Had a cow had twin heifers this past September. Nursed 'em both. Sold the bigger of the two last month, 6 months old , weighed 185 lbs. Hoping the one left will benefit by being the only one on the cow now. Momma cow not a big milker but normally weans a 500 pound calf. Hope your cow is a better milker. BTW, got $1.70/lb for the one I sold, so I'm guessing and hoping that when I sell the other twin and add it to the money for the first I'll end up with the same money total as if I'd had one 500 pounder. Good luck, jgn. But you didn't ask for all that info. Sorry. You asked if heifer twins were fertile. Yes, they are. I would have liked to have retained my heifer twins, but at their rate of growth, they wouldn't have reached maturity until the end of the decade.