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Title: Relationships of milk production of beef cows to postweaning gain of thier calves

Author
item WANG, XIANG - XINJIANG AGR VOC TECH UNV
item Brown, Michael
item GAO, FENG - GRASSLAND RSH INSTITUTE
item LIU, WU - GANSU AGR UNIVERISTY
item WU, JIAN - GANSU AGR UNIVERSITY

Submitted to: International Grasslands Congress
Publication Type: Proceedings
Publication Acceptance Date: 4/12/2008
Publication Date: 6/14/2008
Citation: Wang, X.Z., Brown, M.A., Gao, F.Q., Liu, W.J., Wu, J.P. 2008. Relationships of milk production of beef cows to postweaning gain of thier calves. In: Proceedings of the International Grasslands Congress, Multifunctional Grasslands in a Changing World, June 27 - July 5, 2008, Hohhot, Inner Mongolia, China. 2:139. Available on-line: Available on-line: http://www.rangelandcongress.com/ChinaCongress.htm.

Interpretive Summary: In the U. S., live beef production is segmented into cow-calf, stocker/backgrounder, and feedlot phases. Efficiency in beef production systems depends on proper relationships between each of these segments. Cow-calf producers depend on higher milk production in their cow herds to produce calves that are heavier at weaning since milk yield accounts for over 50% of the variation in calf weaning weight. However, there is some indication that higher levels of milk production preweaning is associated with lower performance in the stocker/backgrounder phase. Research at the USDA-ARS Grazinglands Research Laboratory was done to evaluate the impact of preweaning milk yield on postweaning performance of calves of six sire breeds (Bonsmara, Brangus, Charolais, Gelbvieh, Romosinuano) managed either in feedlot on mixed rations or on wheat pasture. Results of the research indicated that milk yield of the dam is associated with the postweaning performance of her calf but that association depends on both the sire breed of the calf and the postweaning management of the calf. Thus, coordination of cow-calf and stocker production systems will require proper matching milk production of the cow with sire breed of calf and postweaning management system to insure optimal efficiency.

Technical Abstract: Milk yield from 157 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 actual milk yield of cows and their calves’ postweaning average daily gain on two postweaning management systems (drylot or wheat pasture). Milk yield was measured monthly six times per year and averaged over month. Gains in each postweaning system were estimated from initiation of fall grazing (early to mid-November) on wheat pasture through late spring for an average of 166 d. Calf ADG was regressed on dam 24-h milk yield and interactions of linear and quadratic regression coefficients with sire breed of calf , sex of calf, and postweaning treatment (drylot wheat pasture) were evaluated using mixed model least squares procedures. Analyses indicated a milk yield (linear) by sire breed of calf x postweaning management interaction (P < 0.01). This suggests that the relationship of milk yield of the cow with postweaning gain of her calf depends on the sire breed of the calf and the postweaning management of the calf. It was concluded that milk yield of the dam preweaning influences postweaning growth of the calf, but the influence depends on the type of postweaning management for the calf as well as the sire breed of the calf. If cow-calf systems are using cows of higher milk yield to maximize weaning weights, calves from these systems sired by Charolais and Gelbvieh will perform well on wheat pasture while calves sired by Charolais and Brangus will do well in drylot.