Abstract
Twenty-eight ewes were assigned randomly to seven groups (four ewes each) and six of the groups were injected, intramuscularly on day 8, with one of the following doses of prostaglandin F2α (PGF2α): 0 (vehicle only), 1, 2, 4, 6, or 8 mg (Experiment 1). Ewes in the remaining group were untreated. In a second project (Experiment 2), four groups of ewes (four ewes each) were given intramuscular (IM) and intrauterine (IU) injections on day 8 as follows: 1) vehicle IM, vehicle IU (controls); 2) 2 mg PGF2α IM, vehicle IU; 3) 6 mg PGF2α IM, vehicle IU; or 4) vehicle IM, 2 mg PGF2α IU. In Experiment 1, injection of either 6 or 8 mg PGF2α IM shortened (P < .05) the mean length of the treatment estrous cycle and the interval from day 8 to return to estrus. Mean lengths of these two end points were not significantly different among the other five groups (control, 0, 1, 2, or 4 mg). Length of the post-treatment estrous cycle was not significantly altered by PGF2α treatment. In Experiment 2, average corpora lutea (CL) weight was less(P < .05) for each of the groups treated with PGF2α than for the control group. However, the average CL weight was less (P < .05) in ewes given 6 mg PGF2α IM (group 3) or 2 mg PGE2α IU (group 4) than in ewes given 2 mg PGE2α IM (group 2). Average CL weight did not differ significantly between group partial 3 (6 mg IM) and 4 (2 mg IU). The luteolytic effect of PGF2α was more pronounced when given locally (IU) than when given systematically (IM). Copyright © 1973. American Society of Animal Science . Copyright 1973 by American Society of Animal Science.