Genotype x environment interactions in Angus, Brahman, and reciprocal-cross cows and their calves grazing common bermudagrass, endophyte-infected tall fescue pastures, or both forages

Reproductive and preweaning data on 190 Angus (A x A), Brahman (B x B), and reciprocal-cross cows (A x B and B x A) and 434 two- and three-breed-cross calves managed on common bermudagrass (BG), endophyte-infected tall fescue (E+), or a combination of both forages (ROT) were used to evaluate the int eraction of forage type with individual and maternal heterosis and maternal and grandmaternal breed effects. Cows were born from 1988 to 1991, and cal ves sit-ed by 13 Polled Hereford bulls were born from 1995 to 1991. Heteros is for calving rate was larger on E+ than on BG or ROT (P < .05), whereas m aternal effects were larger on BG than on ROT (P < .10). Maternal heterosis for birth weight was negative on BG (P < .11) but positive on E+ and ROT ( P < .10). Grandmaternal effects were evident on BG (P < .10) and E+ (P < .0 1) but not on ROT. Forage effects were generally substantial for 205-d weig ht, calf weaning hip height, and calf weaning weight:height ratio; BG was h ighest, ROT was intermediate, and E+ was lowest. Maternal heterosis for the se traits was generally greater on E+ than on BG (P < .10). Grandmaternal e ffects for 205-d weight, hip height, and weight:height ratio were not impor tant on any forage. Heterosis for weaning weight per cow exposed was substa ntial on all forages (P < .01) and was significantly greater on E+ (P < .01 ) than on BG or ROT, but maternal effects were not significant. Thus, we ob served more advantage to Brahman-cross cows over purebreds on E+ than on BG . We also observed that moving cows and calves from E+ to BCT in the summer will alleviate some, but not all, of the deleterious effects of E+ on calf growth, although it may be more beneficial for reproductive traits in pure bred cows.