Abstract
This study was conducted to research the endocrine mechanisms of postpartum anestrus and determine if the morphology of the CL could be related to function in Korean native goats. At parturition 48 goats were assigned to a nonsuckled group and a suckled group. Serum concentrations of luteinizing hormone(LH), follicle stimulating hormone(FSH), prolactin(PRL), estradiol-17$\beta$(E2) and cortisol were measured at various times after parturitionin the goats. The corpora lutea of pregnancy were examined by a light microscope on the 6th hour and the first, 3rd, 10th, 11th, and 21st days after parturition. The results were summarized as follows : Mean serum LH concentrations were lower after parturition in all treatments and increased gradually with the intervals after parturition(P<0.01). These values did not differ between groups. The levels of serum FSH were lower after parturition and tended to increase gradually between 2 and 21 days. The levels of serum FSH are not significantly different between the groups of goats. Two days after kidding mean levels of serum PRL began to fall in nonsuckling goats but increased in suckling goats. During 3 weeks serum PRL concentrations were different between nonsuckling and suckling goats(P<0.01). Three days after parturition the levels of serum E2 decreased in all treatments. From parturition to day 21 serum E2 concentrations were greater in nonsuckling than in suckling goats(P<0.01). At the sixth hour after parturition the structure of the CL was well preserved. At days 1 and 3 the blood vessels were sparcely distributed, whereas, at days 1 and 3 the blood vessels were sparcely distributed, whereas, at days 10, 11 and 21 tortuous larger vessels with thick walls were observed on the luteal tissue. At days 1, 3, 10, 11 and 21 after parturition the CL of pregnancy showed degeneration and the proportion of tissue occupied by intercelluar substances increased at days 21 postpartum. In conclusion, the present study has shown that regression of the CL of pregnancy is accelerated in the period after parturition and effectively completed within three weeks postpartum.