Heat stress costs the U.S. dairy industry as much as $670 million yearly. Scientists predict it could cause a 6.3 percent drop in milk production by the end of the century. However, some dairy cows in Puerto Rico have a natural mutation recognized as “slick,” which gives them an advantage in hot humid conditions. Slick cows have a shorter coat and more active sweat glands than cows without the mutation. This helps them maintain a more productive body temperature.
Studies show that Holsteins with the mutation can keep their body temperature about 1°F cooler than those without the mutation, so milk production and fertility don’t drop as much when it’s hot.
I get 1,800 pounds [more] of milk per lactation from these cows and they reproduce more effectively. “ – Rafael Lopez-Lopez.
Source: Ambrook Research, August 25, 2023. Link. Research is still in its early days — scientists and farmers say that larger sample sizes will help them better understand under what conditions the mutation is most helpful. (A 2020 study comparing slick calves in Florida and California showed that the advantages of the mutation were more pronounced in the humid heat of Florida than the dry heat of California.)