In vitro assessment of sperm quality from rams of high and low field fertility.

The aim of the present study was to investigate whether differences in field fertility of rams are reflected in differences in several sperm quality parameters. Ejaculates from 8 adult rams, 4 with high and 4 with low field fertility, were collected weekly using an artificial vagina over 6 consecutive weeks. Analyses of sperm motility by computer-assisted sperm analysis (CASA), membrane integrity by acridine orange-propidium iodide combination and sperm DNA fragmentation using the sperm chromatin dispersion test (SCD) were performed at 0, 3, 6 and 24h of incubation at 37°C. Sperm nuclear morphometry was also determined at 0h by computer-assisted sperm morphometry-fluorescence (CASMA-F). Sperm viability and most CASA sperm motility parameters were higher at 0, 3 and 6h in the high fertility rams. These rams had also a higher sperm nuclear area, perimeter and length (P<0.05) determined by CASMA-F. Significant differences between high and low fertility groups were also found in the dynamics in DNA fragmentation, with significant differences at 6h (14.42±1.40 and 20.27±1.77, respectively, P<0.05) and at 24h (22.32±2.03 and 31.24±2.54, respectively, P<0.01). It was concluded that high and low fertility rams present clear differences in several sperm quality parameters. This opens up the possibility of selection of males for artificial insemination based on sperm quality data.