Test herds in dairy cattle breeding programmes 2nd communication: Strategies for finding test herds

As outlined in the first communication, the implementation of test herds in dairy cattle breeding programmes offers a number of advantages. These range from very basic operational advantages like improved logistics arising from the concentration of progeny in a limited number of herds to advantages to be exploited when applying molecular diagnostics. Aim of the present study was the evaluation of strategies to find suitable test herds with respect to the goal of maximization of genetic differences among progeny groups. Results from the estimation of variance components within classes of herd level of production and herd size demonstrate increased heritabilities with increasing production level and herd size. These differences correspond to higher standard deviations of cow breeding values. Yield deviations of cow performance were stratified within sire and then related to herd parameters. More extreme yield deviations were found at increased production levels. A cluster analysis yet again revealed that herds with a higher genetic differentiation of cows (increased s.d. of cow ebv) exhibit increased levels of production. The present study thus demonstrates the feasibility of finding test herds applying scientific methods.