A low starch and high fiber diet intervention impacts the microbial community of raw bovine milk

Authors: Coates, Laurynne; Storms, David; Finley, John; Fukagawa, Naomi; Lemay, Danielle; Kalscheur, Kenneth; Kable, Mary

Submitted to: Current Developments in Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/2022
Publication Date: 4/21/2022
Citation: Coates, L.C., Storms, D.H., Finley, J.W., Fukagawa, N.K., Lemay, D.G., Kalscheur, K., Kable, M.E. 2022. A low starch and high fiber diet intervention impacts the microbial community of raw bovine milk. Current Developments in Nutrition. 6(6). Article nzac086. https://doi.org/10.1093/cdn/nzac086.
DOI: https://doi.org/10.1093/cdn/nzac086

Interpretive Summary: We fed dairy cows a more sustainable low starch and high fiber (LSHF) diet comprised of a high percentage of forages not consumable for humans. We measured the relative abundance of microbes and the somatic cell count (indicative of udder inflammation) in raw milk over time and found that beneficial microbes involved in fiber degradation were enriched with the LSHF diet, while mastitis-associated and spoilage-associated bacteria were depleted. The interaction of diet and time affected somatic cell count. A LSHF diet may reduce the risk of mastitis and milk spoilage, thereby saving money for the dairy industry and consumers.

Technical Abstract: A more sustainable dairy cow diet was designed that minimizes use of feed components digestible by monogastric animals by increasing the quantity of forages. We aimed to determine if feeding lactating cows this more sustainable, low starch and high fiber (LSHF) diet, was associated with changes in raw milk microbial community composition and somatic cell count (SCC). In a cross-over design, we fed lactating Holstein cows a LSHF diet or a high starch and low fiber (HSLF) diet, similar to common dairy cow diets in the U.S., for 10 weeks then placed on the opposite diet for 10 weeks. The LSHF diet differed from the HSLF diet in that it contained greater quantities of forages, beet pulp and corn distillers grain, but contained less canola meal and no high moisture corn. We collected raw milk samples from each cow 4-5 days before intervention and five weeks into each diet treatment. Within four days, we collected additional milk samples for measurement of somatic cell count using Fossmatic 7. The microbial community was determined by sequencing the 16S rRNA gene V4-V5 region and analyzing sequences with QIIME2. The raw milk microbial communities differed by diet and time. Taxa associated with fiber consumption, such as Lachnospiraceae, Lactobacillus, Bacteroides, and Methanobrevibacter, were enriched with the LSHF diet. Meanwhile, taxa associated with mastitis, such as Pseudomonas, Stenotrophomonas, and Enterobacteriaceae, were enriched with the HSLF diet. Relatedly, an interaction of diet and time was found to impact SCC. The microbiota detected in raw milk with the LSHF diet suggests that microbes involved in fiber digestion were selectively enriched and may be associated with reduced udder inflammation. Additionally, consumption of the HSLF diet was associated with higher proportions of bacterial taxa that may contribute to a greater susceptibility to mastitis and greater risk of milk spoilage.