Breeding season is almost upon us. I have been reading selections from McDonald’s Veterinary Endocrinology to get ready.
The ram has pheromones in his wool that stimulate the ewes to ovulate. Oddly enough, presenting ewes with pheromones from the hair of the billy goat will also cause ewes to ovulate.
Goats and sheep are thought to have descended from a common ancestor with 60 chromosomes. Goats have 54 while sheep have 60. It is possible for goats and sheep to mate and even fertilize and egg, but the fetus is rarely viable except when produced in a lab.
In breeds such as the Southdown, which developed in colder climates, the shorter days of late summer and Fall tell the ewe’s body when it is safe to get pregnant. Ewes will begin to come into season 60-120 days after June 21, the longest day of the year. If you move a ewe from Australia to the US, for example (or vice versa) her breeding cycles will easily reverse (December 21 is the longest day of the year in the Southern hemisphere). This is natures’ way of ensuring that lambs are born during warm weather. Breeds developed in the tropics, however, can breed at any time during the year.
A ram can breed all year, but he too is sensitive to the length of the days and is more fertile during the breeding season than during the non-breeding season.