. Additionally, if the mean is signed by two letters e.g., "ac", that means significant difference as compared with means of both signed fattening groups a and c.

#### **4. Discussion**

#### *4.1. The Effect of Gender and Feeding on the Slaughter Value and Physical Traits of Meat*

The results showed that ganders' weight before slaughter as well as carcass weight was 10–15% higher than in female geese but gender did not have an effect on the slaughter yield, which ranged among the groups from 63% to 65%. No significant differences between the carcass tissues obtained from dissection according to gender and feeding method were found, except for leg muscle weight and skin with fat weight. Similar results were obtained by Kapkowska et al. [7] who reported a higher body weight of the male Zatorska and white Kołudzka varieties fed oats up to 17 weeks of life. The authors did not find any significant differences in slaughter yield between the genders, reaching approximately 64%. Nevertheless, in this study, the birds of both genders fed oats obtained a significantly higher slaughter yield by approximately 2 pp as compared with the group fed hybrid rye.

A higher ganders' carcass weight was followed by significantly higher weight of carcass elements but there were no differences in their percentage share in the carcass between the two sexes. The meat weight from legs was higher in ganders than in female geese for all groups (*p* ≤ 0.01) and in females it was only higher if they were fed oats rather than fed hybrid rye or the mixture of both grains (*p* ≤ 0.01). In the group of female geese fed the grain mixture, the abdominal fat content was significantly higher (*p* ≤ 0.05) than in ganders' group. The share of meat from the leg was lower only in those female geese fed the grain mixture (*p* ≤ 0.05). No significant differences were found in the percentage share of breast muscles between the sexes or in skin with a fat share. The results obtained by Kapkowska et al. [7] confirmed a higher yield of breast muscles in male carcasses as compared with female carcasses in both of the Zatorska and white Kołudzka geese.

No significant differences between the sexes were reported in terms of the tested physical breast muscle features such as colour lightness and its' a\* and b\* parameters, meat marbling and drip loss in all feeding groups. A significantly higher pH<sup>24</sup> (*p* ≤ 0.05) value was observed only in ganders from the group fed oats than in female geese, reaching 5.95 and 5.88, respectively. There were no one-way differences between the sexes in meat cooking losses (significant sex–feed type interaction, *p* ≤ 0.01). In the groups fed hybrid rye or the grain mixture, ganders showed higher thermal losses than geese in the group fed oats, which is difficult to explain and justify. The fairly high pH<sup>24</sup> of goose meat was confirmed by the research of Kapkowska et al. [7] in which the value in both sexes of the Zatorska variety reached 6.09 on average. Additionally, meat colour was pretty dark (L = 38.5), similar to the results obtained in this research (L = approximately 36–37). In addition, the muscles of the geese of the southern varieties presented similar L\* values but with a better, lower pH24, reaching 5.78 on average [3].

No significant gender effect on the basic chemical composition of breast muscle was reported in any of the feeding groups. The average water content was approximately from 70 to 70.7%, fat content was approximately 3.6–3.8% (except for the group fed the grain mixture, which was between 4.8% and 5.1%) and protein content was approximately 23–25%. In a study by Biesiada-Drzazga [23] on the meat of White Kołudzka geese, the following parameters were observed in birds which were 10 weeks old: protein content of 21% and fat content between 3.1% and 5.1%, depending on the feeding group. The authors of other publications [6,21,24] depending on the breed, origin, and the diet reported on average 19% to 24% protein and 2.3% to 6.3% fat content, in the breast muscle.

Gender did not have any impact on all of the studied sensory traits (flavour, taste, juiciness, and tenderness) of breast muscle in groups fed hybrid rye or oats, but it did have an effect in the case of hybrid rye and oat mixture feeding. The ganders in this feeding group obtained better scores in flavour (*p* ≤ 0.01), juiciness (*p* ≤ 0.05), taste (*p* ≤ 0.01), and tenderness (*p* ≤ 0.05) than in females and the difference in scores was approximately 0.3 points. The average results of the sensory tests for the studied features ranged from 3.80 to 4.35 points. Better results in the sensory tests of the southern variety geese meat were reported by Lewko et al. [11] who obtained 4.8 points in cooked breast muscles.

A high score, approximately 4 points, in meat tenderness estimated by the sensory test was confirmed by measurements performed with a device measuring the shear force with low values (from 15.30 to 17.49 N), which did not depend on the gender. In contrast, Kapkowska et al. [7] observed significantly higher shear force values (43.2 to 50.2 N) but, as confirmed in the literature, they were still within the range of good meat tenderness, i.e., approximately 50 N [21].

#### *4.2. The Effect of Feeding on Slaughter Traits and Geese Meat Quality*

The different feeding groups did not show differences in terms of body weight, but the geese fed hybrid rye obtained approximately a 2 pp lower slaughter yield than those geese fed oats (*p* ≤ 0.01 in males and *p* ≤ 0.05 in females). The higher slaughter yield in geese fed oats could have been influenced by the higher weight of fat with skin in female geese by approximately 80 g and in ganders by 63 g as compared with the group fed hybrid rye.

Basically, the feeding method did not have any impact on body weight or on the share of carcass elements. The only exception was the weight of geese legs (*p* ≤ 0.01) and the percentage share of wings in males (*p* ≤ 0.05) from the group fed oats. The highest leg weight of female geese was observed in the oat group, whereas the wing share of males was the highest in the hybrid rye group. The feeding method did not have an effect on the weight and percentage share of breast muscles and share of leg muscles, as well as fat with skin percentage and share and weight of abdominal fat. Other authors have obtained different results. According to a study by Kapkowska et al. [7], the carcasses of Zatorska and White Kołudzka geese had a higher fat content with skin share as compared with

the results obtained in this study. Additionally, in a study by Biesiada-Drzazga [2], the abdominal fat share in White Kołudzka geese fed a concentrated feed ranged from 4.2% to 5.8% which indicated a higher fat share than that observed in the geese within this research (2.04% to 2.94% on average). This was also confirmed by Karwowska et al. [25] where the fat share ranged between 6% and 8.5% in the carcasses of White Kołudzka geese fed corn silage and beet pulp, as well as another study by Kokoszy ´nski et al. [26] that applied feeding a corn mixture with 20% addition of oats.

Among the estimated physical features, feeding had an influence on the lower pH<sup>24</sup> value of breast muscles of female geese fed oats, meat marbling (the highest observed in feeding oats, the lowest in feeding hybrid rye), drip loss (no drip with hybrid rye feeding and approximately 1.3% to 2.0% with oats and mixed grain feeding), as well as the thermal losses of breast muscle samples (the lowest in the oat fattening of ganders and the highest in female geese of this oats group). The changes were not directed one-way (i.e., significant sex–feed type interaction). No effect of the feeding method on colour lightness L\* and redness and yellowness parameters was observed but this meat colour should be described as fairly dark (L\* = approximately 36), which was also confirmed by Kapkowska et al. [7] and Okruszek et al. [27] who reported average L\* = 38.5 for geese breast muscles. However, Lewko et al. [11] observed a lighter colour (L = 44.2) in the breast muscles of southern geese varieties fed oats. Low drip loss was also reported by Kapkowska et al. [7] in 17-week-old geese after feeding oats (0.5%), as well as by Biesek et al. [1] in geese fed a mixture with lupin (0.33% to 0.63%), which are also confirmed in this study. Slightly lower thermal losses in cooking (approximately 30% to 32%), as in this investigation, were observed by Gumułka et al. [8] and Kapkowska et al. [7] in the breast muscles of Zatorska geese after being fed oats.

A basic chemical composition analysis proved the significant effect of feeding on fat and protein content. The highest fat content was observed in the muscles of geese and ganders, which were both fed a grain mixture (4.83% and 5.13%, respectively) as compared with those fed hybrid rye or oats (3.60% on average). These observations were confirmed by the results of visual marbling estimation.

Biesiada-Drzazga [24] reported that, in the breast muscle of White Kołudzka geese fed until 10 weeks of age a concentrated feed with soy and sunflower meal, fat content levels reached 5.1%, 4.3%, and 3.1%, in different experimental groups, and the protein content was 21% on average; the significant effect of feeding on protein content was observed in the studied population. In the muscles of birds fed hybrid rye, a significantly higher protein content, approximately 2 pp, was observed in both genders as compared with birds fed a mixture of two both grains. The muscle protein content in female geese and ganders fed oats was similar (24% on average).

The authors of other publications [6,21,22,25] depending on the geese breed, origin, and diet have reported protein contents on average from 19% to 24% and fat contents from 2.3% to 6.3% in breast muscle. In this study, we confirmed that feeding oats or hybrid rye did not affect the chemical composition of the meat but caused the relatively high protein content and lower fat content.

The results of sensory tests in terms of flavour, juiciness, tenderness, and palatability of cooked meat ranged from 3.8 to 4.35 points. Among these features, there was one statistically significant sex–feed type interaction in the flavour estimation (*p* ≤ 0.01). The muscles of female geese had the lowest score (4.05), whereas the goslings in three feeding groups presented, on average, the same values within this parameter (approximately 4.3 points). A statistically significant (*p* ≤ 0.01) feeding impact on meat juiciness and the palatability of female geese was observed. Better scores were observed in the meat of female geese fed hybrid rye (over 4 points). Lewko et al. [11] estimated the sensory traits of southern varieties of goose meat depending on the origin, gender, and diet. Cooked breast muscles obtained 4.8 points for the estimated sensory features.

Meat tenderness measurements using devices did not show the effect of feeding on the shear force that fit within 15.3 and 17.49 N. These data proved the good tenderness of the tested meat. Kapkowska et al. [7] reported a higher shear force for the breast muscle of the Zatorska and White Kołudzka varieties, ranging from 43.2 to 50.2 N and Karwoska et al. [9] obtained, for the same musles of the White Kołudzka variety, a mean of 49.8 N.

In summary, it should be stated based on available studies [28,29] the direction for the development of rye genetics should be to create the new cultivars with reduced levels of antinutritional substances. The high level of monosaccharides, as the best source of metabolic energy, could also contribute to an increase in feed intake. The favourable proportions of carbohydrates and lipids in hybrid rye could also determine its nutritional value and possibility have a positive effect on carcass quality. Additionally, the using of hybrid rye in animal feeding could bring economic benefits, because the price of the rye is lower than the other grains [27].

#### **5. Conclusions**

Our results show the impact of gender on some slaughter value traits and meat quality of young geese slaughtered at 17 weeks old. We found that ganders' carcass weight and their live weight before slaughter was 10–15% higher than that of female geese. The slaughter yield and the share of cuts and same dissection elements such as breast muscles and skin with fat did not differ between sex. No significant differences were found between genders in colour lightness and a\* and b\* colour parameters, as well as marbling, drip losses, and basic chemical composition of breast muscle. The sensory estimation results of ganders were better than young female geese only in the case of those ganders fed hybrid rye and a mixture of oats and hybrid rye.

During the last three weeks before slaughter, the type of feeding (hybrid rye, oats, or hybrid rye and oats mixture) did not have a significant effect on geese body weight, but the birds fed hybrid rye had approximately a 2 pp lower slaughter yield than the geese fed oats. The feeding type did not have an influence on the male carcass weight and the share of majority cuts in both sexes, but it had an effect on pH<sup>24</sup> (it was lower in female geese fed oats), drip losses (none in hybrid rye feeding), marbling (higher in feeding with oats), cooking losses (significant sex–feed type interaction), fat content (higher in mixture feeding), and protein content (higher in hybrid rye feeding). Better sensory estimation results of breast muscles were observed in the young female geese fed hybrid rye or oats.

The obtained results indicate that hybrid rye may be used in the feeding of young geese without causing any negative effects on the final body weight and as a result improving some meat quality traits.

**Author Contributions:** Conceptualization, T.S. and D.L.; methodology, K.B., D.L., K.A. and P.J.; software, D.L.; validation, E.G., B.L., Ł.S. and K.P.; formal analysis, T.S. and D.L.; investigation resources, D.L.; data curation, E.G., P.J., B.L., Ł.S. and K.P. writing—original draft preparation, E.G. and K.B.; writing—review and editing, P.J. and K.B. visualization D.L., T.S. and K.A.; supervision, T.S., D.L. and K.B. project administration, T.S.; funding acquisition, T.S. and D.L. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the National Centre for Research and Development (https:// www.ncbr.gov.pl/en/ (accessed on 24 February 2021)) in Poland and conducted within the Biostrateg program (grant "ENERGYFEED" number BIOSTRATEG2/297910/12/NCBR/2016).

**Institutional Review Board Statement:** All experimental procedures performed on live animals followed the EU Directive 2010/63/EU for animal experiments and the Polish law for the care of animals used in research and education. According to Polish law (Regulation of January 15, 2015 on the protection of animals used for scientific or educational purposes) the ethical approval of research is not formally required if experiments involve only the standard operating procedures typically carried out on a commercial farm. Slaughter of animal aimed to obtain tissues for laboratory analyses is not formally considered as research procedure and the ethical approval of such action is not required.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** We certify that there is no conflict of interest with any financial organization regarding the material discussed in the manuscript.

#### **References**


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