Luteal function and blastocyst development in ewes following treatment with PGF 2α and GnRH

Abstract

Luteal function and blastocyst development were compared in ewes treated with GnRH (100 μg) on Day 1 (Day 0 = day of estrus) or in ewes previously induced into estrus with PGF 2α. In Experiment 1, the duration of estrous cycles of ewes previously treated with PGF 2α were longer (P<0.06) than those that received PGF 2α plus GnRH, GnRH alone, or remained untreated (control) ewes. Progesterone concentrations were lower (P<0.07) on Day 1 and higher (P<0.01) on Days 16 and 17 of the estrous cycles following PGF 2α treatment relative to those of the natural (control) cycles. In Experiment 2, blastocysts of ewes treated with PGF 2α were less developed (P<0.06) by Day 13 of pregnancy than those of the control ewes. The GnRH treatment did not influence any of these characteristics. Treatment with PGF 2α delayed luteal formation during the subsequent estrous cycle, increased the duration of the estrous cycle and slowed the rate of blastocyst development relative to GnRH-treated and untreated ewes.