Mortality of calves is a cost for dairy cattle farmers. Due to legislation reliable recordings of postnatal mortality are available for all Danish cattle today. This offers new possibilities for analysing and reducing the problem. Environmental improvements (e.g. management and housing) are one way to reduce mortality, but these improvements are in general not permanent. Instead, genetic improvements have a permanent effect. However, genetic improvements are only possible if genetic variation for mortality exists. Only few genetic studies of postnatal mortality are available (e.g. Erf et al., 1990 (dairy cattle); Cundiff et al., 1986 (beef cattle)) but they are all based on a scarce number of animals. In a review by Shook (1998), it was concluded that more genetic and economic studies of calfhood diseases and calfhood mortality were needed for making decisions about using these traits in breeding programs. Diarrhoea is believed to be the most important cause to early mortality from 1 to 30 days after birth but later (from 1 to 6 months after birth) respiratory diseases becomes the most important cause of mortality (Agerholm et al., 1993; Menzies et al., 1996). Different genes might therefore affect early and late postnatal mortality. The objective of this study was to estimate and test, if direct and maternal additive genetic variation for postnatal mortality exists and to estimate the genetic association between early and late postnatal mortality.
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 2002. Session 1, , 1.25, 2002
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