Twinning rates are on the rise for high-production cows, and you don’t have to look hard or long to see that is bad news, says Paul Fricke, professor of dairy science at the University of Wisconsin.

For cows, twinning can mean an increased average days open and services per conception during subsequent lactations. It also increases the number of retained placenta, dystocia, metritis and metabolic disorders such as displaced abomasum and ketosis, all of which increase the chances of culling.

It’s not surprising cows calving twins are culled at a higher rate than their herdmates. “Everything bad that can happen to a dairy cow gets worse when she carries twins,” he says.

It’s estimated the negative economic impact of each twinning on dairy farms is worth up to $250.

Fricke says, “The transition period is a challenge for dairy cows, twinning and non-twinning alike, and the metabolic and physiologic changes that occur during this time represent the greatest health risk for the cow during her productive life.”

Twins also increase the rate of spontaneous abortion, stillbirth, neonatal calf mortality and reduced birthweight. There is an increased incidence of calving difficulty and reduced gestation length.

Fricke said studies show twinning decreases the number of replacement heifers, and it’s not just because of freemartins. “Rather, the decrease in replacement heifers per twin pregnancy arises from increased neonatal calf mortality for calves born as twins and a skewed gender ratio resulting in more male twins than female or heterozygous twins.”

Studies showed from 1983 to 2003 the occurrence of twinning went from 2 percent to nearly 5 percent. Non-lactating heifers only have a twinning rate of about 1.2 percent, and that number hasn’t significantly changed over time.

He cited a 2003 study that looked at 107 sets of twins. The research showed 95 percent of the twins were dizygotic (fraternal twins resulting from two fertilized eggs). The remaining 5 percent were monozygotic, meaning they are identical twins (although in dairy that does not mean their markings are the same).

“There is a strong correlation between increased production and double ovulation,” Fricke says. He notes the incidence of double ovulation after an Ovsynch protocol was “greater for cows with above-average milk production near the time of A.I. compared to cows with below-average milk production (20 percent versus 7 percent, respectively), and this relationship was consistent within parity (one, two and three-plus lactations).”

Level of milk production during the 14 days immediately preceding a natural estrus was positively associated with the incidence of double ovulation. Fricke and his colleagues believe this is due to a reduced amount of progesterone in higher-producing cattle.

Fricke says dairy producers may think double-ovulating cows having the highest conception rates is a good thing, but “you will see as time goes on that it is not.”

Double-ovulating cows not only have a higher chance of twins (46 percent of double-ovulating cows were carrying twins at day 32 compared to zero for single-ovulating cows); 39 percent of double-ovulating cows show a pregnancy loss between 32 and 60 days after timed A.I. compared to 15 percent for single-ovulating cows.

The best approach to decreasing the incidence of twinning, according to Fricke, is to submit cows to the first timed A.I. after a Double Ovsynch protocol.

This hormonally manipulates ovarian function to increase progesterone during growth of the pre-ovulatory follicle before A.I. “Hormonal synchronization protocols that increase progesterone during this time increase conception rate, decrease pregnancy loss and decrease double ovulation rate – thereby decreasing twinning in high-producing dairy cows,” he says.

Fricke and his colleague have been studying Double Ovsynch programs and twinning. They have concluded cows that start an Ovsynch protocol in a low-progesterone environment ovulate larger follicles and have an increased risk for double ovulations.

“It is now clear low progesterone during growth of an ovulatory follicle is associated with an increased incidence of double ovulation,” he says.

When a cow is found to be carrying unilateral twins (both fetuses in the same uterine horn), Fricke says the best option is selective reduction. “It’s not always effective, but it is worth trying. Cows that conceive twins once are likely to do it again.

Although cows will sometimes lose the remaining fetus after a selective reduction, at least there is a chance she will carry one calf to term and not have the negative health effects of twins.”

For cows identified with bilateral twins (in different uterine horns), using trans-rectal ultrasonography early during gestation should be allowed to continue gestation with extra assistance provided at calving.

Work with your nutritionist if you know cows are carrying twins, as their energy demands are 50 to 70 percent greater than other pregnant cows. “Feed management strategies may offer an opportunity to mitigate the negative effects of twinning in dairy cattle,” Fricke says.  

ILLUSTRATION: Illustration by Kristen Phillips.

Kelli Boylen is a freelance writer based in Waterville, Iowa.