Reuters reports that, as far as reindeer go, anyway:

sterilized males can grow larger and so are better at digging for food — as Arctic temperatures vary more, thawing snow often refreezes to form thick ice over lichen pastures.

and, interestingly:

Castrated reindeer also keep their antlers for much of the winter while normal males shed their antlers each autumn after the mating season. That implies that Rudolph, pulling Father Christmas’s sled, has been castrated.