Association between breeding values for milk production and animal health in an organic dairy herd

Breeding for high milk yield is very often considered to be a reason for increasing animal health problems. However, since the heritability of most diseases is low, poor management and unbalanced ration formulation gain more importance. Regulations in organic farming considerably limit farm management, mostly in terms of feed ration formulation and medication. These restrictions may limit the options of healthy dairy cow nutrition, which might increase the risk for development of diseases. The aim of this investigation was to determine the association between breeding value for milk yield and animal health on an organically managed dairy farm. Therefore, blood and urine samples were taken and back fat thickness was measured weekly from peripartal cows (three times at 8-0d a.p., 1-8d p.p. and 20-30d p.p.) in an organic dairy herd (according to EU Directive, Biopark and National Organic Program 'NOP') between October 2007 and October 2008. Information regarding milk yield, reproduction and diseases was recorded for these cows. According to their genetic potential for milk yield (RZM), cows were divided into individuals with low, medium, and high breeding value and measured parameters were compared among groups. High genetic merit cows had an on average 1962 kg higher milk yield over 305 days than cows with a low genetic merit. Coincidentally, they had more days to first service and days open and the calving interval was prolonged, whereas the number of inseminations was not increased. However, the high genetic merit did not have a negative effect on health or adaptability of metabolism to physiologic challenges. It was demonstrated in an organic herd that a high potential for milk yield is not inevitably associated with a high susceptibility for diseases.