Is It Common for Beef Cattle to Have Twins
At one point or another, nearly every cattleman will experience the not-so-joyous occasion of twins on the ranch. Understanding the cause and effect of this phenomenon can help breeders make decisions to impact a herd's long-term reproductive success.
The issues directly associated with twinning are many. Freemartin progeny and the stress on cows contributing to difficulty rebreeding are among the most concerning, says Brian Freking, Oklahoma State Extension livestock specialist.
"Other concerns are the potential increase for dystocia, calf mortality and retained placenta," he says. Besides these setbacks, there is also the heavy risk of lost income opportunity on freemartin heifers or dead calves and increased expenses in caring for orphaned or abandoned calves.
Freking suggests beef producers should aim to see no more than 2 to 5 percent of their herd calving twins on a yearly basis. With proper management and the ability to identify contributing factors, cattlemen can make sure they see a lower frequency of twinning calves.
Causes
Twinning is considered to be lowly heritable and fairly unusual. While there is a lot of variance, some studies suggest the instance of twins in beef animals is only about one out of 200 births. More concerning is that certain breeds and types seem to lean toward a higher prevalence of twins.
For example, dairy cattle, particularly Holsteins, are well-known for their twinning tendencies. Of the beef breeds, Simmentals and Charolais lean more toward higher incidences of twins compared to their counterparts. The individuality of each animal is also a big contributor to the likelihood of twins.
Freking points out the tendency to twin is not based solely on the cow's genetics. "Based on the research conducted by MARC (Meat Animal Research Center), sometimes the sire has just as much of an influence in twinning rate as the cow itself," he says. "More recent work shows selection for ovulation rate can be used for increasing the chances of twins. The cattle developed at MARC for twinning would be an obvious germplasm source."
A MARC study from 1991 found ovulation rates in the estrus cycles of breeding-age heifers may be a considerable factor to aid in the indirect selection of animals for twinning rates. It found the correlation rate between ovulation and twinning was as high as 0.80 for cows and 0.90 for breeding-age heifers.
Another factor the study found is: Ovulation rate heritability is at least twice as high as is twinning rate. Because the heritability for this trait is so low, Freking says the chances of a cow with twins having twins again is even lower.
Decision-making
Since passing down a poor trait isn't very concerning, the culling decisions for cows is usually based on their ability to be bred back. "Because the nutritional demand is greater for cows with twins, they tend to have a harder time rebreeding," says Freking, "and therefore might be culled based on pregnancy checks after weaning the current twin offspring when using a defined calving season."
Even if a cow accepts both calves once they're on the ground, some ranchers may decide to bottle-raise one or utilize a surrogate. Freking says these are good options to decrease nutritional stress on the dam post-calving. "If producers looked at this option, they should utilize ultrasound to determine pregnancy status prior to birth for the increased management required," he says.
Theoretically profitable?
The concept of twinning, putting all accompanied cow and calf issues aside, seems like it could hold profitability – in theory. A rancher might imagine doubling the whole calf crop, increasing the amount of profit per cow and herd replacements, if only it could be effective.
Another research study at MARC started in 1981 explored this exact end: creating beef animals that could successfully have and raise twins without a loss of production, income or increased cost.
After many more failures than successes, the long-running project was ultimately abandoned in 2012. This outcome doesn't surprise Freking. "It was my understanding a goal of 140 percent calf crop out of 100 would be the threshold to justify having a twinning herd," he says. "Most producers have not gone down that road based on the added headaches of all that is involved in twinning."
Very similarly, another study was conducted on twinning in Holsteins with the same hypothesis that the trait could be made profitable. It ultimately determined it wouldn't ever be a goal worth pursuing – for the same issues the MARC study ran into.
Although some experts have theorized some cattle lines and breeds may be more apt to carry twins to full term with moderate success, making it feasible is unrealistic. Theoretically, more weaning weight per cow by having twins has some economic benefits.
However, the repeated failed studies, high risk factors and economic losses make it unlikely this route will ever be made successful. Instead, producers should continue to focus on increasing profits through breeding programs as they always have done.
"Reproductive performance is still the biggest driver in profitability," says Freking. "Having twins is probably not the best use of technology versus having one calf every year and having the growth, reproduction and carcass traits targeted for a specific market, for example Certified Angus Beef or other premium markets." 
PHOTO:Beef producers should aim to see no more than 2 to 5 percent of their herd calving twins on a yearly basis. Photo by Getty Images.
Jaclyn Krymowski is a freelance writer based in Ohio.
Source: https://www.progressivecattle.com/topics/herd-health/understanding-the-cause-and-impact-of-twins