can we induce cows/sheep/goats have more twins and other multiple births by giving them fertility drugs? Or is their reproductive system just not as suited for handling multiple births as human one?
Why would we want to? The enormous effort already expended on animal agriculture is a serious threat to the planet.
Possibly but it would probably not be economically viable.
Generally, twin births in animals have a few problems (same as humans, actually):
- lower birth weight. Twins are smaller, thus would take longer/consume more feed in getting to shipping weight.
- lower survival rate. One (or both) twins are more likely to die quickly, which is obviously bad economic news for the breeder.
- more risk of complications to the mother. The mother tends to have problems, and take more time to recover from carrying & birthing twins. Which means longer until she’s back to full productivity, thus an economic loss.
So it’s unlikely animal breeders would want this. In fact, it’s common practice now for animal breeders to have their vet ‘pinch off’ one of the twin fetuses very early on in the pregnancy. So rather than encouraging multiple births, animal breeders are trying to suppress the ones that occur naturally.
Sheep and goats already usually produce twins, triplets and quadruplets are not rare. Aside from the pregnancy and delivery problems t-bonham mentioned, the mother also has to produce enough milk to keep everybody fed. That is difficult at best with 4 babies, impossible with more. Extra babies can be fostered onto mothers who have lost their babies for one reason or another, but sheep and goats are pretty good at refusing babes that aren’t carrying their genetics. So, not a lot of reason to increase the liter size of these species plus a huge increase in hassle.
Cattle also frequently naturally twin. However, due to the configuration of the placenta in cattle, if there is a male fetus and a female fetus, hormones from the male will influence the female, making her intersexed. Since you are breeding animals to make more breeding animals, having an intersexed one is counter-productive. Instead of being kept as breeders, they are “beefed,” which nets the farmer much less profit.
Like t-bonham mentions, twin horses are almost never survive because of the placental configuration, the size of the uterus, and the demands on the mother. It is common to have a vet selectively destroy one of the fetuses.
Dogs, cats, and pigs have adaptations to their uterus and placentas that make them much more successful at carrying multiple fetuses.
Most farmers here selectively bred ewes for twin births. The spring just gone resulted in a lambing percentage of 124% nation wide. I’ve heard of individual farms have a lambing % of 180%.
With cattle, I’ve personally found multiple births to be rare; out of approx 2400 calvings I had something like 5 sets of twins and one set of triplets, these figures would be similar to other farmers I knew. Dairy researchers here desperately want identical twin heifer calves and I think they only manage 25 sets a year out of the whole country. As Pullet said, bull/heifer twins most times end up with the heifer being infertile.
With regard to low birth weights, sheep farmers often get their ewes scanned and those with twins are separated out and fed more to ensure the lambs at birth are larger.
Research I know about:
Sexing sperm so dairy farmers could produce either heifers or bulls as they require.
“Test tube calves” (forget the term) Cows are given drugs so they produce lots of eggs which are then fertilised and implanted into surrogates.
This. A mare’s uterus is so unsuited to carrying twins that twin pregnancies usually fail long before delivery, hence the selective termination of one embryo.
Vocabulary builder: The masculinized female calf is called a freemartin.