ET-Technologies in Small Ruminants

Abstract

In the last decades small ruminants have become increasingly important, and nowadays sheep and goat are continuously increasing in the number of breeds and their geographic distribution. An important feature of small ruminants is that they can live and produce on land that is unfavorable for other forms of agriculture. The increase in small ruminant breeding has been supported more recently by the development and improvement of assisted reproductive technologies (ARTs). However, while some ARTs have reached widespread application, including estrus induction, estrus synchronization, and artificial insemination, other ARTs, such as superovulation and embryo transfer, in vitro embryo production, and embryo cryopreservation, are only rarely used. Multiple ovulation and embryo transfer (MOET) programs in small ruminants are usually restricted to few countries and still remain experimental. The success of this technique is unpredictable due to many limiting factors that contribute to the overall results, such as the reproductive seasonality with a long, naturally occurring anestrus period, high variability of the superovulatory response, fertilization failures, and the need of surgery for collection and transfer of gametes and embryos. However recent progress in better understanding of the follicular wave patterns, the elucidation of follicular dominance, and the integration of this information into superovulation treatments are instrumental in predicting good responders and reducing variability. Protocols that control follicular dominance have been developed to allow the initiation of precise hyperstimulation protocols which are designed to recruit and stimulate a homogeneous pool of small follicles that are gonadotrophin responsive, thereby enhancing superovulatory response and embryo yields. Significant improvements in the development of nonsurgical techniques are paving the way to reducing stress and costs of donors and recipient management, indicating the possible repeated use of individual donors. In addition, the progress with IVP embryos generated from adult and juvenile animals, combined with the genomic analysis of economically productive tracts, is opening new perspectives and could be instrumental for improving MOET programs in small ruminants.