Effect of prostaglandin F2 alpha administration on early pregnancy in ewes

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)