Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/11/1996
Publication Date: N/A
Interpretive Summary: Endophyte-infected tall fescue (E+) produces compounds that lower reproductive and preweaning performance in beef cattle and this forage is responsible for over $600 million in annual losses to the beef cattle industry. Research to manage the toxicity or replace this forage has only been marginally successful. Research at Booneville, AR was initiated to identify a breed or breed cross that might be more tolerant of E+. Angus, Brahman, and crosses of the two breeds were bred to Polled Hereford bulls for four calf crops to produce two- and three-breed cross calves. Half of these cows and calves were managed on E+ while the other half were managed on common bermudagrass. Results from this research indicate that the advantage of the cross between the Angus and Brahman over the average of the purebreds was larger on E+ than CB for 205 d weight, weaning hip height, condition at weaning, and 205 d weight per cow exposed. E+ lowered dproductivity in these traits more in purebreds than the crosses. This suggested a tolerance to E+ in the crossbred cows and their calves independent of hybrid vigor. Thus, use of Brahman x British crossbred cows on E+ appears to be a useful tool for management of the detrimental effects of this forage.
Technical Abstract: Reproductive and preweaning data on 233 Angus, Brahman, and reciprocal cross cows and 455 two- and three-breed cross calves managed on common bermudagrass (BG) or endophyte-infected tall fescue (E+) were used to evaluate the interaction of forage type with individual and maternal heterosis and maternal and grandmaternal breed effects. Cows were born from 1988-1991 and calves from 15 Polled Herefords sires were born from 1991-1994. Heterosis for calving rate was important on both forages (P<.01). Maternal heterosis for birthweight differed between CB and E+ (P<.10) and grandmaternal effects were evident only on BG (P<.05). Forage effects were generally large for 205 d weight, weaning hip height, and weaning weight:height ratio (P<.01) and maternal heterosis for these traits was larger on E+ than BG (P<.01). Grandmaternal effects were detected for Angus for 205 d weight, hip height, and weight:height ratio on CB (P<.05) but not E+. Heterosis for 205 d weight per cow exposed was substantial on both forages (P<.01) and was numerically larger on E+ than CB while maternal effects were not significant. These data suggest a greater advantage for Brahman-cross cows over purebreds on endophyte-infected tall fescue than a similar comparison on common bermudagrass. The data also suggest an advantage for Angus in grandmaternal effects on bermudagrass but not tall fescue.