Consumption of supplementary inulin modulates milk microbiota and metabolites in dairy cows with subclinical mastitis

Milk microbiota and mediated metabolites directly affect the health of the udder in dairy cows. Inulin, a dietary prebiotic, can modulate the profile of gastrointestinal microbiota. However, whether the inulin intake affects the milk microbial population and metabolites remains unknown. In this study, forty subclinical mastitis (SCM) cows were randomly divided into 5 groups. Five inulin addition doses, 0, 100, 200, 300 and 400 g/d per cow, based on the same basal diet were supplemented, respectively. The experiments lasted for 8 weeks. The results showed lower relative abundance of mastitic-causing and pro-inflammation microbes in milk (i.e., Escherichia -Shigella , Pseudomonas , Rhodococcus and Burkholderia-Caballeronia-Paraburkholderia , etc.), and higher probiotics and commensal bacteria, such as, Lactobacillus , Bifidobacterium , etc. in the cows fed 300 g/d inulin, compared with the control group. Meanwhile, the levels of arachidonic acid pro-inflammatory mediators (leukotriene E3, 20-carboxy-leukotriene B4 and 12-Oxo-c-LTB3) and phospholipid metabolites were reduced, and the levels of compounds with antibacterial and anti-inflammatory potential (prostaglandin A1 and 8-iso-15-Keto-PGE 2 , etc.), and participating energy metabolism (citric acid and L-Carnitine, etc.) were elevated. These data suggested that inulin intake might modulate the microflora and metabolites level in extra-intestinal tissue, such as mammary gland, which provided an alternative for the regulation and mitigation for SCM. IMPORTANCE The profile of microbial community and metabolic activity in milk are main determinant of udder health status and milk quality. Recent studies have demonstrated that diet could directly modulate mammary gland microbiome. Inulin is a probiotic dietary fiber, which can improve the microbiota population in gastrointestinal tract. However, whether inulin intake can further regulate the profile of microbiota and metabolic activities in milk remains unclear. In subclinical mastitic cows, we found that inulin supplementation could reduce the abundance of Escherichia -Shigella , Pseudomonas , Rhodococcus , Burkholderia-Caballeronia-Paraburkholderia and the levels of (±)12, 13 - DiHOME, leukotriene E3 and 20-Carboxy-Leukotriene B4 etc., while, elevated the abundance of Lactobacillus , Bifidobacterium , and Muribaculaceae as well as the levels of prostaglandin A1 (PGA1), 8-iso-15-keto-PGE2 and benzoic acid etc., in milk. These data suggest that inulin intake affects the profile of microorganisms and metabolites in milk, which provides an alternative for the regulation of mastitis.