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Title: GENOTYPE X ENVIRONMENTAL INTERACTION FOR MATURE SIZE AND RATE OF MATURING FOR ANGUS, BRAHMAN, AND RECIPROCAL-CROSS COWS ON ENDOPHYTE-INFECTED FESCUE OR BERMUDAGRASS

Author
item SANDELIN, B - UNIV. OF ARKANSAS
item BROWN, A - UNIV. OF ARKANSAS
item Brown, Michael
item JOHNSON, Z - UNIV. OF ARKANSAS
item KELLOG, D - UNIV. OF ARKANSAS
item STELZLENI, A - UNIV. OF ARKANSAS

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/8/2002
Publication Date: 12/1/2002
Citation: SANDELIN, B.A., BROWN, A.H., BROWN, M.A., JOHNSON, Z.B., KELLOG, D.W., STELZLENI, A.M. GENOTYPE X ENVIRONMENTAL INTERACTION FOR MATURE SIZE AND RATE OF MATURING FOR ANGUS, BRAHMAN, AND RECIPROCAL-CROSS COWS ON ENDOPHYTE-INFECTED FESCUE OR BERMUDAGRASS. JOURNAL OF ANIMAL SCIENCE. 2002. 80:3073-3076.

Interpretive Summary: Mature weight and rate of maturing are two traits that greatly affect efficiency of production in beef cattle by influencing nutrient requirements and efficiency of nutrient utilization. It is important to determine if differences among breeds in these traits vary across forages so that the most efficient combinations of breed and forages can be developed. Cooperative research between the Agricultural Research Service and the University of Arkansas concluded that expression of genetic differences in mature weight and rate of maturing did, in fact, depend whether cows grazed tall fesue or bermuda grass. While this research involved a limited number of breed groups and forages, it provided evidence of the necessity of properly matching livestock genetics with production environment in development of efficient beef production systems.

Technical Abstract: Mature weight (A) and rate of maturing (k) were estimated in 177 Angus, Brahman, and reciprocal cross cows grazing bermudagrass (BG) or endophyte-infected tall fescue (E+) over a 4-yr period to evaluate genotype x environment interactions. Data were collected every 28 d until cows were approximately 18 mo of age and then at prebreeding, postcalving, and weaning of calf. All cows with weight data to 42 mo were included in the analysis. Mature weight and k were estimated using the three-parameter growth curve model as described by Brody. Data were pooled over year and analyzed by the general linear model (GLM) procedure of SAS. Included in the models for A and k were the independent variables of genotype, environment and genotype x environment interaction. There was a significant (P < 0.01) genotype x environment interaction for A but not for k. Angus cows had greater (P < 0.01) mean A on E+ than did Angus x Brahman cows on BG (611 vs 546 kg). Angus x Brahman cows grazing BG had lower (P < 0.05) mean A than did Brahman x Angus cows grazing BG or E+ and Brahman cows grazing BG (546 vs 624, 614, and 598 kg). Brahman cows grazing E+ had smaller (P < 0.05) mean A than all genotype x forage combinations except for Angus x Brahman cows on BG. Angus cows had a slower (P < 0.05) mean k than Angus x Brahman and Brahman x Angus cows (0.039 vs 0.054 and 0.049), respectively, and Angus x Brahman cows had a faster (P < 0.05) mean k than Brahman x Angus and Brahman cows (0.054 vs 0.049 and 0.041), respectively. These data suggest that consideration of both breed type and forage is important in developing crossbreeding programs, in that mature size and rate of maturing are critical to the match of animal requirements to available production resources.