If you think you’re seeing more cows calving with twins, you’re right. The rate of twinning in Holsteins has more than tripled in the past 25 years.
Cows that produce 90 lb of milk per day or more are predisposed to produce more twin calves than cows with lower production, says Paul Fricke, a dairy reproduction specialist with the University of Wisconsin. In today’s highly productive herds, that means most cows can be susceptible to higher rates of twinning. And that’s not a good thing.
Cows that have twin calves are at increased risk for a whole host of problems: Calving problems, retained placenta, metritis, displaced abomasum and ketosis. They also, then, are at risk for increased days open and more services per conception in their next lactation. These increased risks sum up to greater chance of early retirement and culling.
The resulting twin calves don’t fare very well either. Twin calves are at higher risk of abortion, stillbirth and reduced birth weight because of shorter gestation length. For those twins who survive, they are then at a disadvantage to grow and thrive into adulthood. Heifers born twin to bull calves are almost always infertile.
While there may be a genetic predilection for twinning in the Holstein breed, most of the problem has to do with low progesterone levels at the time of ovulation. And that is being driven by the high rate of feed intake high producing cows need to sustain stratospheric levels of milk production.
High producing cows will eat well over 50 lb of dry matter per day, and well over 100 lb of feed on an as-fed basis. These high rates of feed intake increase blood flow through the liver, which in turn reduces the amount of progesterone circulating in the blood. Low progesterone, in turn, results in higher rates of double ovulation. Double ovulation does result in higher conception rates, but also more pregnancy losses – and more twins.
“It’s all about progesterone,” says Fricke. “It’s like you turn on a switch.” At about 40 kilograms of milk production (88 lb), about 25% of cows double ovulate. At 50 kg of milk production (110 lb), more than half of cows will double ovulate.
The fix to the problem is two-fold. The first is strict adherence to heat synchronization protocols. “If you use Ovsynch protocols incorrectly, you can increase twinning,” says Fricke.
“If you’re using a Pre-Synch/Ovsynch program and are cherry picking cows to breed based on heat detection, about half of the cows not detected in heat will start the Ovsynch protocol in a low-progesterone environment,” he says. “These cows have an increased risk for double ovulation and twinning, particularly now that we have recommended the second prostaglandin treatment to the Ovsynch protocols.”
The bigger problem comes in the resynchronization of open cows after breeding. “Ten to 25% of these cows at re-synch don’t have a corpus luteum (CL) and are in a low progesterone environment when they start Ovsynch,” Fricke says. “Don’t put a no-CL cow on a Double Ovsynch protocol that includes the second prostaglandin treatment.”
At preg check, if a cow does not have a CL, Fricke recommends treating with GnRH and then inserting a CIDR for one week to increase progesterone levels during the protocol. After seven days, remove the CIDR and proceed with the normal Resynch protocol. That should reduce the rate of double ovulation and the chance of twins, he says.