Studies on motility and fertility of cooled stallion spermatozoa

This study on extended, cooled stallion spermatozoa aimed to compare the ability of three extenders to maintain sperm motility during 24 h of preservation, and to describe pregnancy and foaling rates after artificial insemination (AI) of stallion spermatozoa stored and transported in the extender chosen from the in vitro study. After 6 and 24 h of preservation, motility, both subjective and evaluated by the motility analyzer (total, progressive and rapid), was lower in non-fat, dried skim milk glucose than in both other extenders: dried skim milk-glucose added to 2% centrifuged egg yolk, and ultra high temperature treated skim milk-sugar-saline solution added to 2% centrifuged egg yolk (INRA82-Y). Rapid spermatozoa and sperm velocity parameters, after 24 h, were significantly higher in INRA82-Y. In the fertility trial, semen collected from three Maremmano stallions, diluted in INRA82-Y, and transported in a refrigerated Styrofoam box, was used to inseminate 56 mares of the same breed. Pregnancy rates after the first cycle and per breeding season were significantly higher for the 31 mares inseminated in three AI centres (54.8 and 80.6%, respectively) than for the 25 mares inseminated at the breeder's facilities (28.0 and 52.0%). Foaling rates were not significantly different between the AI centres mares (54.8%) and the other mares (44.0%). In conclusion, INRA82-Y yielded satisfactory pregnancy and foaling rates, especially when employed in the more controlled situation of an AI centre, and can therefore be included among those available for cooled stallion semen preservation.