Improvement of sperm sorting eficiency and fertilizing capacity employing two variations of a new bul semen extender (Sexces®).

The aim of the present study was to analyse the effect of temporary chemical inhibition of sperm motility before and during flow cytometrical sorting on the quality and fertilizing capacity of sex sorted and frozen/thawed spermatozoa. The quality and fertilizing capacity of temporarily immobilized spermatozoa sorted in the presence of sodium fluoride (S-AO-NF) was compared with sorted semen using a standard protocol as developed in our laboratory (S-AO) and with unsorted control (C). Semen from two bulls (Holstein Friesian and Limousine) was used and in total 283 first inseminations with 2 million live, frozen/thawed sex sorted and unsorted spermatozoa were performed on 197 farms. Motility of spermatozoa was completely inhibited after addition of sodium fluoride and after sorting and centrifugation returned to a similar degree as before. Motility after thawing and incubation at 37 C did not differ between groups. After further incubation at 37 degrees C for 12 h and 24 h motility was significantly higher (P < 0.001) in both sorted groups compared to unsorted semen. The percentage of spermatozoa with acrosome abnormalities in frozen/thawed samples was significantly higher (P < 0.05) in S-AO and C group when compared to S-AO-NF group. The same difference was found for morphological sperm abnormalities. The percentage of acrosome reacted and viable spermatozoa was analysed by FITC-PNA/PI staining. The percentage of acrosome reacted spermatozoa was significantly lower (P < 0.001) in both groups of sorted semen when compared to unsorted control. The percentage of viable spermatozoa was significantly higher (P < 0.05) in the S-AO-NF group when compared to groups S-AO and C. Pregnancy rates after artificial insemination with the frozen/thawed semen were not significantly different between sorted spermatozoa and controls (72.7% vs. 73.3% vs. 79.2% for S-AO-NF, S-AO and C respectively).