The effects of endophyte-infected tall fescue on production and reproductive performance parameters of beef cattle and calves

Beef cattle production records from two Virginia Department of Corrections herds from 2012- 2019 were analyzed to determine how the cultivar of tall fescue – toxic endophyte-infected or novel endophyte-infected – impacted cattle productivity metrics. Parameters compared were artificial insemination pregnancy rates, calving rates, body weights, and body condition scores of cows and birth weights and weaning weights of calves. The experimental design was a randomized completed block design with year as the replication. Samples of tall fescue were collected from the farm locations and tested for total ergot alkaloid concentrations. The samples from the farm with toxic endophyte-infected tall fescue all contained toxic levels of ergot alkaloids while the samples from the farm with novel endophyte-infected tall fescue indicated that half of the pastures at this location did not have toxic levels of total ergot alkaloids. Artificial insemination pregnancy rates were greater (P = 0.0011) for cows on novel endophyte-infected tall fescue (52 ± 1%) than for cows on toxic endophyte-infected tall fescue (43 ± 1%). Cows on novel endophyte-infected tall fescue had greater calving rates (94 ± 1%) than cows on toxic endophyte-infected tall fescue (89 ± 1%; P = 0.0243). Body condition scores and body weights at pre-breeding were greater for the cows on novel endophyte-infected tall fescue (P=0.0153 and P=0.0456, respectively). Birthweights were reduced for calves on toxic endophyte-infected tall fescue (34 ± 0.9 kg.) than for calves on novel endophyte-infected tall fescue (38 ± 1.4 kg.; P = 0.0257). Calves on novel endophyte-infected tall fescue had greater weaning weights (278 ± 5.9 kg.) than calves on the toxic endophyte-infected tall fescue (254 ± 5.9 kg.; P = 0.0217). Cattle production was improved on the farm with novel endophyte-infected tall fescue compared to cattle production on the farm with only toxic endophyte-infected tall fescue.