The weight of a calf at 200 days is influenced by many factors. Research has shown that 70% of the variation between the weight of calves at 200 days can be attributed to nongenetic factors (eg. nutrition, disease), 20% to differences between the calf’s genetics for growth and the remaining 10% to differences in the maternal contribution made by the mother. The maternal contribution of the mother is consequently an important consideration for beef enterprises. Differences in the contribution of the dam to the 200 day weight of the calf are influenced by such things as the amount of milk the calf receives, the quality of the milk received and the mothering ability of the dam.
200 Day Milk EBVs are estimates an animal's maternal effect on the 200 day weight of its calf. In the case of sires, this estimates the maternal effect that his daughters will have on the 200 day weight of their progeny. The 200 Day Milk EBV is expressed as kilograms (kg) of calf live weight at 200 days (i.e. the expected difference in the weight of the calf at 200 days due to the maternal effect (milk) of the cow). The 200 Day Milk EBV is calculated by partitioning the difference in the 200 day weight of calves into growth and milk
The optimum level of milk production potential among beef cows is dependent upon the production system and environment in which the cows are run. Selection for increased milk production may be warranted when cows are run under good nutritional conditions and calves are sold as weaners. However, some environments may not support high milking cows.
Larger, more positive, 200 Day Milk EBVs are generally more favourable, depending on the environment. For example, a bull with a 200 Day Milk EBV of +15 kg would be expected to sire daughters with higher milk production than a bull with 200 Day Milk EBV of +5 kg. This higher milk production potential should be reflected through higher weaning weights among the daughter's calves.