“It’s ironic since today’s Holstein cows actually have the genetic capacity (breeding value) to stay in the herd 13.6 months longer than those born in 1975,” says Duane Norman, a technical advisor and industry liaison for the Council on Dairy Cattle Breeding. Jersey cows have the genetics to stay even longer—17.5 months.
The reason they don’t, says Norman, is that dairy farmers are simply choosing to turn cows over more quickly, most likely opting to take advantage of the superior genetics of the younger animals. But numerous studies show this strategy is costing famers’ lots and lots of money. Cows kept in the herd longer produce more lifetime milk which, in turn, also dilutes out the cost of raising them to adulthood.
In his study, Norman compared cows average Productive Life (PL) (which is the time between the date the cow enters the milking herd and the date she leaves) and their breeding value. The breeding value for PL is also determined using genetic evaluations of bulls’ daughters. The two can then be compared to determine differences.
“Cows actual tenure in the milking herd is shorter than it used to be due to management decisions,” says Norman. “But cows have the potential to stay significantly longer than they used to because they have been selected directly for longer productive lives and received selective improvement in a number of other traits that also support longer life (e.g., daughter pregnancy rate).”