SERUM PROGESTERONE AND LUTEINIZING-HORMONE IN EWES TREATED WITH PGE(2-ALPHA) DURING MIDGESTATION AND GONADOTROPIN-RELEASING-HORMONE AFTER PARTURITION

Two studies were conducted to determine if postpartum (PP) reproductive function could be enhanced in ewes by PGE;, during mid-gestation (Trial 1) and GnRH within 10 days PP (Trial 2). Trial 1 utilized 31 ewes (($) over bar x body weight = 84 kg) assigned to two treatment groups to receive (I.M.) either saline (control, n = 17) or PGF(2 alpha) (0.24 mg/kg body weight, n = 14) on day 74 of gestation. Results from the first study indicated success in regressing the corpus luteum (CL) of pregnancy as indicated by decreased serum progesterone (P,, P < 0.05) by 24 hours after treatment. In addition, by 20 days after treatment, serum luteinizing hormone (LH) concentrations in treated ewes were higher (P < 0.01) than in controls. However, ovarian activity was not re-established by 30 days PP in this study. In Trial 2, 35 ewes (($) over bar x body weight = 79 kg) were randomly assigned to one of four groups: no treatment (controls, n = 9), PGF(2 alpha) (no GnRH, n = 9), GnRH (no PGF(2 alpha) n = 9) or both PGF(2 alpha) and GnRH (n = 9). The PGF(2 alpha)-treated animals received 0.14 mg PGE(2 alpha)/kg body weight (I.M.) on day 73 of gestation and GnRH-treated ewes received 50 mu g GnRH (I.M.) on days 2, 6, and 10 PP. As in Trial 1, P-4 concentrations in PGF(2 alpha)-treated ewes were lower (P < 0.02) than in control ewes by 24 hours after treatment. Progesterone remained lower in PGF(2 alpha)-treated animals through day 116 of gestation. However, no differences were detected (P > 0.65) in LH concentrations between the two groups in this same period. Likewise, no differences were observed (p > 0.32) in LH concentrations between the PGF(2 alpha)-treated and control ewes on days 2, 6, and 10 PP. However, elevated (P < 0.07) LH concentrations were noted in ewes receiving 50 mu g GnRH compared with ewes not receiving GnRH. In addition, area under the LH curve (AUC) was greater (P < 0.02) for GnRH-treated animals on days 2, 6, and 10 PP and LH AUC increased over the PP period in GnRH-treated ewes. Three of eight ewes receiving both PGF(2 alpha) and GnRH treatments had ovarian activity within 30 days PP as indicated by P-4 concentrations above 1 ng/ml while no other ewes had ovarian activity during this time period.