Cows twin at a rate of one to seven percent, with dairy breeds twinning two to three times as frequently as beef cows. Most would prefer this number to be zero due to several negative consequences of twinning, including:
Increased risk of calving difficulty, retained placenta and metritis. This often leads to delayed return to fertility. Dairy cows calving with twins are more prone to transition issues such as ketosis and DAs.
Twins more than double the risk of abortion and increases the risk of neonatal mortality five-fold.
Freemartinism is common in twin births. Eighty to ninety percent of heifers born twin to a bull will be reproductively sterile.
Increased risk of sickness and death in neonatal calves. Inadequate colostrum intake in one or both twins is very common. Beef producers should be prepared to supplement if necessary. Monitor closely to be sure that the cow is caring for both calves and intervene as needed.
It is helpful when a veterinarian is able to identify twin pregnancies during pregnancy examination. Twin are more reliably identified at 40-50 days gestation and can often be picked up as late as 80 day gestation. Up to 50 percent of twin pregnancies identified prior to 60 days gestation will be singleton deliveries due to fetal wastage of one twin. If the singleton is a heifer, she is still at risk for freemartinism. It is less common, but still possible, to lose a single twin identified after 60 days gestation.
What should you do if your cow diagnosed with a twin pregnancy delivers a single calf? Here are a few suggestions:
For producers with adequate experience, perform a rectal and vaginal exam to confirm that there is not another calf left in the cow.
If you are unable to perform an exam, monitor the cow's behavior closely. Generally, if she is tending to the calf, eating and drinking normally and shows no abnormal behavior (such as straining or frequent urination), she probably lost the twin earlier in the pregnancy and should not require further intervention.
Call your veterinarian if you are unsure. Early identification of complications usually leads to a better outcome for the cow.