The Effects of Gonadotrophins Administered to Sows and Gilts during Different Stages of the Estrual Cycle

Abstract

The effects of gonadotrophins administered during different stages of the estrual cycle were studied in 22 sows and 45 gilts. Both purebred and grade Poland Chinas and Chester Whites were used. Both artificial insemination and natural mating resulted in semen being deposited directly into the uterus of the sow in the luteal phase of the estrual cycle. Seminal residues persisted for a longer time in the uterus of the luteal phase sow than in that of the follicular one. Ovulation occurred 36–48 hours after an intravenous injection of sheep pituitary extract whether administered on the 6th, 17th, or 20th day of the estrual cycle. The intravenous injection when given alone resulted in a larger number of ovulations when administered to gilts in the follicular phase than to those in the luteal phase. When this injection followed treatment with PMS there was a similar difference between the phases in the sows but not in the gilts. This apparent age difference is not explained. A marked difference in the incidence of fertilized eggs occurred between animals treated in the two phases: Avg. 5.3 in the follicular as contrasted to 0.0 in the luteal in one trial and 8.3 and 6.5 as contrasted to 0.0 and 0.5 in another. Copyright © . .