Embryo recovery results in Hispano-Arabe horse and Spanish donkey breeds

This study was carried out as part of an embryo preservation program undertaken among Hispano-Arabe (H-a) mares and Spanish (Andalusian and Zamorano-Leones) jennies, both considered to be endangered breeds. Over the course of six years, 61 donor mares and 17 donor jennies were monitored and inseminated with chilled semen from 17H-a stallions and six jackasses. A total of 199 uterine flushings (140 in mares and 59 in jennies) were carried out and the embryo recovery rate was recorded and the effect of various factors such as embryo quality and size, flushing effluent quality and individual effects were analyzed. The ovulation rate was significantly lower in donor mares (1.12) than in jennies (1.86) (p < 0.001). Embryo recovery per flush was 35.0% and 40.7% in mares and jennies respectively (p > 0.05), and it was influenced by photoperiod (p < 0.05). Individual effects were also noted for different stallions and jackasses. The embryo size was significantly affected by day of flush (p < 0.05) and embryo morphology (p < 0.001). While the effect of a range of variables is described in this study, it is important to emphasize that the endangered nature of the breeds concerned makes it harder to obtain acceptable results in an embryo transfer program, because it is difficult to select the best animals (donors, recipients and stallions), and this may play a role in the results obtained. However, it is necessary to continue the research in this field in order to improve the tools needed to preserve the pool of genetic heritage and diversity.