INTRODUCTION
The pig industry faces the challenge of meeting global demand for pork, which is expected to grow by 19% from 2019 to 2029 [1]. This must be achieved while also ensuring the production of affordable and high-quality pork that meets consumer preferences and expectations. Pig meat quality and nutritional value are significantly influenced by fatty acid composition in both adipose tissue and muscle [2]. There are numerous ways that fatty acids affect pig’s meat quality and nutritional value, including melting point, firmness, flavor, oxidative stability, and shelf life. A high level of saturated fatty acids (SFA) increases fat melting point and firmness, and a high level of polyunsaturated fatty acids (PUFAs) decreases them [3]. PUFAs also contribute to meat flavor, but they are more prone to oxidation, which can cause rancidity and off-flavors [2]. Dietary composition significantly influences pork quality and nutritional value, particularly through its impact on intramuscular fat content and lipid profile, despite the influence of genetics [4]. Moreover, since the feed cost represents 65%–75% of the overall production cost in swine production [5,6], efforts to lower feed costs are a primary concern for boosting the pig industry’s competitiveness. Therefore, improving feed efficiency is essential for the profitability of pig production [7,8]. By improving feed conversion into body weight gain, less feed is required per unit of meat produced, which lowers production costs and increases profits for pig farmers. There are many factors contributing to optimal feed efficiency, including genetics, diet, feed, management, housing, and environment [9]. One of the key factors in improving feed efficiency is maintaining a healthy gastrointestinal tract for optimal metabolic utilization of dietary nutrients. Thus, a healthy gut facilitates or enhances feed digestion and nutrient absorption [7,10]. Gut health affects nutrient absorption and digestion by influencing the metabolic activity and stability of the gut microbiome, the production and secretion of digestive enzymes, and the function and integrity of the gut immune system [7,11].
The use of synbiotic-glyconutrient (SGN) combinations as a feed additive has gained popularity in recent years due to their positive effects on gut health and growth performance in other livestock species [12-15]. Glyconutrients and synbiotics are substances that can improve the meat quality of pigs by influencing their gut microbiota and fatty acid composition. According to a study by Núñez-Benítez et al. [12], a standardized mixture of SGN as a feed additive in steers fed a finishing diet improved ruminal fermentation, microbial protein synthesis, and carcass traits. Additionally, a study by Chang et al. [16] found that probiotic-friendly pig production improved meat quality and physicochemical characteristics of pigs by reducing drip loss, cooking loss, shear force, and pH value of pork. Moreover, in lambs, the addition of synbiotics and glyconutrients combination enhanced growth, energy, and carcass weight [13].
In our study, we used a SGN mixture composed of probiotics (Lactiplantibacillus plantanum, Bacillus subtilis, and Saccharomyces cerevisiae), prebiotics (yeast cell wall β-glucans), and glyconutrients (simple sugars) [12,17]. L. plantarum is a probiotic bacteria known for its beneficial effects on gut health and immunity [18]. B. subtilis is another probiotic that has been shown to improve digestive function and reduce pathogenic bacteria in the gut [19]. While S. cerevisiae is a yeast commonly used as a probiotic in animal feeds due to its ability to improve nutrient utilization and gut health [20]. Yeast cell wall β-Glucans, a type of prebiotic, act as a source of soluble fiber that feeds the beneficial bacteria in the gut [21]. The glyconutrients in this combination include simple sugars with anti-inflammatory and antimicrobial properties, and are believed to improve cell function and overall health [14]. However, there is inadequate investigation on the effects of this combination on finishing pigs.
We expect that the pigs fed the SGN combination will have improved feed efficiency, with higher average daily gain (ADG), lower feed conversion ratio (FCR), and higher nutrient digestibility compared to the control group. We also anticipate that the treatment will result in a reduction in gas emissions and improvement in meat quality, with a more favorable fatty acid composition. Therefore, the aim of the study was to examine the effects of a standardized SGN combination on growth performance, nutrient digestibility, gas emission, meat quality, and fatty acid profile of finishing pigs.
MATERIALS AND METHODS
The experimental procedure was reviewed and accepted by the Dankook University’s Institutional Animal Care and Use Committee (IACUC) with IACUC #DK-2-2128. The study was carried out at the Dankook Unversity’s pig research farm (Gongju, Korea).
During 10 weeks of the trial, 150 finishing pigs in total (Landrace × Yorkshire × Duroc) initially weighing 58.85 ± 3.30 kg of live body weight (BW) were selected based on BW and sex. Then they were assigned into 30 experimental pens in a completely randomized block design (ten pens for each treatment; with five pigs for each pen; three females and two males per pen). Slatted floors and environmentally controlled rooms were used to house the pigs. Diets based on the corn-soybean meal (Table 1), were created in order to meet or exceed NRC [22] guidelines. The combination of synbiotic and glyconutrient was sourced from Maxcell Global (Seoul, Korea), containing L. plantarum, B. subtilis, and S. cerevisiae of 1 × 107 CFU/g, with yeast cell wall β-glucans of 5% from S. cerevisiae, and 7% of glyconutrients composed of N-acetylglucosamine, D-xylose, and Fucose. A synbiotic is a combination of probiotics and prebiotics [17]. Probiotics are beneficial bacteria that contribute to a host’s health and it’s well-being when given sufficient amounts [23]. Prebiotics are non-digestible feed supplements that help promote the multiplication of beneficial microbiota in the gut [24]. Glyconutrients are simple sugars which act as cell integrity promoters, improving health and energy efficiency [14]. Pigs were fed to three different diets (CON, basal diets; TRT1, CON + SGN 0.15%; and TRT2, CON + SGN 0.30%) in phase I and phase II (weeks 1 to 5 and weeks 5 to 10, respectively). During the trial, feed and water were freely available to the pigs.
Provided per kg diet: Fe, 100 mg as ferrous sulfate; Cu, 17 mg as copper sulfate; Mn, 17 mg as manganese oxide; Zn, 100 mg as zinc oxide; I, 0.5 mg as potassium iodide; and Se, 0.3 mg as sodium selenite. Provided per kilograms of diet: vitamin A, 10,800 IU; vitamin D3, 4,000 IU; vitamin E, 40 IU; vitamin K3, 4 mg; vitamin B1, 6 mg; vitamin B2, 12 mg; vitamin B6, 6 mg; vitamin B12, 0.05 mg; biotin, 0.2 mg; folic acid, 2 mg; niacin, 50 mg; D-calcium pantothenate, 25 mg.
In order to calculate the ADG, BW of every individual pig was recorded on days 1, 35, and 70. In addition, the consumed and remained feeds (per pen) were noted for the calculation of average daily feed intake (ADFI), and ultimately the amount of ADG and ADFI were taken to calculate the FCR.
The 2 g/kg of chromium oxide (Cr2O3) as indigestible marker were mixed with diets seven days before fecal sample collection in order to determine the ATTD of nitrogen (N), dry matter (DM), and gross energy (GE) of pigs. At the completion of the trial, we have selected one gilt and one barrow per each pen for fresh fecal sample collection. The samples were obtained by massaging a pig’s rectum. The samples were directly put into a chilled box. Later on, we transported the samples to the lab, and kept at a temperature of −20°C until they were examined by trained personnel. Following 72 hours of drying at 70°C, samples were finely powdered and sieved through a 1-mm screen. The AOAC [25] methods were applied to assess the digestibility of DM, N, and GE. The analysis of ATTD was conducted using the method utilized in the previous research of Munezero and Kim [26]. A UV absorption spectrophotometric measurement was performed to measure chromium levels (UV-1201, Shimadzu, Kyoto, Japan). A sample of 2 grams of faecal and feed was analyzed using an oxygen bomb calorimeter (Parr, 6400 Instrument Company, Moline, IL, USA). Moreover, in order to calculate the protein, the N was assessed by using Kjeltec 8600 (Foss Tecator AB, Hoeganaes, Sweden).
At the end of weeks 5 and 10 of the study, fecal samples were collected from one gilt and one barrow per pen to measure the concentration of methyl mercaptans, acetic acid, H2S, NH3, and CO2. A plastic box (2.6 liters) was filled with 300g of collected faeces and covered with adhesive plaster to allow fermentation for 24 hours at 25 degree Celsius. Before measurement, each box with a sample was agitated around 30 seconds to homogenize the sample. The level of gas emission was determined by using a GV100 (Gastec, Seoul, Korea).
When pigs attained 110 kg of an average weight, they were sacrificed at a nearby abattoir. In order to ensure that the samples were chilled, the carcasses were kept at 2°C for 24 hours. The sample was taken around the ribs positioned at 10th to 11th. Before testing, meat samples were put at the temperature of 26°C. The color, marbling, and firmness scores were performed at room temperature in accordance with NPPC [27] Standards. The panel had 10 trained personnel who had all been briefed to estimate the sensory features of color, marbling, and firmness. Using a Model CR410 Chromameter, the values of lightness (L*), redness (a*), and yellowness (b*) of each sample were examined immediately after it was cut (Konica Minolta Sensing, Osaka, Japan). Simultaneously, using the pH meter, the pH of each sample were recorded (Model77p, Istek, Seoul, Korea). The water-holding capacity (WHC) was determined using the method described by Sureshkumar et al. [28]. A meat sample was compressed and the region with moisture was drawn and assessed by the use of digitizing area line sensor (MT10S; M.T. Precision, Sinyoung Choukki, Bucheon, Korea). Then we calculated the WHC values, a ratio with lower value indicates a higher WHC). The area of longissimus muscle (LM) was measured by tracing the LM surface at the 10th rib with the previously mentioned digitizing area line sensor. 3g of meat was sampled to determine the drip loss utilizing the plastic bag technique described by Sureshkumar et al. [29], and cook loss was determined as outlined by Sullivan [30].
Samples were collected to examine the fatty acid composition at the end of the experiment (week 10). In brief, a crude fat extractor was used to collect the sample, which was then placed in a cellulose cup. The sample was then mixed to a 5 mL of n-hexane. After that, BF-3 Methanol (3 mL) and 1 ml of extraction sample were added, homogenized, and reacted at 100°C for 1 hour. Following the reaction, 2 ml of saturated saline and 2 mL of Hexane were added, homogenized, and then purified. A Gas Chromatography-FID (Agilent, Santa Clara, USA) was used to analyze the hexane layer (upper layer) in the distribution solution after 30 minutes.
Statistical analysis was performed with General Linear Model procedure of the SAS software (SAS Institute, Cary, NC, USA) using the Tukey’s honest significance test. The pen was taken as the experimental unit. The outcomes from the analysis were illustrated as mean and the standard error of the mean (SEM) values. A p-value < 0.05 was considered significant.
RESULTS
Data and results recorded from week 1 to week 10 are shown in Table 2. In weeks 5 to 10, ADG increased (p = 0.036) as SGN supplementation increased in finishing diets. Finishing pigs supplemented with 0.3% SGN demonstrated higher ADG than other groups. However, the inclusion of SGN in the pigs’ diet did not affect BW gain, ADFI, and FCR (p > 0.05) throughout the experiment.
Table 3 summarizes effects of SGN on ATTD of finishing pigs. SGN supplementation had no effects on ATTD parameters (DM, N, or GE; p > 0.05).
| Items (%) | CON1) | TRT1 | TRT2 | SEM | p-value |
|---|---|---|---|---|---|
| Week 10 | |||||
| Dry matter | 68.69 | 69.17 | 69.54 | 1.58 | 0.929 |
| Nitrogen | 64.11 | 65.41 | 65.88 | 1.58 | 0.722 |
| Gross energy | 70.41 | 71.57 | 71.64 | 1.51 | 0.813 |
Table 4 presents the gas emission results from finishing pigs. The inclusion of SGN to the finishing pig’s diets had no significant change on NH3, H2S, methyl mercaptans, acetic acids, and CO2 emission throughout the trial (p > 0.05).
Table 5 presents the results of the meat color (lightness, redness, and yellowness), WHC, LM area, cooking loss, drip loss, and sensory features. Pigs fed a diet containing 0.3% SGN has indicated a significant lower drip loss than that of other diet-fed pigs on d 7 (p = 0.053). Moreover, due a diet containing 0.3% SGN, the cooking loss tended to improve (p = 0.070). Nevertheless, the significant effects of WHC, longissimus muscle area, meat color, and sensory features were not found (p > 0.05).
The effects of SGN supplementation on fatty acid profiles in the fat of finishing pigs are listed in Table 6. The increased levels of palmitoleic acid (C16:1), margaric acid (C17:0), omega-3 fatty acid (ω-3 FA), omega-6 fatty acid (ω-6 FA), and ω-6: ω-3 ratio (p = 0.034, 0.020, 0.025, 0.007, and 0.003, respectively) were observed in the fat of finishing pigs fed on 0.3% of SGN compared with pigs fed the control diets. Moreover, the SGN tended to increase the concentration of heneicosylic acid (C21:0) and PUFA / SFA in the fat of finishing pigs (p = 0.0813 and 0.0877, respectively).
ΣSFA, sum of saturated fatty acids; ΣUSFA, sum of unsaturated fatty acids; ΣMUFA, sum of monounsaturated fatty acids; ΣPUFA, sum of polyunsaturated fatty acids; MUFA/SFA, ratio of monounsaturated fatty acids and saturated fatty acids; PUFA/SFA, ratio of polyunsaturated fatty acid and saturated fatty acids.
The impact of SGN addition on the fatty acid profiles in finishing pig lean is illustrated in Table 7. SGN tended to increase the concentration of lauric acid (C12:0), palmitic acid (C16:0), and omega 3 fatty acid in the lean of finishing pig (p = 0.094, 0.091, and 0.094 respectively). Furthermore, increased levels of margaric acid (C17:0), linoleic acid (C18:2n6c, LA), arachidic acid (C20:0), omega 6 fatty acid, omega-6 to omega-3 ratio, unsaturated fatty acid, and monounsaturated fatty acid (p = 0.037, 0.052, 0.014, 0.036, 0.033, 0.020, and 0.045, respectively) were observed in the lean of finishing pigs fed diets containing 0.3% of SGN.
FA, fatty acid; LA, linoleic acid; ALA, alpha-linolenic acid; ΣSFA, sum of saturated fatty acids; ΣUSFA, sum of unsaturated fatty acids; ΣMUFA, sum of monounsaturated fatty acids; ΣPUFA, sum of polyunsaturated fatty acids; MUFA/SFA, ratio of monounsaturated fatty acids and saturated fatty acids; PUFA/SFA, ratio of polyunsaturated fatty acid and saturated fatty acids.
DISCUSSION
The actions of this combination are recognized to improve cell communication, which enhances immune responses, mediates inflammation, and reduces cellular stress in general [14]. Our findings indicated that finishing pigs fed SGN-supplemented diets improved ADG in the period of 5–10 weeks. Similarly, an increased growth performance has been observed in SGN supplemented group in poultry and nursery pigs [31,32]. Possibly, synbiotics and glyconutrients may have improved finishing pig growth by modulating the gut microbiota, enhancing intestinal barrier function, and regulating immune responses. Moreover, glyconutrients can increase energy efficiency and health by aiding in the reduction of inflammation and microbial growth [14,33]. In addition, Lee et al. [34] and Chu et al. [35] have demonstrated that pigs fed synbiotic-supplemented diets achieved comparable growth rates as pigs fed antibiotic-supplemented diets. In a disease challenge model, Guerra-Ordaz et al. [36] discovered that synbiotics can improve ADG, but not ADFI and Gain: Feed. There is a possibility that the higher ADG observed in a SGN group is due to a numerically higher ADFI in comparison to the control group.
A lot of attention has been paid to how probiotics and prebiotics help digest nutrients [37,38]. This study did not find any significant effect on nutrient digestibility of DM, N, and GE. It could be possible that SGN have a differential effect on the digestibility of different nutrients, such as protein, fat, and fiber, which was not detected by the overall digestibility measurement used in this study. Currently, there is no research on the impact of glyconutrients on nutrient digestibility in pigs. Similarly, a diet supplemented with Enterococcus faecium and inulin for growing pigs did not impact the digestibility of DM, GE, and N [39]. Moreover, Weiss et al. [40] concluded that Pediococcus acidilactici and oligofructose together had no effect on the ileal DM and crude protein digestibility in piglets. In contrast, combining probiotics from bacteria with prebiotics showed higher digestibility of DM and N in weaning pigs [34]. Increased organic matter digestion with probiotic and prebiotic supplementation is largely due to increases in neutral detergent fiber digestion [41]. The differences in our results compared to other research findings could be due to the different breeds and stages of pigs used in these studies.
It is thought that changes in gut microbiota affect the composition of feces as well as the amount of gases released from manure. Emissions of harmful gases like NH3, H2S, and other gaseous compounds originating from the livestock industry contribute to environmental pollution and have detrimental impacts on the health of both humans and animals [42]. NH3, H2S, methyl mercaptans, and acetic acid have not been affected with probiotic and prebiotic inclusion between treatments in the study conducted by Yun et al. [43]. Although Higgins et al. [44] reported that probiotic supplementation could reduce the NH3 content of broiler excreta, the combination of synbiotic and glyconutrient had no effect on NH3, H2S, methyl mercarptans, acetic acids, or CO2. Perhaps, the microbiome of pigs in the SGN group has not been able to be positively manipulated in a way that can affect noxious gas emissions. Moreover, this could be due to the low sensitivity of the gas measurement method or the high variability of gas production among individual pigs. Furthermore, more accurate and reliable methods of gas emission measurement should be employed to evaluate the environmental impact of SGN in pig diets.
The quality of meat and carcass traits determines taste, tenderness, juiciness, and overall consumer acceptance. Our study showed positive outcomes for cooking and drip loss parameters. SGN may have improved finishing pig pork quality by altering their fatty acid profile and increasing the content of beneficial omega-3 fatty acids, which have positive effects on human health. Consistent with our findings, Zhu et al. [45] found that adding maternal probiotics increased cooking yield and reduced drip loss. Following slaughter, the production of lactic acid through the glycolysis process reduces pH, which is related to drip loss and shear force [46]. According to earlier research, adding L. plantarum ZJ316 to piglets’ diets increased meat quality by raising the pH45min value [47], and adding B. coagulans had a positive impact on meat quality by reducing drip loss [48]. In the study conducted by Zhu et al. [45], maternal synbiotics increased redness while decreasing lightness in the longissimus thoracis muscle. Dietary probiotic consumption has been observed to increase redness but not whiteness [49]. These variations may be related to the feeding stage, the type, and the dose of probiotics or synbiotics and components of glyconutrients applied. Therefore, it would be beneficial to conduct further studies to determine the optimum dosage and absorption mechanism of this combination to gain a deeper understanding of its effects on pig meat quality.
The focus on meat fatty acid composition arises primarily from the desire to produce healthier meat with a higher ratio of polyunsaturated to saturated fatty acids and a more favorable balance between n-6 and n-3 polyunsaturated fatty acids [50]. The fatty acid profile of pork influences its nutritional value, organoleptic properties, and eating quality [2,45,51]. There are several essential fatty acids in pork, including myristic acid, palmitic acid, palmitoleic acid, stearic acid, oleic acid, and linoleic acid [52]. However, fatty acid imbalances can even be harmful to consumers [53]. Pigs store dietary fatty acids in tissues without further modification [54]. Pork, being the most consumed meat globally, often has a high omega-6 (n-6) to omega-3 (n-3) fatty acid ratio due to conventional feeding methods, resulting in its limited availability as a source of n-3 fatty acids [55]. Currently, animal husbandry relies on grain-fed systems, leading to a high intake of omega-6 fatty acids which causes an imbalance between omega-6 and omega-3 [56]. People with this imbalance are more likely to develop cardiovascular disease, inflammation, diabetes, and autoimmune diseases [57]. Furthermore, the increase in linoleic acid could stimulate lipid oxidation in pork, and have a hypocholesterolemic effect and thus slowing the development of atherosclerosis for the consumer [58]. Also, in the body, linoleic acid elongates and desaturates to form C20:4n6, a precursor to pro-inflammatory compounds that can be harmful to health [59]. This prompted a call to rebalance their ratio in the feeds supplied to the animals. Employing nutritional strategies to improve meat fatty acid composition is a beneficial approach. Our study showed that supplementing finishing pigs’ diets with the combination of probiotics, prebiotics, and glyconutrients increased the amount of palmitoleic acid (C16:1), margaric acid (C17:0), omega-3 fatty acid, omega-6 fatty acid, and ω-6: ω-3 ratio in fat of the pig meat. In addition, the higher levels of margaric acid (C17:0), linoleic acid (C18:2n6c), arachidic acid (C20:0), omega 6 fatty acid, omega-6 to omega-3 ratio, unsaturated fatty acid, and monounsaturated fatty acid were observed in the lean of finishing pigs. SGN may have improved fatty acid profiles in pigs due to their prebiotic and probiotic effects, which induce the production of short-chain fatty acids and other metabolites that regulate lipid metabolism. Similarly, probiotics such as Lactobacillus amylovorus and Enterococcus faecium have also been found to boost the C18:2n6c, monounsaturated fatty acids, and PUFA content in pork [54]. Furthermore, our results are constant with a study conducted by Chang et al. [16] who found that omega 3 and 6 fatty acids were significantly higher in the supplemented probiotic group. The addition of probiotics may improve the primary fatty acids content in offspring muscle, resulting in favorable changes in the gut microbiome [60]. Variations in flavor were related to the variability in fatty acid composition [61]. The addition of SGN increased the C16:1 level, which suggests that these additives might improve pork flavor. There is insufficient evidence to confirm that dietary prebiotics and probiotic supplementation effectively alter tissue fatty acid profiles. For example, longissimus dorsi muscle fatty acid profile did not change following the addition of inulin and horse chestnuts [62]. However, the inclusion of inulin into rabbit diets has resulted in an increase in linoleic acid and omega-3-PUFA levels, as well as a decrease in the indices of atherogenicity and thrombogenicity [63]. The probiotics, prebiotics, and simple sugars used in this study likely altered the gut microbiota, which could explain the positive results found. Consequently, this led to an increase in the content of beneficial fatty acids in pork.
CONCLUSION
Results of this experiment indicated that supplementing a diet containing 0.3% SGN improved growth performance, meat quality, and fatty acid profile in both lean and fat tissues. However, the SGN addition had no effect on ATTD and gas emissions of finishing pigs as we expected. The use of SGN combinations as feed additives could lead to improved feed efficiency, higher ADG, and improved meat quality. Nevertheless, this study failed to demonstrate an interaction between synbiotics and glyconutrients when this combination was mixed in the pigs’ diet. Therefore, our team is developing a robust approach to elucidate more deeply the interaction between synbiotics and glyconutrients and their roles in the health and productivity of livestock.
