Reproductive Performance of Angus and Brahman Cows Grazing Common Bermudagrass or Endophyte-lnfected Tall Fescue

Reproductive performance of approximately 80 purebred Angus and 80 purebred Brahman managed on either endophyte-infected tall fescue or common bermudagrass was evaluated over 4 yr. Calving percentage averaged 7.6% higher on common bermudagrass compared to tail fescue 05) and this difference was similar in both breeds. Breed differences in calving percentage were similar in each year and forage with the exception of tall fescue in 1991 where Brahman exceeded Angus by 20.9% (P < .05). Averaged over years, calving interval (days from first bull exposure to calving) was significantly affected (P < .05) by forage in the Brahman breed. Brahman on bermudagrass had an average 7-d longer calving interval than Brahman in tall fescue. Calving interval for Angus cows was not affected by forage type. There was little evidence of forage effects on calving difficulty but Angus cows bred to Brahman bulls and producing a bull calf had higher levels of calving difficulty than other breed of sire × breed of dam × sex classes (P < .01). Dystocia requiring major intervention lowered calving percentages by an average 39.8% the following year (P < .01), and open cows were similar in calving percentage the following year to cows experiencing no or minor calving difficulty with the possible exception of Brahman on tall fescue. Based on observed forage availabilities for the different years, there was some evidence in the study that lower nutritional levels increased effects of calving difficulty on subsequent reproduction. These data suggest that tall fescue reduces calving rates equally in both breeds and may be of some advantage in Brahman cows in date of conception, although this advantage may be partially offset by effects of lactation on subsequent reproduction in the Brahman on tall fescue.