Calving performance as an important element of profitable cattle breeding has in recent years received considerable attention. Several surveys o f dairy and dual-purpose breeds have shown a high frequency o f d iffic u lt births in^ h eifers, ranging from 3% to 19%, and a lower occurrence in cows, between 1% to 8% (Philipsson 1976, Smidt and Huth 1979, Thompson et al. 1980). The genetic model of dystocia is the same as the model for feta l effects (Van Vleck 1978). The estimates of h eritab ilities of calving performance considered as a tra it o f the dam, or a tra it o f the ca lf were usually low. However, the existing genetic variability of this character ju stifies the evaluation of sires for calving ease (Philipsson et al. 1979). In Polish dual-purpose Lowland cattle there is lit t le information on incidence of dystocia and the estimates of genetic parameters are not available. The purpose o f this preliminary study was to provide such estimates.

A. Zarnecki

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 8. Symposia (2), , 228–231, 1982
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