Scientists have found a genomic deletion that affects fertility and milk yield in dairy cattle at the same time. The discovery can help explain a dilemma in dairy cattle breeding: the negative correlation between fertility and milk production. The work was published online on January 2, 2014 in the open-access journal PLOS GENETICS. For the past many years, milk yield in Scandinavian dairy cattle has gone in one clear direction: up. This has been due to targeted breeding programs and modern breeding methods. Despite putting large weight on the breeding goal in Nordic countries, almost no improvement is achieved for fertility. It now seems that this unfavourable correlation between milk yield and fertility is partially affected by a deletion of a simple gene sequence. The presence and effects of this mutation have recently been discovered by scientists from Aarhus University, the University of Liège, and MTT Agrifood Research Finland, in collaboration with the Danish Agricultural Advisory Service and the Nordic Cattle Genetic Evaluation. Scientists, farmers, and advisors have generally assumed that the reduction in fertility is primarily due to the negative energy balance of high-producing cows at the peak of their lactation, but now the scientists have also found a genetic explanation. “We have discovered a deletion encompassing four genes as the causative variant and shown that the deletion is a recessive embryonically lethal mutation,” explains Dr. Goutam Sahana. This means that the calves die while they are still embryos and are aborted or reported as insemination failure. The fact that the mutation is recessive means that both parents must carry it and pass the genes on to their calf for the calf to be affected.
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