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Variance of milk production is a promising new trait to increase resilience in cows
Genetic improvement of resilience and health are important in dairy cattle and other species. More resilient animals need less labour, less antibiotics and are societally more accepted. In a study that was just published in Journal of Dairy Science, researchers of Wageningen University and Research Animal Breeding and Genomics and CRV BV found that the variance of daily milk yield of dairy cows is heritable. Also this trait is genetically associated with longevity of cows and important diseases such as mastitis and ketosis. Therefore, the variance in milk yield can be used as a resilience indicator to breed healthy cows.
Fluctuations in milk yield can be the result of health issues, because sick cows have usually a lower milk yield and increased variance of daily milk yield. The heritability of variance of milk yield was 0.1, similar to many health related traits. Furthermore, the variance of milk yield had the strongest genetic correlations (0.3-0.5) with existing traits such as udder health, ketosis and longevity. These correlations indicated that cows with a genetically low variability in milk yield have genetically less mastitis, ketosis and have a higher longevity than cows with an average variability. The correlations with mastitis and ketosis are likely due to that both diseases are frequently occurring and cause a decrease in milk yield. In addition, it is expected that cows with a low variance in milk yield are more resilient to other environmental perturbations such as heat stress. Therefore, the variance of milk production is a promising new trait to increase resilience in cows with genetic selection.