Canadian Health&Care; Mall

All experiments were performed according to Federation of Animal Science Society guidelines for the use of agricultural animals in research, and each experiment was reviewed and approved by the MARC Institutional Animal Care and Use Committee. Experiment 1 Intact white crossbred gilts were unilaterally hysterectomized-ovari-ectomized at approximately 160 days of age. At 200 days of age, these gilts were observed once daily for estrous behavior and were mated after at least one estrous cycle of normal length (17-23 days) using artificial insemination with semen collected from mature white crossbred boars. Gilts were then randomly assigned to receive 1) no treatment (control), 2) estradiol valerate treatment (5 mg estradiol valerate in corn oil given on Days 11 and 12 of pregnancy), or 3) progesterone treatment (200 mg/day progesterone in corn oil given on Days 2 and 3 of pregnancy). At approximately 105 days of pregnancy, gilts were killed, and the remaining gravid uterine horn was recovered and opened. A blood sample was collected from each live fetus, each fetus was separated from its placenta and weighed, and each placenta was dissected from the endometrium and weighed. The total number of live (determined by the presence of a heartbeat) and dead fetuses and the number of corpora lutea (CL) were recorded for each gilt.