(NAFB.com) – A sharp decline in the number of dairy heifers available to replace older cows exiting the U.S. dairy herd could limit meaningful growth in milk production. The number of dairy replacement heifers has fallen almost 15 percent in the last six years to reach a 20-year low. While the global demand outlook for U.S. dairy products is murky due to export market uncertainties, any potential growth opportunities may get stymied by an inability to expand U.S. milk production. A new report from CoBank’s Knowledge Exchange says the rising cost of rearing dairy heifer calves has far outpaced increases in heifer values over the last several years. That imbalance has prompted dairy farmers to reduce their replacement heifer inventories, doing so, in large part, by breeding more dairy heifers and cows to beef bulls. “Farmers can cut costs associated with heifers and generate additional income from beef,” says Cory Geiger of CoBank.