The days of guess work in breeding dairy cattle are gone. Today's DNA sequencing means more productive cows and less pollution.
Breeding cattle through artificial insemination began in the 1940’s. Farmers bred cows with bulls who fathered fertile, healthy and robust daughters. Today animal breeders choose mates based on their DNA.
Alison Van Eenennaam, an animal geneticist at UC Davis says selective breeding has enabled farmers to dramatically reduce the size of the dairy herd in the United States.
"We used to have somewhere roundabouts 25 million dairy cows in the United States, and we're down to nine million now,” says Van Eenennaam.
She says selective breeding is good for the planet because fewer dairy cows are releasing methane – a harmful green house gas.
"It [has] actually reduced the environmental footprint of a glass of milk by two-thirds relative to the 1950’s," says Van Eenennaam.
Mapping the cow genome was completed in 2009. Van Eenennaam says teasing out which genes contribute to specific traits will continue to help animal breeders improve the dairy industry's productivity.
Van Eenennaam is currently studying cattle genomics to understand the animals' susceptibility to respiratory disease. The USDA Agriculture and Food Research Initiative is funding the research.