Selecting for Milk Yield in the Beef Herd

The trait, maternal weaning gain, is often referred to inappropriately as milk, although milk yield is not measured directly. Evaluation of beef cattle for milk yield in commercial operations is accomplished through maternal weaning gain evaluations. Maternal weaning gain evaluations involve splitting the weaning gain of the calf into a contribution from the calf's genetic potential for growth (direct weaning gain) and a contribution from the maternal environment attributable to the cow's genetics (maternal weaning gain). A large portion of the maternal environmental contribution of the cow to calf growth is thought to be due to milk yield. University of Guelph researchers evaluated the genetic relationship between actual milk yield and maternal weaning gain of the beef cow.

Data collected from 1980 to 1993 involved primarily 8 breeds, and resulted in collection of 2207 records on weaning gain and 1826 records on milk yield. Two to four milk yield records were collected on each cow during her lactation. Milk yield records were determined using machine milking following oxytocin injection after a 6 hour calf removal. Year, age of cow, sex of calf, breed composition of cow and calf, parity, heterosis, genetic and environmental effects were included in the model.

Miller and Wilton (1996) found the genetic correlation estimated between maternal weaning gain and milk yield was high (0.76) and in agreement with past research. The high genetic correlation indicates that maternal weaning gain evaluations are good indicators of cow milk yield and can be used indirectly to select for milking ability in the beef cow herd.

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