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Article

Effects of the Oil and Fat Feeding Period on the Nutritional Composition and Functional Properties of Eggs

by
Zhouyang Gao
1,
Yuhui Qin
2,
Jiangxia Zheng
2 and
Guiyun Xu
2,*
1
State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing 100193, China
2
Key Laboratory of Animal Genetics and Breeding of the Ministry of Agriculture, College of Animal Science and Technology, China Agricultural University, Beijing 100193, China
*
Author to whom correspondence should be addressed.
Agriculture 2024, 14(2), 181; https://doi.org/10.3390/agriculture14020181
Submission received: 13 November 2023 / Revised: 3 December 2023 / Accepted: 24 January 2024 / Published: 25 January 2024
(This article belongs to the Section Farm Animal Production)
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Abstract

:
Lipids are commonly incorporated into the diets of laying hens at a rate of 1% to 2% during production. However, the effects on egg quality can vary based on the source and timing of lipid addition. Hence, this experiment was conducted to investigate the impacts of adding the same concentration of soybean oil, lard, and mixed oils (1.5%) to the daily feed of layer during two feeding periods. This study aimed to assess the changes in nutritional composition and functional properties and offer valuable insights to determine suitable types of oils and fat. In this study, the experiment was conducted in two test periods, 7 days and 21 days after the addition of the lipids, to assess the effects on the nutritional composition and functional properties of eggs. The study revealed the following results: (1) Changes in the yolk’s nutritional composition. Compared to the 7-day addition period, the inclusion of lard significantly increased the unsaturated fatty acids after 21 days; (2) Changes in the albumen’s nutritional composition. Compared to the 7-day addition period, the inclusion of lard and mixed oils significantly reduced the essential and nonessential amino acids after 21 days; (3) Changes in the functional characteristics of the eggs. After 21 days of addition, the eggs from the soybean oil group exhibited significantly higher foaming and emulsifying properties compared to the groups supplemented with lard and mixed oils; (4) Changes in the antioxidant capacity of the eggs. Compared to the 7-day addition period, the inclusion of all oils and fat significantly increased the superoxide dismutase (SOD) content in egg yolk after 21 days. The aim of this experiment was to provide valuable scientific data to assist producers in making informed decisions regarding the utilization of feeding oils.

1. Introduction

In poultry production, fat is utilized as an energy feed due to its higher energy value compared to carbohydrates and proteins [1]. Consequently, lipids have become a preferred source for laying hen farming. Numerous studies have been conducted on the effects of lipids on laying hens, which can be broadly categorized into the following areas: providing energy and reducing costs [2], promoting the absorption of fat-soluble vitamins [3], reducing dust and preventing diseases [4], supplying essential fatty acids and influencing lipid metabolism [5], impacting the structure and function of intestinal microbiota [6], affecting production performance [7], and influencing the nutritional composition of egg yolk [8]. Currently, feeding oils can be classified as vegetable oil, animal oil, and mixed oils based on their sources. Vegetable oil primarily includes soybean oil, rapeseed oil, and flaxseed oil [9], while animal oil comprises fish oil, lard, and black soldier fly larvae oil. Mixed oils refer to a combination of different types and proportions of fat. However, due to the complex interactions between different types of oils, it is challenging to control and explain their effects.
Eggs are renowned for their rich nutritional value, pleasant taste, and high digestibility. They are not only essential raw materials in the food industry but also a crucial part of people’s daily diets [10]. The main components of eggs include the albumen (57%), egg yolk (32%), eggshell (10%), and eggshell membrane (<1%) [11]. Due to their nutritional density, eggs have been hailed as an “ideal source of nutrition for humans [12].” Among these components, egg yolk offers various health benefits, such as preventing atherosclerosis, promoting the nervous system, bodily development, and enhancing metabolic and immune functions [13]. Furthermore, egg yolk is abundant in selenium, which possesses anticancer properties [14]. On the other hand, the albumen consists primarily of water, proteins, and amino acids, providing essential amino acids needed by the human body. The amino acid composition of albumen closely resembles that needed for synthesizing human tissue proteins, making it easily digestible and absorbable [15]. When lipids are added to the diet of laying hens, the composition and physical properties of lipids from different sources and types vary significantly, resulting in differences in the nutritional composition and functional properties of eggs. Short-term addition of lipids to eggs may have minimal impact on their nutritional composition, as the mechanisms through which lipids influence the eggs may not fully manifest. However, if the period of lipid addition is prolonged, it could impose a certain burden on the lipid metabolism of laying hens and even affect the nutritional composition of their eggs [16]. Therefore, further investigations are warranted to explore the optimal duration and underlying mechanisms of lipid addition in the diets of laying hen.
In daily life, consumers are concerned about the quality of eggs. These concerns can be categorized into concerns about the internal and external quality. Internal quality mainly refers to nutritional content, protein status, and yolk condition [17], while external quality encompasses eggshell condition, egg shape index, and egg weight [18]. Research has shown that when lipids are added to the diet of laying hens, they pass through the ovaries and enter the eggs [19]. The composition and proportion of fatty acids in the feeding oils influence the content of fatty acids in egg yolk. Fatty acids can be divided into saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids (PUFAs) based on their levels of saturation [20]. Fatty acids with different saturation levels have distinct nutritional functions. The yolk typically contains approximately 26.4–33.8% fat, with unsaturated fatty acids accounting for approximately 60–70% of the total fat content [21,22].
Due to their excellent processing characteristics, eggs are extensively utilized in the food processing industry [23]. Despite being a major producer of poultry eggs, China primarily consumes fresh eggs, with only a small portion used for further processing. Consequently, the egg industry is relatively underdeveloped. The functional properties of eggs mainly include the foaming and gelling properties of the albumen, as well as the emulsifying and functional stability of the egg yolk [24]. Moreover, the amino acids in the albumen play a vital role in determining the taste and palatability of processed egg products. Certain amino acids, such as glutamic acid and arginine, can enhance the freshness and aroma of food, improving the overall sensory experience [25].
The quality and functional characteristics of eggs are significantly influenced by various factors, including the age and breed of hens, additives in their diet, and storage conditions. Compared to the broiler breed, there is relatively little research on the application of lipids in laying hens. For poultry, egg yolks contain abundant fat-soluble organic compounds, which provide a theoretical basis for altering the taste of egg yolks by changing the feed composition. With the continuous advancement of technology, the correlation between food flavor and its composition can be studied [26]. Adding oils and fat to feed can affect the flavor of egg yolks, possibly due to the composition of fatty acids in the yolk [8,27]. Some studies suggest that the flavor of egg yolks primarily comes from the presence of fatty acids such as palmitic acid, oleic acid, and arachidonic acid [28]. Therefore, it is meaningful to investigate the effects of different sources of oils and fat on the nutritional composition of eggs.
In our previous research, it was found that adding a high concentration (3%) of lipids to the diet of laying hens negatively affected their production performance [25]. Therefore, in this experiment, the same concentration (1.5%) of soybean oil, lard, and mixed oils was added to the basal diet of laying hens. The effects of different sources of oils and fat on the nutritional composition, antioxidant properties, and functional characteristics of the albumen and yolk were analyzed as the feeding cycle progressed. In addition, this experiment innovatively studied the changes in the yolk index after eggshell breakage after different treatments. The findings of this study will provide valuable insights for producers, helping them to choose suitable lipid sources and determine the optimal duration of poultry production.

2. Materials and Methods

2.1. Ethics Committee

All experimental procedures were performed following the Guidelines for Experimental Animals set forth by the Animal Care and Use Committee of China Agricultural University (permit number: AW52501202-1-1) [29].

2.2. Animals, Treatments, and Experimental Design

This study used 40-week-old Hy-Line Brown hens sourced from the Poultry Experimental Base of Shandong Academy of Agricultural Sciences. A total of 480 hens with similar body weights (2000 ± 130 g/each) were selected and randomly divided into four experimental groups. Each group had three replicates, with 40 hens per replicate (four hens per cage). The control group was fed a corn and soybean diet, while the other three groups received a basal diet supplemented with 1.5% soybean oil, 1.5% lard, or 1.5% mixed oils. Throughout the experimental period, the temperature in the chicken house was maintained at approximately 23 ± 2 °C, with a relative humidity of 50% to 60%. The lighting schedule followed a 16 h light and 8 h dark cycle (16L:8D).
The entire experimental period lasted for 28 days, comprising a 7-day pre-feeding period and a subsequent 21-day formal trial period. During the pre-feeding period, the health of hens was monitored, and adjustments were made to the groups based on their performance. Observations were made regarding egg production, feed intake, and the overall health of the laying hens during this period. Adjustments to temperature and humidity conditions in the housing were made as necessary based on their performance. The lipids used in the experiment were stored in a cool and well-ventilated area to prevent oxidation and spoilage. Daily monitoring of the hen’s performance was conducted, ensuring that they had an adequate supply of water and food each day. After this period, the hens entered the formal trial period, which lasted 21 days. Throughout the study, daily monitoring ensured that the hens had sufficient access to water and feed. On the 7th and 21st days following the addition of oils and fat to the diets, eggs were collected from each treatment group. These eggs were then analyzed to measure their nutrient content and other relevant parameters.

2.3. Diets and Composition

This study utilized soybean oil (saturated fatty acids: 14%, monounsaturated fatty acids: 25%, polyunsaturated fatty acids: 60%, and phospholipids: 1%), lard (saturated fatty acids: 40%, monounsaturated fatty acids: 45%, polyunsaturated fatty acids: 13%, and phospholipids: 2%), and mixed oils. The composition of the mixed oils included soybean oil, soy lecithin oil, coconut oil, rice bran oil, and antioxidants. The lipids were purchased from a store. Based on the National Research Council (NRC) [30], a basal diet consisting of corn–soybean meal was formulated in appropriate proportions. In the experimental groups, 1.5% soybean oil, lard, and mixed oils were individually added to the basal diet of the control group. For detailed information about the nutritional composition of the diet in each experimental group, please refer to Table 1 and Table 2.

2.4. Egg Nutrient Content Determination at 7, 21 Days

The determination of nutrient content in the egg yolks was conducted as follows: in the formal trial, three eggs were randomly chosen from each replicate on the 7th and 21st days, resulting in a total of nine eggs per experimental group. The raw yolk was separated from the eggs and mixed thoroughly. The fatty acid content in raw egg yolk was determined following the guidelines set by the Chinese food safety standard (GB 5009.168-2016). Determination of nutrient content in the albumen was conducted as follows: in the formal trial, three eggs were randomly chosen from each replicate on the 7th and 21st days, resulting in a total of nine eggs per experimental group. The raw egg yolk was separated from the eggs, and the entire albumen was retained and mixed thoroughly. The amino acid content in the albumen was determined based on the Chinese food safety standard (GB 5009.124-2016). The protein content in the albumen was measured based on the Chinese food safety standard (GB 5009.5-2016). Fatty acids and amino acids were measured using a kit from Qingdao Sci-Tech Quality Co. (Qingdao, China)

2.5. Determination of Antioxidant Enzyme in Egg Yolk

During the formal trial, three eggs were randomly selected from each replicate on the 7th and 21st days, resulting in a total of nine eggs being selected from each experimental group. The eggs were broken, and the yolks were separated to measure the activity of the antioxidant enzymes in the raw yolks. The determination of peroxidase (POD) content in the raw egg yolk was carried out following the guidelines set by the Chinese food safety standard (GB 5009.181-2016). The content of superoxide dismutase in egg yolk was determined using a SOD kit. The content of glutathione peroxidase in the egg yolk was determined using a glutathione peroxidase (GSH-PX) kit (Nanjing Jiancheng Bioengineering Institute, Nanjing, China).

2.6. Egg Functional Property Determination

2.6.1. Determination of Emulsifying Properties and Stability of Egg Yolks

On the 21st day of the formal trial, 9 eggs were randomly selected from each treatment group. The process began by cracking the eggshells and placing the egg contents on a separator. The yolk membrane was then pierced, allowing the yolk to flow into a beaker. Using an electric stirrer, the mixture was stirred at a slow speed for 5 min, resulting in a diluted yolk solution.
From the prepared diluted yolk solution, 20 mL was taken and mixed with 5 mL (20%) soybean oil. The mixture was then subjected to centrifugation at 12,000 r/min for 1 min to obtain an emulsion. Once the emulsion was prepared, 200 μL was withdrawn from the bottom and added to 20 mL of a 0.1% SDS (sodium dodecyl sulfate) solution for further dilution. The dilution solution was vortexed, and the absorbance was measured at 500 nm using a UV-visible spectrophotometer. The emulsification index was calculated using the following formula:
E A I = 4.606 × A 0 × D C × 1 − Φ × 10
where A0 is the absorbance at 500 nm; D is the emulsion dilution factor (100); C is the concentration of protein aqueous solution (mg/mL); Φ is the proportion of oil added to the emulsion (0.2).

2.6.2. Determination of Foaming Properties and Stability of Albumen

On the 21st day of the formal trial, 9 eggs were randomly selected from each treatment group. The cracked eggs were separated using an egg separator, and the yolk was removed. The albumen was mixed thoroughly with a glass rod to obtain an albumen solution. A specific amount of the albumen solution with a height of h was transferred into a 50 mL centrifuge tube. The tube was then subjected to high-speed agitation at 12,000 r/min for 1 min using a high-speed homogenizer. The height of the liquid level, h1 (cm), and the total foam height, h2 (cm), were measured using a ruler. The average values were calculated as indicators of the foaming properties of albumen. The prepared samples were left undisturbed for 30 min. The average values were taken as indicators of foam stability.
Albumen foaming, %= (h2 − h1)/h1 × 100
Foaming stability, % = (h2’ − h1’)/(h2 − h1) × 100

2.6.3. Determination of Albumen Gel Properties

On the 21st day of the formal experiment, 9 eggs were randomly selected from each group. The albumen was separated and subjected to heat (85 °C) for 0.5 h. Subsequently, the sample was cooled and stored overnight in a refrigerator at 4 °C. The following day, an A-XT Plus Texture Analyzer (Godalming, UK) was used to analyze the samples using the following texture parameters: pretest speed, test speed, and posttest speed set at 1 mm/s; compression strain set at 70%; and trigger force set at 10 g.

2.6.4. Determination of Yolk Index at Different Time Points after Breaking the Eggshell

On the 21st day of the formal experiment, 30 eggs were randomly selected from each repetition of the 1.5% lipid treatment group and control group. The eggs were collected and stored in a refrigerator at 4 °C for 12 h before the initial measurements were taken. The eggs were then cracked, and the weight and yolk index were measured at 0, 8, 16, and 24 h of storage. The changes in the yolk index at these time points were analyzed.
The measurements were conducted under controlled environmental conditions with a temperature of 25 ± 2 °C and a humidity level between 30% and 40%. Measuring instruments included Vernier calipers, electronic analytical balances, Petri dishes, transparent glass covers, thermometers, and hygrometers. The yolk index was calculated as the ratio of height to diameter.

2.7. Statistical Analysis

The data are presented as the mean ± SD and were considered significantly different at p < 0.05 or p < 0.01 [31]. All statistical data were analyzed by SPSS 24.0 (SPSS, Chicago, IL, USA). Statistically significant differences among treatments were determined by Tukey’s test. GraphPad Prism 9 was used for graph design [32].

3. Results

3.1. Effect of Oils and Fat on Egg Nutrition at 7 and 21 Days

The results of the nutritional composition analysis of egg yolk and albumen on days 7 and 21 after the addition of lipids are presented in Figure 1 and Figure 2. This study showed significant variations between day 7 and day 21. In terms of fatty acids in egg yolk, the soybean oil and lard treatment groups exhibited a significant increase in saturated fatty acids (p < 0.05). Additionally, the addition of lard significantly increased the content of unsaturated fatty acids in the yolk (p < 0.05). In terms of amino acids in albumen, the content of both essential and nonessential amino acids showed a significant decrease after adding lard and mixed oils (p < 0.05). However, no significant difference in amino acid content was observed in the soybean oil group after the two different feeding periods (p > 0.05).

3.2. Effect of Oils and Fat on Egg Yolk Antioxidant Capacity at 7 and 21 Days

The results of the oils and fat on egg yolk antioxidant capacity on days 7 and 21 after the addition of lipids are presented in Figure 3. In this experiment, the content of POD in the egg yolk significantly increased on day 21 compared to day 7 after the addition of the soybean oil, lard, and mixed oils (p < 0.05). However, in terms of GSH-PX and SOD, there were no significant reductions after the addition of soybean oil, lard, and mixed oils (p > 0.05).

3.3. Effect of Oils and Fat on Egg Functional Properties

As shown in Table 3, the addition of lipids had a notable impact on the functional properties of eggs. After 21 days of lipid incorporation, the soybean oil group exhibited significant improvements in the foaming of the albumen and the emulsification of the egg yolk compared to the lard and mixed oil groups (p < 0.05). Additionally, the soybean oil group demonstrated a reduction in the gel hardness of albumen (p < 0.05).

3.4. Effect of Oils and Fat on the Change in Egg Yolk Index after Shell Breaking

To better assess the freshness of the eggs, this experiment comprised a control group without added lipids and groups with added lipids. Therefore, a one-time determination method was used to assess the egg yolk index, and the changes in the egg yolk index at various points in time after shell breakage under different treatments were analyzed. The results are shown in Table 4. According to the results, it is evident that the percentage decrease in the egg yolk index differed significantly among all groups at 0–8 h, 0–16 h, and 0–24 h (p < 0.05). Compared to the basic diet group, the soybean oil and mixed oil groups had a stronger influence on the decrease in the egg yolk index, with the most substantial reduction treated with 1.5% soybean oil, resulting in a 38.18% decrease.

4. Discussion

Currently, the increasing demand for agricultural products, including meat, eggs, and milk, parallels the improvement in people’s living standards. Consumers not only seek basic nutrients from their food but also have higher expectations for food quality, nutritional composition, and functionality. Among these agricultural products, eggs are beloved by people due to their rich content of nutrients. Based on our previous research experiments, it was found that after adding 1.5% soybean oil, lard, and a mixed oils to the basal diet, there were no significant differences in egg production rate, average egg weight, and egg quality indicators compared to the basal diet group. Therefore, we further investigated the changes in nutritional composition and functional properties of eggs during different feeding periods with the addition of different oils [25].
Soybean oil is rich in fatty acids, including a large amount of unsaturated fatty acids. Studies have found that adding soybean oil to the feed of laying hens can not only increase the levels of linoleic acid, n-3, and n-6 PUFAs in eggs but also enhance the color of egg yolks [33]. As one of the fatty oils, lard is commonly used in laying hen diets. Research has found that adding lard can improve the nutritional content of eggs, such as the content of saturated fatty acids (SFAs) and the yellow color of eggs [34]. Currently, mixed oils have become a research hotspot. However, due to the mutual influence of different types of oils, it is challenging to control their effects. Moreover, insufficient research on the underlying mechanisms makes it challenging to determine and explain their effects. Therefore, the exploration of the nutritional composition of eggs with different sources of oils and fat is highly meaningful.
Egg yolk is rich in neutral fat, protein, minerals, and vitamins [35]. The amino acid and protein composition of the albumen are highly suitable for human utilization [36]. The human body requires eight essential amino acids from food, namely isoleucine, leucine, lysine, methionine, phenylalanine, threonine, valine, and tryptophan [37]. Lysine is the first limiting amino acid in the human body, as it cannot be synthesized internally and needs to be obtained through high-quality protein sources [38]. Lysine plays a crucial role in protein breakdown, immune antibody production, digestive enzyme synthesis, and growth factor synthesis. Methionine, the second limiting amino acid in the human body, prevents excessive obesity and effectively reduces the risk of fatty liver and cardiovascular problems. It can also act as a potent antioxidant and eliminate heavy metals [39]. In the past, nonessential amino acids were considered less important than essential amino acids in their effects on the human body. However, nonessential amino acids are vital for protein synthesis and affect the requirement for essential amino acids. Imbalances or excessively high or low levels of amino acids for endogenous protein synthesis can pose risks to human health [40,41]. The results of this experiment revealed that, although the content of the unsaturated fatty acids in the egg yolk of the lard treatment group gradually increased with the duration of oil addition, the contents of essential and nonessential amino acids decreased gradually.
The antioxidant enzyme system mainly consists of POD, GSH-Px, and SOD [42]. Its primary function in animals is to protect against reactive oxygen species (ROS) by preventing lipid peroxidation and inhibiting the oxidation of proteins, which can lead to the production of harmful toxins [43]. In livestock production, lipids have an impact on immune function [44]. In this study, POD activity was significantly increased in all groups, possibly due to the oxidized substances in the lipids being deposited in the ovaries as the oil addition period was prolonged, and this was effectively enriched in the yolk. One possible explanation for these findings is that when oils are added, the immunoreactive substances within the oils are deposited in the ovaries and subsequently enriched in the yolk, leading to increased antioxidant enzyme content. Currently, most experimental studies focus on the antioxidant performance and defense enzyme activity of feeding oils on laying hens’ bodies, whereas the content of the antioxidant enzymes present in eggs has received less attention. Therefore, further research is needed to explore the oxidation mechanisms of different oil sources on eggs.
Eggs not only provide abundant nutrients and energy for the human body but also possess excellent physicochemical functional properties, such as solubility, emulsification, foaming, and gelation [45,46]. When lipids from different sources are added, these functional properties undergo significant changes, thereby affecting the composition and physical properties of eggs. These changes play a crucial role in egg products. Generally, the functionality of eggs is positively correlated with their foaming and emulsifying properties [47], while the texture of albumen, indicated by gel hardness, negatively affects the palatability of eggs [48]. Previous studies have demonstrated that structural changes in albumen and yolk occur when naturally occurring protein molecules are subjected to external forces [47]. Hence, based on the findings of this experiment, it can be inferred that different fatty acid contents in oils alter the lipid metabolism of laying hens, resulting in various effects on the process characteristics of eggs. Currently, most research mainly focuses on altering the functional properties of eggs through direct treatments of the albumen or egg yolk in vitro, while there are limited reports on the influence of exogenous additives on the process characteristics and texture indicators of eggs. This deserves further exploration and investigation.
In recent years, there have been reports of “rubber eggs” in the market [49]. These eggs exhibit yolk with retained toughness and elasticity even after being opened, and their egg yolk index remains significantly higher than that of normal eggs for a certain period. However, because of their poor texture, “rubber eggs” negatively impact consumers’ desire to purchase. The egg yolk index indirectly reflects the quality of eggs, and the traditional viewpoint holds that the higher the yolk index value is, the fresher the egg is considered [50]. The egg yolk index is primarily influenced by factors such as the height and diameter of the yolk, as well as environmental conditions such as pH and temperature [51]. From the results of this experiment, it is evident that the egg yolk index of fresh eggs significantly decreased at different time points (0, 8, 16, 24 h) after cracking the eggs and that the decreasing trends were similar. This may be attributed to the changes in yolk during storage caused by the penetration of water from the albumen through the yolk membrane [52]. By measuring the egg yolk index multiple times and analyzing the variations between time points after cracking fresh eggs, this study provides valuable reference data on the changes in the egg yolk index at different time points.

5. Conclusions

In this study, we aimed to investigate the impact of the same concentration of soybean oil, lard, and mixed oils (1.5%) on the nutritional composition of eggs. During the experiment, we conducted two feeding periods with laying hens and analyzed the changes in the nutritional composition and functional properties of albumen and yolk. Our goal was to gather technical parameters for the development of functional eggs using different lipid sources. It also provides a relevant theoretical basis for the development of functional egg products. In our results, we suggested adding 1.5% soybean oil to the daily diet of laying hens. However, the short duration of the feeding period may not fully demonstrate the complete impact of lipids on the organism. Further research is needed to investigate the effects of lipids on the nutritional composition and functional properties of eggs.

Author Contributions

Conceptualization, Z.G. and G.X.; methodology, Z.G.; validation, Z.G. and Y.Q.; formal analysis, Z.G.; writing—original draft preparation, Z.G.; writing—review and editing, Z.G.; visualization, G.X.; supervision, J.Z. and G.X.; project administration, Y.Q.; funding acquisition, G.X. All authors have read and agreed to the published version of the manuscript.

Funding

This study was supported by the China Agriculture Research Systems (CARS-40).

Institutional Review Board Statement

The hen housing conditions were approved and conducted in accordance with the Animal Ethics Committee guidelines of China Agricultural University and the National Institutes of Health Guide for the Care and Use of Laboratory Animals. The experimental protocols and animal care in this study were approved (Approval date: 11 December 2020) by the guidelines of the Animal Care and Use Committee of China Agricultural University (CAU20160916-2). The experiments were conducted according to the regulations and guidelines established by this committee.

Data Availability Statement

The data that support the findings of this study are available upon request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.

Acknowledgments

We gratefully acknowledge our colleagues at the College of Animal Science and Technology of China Agricultural University for their assistance with sample collection. All the authors acknowledge and thank their respective institutes and universities for providing library facilities.

Conflicts of Interest

The authors declare no conflicts of interest.

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Agriculture 14 00181 g001
Figure 1. Changes in the nutritional composition of the egg yolk at 7 and 21 days. S: 1.5% soybean oil added to the base diet; L: 1.5% lard added to the base diet; and M: 1.5% mixed oils added to the base diet. SFAs: saturated fatty acids; UFA: saturated fatty acids; and TFA: total fatty acids. The fatty acids measured in this project include C14:0, C14:1, C15:0, C16:0, C16:1, C17:0, C18:0, C18:1n9c, C18:2n6c, C18:3n6, C18:3n3, C20:1, C20:2, C22:0, C20:3n6, C20:4n6, and C24:1. Values are the mean ± SEM. The significance level * p < 0.05 was used as the criterion for tendency.
Figure 1. Changes in the nutritional composition of the egg yolk at 7 and 21 days. S: 1.5% soybean oil added to the base diet; L: 1.5% lard added to the base diet; and M: 1.5% mixed oils added to the base diet. SFAs: saturated fatty acids; UFA: saturated fatty acids; and TFA: total fatty acids. The fatty acids measured in this project include C14:0, C14:1, C15:0, C16:0, C16:1, C17:0, C18:0, C18:1n9c, C18:2n6c, C18:3n6, C18:3n3, C20:1, C20:2, C22:0, C20:3n6, C20:4n6, and C24:1. Values are the mean ± SEM. The significance level * p < 0.05 was used as the criterion for tendency.
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Figure 2. Changes in the nutritional composition of the albumen at 7 and 21 days. S: 1.5% soybean oil added to the base diet; L: 1.5% lard added to the base diet; and M: 1.5% mixed oils added to the base diet. EAA: essential amino acid; N-EAA: nonessential amino acid. The amino acids measured in this project include Asp, Thr, Ser, Glu, Gly, Ala, Cys, Val, Met, Ile, Leu, Tyr, Phe, Lys, His, Val, Arg, and Pro. Values are the mean ± SEM. The significance level was * p < 0.05 was used as the criterion for tendency.
Figure 2. Changes in the nutritional composition of the albumen at 7 and 21 days. S: 1.5% soybean oil added to the base diet; L: 1.5% lard added to the base diet; and M: 1.5% mixed oils added to the base diet. EAA: essential amino acid; N-EAA: nonessential amino acid. The amino acids measured in this project include Asp, Thr, Ser, Glu, Gly, Ala, Cys, Val, Met, Ile, Leu, Tyr, Phe, Lys, His, Val, Arg, and Pro. Values are the mean ± SEM. The significance level was * p < 0.05 was used as the criterion for tendency.
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Figure 3. Changes in the antioxidant capacity of egg yolk at 7 and 21 days. S: 1.5% soybean oil added to the base diet; L: 1.5% lard added to the base diet; M: 1.5% mixed oils added to the base diet. POD: peroxidase; SOD: superoxide dismutase; GSH-PX: glutathione peroxidase. Values are mean ± SEM and significance levels of * p < 0.05, ** p < 0.01 were used as the criterion for tendency.
Figure 3. Changes in the antioxidant capacity of egg yolk at 7 and 21 days. S: 1.5% soybean oil added to the base diet; L: 1.5% lard added to the base diet; M: 1.5% mixed oils added to the base diet. POD: peroxidase; SOD: superoxide dismutase; GSH-PX: glutathione peroxidase. Values are mean ± SEM and significance levels of * p < 0.05, ** p < 0.01 were used as the criterion for tendency.
Agriculture 14 00181 g003
Table 1. Ingredients and calculated analysis of the layers’ basal diet.
Table 1. Ingredients and calculated analysis of the layers’ basal diet.
Items%
Ingredient
Corn65
Soybean meal20
Wheat bran2.5
Stone powder8.5
Premix 14
Nutrient composition, %
AME (MJ/Kg)12.47
Crude protein12.78
Crude fat8.93
Nacl (g/100 g)0.3
Moisture≤10
1 The premix provided the following per kg of feed: vitamin A, 20,000 IU, vitamin D3, 10,000 IU, vitamin E ≥ 300 IU, vitamin K3, 60 mg, vitamin B1 ≥ 45 mg, vitamin B2 ≥ 154 mg, vitamin B6 ≥ 61 mg, niacin ≥ 700 mg, folic acid ≥ 21.9 mg, and pantothenic acid ≥ 241.5 mg. And the mineral premix provided the following per kg of feed: Mn 2.5 g, zinc 2 g, Fe 15.75 g, Cu 0.4 g, I 20 mg, and selenium 10 mg.
Table 2. Ingredients and composition of experimental diets (as-fed basis).
Table 2. Ingredients and composition of experimental diets (as-fed basis).
ItemsSoybean Oil (1.5%)Lard (1.5%)Mix Oils (1.5%)
Ingredient, %
Corn63.6362.4263.31
Soybean meal24.0625.2824.35
Stone powder8.68.68.6
Wheat bran2.32.32.3
Premix1.411.401.44
Nutrient composition, %---
AME (MJ/Kg)11.7111.7211.72
Crude protein13.1813.1713.16
Crude fat8.798.768.75
Nacl (g/100 g)0.30.30.3
SFAs (oils or fat)8.0015.6615.02
USFAs (oils or fat)86.9258.1280.87
Table 3. Effects of the oils and fat on the foaming, emulsifying properties, and hardness of eggs.
Table 3. Effects of the oils and fat on the foaming, emulsifying properties, and hardness of eggs.
IndexGroups 1
1.5%S1.5%L1.5%M
Albumen foaming, %139.28 ± 1.54 a82.22 ± 1.82 b72.41 ± 2.36 c
Foaming stability, %88.29 ± 2.3290.20 ± 2.2091.20 ± 2.04
Yolk emulsifying, (m2/g)3.99 ± 0.12 a2.46 ± 0.11 b2.03 ± 0.02 c
Emulsifying stability, min5.28 ± 0.035.24 ± 0.045.25 ± 0.02
Albumen gel hardness, g860.35 ± 32.42 b975.90 ± 45.28 ab1035.40 ± 30.48 a
1 S: 1.5% soybean oil to the base diet; L: 1.5% lard to the base diet; and M: 1.5% mixed oils to the base diet. Values are the mean ± SEM, and different litters (a–c) showed significant differences (p < 0.05).
Table 4. Changes in the egg yolk index at 0, 8, 16, and 24 h.
Table 4. Changes in the egg yolk index at 0, 8, 16, and 24 h.
Items 1The Proportion of the Egg Yolk Index Decreased
0–8 h (%)0–16 h (%)0–24 h (%)
Control18.73 ± 0.01 c24.17 ± 0.02 b29.91 ± 0.01 a
1.5% S29.56 ± 0.03 c34.40 ± 0.01 b38.18 ± 0.01 a
1.5% L18.53 ± 0.01 c20.71 ± 0.01 b29.77 ± 0.02 a
1.5% M20.99 ± 0.02 c26.85 ± 0.02 b32.14 ± 0.01 a
1 Control: layer basal diet (corn–soybean meal type, no oils or fat added); S: 1.5% soybean oil to the base diet; L: 1.5% lard to the base diet; and M: 1.5% mixed oils to the base diet. Values are the mean ± SEM and different litters (a–c) showed significant differences (p < 0.05).
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Gao, Z.; Qin, Y.; Zheng, J.; Xu, G. Effects of the Oil and Fat Feeding Period on the Nutritional Composition and Functional Properties of Eggs. Agriculture 2024, 14, 181. https://doi.org/10.3390/agriculture14020181

AMA Style

Gao Z, Qin Y, Zheng J, Xu G. Effects of the Oil and Fat Feeding Period on the Nutritional Composition and Functional Properties of Eggs. Agriculture. 2024; 14(2):181. https://doi.org/10.3390/agriculture14020181

Chicago/Turabian Style

Gao, Zhouyang, Yuhui Qin, Jiangxia Zheng, and Guiyun Xu. 2024. "Effects of the Oil and Fat Feeding Period on the Nutritional Composition and Functional Properties of Eggs" Agriculture 14, no. 2: 181. https://doi.org/10.3390/agriculture14020181

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