Physiology and Endocrinology: Reproductive Endocrinology

The aim of the present study was to investigate the endocrinology of periestrus period and the days after until estrus in ewes (n = 40) synchronized out of breeding season and diagnosing the related pregnancies after laparoscopic insemination comparing to different doses of PMSG that was used. Animals treated for 12 d with CIDR followed by administration with different doses (0, 450, 550, 650, 750, 850 IU) of PMSG after CIDR withdrawal. Number of ewes in each group was 7 except for control group that was 5. 48 h after CIDR removal, ewes were inseminated by frozen semen using laparoscopy method. Blood samples were collected once daily from the jugular vein into heparinized tubes beginning at day CIDR removal until the day of estrus. Plasma was harvested and stored at −20°C until progesterone or estradiol assay. Concentrations of progesterone (Progesterone RIA, Biosource, Belgium) and estradiol (estradiol RIA, Biosource, Belgium) were determined. Pregnancies were diagnosed using ultrasonography at d 30 following insemination in ewes. Progesterone levels did not differ between groups during periestrus period. Estradiol levels also did not differ between groups during the days CIDR removal and one day later. However, estradiol levels in the control group comparing to groups 550 and 850 was significantly lower and higher (control: 12.14 pg/mL, 550:19.91 pg/mL, 850:8.98 pg/mL) at estrus, respectively. Pregnancy diagnosing showed that, the number of nonpregnant ewes was lower in group 550 and higher in group 850 comparing to control group (control:3, 550:0, 850:4). The result of this study demonstrated that 550 IU PMSG would be the best dose to increase the plasma estradiol at the onset of estrus and also for synchronizing Shall ewes out of breeding season and have the best lambing rate in this breed.