The value of microscopic semen motility assessment at collection for a commercial artificial insemination center, a retrospective study on factors explaining variation in pig fertility.

This study was conducted to evaluate the relationship between boar and semen related parameters and the variation in field fertility results. In 8 years time semen insemination doses from 110 186 ejaculates of 7429 boars were merged to fertility parameters of inseminations of 165 000 sows and these records were used for analysis. From all ejaculates boar and semen related data were recorded at the artificial insemination (AI) centers. Fertility parameters, such as farrowing rate (FR), ranging between 80.0% and 84.0%, and the total number of piglets born (TNB), ranging between 12.7 and 13.1, were recorded and from these the least square means per ejaculate were calculated. Only 5.9% of the total variation in FR was due to boar and semen variability of which 21% (P 0.0001) was explained by genetic line of the boar, 11% (P 0.047) was explained by laboratory technician, and 7% (P 0.037) was explained by the AI center. For TNB the total variation was 6.6% boar and semen related of which 28% (P 0.0001) was explained by genetic line of the boar and 7% (P 0.011) was explained by the AI center. Only 4% of the boar and semen related variation was caused by sperm motility (microscopically assessed at collection, ranging from 60% to 90%). Other variation in FR and TNB was explained by management and semen related parameters (age of boar, 3%; P 0.009; and 8%; P 0.031, respectively), days between ejaculations (1%; P 0.0001 of FR), number of cells in ejaculate (1%; P 0.042 of TNB), year (9%; P 0.032), and 13%; P 0.0001, respectively), and month (11%; P 0.0001; and 5%; P 0.0001, respectively). Although semen motility is considered an important parameter to validate the quality of the ejaculate processed, it only minimally relates to fertility results under the current Dutch AI practice. Other boar and semen related parameters, like genetic line of the boar, are more relevant factors to select boars for AI purposes