I have no firsthand experience with cattle, sheep, goats, or fowls. But in any context where I’ve heard them mentioned, it seems that there are never nearly as many roosters, bulls, rams, and billygoats as there are hens, cows, ewes, and nannygoats. This would seem suited to the goal of maximum propagation of the species; one male can go on servicing as many females as he can until…well, until he’s exhausted; thus, in a few months we have lots of new herdlings/chicks.
But how does this situation come to pass? Are more females than males born naturally, or are they roughly 50-50 to begin with, as with humans, and the males start killing each other off as they fight for mating rights?
Or is my whole premise wrong and the gender balance of the adult animals is roughly the same as in humans, i.e. about 50-50?
I know that with cattle, roughly equal amounts of males and females are born, and the ranchers will sell off the males to be slaughtered at a younger age, on average, than the females.
In the wild, gender ratios at birth will tend towards 50-50. Suppose it were otherwise: Suppose, for instance, that many more females are born than males. In such an environment, it’s great to be a male, and not just in a subjective sense. Each male will have more offspring, on average, than each female. So if you have some mutation that causes an individual to have more male offspring than usual, that individual will, on average, have more decendants, so that trait will spread through the gene pool and the birth ratio will be pushed back to 50-50.
Fisher’s sex ratio theorem: cool, learned something.
In the wild, among horses, the males will fight and the winner keeps a harem. The males that are driven off tend to form small groups. (no good cite, just what you’d read in Western-set fiction).
The answer for domesticated animals is rather simple: the ratio at birth is basically 50:50, then most of the undersirables (generally males) are killed.
[Side note: Have we really reached the state where the sex of animals is to be known as “gender?” Sounds awfully bowdlerized.]
You might be interested in a book called The Selfish Gene by Richard Dawkins. I know he devoted quite a few pages explaining why one gamecock services several females.