1. Introduction
Pork meat has gained significant prominence and emerged as a highly consumed meat in Asia and Europe [
1] due to its high protein content and essential fatty acids, particularly saturated fatty acids, which are intricately linked to human health considerations [
2]. Recently, there has been increasing interest in how to produce high-quality pork. Indeed, the quality of pork can be evaluated by various characteristics such as sensory traits, intramuscular fat (IMF) content, and fatty acid composition. IMF is primarily distributed in the layers of skeletal muscle (epimysium, perimysium, and endomysium) and has a positive correlation with meat quality such as flavor, tenderness, and juiciness [
3]. Diets, genetics, environment, management practices, and production systems [
4] can influence the meat quality and thus it is highly ideal to explore effective strategies to enhance the pork quality. Dietary intervention is one of the most common methods to improve the performance of animal and to increase the meat quality.
Prebiotics (yeast cell walls and mannan polysaccharides) are defined as “a nondigestible food ingredients [
5] that beneficially affects the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon” [
6]. Probiotics, a “live microbial feed additive”, are known to improve the performance of the host by improving their gut microbial balance [
7]. Some studies indicate that probiotics could modify the muscle fatty acid (FA) profile in broilers [
8,
9]. The combination of pre-and probiotic in the form of synergism is known as “synbiotics” [
10]. Such a synergistic synbiotic contains a substrate that is selectively utilized by co-administered microorganism(s) [
11]. The primary reason for using synbiotics in food products is that probiotics do not survive well in the digestive tract without prebiotic foods. Without the necessary food source for probiotic bacteria, their tolerance to temperature, oxygen, and pH level may decrease [
12]. Previously, Hassanpour et al. [
13] demonstrated that broilers fed a diet supplemented with synbiotics had better feed efficiency. Similarly, Ghasemi et al. [
14] pointed that the inclusion of 1 g/kg synbiotics to the broiler diet significantly decreased plasma cholesterol and LDL concentrations. Glyconutrients (plant sugars) are rich in anti-inflammatory and antimicrobials properties. They can increase the energy efficiency and health of the host and promote their cellular integrity [
15]. Earlier studies have demonstrated the beneficial effects of pre and probiotics in the monogastric animal diet. For instance, De Vries et al. [
16] noted that inclusion of yeast cell wall ß-Glucans significantly increased the gut health of pigs. Similarly, Awad et al. [
17] reported that dietary inclusion of synbiotics at a concentration of 1 g/kg improved the body weight gain and feed efficacy in broilers. On the other hand, Lee et al. [
18] noted that dietary inclusion of synbiotics containing a probiotic originating from anaerobic microbiota (bacteria—10
9 CFU/mL, yeast—10
5 CFU/mL, molds—10
3 CFU/mL) and a prebiotic (MOS, sodium acetate, ammonia citrate) has improved digestion of nutrients in weaning pigs. Additionally, Aksu et al. [
19] stated that broilers fed a diet supplemented with probiotics showed increased lipid oxidation stability, water-holding capacity, tenderness, and sensory properties, while Zhang et al. [
20] found no impact on chicken meat with pre-and probiotic supplements. So far, several studies addressed the combination effect of synbiotics and glyconutrients (SB-GLN) in ruminants’ performance and meat quality. For example, Valencia et al. [
21] reported that a combination of probiotic-glyconutrient has increased live weight gain, decreased the mortality rate, and lowered the non-esterified fatty acids in Holstein calves. Similarly, Castro-Perez et al. [
22] noted that dietary SB-GLN improved the growth performance and carcass weight in lambs. The above-mentioned literature has provoked us to hypothesize and initiate this research to know whether the inclusion of the SB-GLN combination could enhance the growth performance, fatty acid profile, and meat quality of pigs or not. Therefore, the goal of this research was to examine the growth performance, fatty acid profile, and the quality of pork meat by adding an SB-GLN additive to finishing pigs’ diet.
3. Results
The effect of SB-GLN on growth performance of finishing pigs is shown in
Table 2. Pigs fed a diet supplemented with SB-GLN showed a linear increase in (
p < 0.05) BW at the end of weeks 5 and 10. Compared to the CON group, the SB-GLN-treated group pigs showed higher (
p < 0.05) ADG and ADFI at the end of weeks 5 and 10. Moreover, dietary supplement with SB-GLN showed linearly increased (
p < 0.05) ADG and ADFI, and tended to decrease (
p < 0.1) the G:F ratio during the overall experimental period.
The effect of SB-GLN on finishing pig meat quality is shown in
Table 3. Pigs that received a graded level of SB-GLN showed a tendency to increase (
p < 0.1) LTL muscle area, and linearly decreased (
p < 0.05) cooking loss compared to CON. Whereas at the end of week 10, the visual appearance of pork color (L*, a*, b*), sensory traits (color, marbling, firmness), pH value, WHC, and drip loss remained more or less similar in all groups.
Synbiotic-glyconutrient efficacy on the sensory traits and texture profile analysis (TPA) on finishing pig meat is shown in
Table 4. The pork belly meat of the SB-GLN-treated group showed a tendency to increase (
p < 0.1) tenderness and linearly increase (
p < 0.05) in juiciness compared to the CON group. Moreover, the loin meat of the SB-GLN-treated group showed a linear increase (
p < 0.05) in flavor. However, there were no differences observed on the texture and preference in pork belly and loin meat. The TPA parameter of hardness 1, cohesiveness, and gumminess and hardness 2, chewiness, and stringiness were higher (
p < 0.05) in the SB-GLN group belly and loin meat, respectively. However, there were no differences observed on adhesiveness, fracture, and springiness Index.
Table 5,
Table 6 and
Table 7 illustrate the supplemental effect of synbiotic-glyconutrient on the fatty acid profile in pork belly fat, belly-lean meat, and loin-lean meat, respectively. The values of FA like butyric acid (C4:0), caproic acid (C6:0), undecylic acid (C11:0), tridecylic acid (C13:0), myristic acid (C14:0), pentadecyclic acid (C15:1), palmitic acid (C16:0, C16:1), margaric acid (C17:0, C17:1), stearic acid (C18:1,t; C18:1,c), eicosapentaenoic acid (C20:3n3; C20:4n6; C20:5n3), and lignoceric acid (C24:0) were significantly higher in the SB-GLN-treated group pork belly fat compared to CON (
Table 5). Moreover, pigs that received SB-GLN exhibited a higher crude fat and lauric acid, myristic acid, pentacyclic acid, palmitic acid, margaric acid, Octadecanoic acid, Oleic acid, linoleic acid (C18:2n6c, LA), and Eicosapentaenoic acid (C20:5n3, EPA) profile in belly-lean meat (
Table 6). Also, the FA profile of the SB-GLN-treated group loin-lean meat showed increased lauric acid (C12:0), myristic acid, palmitic acid, margaric acid, stearic acid, Oleic acid, linoleic acid, alpha-linoleic acid, and Eicosapentaenoic acid (
Table 7). Furthermore, fatty acid content in pork belly fat, belly lean meat, and loin-lean meat of the SB-GLN-treated group showed increased docosahexaenoic acid (C22:6n3, DHA), nervonic acid (C24:1n9), omega 3, Σ saturated FA, Σ un-SFA, Σ mono-USFA, Σ poly-USFA, MUFA/SFA, and PUFA/SFA, and reduced omega 6, ω-6: ω-3 compared to CON (
Table 5,
Table 6 and
Table 7).
4. Discussion
Genetic factors and rearing conditions such as nutrition are the key factors to determine the efficiency of pig farming and the production of high-quality pork [
30]. In this regard, feed additives play a vital role, as they could improve the health of animals by utilizing nutrients and shaping their gut microbiome. The present study demonstrates that the inclusion of SB-GLN to finishing pigs’ diet linearly improved the body weight and increased the daily feed intake and daily weight gain. In line with this study, Chlebicz-Wójcik et al. [
31] reported that symbiotic additives contribute to better weight gain in weaning-finishing pigs. On the other hand, Munezero et al. [
32] stated that the inclusion of 0.5% SB-GLN to the finishing pig diet revealed better growth performance. Awad et al. [
17] reported the dietary inclusion of synbiotics at the concentration of 1 g/kg showed improved body weight gain (BWG) and feed conversion ratio (FCR) in broilers. We presume that the reason for improved growth performance is mainly due to the effects of synbiotics, which helps the pigs to maintain beneficial microbial communities in their gut and improve feed digestion by altering bacterial metabolism. However, the previous literature reported the controversial impact of synbiotics on growth performance in monogastric animals. For example, Liong et al. [
33] reported that the inclusion of a synbiotics (
Lactobacillus acidophilus ATCC 4962, mannitol, fructooligosaccharide, and inulin) supplement to a high-fat or low-fat diet reveals no significant effects on the growth performance of growing pigs. Similarly, Erdogan et al. [
34] reported that broilers fed a diet supplemented with 1 g/kg synbiotics had no effect on BWG and FCR. On the other hand, Hassanpour et al. [
13] stated that broilers that received a 1 and 2 g/kg synbiotic additive showed improved daily weight gain without affecting feed efficacy. Furthermore, Cheng et al. [
35] reported that the inclusion of a 1 g/kg symbiotic supplement (prebiotics-yeast cell wall and xylooligosaccharide; probiotics-
Clostridium butyricum, Bacillus licheniformis, and
Bacillus subtilis) to late-finishing pig’s diet had no improvement on their growth performance. These inconsistent findings could be partly explained by strain and number of microorganisms in the synbiotic components, survivability of the live organisms in the feed, prebiotic ingredients, inclusion level, or due to the dietary nutrient levels.
The quality of meat is usually determined by appearance and wholesomeness, and consequently influences the meat purchasing decision by consumers [
36]. In the present study, pigs fed a diet supplemented with SB-GLN showed no changes in meat color in either SB-GLN or CON samples, which is in accordance with the results of Cheng et al. [
35], who found similar effects in pigs fed a probiotic diet. The pH value of the meat is an important index to reflect the muscle contraction and glycolysis rate of pigs. Such pH values of the SB-GLN group meat ranged from 5.63 to 5.68% without significant differences observed between the CON groups. The current finding correlates with the results of Pieszka et al. [
37]. The WHC of the meat is defined by the ability of fresh meat to retain its water during drip and cooking loss [
38]. Additionally, drip loss and cooking loss greatly influence the juiciness of meat [
39]. In the present study, the SB-GLN meat sample exhibited lower cooking loss than the CON group, which correlates with Liu et al. [
40], who observed the reduced cooking loss of pork with dietary probiotics (yeasts, lactic acid-producing bacteria, and Bacillus subtilis). Similarly, Rybarczyk et al. [
41] reported that the addition of the EM
® Bokashi probiotic to the pig’s diet resulted in a higher drip loss. The observed inconsistence in this result is probably due to the lesser physical resistance of immobilization of the water fraction which transverses the meat structural matrix and overcomes the fiber orientation to show variation in the drip loss [
42].
Sensory evaluation is the result of scoring performed by trained panelists in order to provide the particular information on the acceptability or preference for one kind of meat [
43,
44]. Such sensory impression plays an important role in predicting the quality and purchasing decisions made by the consumers [
45]. In 2004, Hansen et al. [
46] reported that the sensory quality of pork was influenced by the manipulation of feed ingredients, including fructooligosaccharides, but in this study, finishing pigs that received a synbiotic glyconutrient supplement revealed a higher sensory profile of tenderness and juiciness (pork belly meat) and strong flavor (loin meat). On the other hand, Grela et al. [
47] found less hardness of meat by dietary pre (inulin)-and probiotics (
Lactococcus lactis,
Carnobacterium divergens,
Lactobacillus casei Lactobacillus plantarum and
Sacharomyces cerevisiae). The reason for the increased tenderness and juiciness of belly and loin meat are probably due to the presence of fat which enhances WHC by lubricating the muscle fibers during cooking and increasing the tenderness of meat to reveal the sensation of juiciness [
48]. Furthermore, the high flavor scores of the loin meat are likely due to rich flavor substances via lipid oxidative degradation. Previously, de Huidobro et al. [
27] proved TPA as a viable method for the evaluation of the texture of various food items, with one advantage to assess multiple variables such as hardness, cohesiveness, springiness, and chewiness at one time. Such TPA parameters of hardness 1, cohesiveness, and gumminess were higher (
p < 0.05) in the SB-GLN group belly, and hardness 2, chewiness, and springiness were higher (
p < 0.05) in the loin meat. The higher values of hardness, chewiness, and gumminess of pork meat are likely due to the presence of myofibril proteins in meat, which cause a tougher network formation internally by enhancing the resistance to compression [
49].
Pork lean meat is rich in PUFA due to the constant proportion of cell membrane phospholipids [
50]. Previously, Chang et al. [
51] reported that the pork meat of the probiotic-supplemented group (
Lactobacillus plantarum) showed higher PUFA contents, with significantly higher levels of linolenic and linoleic acid, which corresponds with current findings. Additionally, Narayan et al. [
52] reported that long chain
n-3 FA possess health-promoting properties including EPA (C20:5
n-3) and DHA (C22:6
n-3), which were significantly higher in the SB-GLN-treated group meat compared to CON. Moreover, palmitic acid (C16:0) and stearic acid (C18:0) are considered to be predominant SFA in commercial pork meat [
53]; such an FA profile was linearly increased in the SB-GLN-treated group pork belly fat, belly lean, and loin-lean meat. In 2012, Ross et al. [
54] reported that meat samples of pigs that were supplemented with probiotics showed higher PUFA contents with significantly higher (
p < 0.05) concentrations of linoleic acid (C18:2) and significantly lower monounsaturated FA; this partially agrees with the current findings. According to Pork Composition and Quality Assessment Procedures [
55], the concentration of the linoleic acid and linolenic acid ratio should be around 5:1 to promote health and to reduce the risk of cardiovascular disease. Although the meat of the SB-GLN group showed higher linolenic and linoleic acid compared to the CON group, the
n-3 and
n-6 in the present study were also higher than recommended levels, indicating that this pork meat is well suited for human consumption.