An investigation of boar sperm motility using a novel computerized analysis system

A novel computer-assisted sperm analysis (CASA) system was validated and used to investigate the value of sperm motility in predicting the fertility of semen samples. Appropriate Hobson Sperm Tracker set-up parameters were derived for the analysis of boar spermatozoa and techniques developed to facilitate CASA analysis of this species. The accuracy and precision of the system were evaluated and minimum sperm number and minimum velocity criteria were developed to ensure the quality of the analyses performed. Relationships between the CASA measurements were investigated and ejaculates compared before and after storage. Cluster analysis of the track data was performed to investigate whether sub-populations of sperm could be distinguished. Using this methodology, hyperactivated boar spermatozoa could be identified from the quantitative analysis of motility data. The motility characteristics of semen samples during incubation at 39°C were compared to data from two artificial insemination trials. Each employed a controlled sperm dose (1.5 × 109 spermatozoa) and standardized semen preparation and insemination protocols. The results revealed a significant relationship between sperm motility measurements and the fertility data (maximum correlation with average litter size P=0.007; maximum correlation with non-return rate P=0.00002). Overall, sperm velocity over a two hour incubation period proved to be the most informative motility characteristic. The quality of sperm motility is altered on interaction with the zona pellucida and objective analysis of this response might be useful for fertility estimation. Zonae ghosts were collected and solubilized; the addition of this preparation to boar sperm samples severely impaired motility and prevented analysis using the Hobson Sperm Tracker. Further experiments indicated that this was a calcium-dependent effect. This research supports the hypothesis that sperm movement characteristics are indicative of fertility.