Hormonal control of oestrous cycle in the ewe (a review)Contrôle hormonal de l'oestrus chez la brebis: revueHormonelle Kontrolle des Brunstzyklus beim Mutterschaf |
| |
| Authors: | J Thimonier |
| |
| Institution: | INRA Station de Physiologie de la Reproduction, 37380 Nouzilly, France |
| |
| Abstract: | During the cycle, the secretion of progesterone by the corpus luteum inhibits the positive feedback of oestrogens and thus prevents the LH discharge, and also primes the central nervous system for oestrous behaviour. Prostaglandin F2α has been identified as the hormone produced by the uterus which causes luteal regression. The LH discharge leading to ovulation follows the demise of the CL. None of the characteristics of the LH surge (duration, maximum level, total release) can be related to ovulation rate. However, the interval from onset of oestrus to the beginning of the LH discharge is greater in highly prolific breeds than in less prolific ones.The knowledge of these physiological processes leading to oestrus and ovulation makes possible the control of ovarian activity in the ewe. In cyclic females, the control of the timing of the LH discharge and ovulation can be obtained either by inducing luteolysis with PGF2α or its synthetic analogues after day 4–5 of the cycle, or by artificially lengthening the luteal phase with exogenous progesterone or progestagens.During the seasonal and post-partum anoestrus, PGF2α is ineffective and progesterone or progestagens alone are generally unable to induce oestrus and ovulation. Addition at the end of progestagen treatment of inducers of follicular growth and LH release is necessary. Both PMSG and synthetic GnRH are used for this purpose. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
