A novel automated fluorometric assay to evaluate sperm viability and fertility in dairy bulls

The artificial insemination (AI) industry is in need of an objective and ra pid, but inexpensive method to evaluate frozen thawed bull semen ejaculates . This study presents a new fluorescence method that uses an automatized fl uorometer and fluorophore stain propidium iodide that stains only those cel ls with damaged membranes. The fluorescence of the semen sample and the tot ally killed subsample were measured simultaneously, and viability was calcu lated. Every semen batch was analyzed before use in Al. For fertility evalu ation, the nonreturn rates (NR%) obtained from 92,120 inseminations with th e analyzed batches were recorded from 166 bulls (436 batches). This study c onfirms a 3.9% better NR% for the Finnish Holstein-Friesian breed than for Finnish Ayrshire. There was a clear seasonality in NR%: it differed (5.3%) significantly, being best in summer to autumn (June to October) and lowest in winter (January to March). The fluorometer method was fast and easy. The correlation between the total number of viable spermatozoa in an insemination dose and field fertility w as low but significant (r=0.051, P=0.016), suggesting that the plasma membr ane integrity evaluation can serve as a cost-beneficial quality control met hod of frozen-thawed semen at bull stations. (C) 2001 by Elsevier Science I nc.