Comparison of Spring-Calving Cows Grazing Either Endophyte-Infected Fescue or Annual Ryegrass

In Trial 1, the effects of grazing pastures containing endophyte-infected tall fescue (Festuca arundinacea) managed in combination with bermudagrass/ bahiagrass were compared with the effects caused by grazing similar bermudagrass (Cynodon dactylon)/ bahiagrass (Paspalum notatum) pastures that were sod-seeded with annual ryegrass (Lolium multiflorum). Springcalving cows grazed two replicates of each treatment. Trial 1 was conducted over 2yr. There was no difference in cow BW prior to calving (P=0.25) or at the start of the breeding season (P=0.29), but cows that grazed pastures over-seeded with ryegrass were heavier at the end of the breeding season (P=0.05) compared with cows that grazed pastures that contained tall fescue. The BW differences between the two groups disappeared (P=0.31) by weaning. Fall conception rates of cows that grazed pastures planted in tall fescue were lower (P=0.01) than those of cows that grazed pastures over-seeded with ryegrass (64.2% vs 87.4%). Calves from cows grazing pastures over-seeded with ryegrass were heavier (P=0.07) by the end of the breeding season, and this BW advantage was maintained (P=0.05) through weaning. In the second trial, both the pastures planted with fescue and pastures over-seeded with annual ryegrass were over-seeded with white and crimson clovers. All other procedures remained the same as in Trial 1. Cows grazing pastures over-seeded with ryegrass and clover were heavier at the end of the breeding season (P=0.05) compared with cows that grazed pastures planted with fescue and over-seeded with clover. This difference in BW was maintained through weaning (P=0.05). Cows grazing pastures planted with fescue and clover had lower (P=0.03) reproduction rates than cows grazing pastures over-seeded with ryegrass/clover (70.4% vs 91.6%). Calves from cows that grazed pastures containing fescue and clover were lighter (P=0.01) at weaning. Results from this study demonstrate the negative effect that endophyte-infected fescue grown on the Southern Coastal Plains has on reproduction of spring-calving cows and on BW gain of their calves.