Effects of Toxic Fescue Exposure on Vaginal Microbial Communities of Crossbred Beef Cows

The consumption of toxic fescue by beef cattle results in several adverse physiological effects such as reduced reproductive success, severe vasoconstriction resulting in hoof sloughing, low body condition scores, hyperthermia, decreased prolactin levels, and reduced hair shedding. The purpose of this study is to characterize bacterial community of the reproductive tract as a potential predictor for toxin exposure. One-hundred fall-calving crossbred cows were allocated to graze Toxic (Toxic: n=50) or Novel (Novel: n= 50) fescue pastures for five months (March-August). Treatments were blocked by sire breed (Charolais or Hereford) and by parity (first, second, third). Animals rotated pastures biweekly and pastures were monitored monthly for ergovaline concentration. Twenty-five animals allocated to Novel treatment were exposed to a toxic pasture two weeks each month in rotation with two weeks exposure to novel pasture. This group was defined as an alternating treatment condition (Alt: n=25). Rectal temperatures, hair score, body condition score, and body weight were collected each month as verification of fescue toxicosis in each animal. In August, the reproductive tract was swabbed using a Morgan swab at the vaginal-fornix junction for 16s rRNA-based microbiota analysis. The V4 region was amplified and sequenced using the Illumina Miseq platform. Data was processed using Mothur v.1.39.5. Significant difference in bovine vaginal bacterial community structure was observed between Toxic and Novel treatments based on Bray-Curtis distance (ANOSIM, R= 0.429223, P\u3c .001). Similarly, the bacterial communities of Toxic pasture also differed significantly from those of the Alt pasture (ANOSIM, R= 0.445697, P\u3c 0.001); however, Novel and Alt treatments did not differ (R = -0.0077, P =.536). Charolais exhibited greater (p= 0.0427) Shannon diversity than Herefords, and diversity increased with parity number with no difference (p=0.7312) observed between parities one and two. Smith-Wilson evenness was greater (p=0.0008) for Novel animals than Toxic animals. The suppression of Pseudomonas was the best indicator of toxin exposure. Novel animals hosted 16.5 times more (p=0.0057) Pseudomonas than toxic animals. Ureaplasma was the second most abundant OTU and 2nd most predictive of pasture type. Novel animals hosted 3.8 times more (p=0.0004) than novel animals. Burkholderia was the most abundant OTU and the third most predictive of treatment. Burkholderia represented 41.74% of the bacterial community in the Toxic treatment reproductive tracts and 14.67% in Novel animals