Mutation in Dairy Cattle Increases Milk Yield, But Kills Embryos

Scientists have made an important discovery in dairy cattle. They've found a mutation that has a positive effect on milk yield, but causes embryonic death in dairy cattle. The findings could help explain a dilemma in dairy cattle breeding--the negative correlation between fertility and milk production.

Milk yield in Scandinavian dairy cattle has continued to increase over the years. This has been largely due to targeted breeding programs and modern breeding methods. Yet despite putting large weight in the breeding goal in Nordic countries, almost no improvement has been achieved for fertility. Now, though, it seems that this negative correlation between milk yield and fertility could be partially affected by a deletion of a simple gene sequence.

"We have discovered a deletion encompassing four genes as the causative variant and shown that the deletion is a recessive embryonically lethal mutation," said Goutam Sahana, one of the researchers, in a news release. In other words, this means that the calves die while they're still embryos and are either aborted or reported as insemination failure.

That's not all researchers found, though. While this gene is recessive, it has become fairly common in Nordic Red cattle. In addition, it's estimated that 2.89, 1.32 and .42 percent of embryos are dying in Finnish Ayshire, Swedish Red and Danish Red cattle respectively due to this mutation. It's likely that it's become so common because it has such a strong positive effect on milk yield. By selecting for high milk yields, breeders have also selected for embryo mortality.

The findings reveal how important it is to consider all characteristics of a particular mutation when it comes to breeding cattle. While breeders have selected for higher milk yields, they've also selected for lower fertility. This could have negative consequences for breeding practices now and in the future. That said, the research also provides information that breeders can use; it's possible that they will be able to choose cattle that produce more milk while still maintaining fertility.

The findings are published in the journal PLOS Genetics.