STEPHENVILLE -- Think you're uncomfortable in the extreme Texas summer heat? Try being an ovulating 1,200-pound mother cow.
Studies have shown that heat-stressed dairy cows suffer from damage to their ovarian follicles. Moreover, the eggs produced by the damaged follicles may also be damaged, said Dr. Todd Bilby, Texas AgriLife Extension Service dairy specialist.
Worse, after becoming heat-stressed, other studies have shown the eggs she ovulates for the next 40 or 50 days are likely to be damaged as well, according to Bilby.
Bilby and his graduate student, Brandi Stewart, have found a way to double pregnancy rates during the summer and increase the number of heifers born as compared with conventional artificial insemination commonly used on dairy farms. They believe this method could save dairies in Texas and throughout the country lots of money.
Thus heat stress puts "the heat on a dairy operator" in a number of ways, Bilby said. Not only does it reduce milk production, but by lowering fertility and increasing miscarriages, it costs the American dairy industry $1.5 billion annually.
"That's an estimated economic loss of $132 million to the Texas dairy industry alone," Bilby said.
Heat stress is also hard on the developing embryo if the mother cow does become pregnant. Consequently, it may die in the first two to three days of its development, he said.
"If a lactating dairy cow's egg actually becomes fertilized during summer, for which she only has a 50 percent chance, then there is still a very good chance the cow will not become pregnant because the early growing embryo is more likely to die within the first three days of life," Bilby said.
This is also bad news for the dairy cow and reduces profit margins for the dairy operator. When a heifer or a mature mother cow doesn't become pregnant, the dairy operator not only loses a calf, but the cow won't be giving birth, which in turn means she
|Contact: Robert Burns|
Texas A&M AgriLife Communications