|BROWN, JR., A|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/2001
Publication Date: 7/1/2001
Citation: Brown, M.A., Brown, Jr., A.H., Jackson, W.G., Miesner, J.R. 2001. Genotype by environment interactions in milk yield and quality in Angus, Bbrahman, and reciprocal-cross cows on different forage systems. Journal of Animal Science. 79:1643-1649.
Interpretive Summary: Endophyte-infected tall fescue (E+) is implicated in losses exceeding $600 million dollars annually for cattle producers in the U.S. Technology to reduce these losses has been only moderately successful. Research at Booneville, AR was conducted to determine if the use of crossbred cows in combination with removal from E+ in the summer would reduce the negative effects of this forage on the milk yield of cows. Results from this research indicated that losses in milk yield could be reduced by removal of cows from E+ in the summer. However, there was no additional advantage to removal from E+ in summer in crossbred cows compared to purebreds. Somatic cell counts were lower in crossbred cows compared to purebreds and Brahman-sired cows had lower sometic cell counts compared to Angus-sired cows, indicating potential genetic mechanisms for controlling a disease, subclinical mastitis.
Technical Abstract: Milk yield and quality were observed on 93 Angus (AA), Brahman (BB), and reciprocal-cross cows for three years to evaluate interactions of direct and maternal breed effects and heterosis with forage environment. Forage environments were common bermudagrass (BG), endophyte-infected tall fescue (E+), and a rotational system of both forages where each forage (BG or E+) was grazed during periods of active growth (ROT). Milk yield (MY) was estimated each of six months (April-September) via milking machine. Milk fat (MF), milk protein (PRO), and somatic cell count (SCC) were measured by a commercial laboratory. Heterosis for 24-h MY was similar among forages, averaging 2.4 kg (P<.01). There was little evidence of maternal effects for MY. Direct effects for MY were similar among forages and averaged 2.20 kg in favor of BB (P<.10). There was little evidence of heterosis or maternal effects for MF. Direct effects for MF were similar across forages sand averaged .86% in favor of BB (P<.01). There was little evidence of effects for PRO. Crossbred cows had lower SCC than purebreds on BG (P < .05), E+ (P < .01), and ROT (P > .30). Maternal effects for SCC favored AA on ROT (P < .10) with a similar trends on BG and E+. Direct effects for SCC favored BB on ROT (P < .10) with similar trends on BG and E+. These results suggest that rotation of cows from E+ to BG in the summer can reduce negative effects of E+ on milk yield. The results suggest genetic effects for milk yield and quality were relatively stable across the forage systems evaluated. Conclusions from the research also suggest an advantage to crossbred cows in SCC and provide evidence of both direct and maternal breed effects for this trait.