The invention provides methods for identifying a genetic polymorphism associated with altered milk production traits in dairy cattle.

Farmers could inject the hormone directly into dairy cattle to increase their milk production.

The method particularly enables to substantially increase global milk production and improve economy of the dairy industry, without negatively affecting the wellbeing of dairy cattle.

The present invention is directed to a new method and feed additive and a method for enriching nervonic acid (NA) in expressed milk of ruminants, for example, dairy cattle.