Wednesday evening cow number 976 had a calf. It was a heifer. The calf was pretty small, which is generally a good thing because its easier on the cow. But this time it had us puzzled; 976 was 5 days overdue, and it’s unusual for an overdue calf to be that small. The cow was up and had cleaned the calf off, so we moved her to a hut, fed her colostrum and covered her in straw to help her keep warm. Fifteen minutes later I walked by the barn, and 976 had delivered a second calf. This one was a bull.
We were disappointed for several reasons. We never like for a cow to have twin calves because it’s tough on her. On top of that, when the twin calves are different genders, often the heifer is a freemartin. This means she has received testosterone through a shared blood stream and is infertile. A freemartin heifer appears to have the reproductive parts of a female, but she grows and behaves more like a steer (castrated bull). Not all mixed twin heifers are freemartins, though. It depends on when the embryo divides. Since we couldn’t see that, we needed another way to assess the situation.
We were aware that there were indicators that could predict if the heifer was fertile, but in the past we had just raised them and waited to find out. This is where the awesomeness that is twitter comes in. We asked a couple of friends who we thought might have experience with this, and within minutes we had a free and easy check to try. The explanation that follows isn’t dinner-table conversation for most people (it is here..), but I think it’s worth sharing.
If the heifer is a freemartin it’s likely that the length of her reproductive parts would be reduced, so we used a small blood test tube (blunt with rounded edges, so it won’t puncture or tear anything) with AI lube on it and inserted into her vulva and applied gentle pressure to see how far it would go. The tube stopped at about 2 1/4″. Based on the guidance we were given, anything over 2″ means it’s worth raising her and trying to breed her. If the tube had stopped only an inch or so in, the odds of her breeding would be very low, and we would most likely sell her as a calf. Thankfully, we don’t have to worry about that.
We had a beef farmer stop earlier that evening looking for a bull calf to put on a cow who had lost her calf. We didn’t have one at the time, but he was still interested a few hours later. After we fed the bull it’s colostrum that night and in the morning, we sold him to that farmer. The heifer is a lot smaller than another calf born the same day, but hopefully she’ll start catching up soon. We’ll find out for sure if she’s fertile in 12-14 months.