Effects Of Dietary Protein Source On Intestinal Microbiota And Protease Producing Strains Of Pigs

In order to investigate the effect of dietary protein source on the intestinal bacteria of pigs feeding the low protein diets, cottonseed meal, fish meal and corn germ meal were used as the main protein source in diets to investigate the intestinal microbiota and protease producing bacteria of weaned piglets and finishing pigs. This study includes three tests.Trial one was conducted to investigate the effect of dietary protein sources on the gut microbiome of weaned piglets. A total of 48 healthy weaned piglets were allocated randomly to four treatments with 12 piglets in each group. The weaned piglets were fed with diets containing soybean meal(SBM), cottonseed meal(CSM), SBM and CSM(SC) or fish meal(FM). The intestinal content samples were taken from five segments of the small intestine and tested by Illumina Miseq. The results showed the microbiota of the contents of the small intestine in different groups had great differences. Four bacterial populations(i.e. Firmicutes,Proteobacteria, Bacteroidetes and Acidobacteria) were the most abundant bacterial groups. The genera Lactobacillus and Clostridium were found in slightly higher proportions in the groups with added CSM compared to the other groups. The proportion of reads assigned to the genus Escherichia/Shigella was much higher in the FM group. In conclusion, dietary protein source had significant effects on the small microbiome of weaned piglets.Trial two was investigated the effect of low protein diets with different protein sources on the gut microbiome of finishing pigs. Thirty-six Duroc × Landrace × Large White finishing barrows(58.65± 3.71 kg) were randomly allocated to four groups, which were offered a normal protein(15% CP) SBM-based diet(SBM15) and three low protein(11% CP) diets with SBM(SBM11), 50% replacement of SBM with CSM and CGM(SCCM) and 100% replacement of SBM with CSM and CGM(CCM) as the main protein source, respectively. After 28 days feeding, the ileum content and feces were collected for microbial analysis. The results of sequencing of the V3-V4 region of the 16 SrRNA genes using Illumina Miseq showed that the SCCM diet significantly increased the bacterial diversity and the abundance of beneficial microorganisms(i.e. Lactobacillus and Bifidobacterium) in the gut of pigs. Moreover, the relative abundance of Ruminococcus, Prevotellaceae and Bacteroides in the LP groups also significantly higher than in the SBM15 group in the feces. These results suggest that mixture of SBM, CSM and CGM as the main protein source in finishing pig diet can regulate the intestinal microbiota and maintain normal growth of the pigs.In the trial three, protease producing bacterium was isolated from the small intestine of weaned piglet and identified as Bacillus cereus by 16 SrRNA gene sequencing. Protease production and substrate protein digestibility(SPD) were detected to confirm the influence of different protein source on the strain. Soybean meal(SBM), cottonseed meal(CSM), mixture of soybean meal and cottonseed meal(SCM), fish meal(FM) were used as protein source in this article. The maximum activity of protease in SCM was appeared within the shortest timeframe(21.31 U/mL) and PSD was observed as the highest compared with the other three at 36 h. The mixture of soybean meal and cottonseed meal was considered as the better protein source improved the ability of protein-utilization of the main protease-producing bacteria(Bacillus cereus strain 2L6) in the small intestine of the weaned piglets.Based on this study, it was concluded that cottonseed meal and corn germ meal as the main protein source in pig diets could improve the piglets and fattening pig gut microbial components and improve the protease activity of intestinal protease producing strains. Hence, it is suggested that CSM and CGM can be successfully fed in LP pig diets throughout the weaning and finisher periods as alternatives to SBM.