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Title: Relationships of Milk Production of Beef Cows to Postweaning Gain of their Calves.

Author
item WANG, XIANG - XJ AGR. VOC.UNIV.
item Brown, Michael
item GAO, FENG - GRASSLAND RES. INST. CAAS
item WU, JIAN - GANSU AGR. UNIV.
item LALMAN, DAVID - OK STATE UNIV.
item LIU, WU - XJ AGR. UNIV.

Submitted to: Professional Animal Scientist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2008
Publication Date: 6/1/2009
Citation: Wang, X.Z., Brown, M.A., Gao, F.Q., Wu, J.P., Lalman, D.L., Liu, W.J. 2009. Relationships of milk production of beef cows to postweaning gain of their calves. Professional Animal Scientist. 25:266-272.

Interpretive Summary: The relationship between maternal performance in the cow-calf phase of beef production and the subsequent postweaning gain in the stocker/backgrounding phase is important in the design of efficient beef production systems because of a potential negative relationship between milk production of the cow and postweaning gain of her calf. Although this research found some evidence to support the hypothesis that greater levels of dam milk yield were associated with lesser postweaning calf average daily gain (ADG), the results of this research clearly demonstrated that the impact of maternal performance of the dam on calf postweaning ADG depended on both calf sire breed of the calf and the postweaning management, whether drylot on mixed grain rations, or wheat pasture grazing. Thus, calf sire breed differences in postweaning ADG may depend on milk production of the cow as well as postweaning management of the calf. Consequently, development of efficient integrated cow-calf and calf postweaning systems will need to take into consideration the milk yield of the cow herd during the preweaning phase, sire breed of calves, and postweaning management of calves to result in optimally efficient production systems.

Technical Abstract: Knowledge of the relationship of maternal performance during the preweaning period to calf postweaning growth is important in the development of integrated cow-calf and calf postweaning production systems. Milk yield from 158 Brangus cows bred to 6 breeds (Bonsmara, Brangus, Charolais, Gelbvieh, Romosinuano) was measured over a 3-yr period with a single-cow milking machine to estimate the relationship of milk yield of cows to their calves’ postweaning average daily gain in two postweaning management systems (drylot on mixed grain rations or wheat pasture). Milk yield was measured once monthly for six months, expressed as 24 h yield, and averaged over month. Calf postweaning ADG was calculated from the initiation of postweaning management treatments in fall to end of spring grazing. Calf ADG was regressed on dam 24-h milk yield and interactions of linear and quadratic regression coefficients with sire breed of calf and postweaning treatment of calf were evaluated. Generally, regression analyses indicated that calf postweaning ADG was linearly related to dam milk yield but the relationships depended on calf sire breed and the postweaning treatment (P < 0.01). On drylot management, heavier milk production in the cow was associated with lesser postweaning ADG in Gelbvieh- (P < 0.05) and Bonsmara-sired (P < 0.01) calves while heavier milk production in the cow was associated with greater postweaning ADG in Brangus- (P < 0.01) and Charolais-sired (P < 0.19) calves. On wheat pasture management, heavier milk production in the cow was associated with greater postweaning ADG in Gelbvieh-sired calves (P < 0.11) while there was a trend for heavier milk production in the cow to be associated with lesser postweaning ADG in Romosinuano-sired calves (P < 0.25). Results from these data indicate that accurate determination of the relationship of dam milk production and calf postweaning ADG will require consideration of both calf postweaning management and calf sire breed.