Compensability of morphological sperm defects: A basis for the revision of minimum requirements for the use of boar semen

It is well known that some sperm deficiencies can be compensated by an increase of sperm numbers in the insemination portion so that fertility is not affected. The situation, however, is less clear for re-tained cytoplasmic droplets (CD) which present the most common sperm abnormality in boar semen. Current minimum requirements defined by the German Livestock Association (BRS e.V.) set 15% of sperm with CD as the upper limit for useable boar semen. We hy-pothesized that a higher prevalence of CD can yield high fertility by compensation with high sperm numbers. Retrospective analysis of extended spermatology from 130 young boars and field insemi-nation data (n = 1497 sows) using breakpoint analysis and group comparisons with Dunn's Multiple Comparison Test showed high farrowing rates and litter sizes in the three groups with low (<10%), moderate (10%–15%) and high (>15%) prevalence of sperm with CD. Interestingly, a slightly higher farrowing rate (p < .001) was seen in the high CD group compared to the low and moderate CD groups, which coincided with a higher motility (p < .001) and a higher re-sistance to thermic stress (p < .001). Sperm numbers per dose were ≥2 × 109 sperm and had no effect on fertility. In conclusion, these results together with our previous single-cell observation on high motility of CD-bearing sperm (Henning et al., under review) prompt to revise the current minimum requirements for useable boar semen, ideally with consideration of motility, resistance to thermic stress and a minimum sperm number per insemination dose.