Tributyrin administration improves intestinal development and health in pre-weaned dairy calves fed milk replacer

Butyrate and its derivatives possess various nutritional and biological benefits for mammals,whereas its effects on dairy calves have not been well characterized.This study evaluated the effects of tributyrin administration on blood immune,intestinal immune and barrier functions,and microbial composition of pre-weaned dairy calves.Twenty newborn Holstein bull calves were randomly assigned into a control group (no tributyrin supplementation,CON;n=10) or a treatment group (supplemented with tributyrin at 2 g/L of milk,TRB;n=10).The results showed that diarrhea frequency was decreased significantly by tributyrin administration from d 29 to 56 (P<0.001) and the whole period (P=0.003,d 1 to 56) though no significant effects were observed on growth performance.For blood metabolites,tributyrin administration significantly reduced the concentration of interleukin-1β (IL-1β) on d 28 (P=0.001) and tended to reduce the concentration of serum amyloid A on d 56 (P=0.079),whereas serum oxidative status parameters were not affected.For intestinal development,tributyrin administration increased the villus height (P<0.001) and the ratio of villus height to crypt depth (P=0.046) in the jejunum,and the villus height in the ileum (P=0.074).Furthermore,toll-like receptor 2 (TRL2,P=0.045) and IL-1β (P=0.088)gene expressions were downregulated,while claudin-4 (P=0.022) gene expression was upregulated in the jejunum following tributyrin administration.In the ileum,claudin-4 (P=0.029) and G-protein coupled receptor 41 (P=0.019) gene expressions were upregulated in the TRB group compared to CON.No significantly higher abundances of microbiota were found in the jejunum or ileum of calves in the CON group.In the TRB group,supplementing tributyrin significantly increased the abundance of shortchain fatty acid (SCFA)-producing bacteria,including Ruminococcaceae,Lachnospiraceae,Prevotella and Rikenellaceae (LDA>3.5,P<0.05),which was negatively associated with inflammatory gene expression(TLR2 and IL-1β) but positively associated with intestinal barrier genes (claudin-4) and morphological parameters (P<0.05).In conclusion,supplementing tributyrin in milk replacer could improve intestinal development and health of pre-weaned dairy calves by stimulating SCFA-producing bacteria colonization,enhancing intestinal barrier functions and suppressing inflammatory responses.