Probiotic treatment using Bacillus subtilis PB6 improves the growth performance, intestinal morphology, enzyme activities and barrier function in low birth weight piglets

Abstract Text: This study aimed to investigate the effects of Bacillus subtilis PB6 supplementation in milk formula on growth performance, intestinal development and immune function in low birth weight (LBW) piglets. Piglets with a birth weight near the mean litter birth weight (SD 0.5) were identified as normal birth weight (NBW), whereas those with at least 1.5 SD lower birth weight were defined as LBW. Fourteen pairs of NBW and LBW piglets (7 day old) were randomly assigned to receive the formula milk or formula milk with Bacillus subtilis PB6 for a period of 21 day. At day 28, blood samples, intestinal tissues and digesta were collected at necropsy and analyzed for morphology, digestive enzyme activities, immune cells, gene and protein expressions as well as microbial population. Data were analyzed by SPSS software using the MIXED procedure. Regardless of the diet, LBW decreased the average daily dry matter intake (-31%, P < 0.001) and the average daily growth (-28%, P < 0.001). Moreover, LBW decreased plasma concentration of immunoglobulin A (-17%, P < 0.001), interleukin-1β (-12%, P = 0.006), the count (-33%, P = 0.021) and percentage (-13%, P = 0.025) of blood lymphocytes compared to NBW piglets. LBW decreased the villous height (-8%, P = 0.039) and enzyme activity of maltase (-24%, P = 0.011), as well as the mRNA abundances of Toll-like receptor 9 (-34%, P =0.020) and Toll-interacting protein (-21%, P = 0.001) in ileum. Regardless of body weight, the supplementation of Bacillus subtilis PB6 markedly decreased the feed: gain ratio (-10%, P = 0.034), which could be related to the better intestinal morphology, increased enzyme activities of maltase (+19%, P = 0.082) and sucrase (+23%, P = 0.095) in jejunum. Moreover, the protein abundances of Zonula occludens-1 and Claudin-1 (+33～54%, P < 0.05) in ileum, as well as the copy number of Bacillus (P = 0.01) in colonic digesta were increased in piglets supplemented with Bacillus subtilis PB6 relative to piglets with control diet. Our results indicated that LBW impaired the growth and intestinal development as well as immunity of piglets, however, dietary supplementation of Bacillus subtilis PB6 improved the growth performance with better intestinal development and barrier function in both NBW and LBW piglets.

Keywords: low birth weight, probiotic, immunity