Effect Of Dietary Bacillus Subtilis Supplementation On Growth Performance And Meat Quality Of Growing-finishing Pigs

With the improvement of people’s living standard,pork with good quality and flavor is becoming more and more popular in the market.Meanwhile,high quality livestock products and antibiotic-free farming become the guidelines for future pig production along with the national ban on the abuse of antibiotics in pig production.Probiotics can improve pork quality and economic efficiency by regulating intestinal microbial composition and metabolites.The Bacillus subtilis has promising application in pig production due to its properties such as high temperature resistance,acid and alkali resistance,secretion of antibacterial substances,digestive enzymes and short-chain fatty acids.In this experiment,160 grow-finishing pigs in healthy condition and weighing 38.62±0.20 kg were used;they were randomly divided into two groups with five replicates of 16 pigs in each group.One group was randomly selected as the control group and fed the basal diet;the other group was fed the basal diet and supplemented with 1000 mg/kg of Bacillus subtilis（2×10⁹CFU/g）.At the end of the feeding period,the finishing pigs were slaughtered after collecting serum,and growth performance and meat quality related indicators were determined;the following results were obtained:1.Dietary Bacillus subtilis supplementation can improve carcass traits of growing finishing pigs.In this trial,carcass weight（P=0.016）and slaughter rate（P=0.045）of growing-finsihing pigs in the Bacillus subtilis group were significantly higher,indicating improved carcass traits and increased farm profitability.Meanwhile,dietary Bacillus subtilis supplementation significantly increased the serum levels of albumin（P=0.047）,globulin（P=0.039）and total protein（P=0.015）in growing finishing pigs,indicating the improvement of health status and immunity of pigs.2.Dietary Bacillus subtilis supplementation significantly improved pork quality.In this trial,dietary Bacillus subtilis supplementation significantly increased redness values（P=0.007）,pH₂₄（P=0.045）,and significantly decreased shear force（P=0.027）in the longest dorsal muscle;it also had a tendency to decrease brightness values（P=0.088）.In this trial,dietary Bacillus subtilis supplementation significantly increased redness values（P=0.007）,pH₂₄（P=0.045）,and significantly decreased shear force（P=0.027）in the longissimus thoracis（LT）;it also had a tendency to decrease brightness values（P=0.088）.The muscle fiber type genes and protein levels were examined by RT-qPCR and western blot,and dietary Bacillus subtilis supplementation significantly promoted the expression of MyHC-Ⅰand MyHC-Ⅱa（P<0.05）and significantly decreased the m RNA abundance of MyHC-Ⅱx（P<0.05）;at the protein level,Bacillus subtilis significantly promoted the abundance of slow muscle protein in LT（P<0.05）.In addition,dietary Bacillus subtilis supplementation was able to significantly increase the content of inosinate in LT（P=0.001）.3.Dietary Bacillus subtilis supplementation promotes the expression of subcutaneous lipolytic genes and improves the antioxidant capacity of LT.In this trial,dietary Bacillus subtilis supplementation significantly promoted the expression of lipolytic genes（ATG,HSL）and inhibited the expression of lipogenic genes SCD（P<0.05）;the average subcutaneous adipocyte cross-sectional area in the Bacillus subtilis group had a tendency to decrease（P=0.088）.It suggests that Bacillus subtilis has the potential to reduce back fat deposition.In LT,dietary Bacillus subtilis supplementation significantly increased the levels of glutathione peroxidase and catalase（P<0.05）,and significantly increased the total antioxidant capacity（P<0.05）.In conclusion,dietary Bacillus subtilis supplementation can improve carcass traits and pork quality in growing finishing pigs;it can regulate fatty acid composition and inosinic acid content to improve pork flavor and quality;it can improve the antioxidant capacity of LT,indicating an extended shelf life;this indicates that bacillus subtilis has a broad application in pig production.