As well all know, in the human world, brothers and sisters getting it on making babies is a bad thing; it results in birth defects, insanity, country music, Joffrey Baratheon, and the like.
So we were wondering yesterday, how do farmers prevent siblin-humpin’ amongst their livestock? I believe dog breeders, and horse breeders, are careful about the lineage of animals allowed to breed to ensure they don’t end up with five-legged offspring. But if the pigs and cows and whatnot are milling around how do you know children of the same parents aren’t making babies? Could a rooster screw a sister hen? Would it matter? Or do pigs, say, have a natural aversion to porking their brothers and sisters (see what I did there?)
Bulls, rams, cocks and boars are normally separated from the herd/flock before they reach sexual maturity. For the most part they are worth much less than the females and may well be killed at birth or sold off for meat as soon as possible. Only prize specimens are allowed to breed.
Inbreeding combined with culling can be used to eliminate recessive genes. It’s not necessarily the best way, but if both siblings carry a recessive gene for an undesirable trait, one out of four offspring will have both genes and can be culled, two out of four will carry the recessive, and one will be free of the recessive. Obviously, it works best when you don’t mind losing one out of four offspring, so ideally a short reproductive cycle helps, and this is oversimplified to beat hell.
As for cattle, bulls are kept seperate outside of breeding season. This also has the calves been born in a certain window of time. In a commercial operation (commercial as in animals raised for beef vs registered operations which are raising pureblood breeding stock), all the bull calves are casterated and breeding bulls are bought froim the registered operations.
The best heifers are kept as replacements so there is a chance of being breed to their father but bulls are usually replaced fairly often and in a big herd there will be multiple bulls. Dad used 1 bull for every 20-25 cows. Birth defects do happen but are rare and there are other factors.
Pureblood operations do use line breeding to try to concentrate good traits and this can lead to genetic defects showing up.
I assume other livestock are similiar with even more control as hogs, chickens, and dairy aren’t “free range” operations.
Any decent-sized farm is going to have detailed logbooks keeping track of which animals mated with which others, going back for generations. Mating is a strictly controlled business - you don’t just let males and females go out and hang out together.
Isn’t it also the case that males of many species can be aggressive and dangerous, especially if you interrupt them while they are “excited” and doing something about it, or if placed with rival males - so the farmer typically will keep males segregated except when they need their services.
Not really true. The only time you would keep logbooks is if you are raising registered purebloods. In my Dad’s commercial operation, around 12 bulls were turned in a pasture with 300 cows for 2 months. To be able to keep track of which bull bred which cow you would need 12 seperate pastures. Even that’s not a guarantee since bulls don’t show much regard for fences when there are cows in cycle.
A long time ago, when I was a kid, we bought a single, female rabbit that happened to be pregnant. Next thing you know, we were up to our asses in bunnies because they bred like, well…rabbits. They didn’t seem to care if it was incest.
Many wild animals do have social structures and other mechanisms that tend to decrease the incidence of incest. Though if those structures are bypassed somehow, they’ll still do it anyway. For instance, male lions will leave the pride where they were born before finding mates for themselves, while female lions will stay with their birth-pride.
A British sheep farmer does much the same thing with rams. The difference is that each ram is fitted with a dye known as raddle, which gets transferred to the ewes back. This lets the farmer know which ewes have been served and by which ram.
When I was a kid we had guinea pigs. They were closely related, and breed anyway. We had a lot of piglets with birth defects. Some were just oddly colored, some were mentally retarded. Yes, even guinea pigs can be mentally retarded in a way people can notice.
Inbreeding is an important tool wild animals have that allows them to quickly adapt to minor changes in their enviroment. If you have only two surviving raccoons in an area that has gone through some recent dramatic changes and those two happen to be related chances are they are carrying some trait that gives them a better chance of survival and they stand a ggod chance of passing that trait down.