L’effet mâle chez les ovins de la race Rembi

Abstract

During these last years, the requirements of mastering the reproduction to increase the return of flocks of sheeps led the stock breeders and researchers to give more importance to distinctive methodes of induction and heat synchronizations. Currently, it is the only practice that allows inducting and gathering the heats out of peak-season without resorting to hormones. In order to get « natural » products. This study has been undertaken in the state farm « Cherif El Dine » in Sougeur’s region and the experimental farm of the Institute of Veterinary Science, both farms are situated in Tiaret. This study examines the evaluation of Rembi ewe’s responses to male effects after the separation of rams as far as it is an ongoing technique that controls reproduction, thus the comparison of these performances concerning ewes within the same race, however the male is permanently present. Our research has been carried out in three months, it is devided in two parts : 1. The first part has carried 10 female of the same race of the state farm « Cherif El Dine ». It evaluates the performances of reproduction in particular cyclicality and pregnancy after the application of male effect by measuring serum progesterone after realization of blood samples 2. The second part just as well carrying 10 ewes takes place in the experimental farm of the Institute of Veterinary Science where these ewes were not seperated from males. Blood samples for progesteroneemia have been done. Putting rams with a group of ewes in anovulatory anoestrus in two to four days leads to a silent ovulation, this is to say not associated with a behavior of heat, followed by either ovulatory cycle of normal duration ( approximately seventeen days ) then, a new ovulation associated with a behavior of heat, or a short ovulatory cycle yet constant( six days) followed by a new ovulation, after a cycle with a normal period by new ovulation associated with a behavior of heat. This study presents the acquired knowledge during the last years on the physiological mechanisms involved in ovulation induction by male effect and gives it some rules of using this methodes in breeding, while specifying its limits. The two main parts to use effectivelly this technique are : on the one handknowledge of the reproductive ability (seasons) of the breed in its environment, and on the other hand the possibility of separating males from females for a minimum period of two months prior to their physical contact. After obtaining progesterone test results; It was found that the ewes separated from the male all had values greater than or equal to 0.5 ng / ml; Generally, progesteroneemia ranged from 0.503 ng / ml as a minimum value to 20.66 ng / ml as the maximum value which allowed them to have a percentage of 100% gestation. On the other hand for ewes not separated from the male, their progesterone results show that three ewes have values of less than 0.5 ng / ml and which are: 0.28, 0.331 and 0.348 ng/ml. The residues (07 ewes) have values ranging from 0.754 and 12.8 ng/ml. So the percentage of empty females is 30% whereas that of those who are pregnant is 70%. These results would argue in favor of the hypothesis of a male effect as the current technique of reproductive control.