Longevity in dairy cattle breeding: a review

Results from various selection experiments and field data as well as from Monte Carlo studies and model calculations are reviewed to indicate some crucial features concerning longevity in dairy cattle breeding. The following conclusions were drawn: (i) There is some evidence from selection experiments for a significant antagonism between early maturity and longevity. (ii) Estimates of the genetic correlation between first lactation milk yield and longevity traits show a severe upward bias due to voluntary culling on milk yield. Adjustment of herd life for within-herd milk production is recommended but may not prevent estimation biases in general. (iii) The relative economic value of longevity compared to milk yield depends on the level of herd life in the population and the actual quota scenario; a rough average is 1.2. (iv) Type and conformation traits cannot serve as sufficient selection substitutes for longevity traits. (v) Survival analysis is the adequate method for genetic evaluation of lifetime data. (vi) Both selection on determinants of involuntary culling and on measurements of longevity may be used as breeding strategies to improve longevity. (C) 1998 Elsevier Science B.V. All rights reserved.