277 EFFECTS OF SEMINAL PLASMA ON SEX-SORTING BOVINE SPERM

Abstract

This experiment evaluated how characteristics of bovine ejaculates affect the sortability of X- and Y-bearing spermatozoa. Ejaculates were collected by artificial vagina, 2 each from 10 bulls with an average of 1 h between collections. Only ejaculates with at least 60% motile and 70% normal sperm were used. Semen was centrifuged at 1 000 × g for 15 min to separate sperm from seminal plasma; seminal plasma was clarified by 10 min of additional centrifugation at 2 000 × g. Sperm were rediluted to 160 million sperm/mL with TALP (pH 7.4) and 0, 5, 10, or 20% seminal plasma, from the same ejaculate or reciprocally from first/second ejaculates. Following incubation with Hoechst 33342 for 45 min, an equal volume of TALP (pH 5.5) containing red food dye was added, and sperm were analysed on a MoFlo (Dako, Glostrup, Denmark) flow cytometer for percentage live-oriented cells, X sort rate, coincidence rate, percentage dead or dying (sperm membrane permeable to red dye), and splitability (peaks to valley ratio). The percentage live-oriented sperm was higher for treatments with 0% seminal plasma (64.4%) than for 5 (59.6%), 10 (59.0%), and 20% (57.8%) seminal plasma (P < 0.01). The percentage live-oriented sperm was higher for second (63.0%) than for first ejaculates (56.2%). Sort rate was higher for 0% seminal plasma and second ejaculates (P < 0.05). Dead/dying rates were lower for 0% (16.5%) than for 5 (21.9%), 10 (23.6%), or 20% (23.4%) seminal plasma (P < 0.003); and for first ejaculates (25.9%) compared with second ejaculates (18.2%). Seminal plasma percentage and ejaculate had no effect on splitability, and there was no difference in sorting parameters whether the seminal plasma was from the first or second ejaculate. The initial sperm concentration of the ejaculate (range, 1.3 to 3.4 billion sperm/mL) did not affect any sperm sorting parameter. Thus, effects of sperm concentration on sortability need to be reconsidered, as current practice is to select ejaculates to sort based on initial sperm concentration. The initial pH, percentage morphological abnormalities, initial seminal plasma pH, and age of bull did not affect sorting parameters. In conclusion, the presence of seminal plasma during staining and sorting may decrease sort rate and percentage of live-oriented cells, as well as increase death rate. In addition, sorting second ejaculates may be more advantageous than sorting first ejaculates. Future studies are needed to determine if the results hold true if sperm are stored for several hours and how the various factors affect sperm post-thaw viability.