GENOTYPE X ENVIRONMENT INTERACTIONS IN ANGUS, BRAHMAN, AND RECIPROCALCROSS COWS AND THEIR CALVES GRAZING COMMON BERMUDAGRASS AND ENDOPHYTE-INFECTED TALL FESCUE PASTURES

Reproductive and preweaning data on 233 Angus (A), Brahman (B), and re ciprocal-cross cows (AB, BA) and 455 two- and three-breed cross calves managed on common bermudagrass or endophyte-infected tall fescue were used to evaluate the interaction of forage type with individual and m aternal heterosis and maternal and grandmaternal breed effects. Cows w ere born from 1988 to 1991 and calves from 15 Polled Hereford sires we re born from 1991 to 1994. Heterosis for calving rate was similar and important on both forages (P < .01), but maternal effects were small o n each forage. Maternal heterosis for birth weight differed between co mmon bermudagrass and tall fescue (P < .10) and grandmaternal effects were evident on bermudagrass (P < .05) but not tall fescue. Forage eff ects were generally substantial for 205-d weight, weaning hip height, and weaning weight:height ratio (P < .01), and maternal heterosis for these traits was larger on tall fescue than on common bermudagrass (P < .01). Grandmaternal effects were in favor of Angus for 205-d weight, hip height, and weight:height ratio on common bermudagrass (P < .05) but not on tall fescue. Heterosis for 205-d weight per cow exposed was substantial on both forages (P < .01) and was numerically larger on t all fescue than on bermudagrass, but maternal effects were not signifi cant. These results suggest more advantage for Brahman-cross cows over purebreds on endophyte-infected tall fescue than a similar comparison on common bermudagrass. They also suggest an advantage for Angus in g randmaternal effects on bermudagrass but not tall fescue.