Induced estrus in anestrous ewes: using syncro-mate and PMS

The frequency of lambing end the number of lambs born per pregnancy are two factors that affect lambing rate. When the physiological processes involved and their mechanisms of action are more completely understood, it may be possible to control the internal and external environment in a larger proportion of ewes and regularly produce two larabings per year. Two iamb crops per year should be the goal because of the numerous management and economic advantages over other lambing frequencies, such as three lamb crops in two years. The application of this Information might also increase the incidence of multiple births, which is currently low in most breeds. Both selection and hormonal administration are utilized to control the time of onset of estrus and to increase the number of ova shed. Sheep that are bred specially for the purpose of lambing at six to eight month intervals are being developed by the United States Department of Agriculture. Improvement through selection involves many generations and it will take time to develop a satisfactory breed, A more Immediate solution to this problem may reside in successful treatments to control the breeding activity of the ewe. The onset of the breeding season in sheep appears to be a gradual process and it appears that the level of endocrine activity is Perhaps the most important factor responsible for this phenomenon. Environmental factors such as the length of day and temperature are known to influence the onset of the breeding season in sheep and mediate their action through endocrine activity. In the trial described here, an attempt was made to induce estrus and ovulation in anestrous ewes through the use of exogenous hormones.