There are more Holstein dairy twins today than in the past – from just over 3 percent in 1975 per herd to 10 percent or more today.
High milk production seems to figure into more twins, and the vast majority of Holstein twins are fraternal. These twin calves come from separate eggs that are released at the same time from an ovary, but are fertilized by separate sperm.
The result is a challenging situation for many dairy farms. The cow’s nutritional requirements are large. The cow may have difficulty giving birth to twins and passing the afterbirth. It’s possible the dairy will lose both the valuable cow and the twin calves.
“It appears that cows that have some predisposition for double ovulating have a great chance of double ovulation under a low progesterone environment,” said Richard Pursley, Michigan State University professor of reproductive management. “If we grow these follicles under low progesterone, we get a really high rate of double ovulations – that is not a good thing.”
This process is explained by Paul M. Fricke, University of Wisconsin professor of dairy science as “increased hepatic metabolism of progesterone as a result of the increased feed intake associated with high milk production provides a physiological mechanism for decreased progesterone levels in high-producing dairy cows resulting in an increase in dizygotic twinning.”
Fricke’s research indicates that double ovulation can be decreased in high-producing Holstein cows by “manipulating ovarian function to increase progesterone during growth of the preovulatory follicle before timed AI,” he wrote in a 2015 paper called, “Double Vision: management of twinning in dairy cows.”
Pursley’s recent research showed similar results, and he shared his results in an April Dairy Cattle Reproductive Council webinar entitled “Ovulation Synchronization Programs: An Update.”
In an interesting aside, Pursley mentioned that studies on Holstein dairy cows 20 years ago showed a 5.5 percent loss of calves from 98-282 days of gestation. In his recent studies, he found that dairy cow stillborn losses have only slightly improved today for the latter portion of gestation.
The vast majority of noted embryo losses occur in the first two to four weeks after a pregnancy is confirmed.
In his recent studies, Pursley found that cows were also much more likely to lose their pregnancies when they had double ovulations verses single ovulations.
In an attempt to reduce double ovulations, Pursley manipulated progesterone to test the role of progesterone during the first four days of follicle development and the last three days of follicle development.
“We were able to create a situation where we had high progesterone verses low progesterone in essence and testing whether or not that impacts fertility or not in these cows,” he said. “Our hypothesis was that cows under high progesterone would have higher fertility. The outcomes. It didn’t turn out exactly like we would expect it.”
The scientists knew that low progesterone leads to more double ovulations.
They also learned that when they manipulated cows into four groups of progesterone levels (high for the first four days/high for the last three days; and similarly, with high/low, low/high and low/low progesterone levels) the greatest percent of pregnancies 23 days following AI occurred with the low/low progesterone level (66 percent).
The next greatest pregnancy rate was the low/high progesterone group at 61 percent, followed by high/low progesterone at 60 percent, and high/high progesterone at 49 percent.
“We saw about a doubling of double ovulations in cows under low progesterone,” he said.
Twinning is a significant concern in many dairies today, and dairies and researchers will continue to look into methods to reduce double ovulating resulting in twins in the first place.
Source: Minnesota Farm Guide
