Cooled semen artificial insemination in donkeys: field results

Semen cooling and artificial insemination (AI) in small populations and endangered breeds allow a better gene distribution reducing inbreeding. Data on field fertility after AIs with cooled donkey semen are scarce. The aim of this study was to evaluate retrospectively the results obtained in the field after AIs performed by several clinicians with cooled semen obtained from five Amiata donkeys and produced by the Semen Production Centre of Region Tuscany between 2004 and 2014. Overall, from 63 ejaculates, 68 semen doses were obtained to be used in 40 females (31 jennies and 9 mares). Semen doses contained between 1 × 109 and 3 × 109 spermatozoa with >80% total motility and >55% progressive motility (CEROS 12.1 Hamilton Thorne Research, Beverly, MA), diluted in either INRA82EY (n = 5) or INRA96®. Jennies were inseminated for a mean of 1.52 cycles/season and in 8 cycles two semen doses were requested. The following per-cycle and per-season pregnancy rates (39.6% and 61.3%) and per-cycle and per-season foaling rates (34.9% and 51.7%, respectively) were obtained in jennies. With a single AI/cycle, the number of spermatozoa per semen dose (≤1500 × 106 or ≥2000 × 106) had not a statistically significant effect on per-cycle pregnancy rate (25.0% and 38.5%, respectively). Two AIs/cycle resulted in a 50% pregnancy rate. Transport time (used on the same day or shipped overnight) had no effect on pregnancy rate (33.3% and 44.4%, respectively). In mares, per-cycle and per-season pregnancy rates (63.6% and 77.8%, respectively) were not statistically different from those observed in jennies (p > 0.05). In conclusion, cooled donkey semen can be used in the field for AIs of both jennies and mares with acceptable results (Funding: Ente Terre Reginali Toscane).