“Understanding the impact of different beef sire breeds on gestation length allows dairy farmers to plan for the longer pregnancies and adjust their operations accordingly,” said the study’s lead author Bailey Basiel, who graduated in May with a doctoral degree in animal science.
Significantly, cows that carried beef-sired calves did not differ in milk, milk fat or milk protein yield when compared with those that carried Holstein-sired calves, noted team leader Tara Felix, associate professor in the Department of Animal Science in the College of Agricultural Sciences and beef specialist in Penn State Extension.
“Our results suggest that current beef-dairy sire selection parameters in the United States are not negatively affecting the dairy cow,” she said.
The study did not uncover any negative effects of Holstein dairy cows carrying and giving birth to beef crossbred calves, according to Basiel. That was likely because Holstein dairy cattle have large frames and are physically able to accommodate the beef crosses, she suggested.
“We didn't see any ill effects, at least in these herds that are using Holstein cows, and I think that's pretty reflective of the U.S. dairy population — we milk mostly Holsteins in this country,” she said. “But the second most popular breed is Jersey. And when you compare a Jersey and a Holstein, physiologically, Jerseys are a lot smaller. Follow up research will determine whether Jerseys can safely produce beef crossbreds without suffering health and milk-yield problems.”
One important caveat to the study, Basiel pointed out, is that the Holsteins were all “multiparous cows,” meaning they had already given birth at least once.
“It was not the first time they’d had a calf, and statistically, traumatic experiences during birthing are a lot more likely to happen the first time a cow is giving birth, because she's smaller and she's never done it before,” Basiel said. “So, at least in these older cows — cows that have at least had one lactation before — we saw no differences in calving ease or stillbirth.”
Adrian Barragan, associate research professor in animal science and extension veterinarian, and Chad Dechow, associate professor of dairy cattle genetics, contributed to this research.
A predoctoral fellowship award from the U.S. Department of Agriculture’s National Institute of Food and Agriculture supported this work.
Source : psu.edu