Evaluation of Rumen Microbiota and the Associated Milk Composition Profiles of Crossbred Dairy Cattle Using Novel Molecular Genetic Markers

Abstract

Dairy cow milk is both economically and nutritionally important to humans. Diet has been termed as the main driving force toward differences in milk production and composition. The effectiveness with which ruminants convert fibrous plant material into usable energy and human utilizable derivatives like milk is dependent upon the existing consortium of rumen microbes. However, little is known about the relationship of these microbes with milk composition constituents towards producing quality milk. Therefore, this study profiled the rumen microbes after subjecting the crossbred dairy cows to diets containing different concentrate levels and later assessed the correlation between the profiled bacterial taxa and milk composition parameters. A 4X4 Latin square design was conducted within 80 experimental days. The experimental four diets were formulated to contain 10%, 20%, 30%, and 40% commercial dairy concentrate and to meet the nutritional requirements of dairy cattle yielding 12 kg of milk per day. Rumen liquor and milk samples were collected after every ten days. Microbial composition was assessed using R software V4.1.2; then Spearman correlation was used to determine the relationship between bacterial taxa communities and milk production and composition constituents. The results obtained showed that an increase in concentrate ratio across the diets led to an increase in the abundance of Bacteroidetes (P≤0.05) and Proteobacteria while Firmicutes and Fibrobacter decreased. Bacteroidetes and Firmicutes were the dominant bacteria, making up 83.7% of the total rumen bacteria. Further, indicating that dietary changes significantly affected some rumen bacterial community composition and diversity. On the other hand, a positive and significant correlation was exhibited between Prevotella (P≤0.05), Lentispaerae (P≤ 0.01), Synergistetes (P≤0.01) with milk protein. BF311 was also positively and significantly correlated with milk fat (P≤0.05). Phylum Fusobacteria showed a negative

correlation with milk lactose (P≤0.01) as well as Tenericutes with milk protein (P≤0.01). These associations between the rumen microbiota and host phenotypes revealed utilization relationships and productive associations between dietary nutrients, affected bacterial groups, and milk composition constituents.