RESUMO
A simple and rapid flow cytometric method has recently been developed for simultaneous determination of sperm concentration and viability in semen from domestic animals. Use of SYBR-14 trade mark in combination with propidium iodide (PI) allows estimation of the proportion of live sperm (viability). An internal standard of fluorescent microspheres (beads) makes it possible to determine the sperm concentration during the same analysis. In the first experiment, the relationship between sperm viability and litter size was investigated. The second experiment explored whether a smaller variation in the number of motile sperm per insemination dose could be obtained using the FACSCount AF flow cytometer than using a spectrophotometer. Results in the first experiment show that sperm viability is closer related to litter size than is the traditionally used motility parameter. Although the flow cytometer is precise and objective, a limited effect on litter size should be anticipated if ejaculates are selected for insemination according to the percentage of viable sperm. However, the present trial used large insemination doses (2.3 x 10(9) motile sperm/dose) which partially compensate for the differences in motility and viability between boars and ejaculates. In the second experiment it was found that variation in the number of motile sperm per insemination dose could be reduced significantly if the FACSCount AF flow cytometer rather than the Corning 254 spectrophotometer was used for determination of sperm concentration in the raw semen. It is concluded that the FACSCount AF flow cytometer is a strong tool for improvement of the quality control in artificial insemination (AI) centres.