Calving difficulties are a major source of economic losses and inconvenience for dairy farmers (Berger, 1994) and are also of concern when considering the management and welfare of cows (Philipsson et al., 1979). Economic losses are due to increased likelihood of losing the calf or the cow, increased costs of medication, veterinary assistance and time input from the farmer (Philipsson, 1996). Further losses are incurred due to reduced milk production and fertility (Meijering, 1984; Meyer, 2002). The aim of this research is to develop a more accurate system for calving ease evaluation in Australia, which will allow farmers to select calving ease bulls, resulting in reduced economic losses, improved animal welfare and increased export sales of pregnant heifers. The accuracy of breeding values depends on the quantity and quality of the data collected. Approximately 64% of recorded calvings in Australia from registered Holstein bulls are classed as unobserved. These are not currently used for estimation of calving ease breeding values, on the assumption that unobserved calvings are unreliable resulting in possible reduced accuracy. However, there are calvings that are described as “unobserved – not ok” (70% of male calves born to heifers in this category die), and discarding these may well involve the loss of useful data with a high incidence of dead calves. Overall, exclusion of all unobserved calvings results in the discarding of more than half of the calving ease records. In addition, the majority of herds record no calving difficulties in a season, so the value from them is uncertain. The aim of this paper is to determine whether some of the data that has been traditionally discarded can be retained and used to enhance the reliability of the calving ease EBV.
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 2002. Session 1, , 1.22, 2002
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