Utilización de leche descremada ultrapasteurizada como diluyente de semen refrigerado de burro, destinado a la inseminación de yeguas

The objective of this study was to evaluate the use of commercial ultrapasteurized non-fat milk as an extender for donkey semen to be used for the insemination of mares, and to compare it with Kenneys extender, which is widely used for equine semen. A total of 28 mares were used, and divided in two groups. Mares in the control group (n = 11) were inseminated with semen prepared in Kenneys extender, while those in the experimental group (n = 17) were inseminated with semen extended in ultrapasteurized non-fat milk. Semen from a single Kentucky donkey of proven fertility was used in all inseminations. All mares were monitored by ultrasonography in order to identify the optimum time for insemination. Pregnancy diagnosis was carried out 15 days after insemination by the ultrasonographic detection of an embrionic vesicle. Conception rate was 54.5% for the control group, and 76.5% for the mares inseminated with semen diluted in ultrapasteurized non-fat milk. Results of this study suggest that ultrapasteurized non-fat milk can be used to extend equine semen with comparable efficiency to that obtained with chemically defined extenders. The use of commercial milk offers considerable advantages: it is low priced, widely available, remains sterile until opened, and is ready to be used without any further preparation.