| Abstract: | Two trials were conducted with ewes to determine the effects of prostaglandin F2 alpha (PGF) administration during the first week of gestation. In trial 1, ewes (n = 134) were checked for breeding activity once daily and half of them received 10 mg PGF im at either 0, 24, 48, 72, 96, 120 or 144 h after detection of a breeding mark. The other half served as uninjected controls. In trial 2, ewes (n = 153) were checked for breeding activity twice daily. Two-thirds of the ewes received 10 mg PGF at either 24, 36, 48, 60, 72, 84, 96, 108, 120 and 132 h following detection of a breeding mark. The other one-third of the ewes served as uninjected controls corresponding to treatment times of 24, 48, 72, 96 or 120 h. In trial 1, the percentage of ewes lambing as a result of first service decreased as time of administration of PGF increased. The first-service pregnancy rate was 87.5% for ewes given PGF at 0 h and 0% for ewes given PGF at 144 h. Fewer (P less than .05) ewes given PGF at 96, 120 or 144 h after first mating lambed than control ewes. Similarly in trial 2, fewer (P less than .05) ewes given PGF at 96, 108, 120 or 132 h after first mating lambed than did controls. The total number of ewes lambing as a result of the entire breeding season did not differ (P greater than .05) between treated and control ewes in trial 1 (88.2 vs 87.3%) or trial 2 (85.7 vs 83.3%).(ABSTRACT TRUNCATED AT 250 WORDS) |
