A farmer I called on the phone last week said he would have to call me back. He had a beef heifer trying to have a calf and she was in trouble. The calf was too big. Bred to a bull that was supposedly good for heifers because he was rated high for easy calving, he threw an exceptionally large calf. It took the vet to remove the calf surgically. The calf didn't survive, but fortunately the heifer did.
Growing up around a dairy farm it's not the first time I've heard of calves being too big from bulls that weren't supposed to throw big calves. It's also not the first time I've heard about a calf that had to be removed surgically. You're not always lucky enough to at least save the mom. I've learned that the hard way.
A farmer also reports that if you line breed too long in cattle – where you breed animals with close pedigrees back to each other – you eventually get an animal or two that isn't productive, or isn't formed correctly. If the genetics line up correctly and you get the right mix, you can get an excellent animal. Its brother or sister might be a dud.
If you raise sheep, especially Southdowns, you might be aware of what's called 'hairy lamb.' If you Google it on the Internet you may find 'hairy shaker lamb' which is a totally different condition caused by disease, not genetics.
Hairy lamb, according to animal scientists, is a strictly genetic recessive trait. If both the ram and ewe carry the recessive trait, there's a 25% chance of getting a hairy lamb. There's a 50% chance the lamb will be normal but be a carrier, and a 25% chance the lamb won't even be a carrier.
There are commercial tests available, but at least in the early days of testing for this somewhat recent condition, sheep owners say the testing wasn't 100% accurate.
A hairy lamb is born with snow white, straight or curly white hair, and often has a parrot mouth, with a longer than normal muzzle. It may live for a while and seem fine, then succumbs to pneumonia or some other stress. The longest known survival time reported here so far for a hairy lamb is 30 days.
One shepherd reports getting a hairy lamb when the ram was supposed to be free of the gene. Obviously the test was wrong. Since hairy lambs don't live to reproductive age, the only way to get one is to get the recessive gene from both the ram and the ewe.