Aspects of controlled reproduction in sheep and goats

Controlled reproduction in small ruminants is an important economic factor. Of major interest is estrus induction or synchronization as a prerequisite for timed insemination, as well as the control of seasonality and the increase of numbers of offspring, which can be achieved by medication or bytaking advantage of biological effects. The aim of the review is to summarize standard techniques and research efforts in controlled reproduction in sheep and goats under consideration of the advances of knowledge in reproductive physiology. Estrus induction or synchronization is usually performed by manipulating or simulating the luteal phase of the cycle with exogenous progestagens, or with prostaglandin analogues in order to induce premature luteolysis in the presence of functional corpora lutea, while ovarian follicular development is enhanced with pituitary or extrapituitary gonadotrophins. Fertility reported following application of controlled reproductive techniques varies noticeably. This might be a result of failures in follicular development, gamete transport and fertilization, increased embryonic mortality, premature corpus luteum regression, or from species and breed differences. In order to improve pregnancy rates subsequent to timed artificial insemination, international research efforts concentrate on the establishment of optimal dose levels and of shortened synchronization protocols for estrus and ovulation under consideration of the ovarian dynamics. In Germany the availability of pharmaceuticals for small ruminants is restricted by national guidelines. This limits the use of controlled reproduction in these species.