Effect of passive immunization with different doses of anti-testosterone antiserum on the reproductive performance of Scottish Blackface ewes in different levels of body condition at mating

Abstract

ABSTRACTThe effect of injection of 0, 0·5, 1·0, 1·5, 2·0 or 5·0 × standard doses of anti-testosterone antiserum on the reproductive performance of Scottish Blackface ewes was investigated using a total of 423 ewes with body condition scores ranging from < 2·00 (low) to > 2·75 (high). Increased mean litter sizes and lambing rates were obtained in ewes in all levels of body condition following immunization with a range of antibody doses (P < 0·05). However, it is concluded that there is an intermediate optimum dose, probably approximately 1·5 × standard doses, for ewes of this breed, at a non-synchronized mating. The limiting effect of body condition on reproductive performance could not be completely overcome by increasing the antibody dose. Circulating antibody titres were directly related to the dose administered but there was no direct relationship between circulating titre and reproductive performance.