While there are more than 8 million Holstein dairy cows in the United States, there is exactly one bull that has been scientifically calculated to be the very best in the land. He goes by the name of Badger-Bluff Fanny Freddie. Already, Badger-Bluff Fanny Freddie has 346 daughters who are on the books and thousands more that will be added to his progeny count when they start producing milk. This is quite a career for a young animal: He was only born in 2004. In January of 2009, before he had a single daughter producing milk, the United States Department of Agriculture took a look at his lineage and more than 50,000 markers on his genome and declared him the best bull in the land.
And, three years and 346 milk- and data-providing daughters later, it turns out that they were right. Dairy breeding is perfect for quantitative analysis. Pedigree records have been assiduously kept. There are a relatively small and easily measurable number of traits: milk production, fat in the milk, protein in the milk, longevity, udder quality that breeders want to optimize. Each cow works for three or four years, which means that farmers invest thousands of dollars into each animal. So it's worth it to get the best semen money can buy.
The economics push breeders to use the genetics. In 1942, cows were producing 5,000 pounds of milk and today they are producing 21,000 pounds of milk. Cows are no longer bred for their milk, because 22 percent of the genome of Hostein dairy cattle has been altered through genetics in these past 40 years.