|Brown Jr, A - UNIV OF AR, FAYETTEVILLE|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 30, 1999
Publication Date: September 30, 1999
Citation: Brown, M.A., Brown Jr, A.H., Jackson, W.G., Miesner, J.R. 1999. Genotype x environment interactions in Angus, Brahman, and reciprocal crosscows and their calves grazing common bermudagrass, endophyte infected tall fescue, or both forages. Journal of Animal Science. 78:546-551. Interpretive Summary: Tall fescue is a productive grass used for cattle grazing in the Mid-south. However, much of the tall fescue in the Mid-south contains a fungus within the plant which causes it to produce compounds that adversely affect the growth, milk production, and/or reproduction of cattle that eat the grass. This endophyte-infected tall fescue is responsible for losses of more than $600 million per year in the cattle industry in the Mid-south. Recent research has identified crosses of cattle that are more tolerant of this forage but there is a need to evaluate these tolerant crosses under management schemes that might lessen effects of endophyte-infected tall fescue. One such management scheme is to move cattle from endophyte- infected tall fescue in the summer to another forage type. Research at Booneville, AR compared the performance of purebred Angus, purebred Brahman and Angus-Brahman cross cows and their calves where the cattle were managed don three forages systems: common bermudagrass all year; endophyte-infected tall fescue all year; and a rotation where cattle were grazed on endophyte-infected tall fescue in the fall and spring and were moved to common bermudagrass in the summer. This research substantiated the tolerance of the crossbred cows and their calves to endophyte-infected tall fescue. It also showed that the rotational system will alleviate some, but not all, of the adverse effects of endophyte-infected tall fescue on calf growth, and that the rotational system improved reproduction in the purebred cows compared to purebreds on endophyte-infected tall fescue.
Technical Abstract: Reproductive and preweaning data on 190 Angus (A x A), Brahman (B x B), and reciprocal cross cows (A x B, 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 interaction of forage type with individual and maternal heterosis and maternal and grandmaternal breed effects. Heterosis for calving rate was larger on E+ compared to BG or ROT (P < .05), while maternal effects were larger on BG than ROT (P < .10). Maternal heterosis for birth weight was favorable on BG (P > .10) but unfavorable on E+ and ROT (P < .10). Grandmaternal effects were evident on BG (P < .10) and E+ (P < .01) but not ROT. Forage effects were generally substantial for 205-d weight, weaning hip height, and weaning weight to height ratio with BG highest, ROT intermediate, and E+ lowest, and maternal heterosis for these traits was generally greater on tall fescue than common bermudagrass (P < .10). Heterosis for weaning weight per cow exposed was substantial on all forages (P < .01) and was significantly greater on tall fescue (P < .01) than BG or ROT while maternal effects were not significant. The data suggest more advantage to Brahman-cross cows over purebreds on E+ than a similar comparison on BG. The data also suggest that moving cows and calves from E+ to BG in the summer will alleviate some but not all of the deleterious effects of E+ on calf growth but may be more beneficial for reproductive traits in purebred cows.