(P20-012-23) Increasing Fiber in Dairy Cow Feed Is Associated With Altered Milk Composition Which May Support a More Beneficial Milk Microbial Community for Cows and Humans

Objectives: Dairy cow diets with predominantly ruminant digestible forages (fibers) and low quantities of grain crops could help improve agriculture sustainability. Therefore, we examined how a high fiber feed can affect the composition of microbes detected in bovine milk and how those microbes correlate with mammary inflammation, milk glycans and milk fatty acids.

Methods: In a cross-over design, Holstein dairy cows were fed a high fiber/low starch diet and a low fiber/high starch diet in consecutive interventions of 10-weeks each. The 16S rRNA V4-V5 gene region was sequenced from raw milk samples collected at baseline and during each intervention. Milk fatty acids (MFAs) were measured by gas chromatography with flame ionization detection, lactose abundance by Fourier transform infrared spectroscopy, and milk oligosaccharides (MOs) by liquid chromatography quadrupole time-of-flight tandem mass spectrometry. Differential abundance of milk microbes with diet was determined using the Friedman test and pairwise Wilcoxon signed rank test. Associations among milk microbes and milk components were determined using generalized linear mixed effects modeling.

Results: Taxa involved in fiber digestion, such as Lachnospiraceae, Lactobacillus, Bacteroides, and Methanobrevibacter, were enriched with the high fiber diet and were positively associated with branched-chain MFAs (BCFAs) that were also enriched with the high fiber diet. Potential mastitis and/or spoilage taxa, such as Pseudomonas, Stenotrophomonas, and Enterobacteriaceae, were depleted with high fiber diet and negatively associated with several BCFAs. The seven MOs that positively associated with high fiber diet had mostly negative associations with symbiotic microbial genera and mostly positive relationships with opportunistic pathogens.

Conclusions: High fiber dairy cow feed results in milk microbial changes that might benefit udder health. These changes in milk microbiota may be partly due to increased BCFAs. Negative associations between MOs and common mammalian gut commensals, suggest that milk glycans might not serve strong prebiotic roles in mammary tissue.

Funding Sources: United States Department of Agriculture-Agricultural Research Service