|BROWN, JR., A|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/12/2002
Publication Date: 10/1/2002
Citation: BROWN, M.A., BROWN, JR., A.H. RELATIONSHIP OF MILK YIELD AND QUALITY TO PREWEANING GAIN OF CALVES FROM ANGUS, BRAHMAN, AND RECIPROCAL-CROSS COWS ON DIFFERENT FORAGE SYSEMS. JOURNAL OF ANIMAL SCIENCE. 2002. v. 80(Suppl.10): p. 2522-2527.
Interpretive Summary: The mothering ability of beef cows has been shown to be a critical component of early growth in their calves as well as profit potential in the herd. Consequently, considerable emphasis has been given to improvements in traits such as milk production in beef cows. What the cow eats is an obvious factor influencing milk yield and quality, but little work has been done to evaluate the influence of both breed group and type of forage on the relationship of milk yield and quality with early calf growth. The current research has shown that observed improvements in milk yield, yield of milk fat, and yield of milk protein in beef cows are associated with improvements in early growth in their calves. However, the amount of improvement appears to depend on the breed group and(or) type of forage. In general, breed groups of cows or forage types with higher levels of milk or component yield produced less pounds of calf weight per pound of milk or milk component, but there were some exceptions. This suggests that improvements in milk or component yield in breed groups or forage types that support higher milk production may generally be less effective in improving calf growth than in breed groups or forage types at lower levels of production. However, the exceptions suggest that improvements in calf productivity may be possible, even at higher levels of milk or component production, in certain breed groups and forages. Consequently, matching breed group to forage remains a consideration in improvement of mothering ability in beef cows.
Technical Abstract: Milk yield and quality were observed on Angus (n=109), Brahman (n=103), Angus x Brahman (n=49), and Brahman x Angus (n=49) cows and preweaning ADG was observed on their calves to evaluate interactions of regressions of preweaning ADG on dam milk yield and quality with breed group and forage environment. Data was collected over a 9 yr period from 1989 to 1997. Forage environments were common bermudagrass, endophyte-infected tall fescue, and a rotational system of both forages, in which each forage was grazed during its appropriate season, usually June through October for bermudagrass and November through May for tall fescue. Milk yield was estimated monthly 6 times during lactation from spring through fall and converted to a 24-h basis. Milk fat, milk protein, and somatic cell count were analyzed by a commercial laboratory. In the first three years of the study (Phase I), the relation of preweaning ADG to milk yield, milk fat yield, and protein yield was higher in Brahman cows on bermudagrass than Angus on bermudagrass (P < 0.05). In the last six yr of the study (Phase II), the relation of preweaning ADG to milk yield, milk fat yield, and milk protein yield was higher in purebred cows compared to reciprocal cross cows (P < 0.01, P < 0.11, P < 0.01, respectively). The regression of preweaning ADG on milk yield and milk protein yield was higher on tall fescue than bermudagrass (P < 0.05) in Phase II. The regression of preweaning ADG on milk fat yield was higher on tall fescue than on bermudagrass (P < 0.10) in Phase I in calves from Angus cows. These results suggest that the influence of milk yield and quality on calf growth may differ among breed types and production system, and the efficacy of improvements in milk traits may depend on the breed type and forage environment.