Metagenomic Composition and Predicted Metabolic Pathway Analyses of the Endometrial and Rectal Microbiota in Dairy Cows Following the Introduction of a Complex Feed Additive.

Background: The microbiome composition in dairy cows (Bos taurus) directly impacts on health and reproductive performance. This study aimed to determine the metagenomic composition and predicted microbial community functions in the endometrium and rectal chyme of cows fed a complex feed additive (CFA). The latter included the Bacillus mucilaginosus 159 strain, a short-chain fatty acid, plus essential oils.

Methods: Clinically healthy cows were divided into two groups (n = 15 in each): (I) a control group fed the standard diet, and (II) an experimental group. CFA was introduced into the diet of Group II during the entire transit period at a dose of 50 g per animal per day; moreover, all animals received Pen-Strep 400 antibiotics to prevent endometritis and other pathologies. The microbial community composition from the endometrium and rectal chyme biotopes was assessed using targeted next-generation sequencing.

Results: Significant changes were observed in the composition and predicted metabolic pathways due to the CFA administration, with the endometrial microbiota being more responsive to CFA than the intestinal chyme microbiome. Remarkably, the Actinobacteriota representatives disappeared in the endometrium of Group II animals compared to controls, whose content ranged from 0.34 to 3.3%. The use of CFA also resulted in a less pronounced effect in four predicted metabolic pathways for microbial degradation of catechol in the endometrium compared to controls (p < 0.05).

Conclusions: Our findings support the concept of a relationship between the gut microbiome and the reproductive system microflora of cows, as we observed changes in the composition and predicted metabolic pathways of the endometrial microbiota after orally administering CFA. This emphasizes the need for an integrated approach combining the correction of microecological disorders in the intestines and the reproductive system simultaneously.