title: The estrous cycle and induction of estrus in the australian feral sow (Sus scrofa).
abstract: In the first of 2 experiments, the estrous cycles of 11 Australian feral sows were studied. In 9 of the 11 sows the cycle was characterized by cyclic occurrences of low (0 to 2 ng/ml) and high (24.2 to 47.2 ng/ml) levels of progesterone. The low levels were associated, in all sows but one, with the standing response, lasting from 1 to 4 days, to a feral boar. Concomitant cyclic changes in vulval swelling and consistency of the vaginal mucus were also observed. Using intervals between the standing estrous response or the marked changes in the secretion of progesterone, the mean length of the cycle was calculated as 19.8 and 20.0 d, respectively. Two of the sows did not exhibit cyclic changes in any of the parameters measured, and on no occasion did either stand for service. In the second experiment, it was shown that estrus can be reliably induced in feral sows by either 1 of 2 methods: first, sows were induced to abort by prostaglandin injection. They were then administered gonadotrophin 48 to 72 h post abortion, and came into estrus 4 to 5 days later. Second, estrus was suppressed by feeding sows altrenogest, and was induced again about 9 days following altrenogest withdrawal.
authors.forename: R J
authors.initials: RJ
authors.lastname: Kilgour
authors.forename: D
authors.initials: D
authors.lastname: Choquenot