Horses and Donkeys are known to differ phenotypically and karyotypically, although they can interbreed freely (Allen et al., Journal of Heredity, 1997;88(5), 384-392). The present study aimed to describe the outcome in terms of pregnancy rates of mares and jennets, after AI with either pooled horse or donkey semen of proven fertility. Semen was collected from four fertile horse (N=2) or donkey (N=2) stallions. Each insemination dose consisted of 1 × 10 9 total spermatozoa, at a 1:1 ratio for the two stallions of the same species, diluted with INRA96 to a final volume of 10 ml and with subjective total motility > 85%. AIs were performed every 48 hours until the detection of ovulation. A first pregnancy diagnosis was performed on day 10 after ovulation and repeated every day until embryo detection or day 16. At the first detection, embryos were collected for other studies. Differences between groups were examined using Fisher's Exact test, and differences were considered statistically significant when P<0.05. Results of the pregnancy rates are presented in Table 1. No statistical differences were found (P>0.05) when comparing interspecific artificial inseminations (mare x donkey versus jennet x stallion), or the male effect (horse versus jack). In the literature, the interspecies mating of a mare to a jack donkey is reported to be as fertileor even more than the intraspecies mating (Allen et al., Journal of Heredity, 1997;88(5), 384-392); by contrast, the cross between the jennet and the horse stallion is reported to be considerably less fertile. In our study, jennets gave much poorer results than mares, and hinny hybrids (jennet x horse) resulted in the lowest number of pregnancies. Further studies are required to better investigate the mechanism involved in this apparently poorly compatible gamete interaction between jennets and stallions.