Breeding aspects of the calving process, rate of stillbirths and longevity in dairy cattle

Fitness related traits as cost reducing factors are exceedingly important in all dairy cattle breeds. With respect to these traits, calving ease and stillbirth rate as well as length of productive life are of particular interest. In most dairy populations the phenotypic trend is declining while the genetic trend is rather stable. Heritabilities are generally low. Estimates are in the range of 1 to 10 % for calving ease and stillbirth rate, for longevity slightly higher values may also be found. For both trait groups, many auxiliary traits with sufficient genetic relationships may be used to increase the reliabilities of breeding values. For calving traits, both the direct (paternal) and maternal genetic component have to be estimated simultaneously. The use of multivariate approaches may favourably affect the reliabilities of the breeding values. Survival analysis is applied to estimate breeding values for length of productive life. By the use of censored data, live animals are statistically correctly included. The main criterion in animal breeding is functional longevity, which is length of productive life corrected for yield dependent culling. The inclusion of functional traits in a total merit index according to their economic weights should result in rather stable future genetic trends.

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