33 Dietary Impacts on Rumen, Vaginal, and Uterine Microbiota in Beef Heifers

Abstract

This experiment investigated the effects of diet composition on rumen, vaginal, and uterine microbiota of beef heifers. Fifteen rumen-cannulated, pubertal Angus-influenced heifers were used in a replicated 3 x 3 Latin square design (28-d periods and 21-d washout intervals). Dietary treatments included diets based on (as-fed) 100% grass hay (HF), 61% grass hay + 39% corn-based concentrate (INT), or 25% grass hay + 75% corn-based concentrate (HG). Treatments were offered individually to heifers once daily at 2% BW. Heifers also received 280 g/d of a mineral mix containing melengestrol acetate. Rumen, vaginal, and uterine samples were collected on d 0 and 28 of each period for bacterial profiling of the 16S rRNA gene and pH measurement. Data were analyzed using the MIXED procedure of SAS using results from d 0 as independent covariates, and heifer as the experimental unit. Ruminal pH on d 28 was greater (P < 0.01) in HF compared with INT and HG, and greater (P < 0.01) in INT compared with HG. Uterine and vaginal pH on d 28 did not differ among treatments (P > 0.10). In the rumen, Bacteriodetes was the most abundant phylum with the relative abundance being significantly greater (P < 0.01) in HF and INT (64.9 and 62.6%, respectively) when compared with HG (53.9%). Prevotella was the most abundant genus of bacteria within the rumen but did not differ (P > 0.10) by dietary treatment. While there were no significant differences (P > 0.10) for bacterial phyla in vaginal samples, Prevotella was the most abundant genus with the relative abundance being significantly greater (P < 0.01) for the HG (18.62%) when compared with HF and INT (7.78 and 10.35%, respectively). There were no significant differences (P > 0.10) for bacterial phyla in uterine samples, and while Prevotella was the most abundant, it was unaffected (P > 0.10) by diet. Therefore, diet impacted rumen microbiota and appears to have an influence on vaginal microbiota of beef heifers.