Active or passive immunization against an ovarian steroid, androstenedione, to improve reproductive performance in sheep and goats

Abstract

Ovulation rate is increased, although seldom over two. It results in an increase in litter size through an increased proportion of twin born. This increase is usually higher when the treated ewes are of poor natural prolificacy. Fertility is not affected by immunization provided the booster to mating time interval is at least three weeks. When analyzed for a given litter size, birth weight is unaffected by immunization. The growth rates of young born from immunized or control ewes are usually close. The onset of puberty is also unaffected by immunization. Hence immunization may be a valuable technique for sheep breeders.