Maya Robertson, Eloise Spanner, Simon de Graaf and Jessica Rickard
Laparoscopic artificial insemination (AI) is an advanced reproductive technology that utilises frozen-thawed semen for the widespread dissemination of elite sire genetics. However, recent reports within the sheep industry have indicated significant variation exists between AI programs recording varying pregnancy rates. A potential source of the variation seen in AI success can be attributed to sire fertility and, more specifically, factors of poor semen quality, including abnormal sperm morphology and deoxyribonucleic acid (DNA) fragmentation. The correlation of these two factors and their impact on laparoscopic AI success rates have yet to be investigated in sheep. As such, in the present study, we aimed to examine the impact of DNA integrity and morphology on pregnancy rates in sheep following laparoscopic AI. Frozen semen from sires (n=255) used in industry AI programs (n=20) across two breeding seasons were analysed. Using Acridine Orange (AO) staining, DNA fragmentation at 0 and 6 hours, post-thaw, and subjective morphology for each sire were measured and compared to the corresponding pregnancy outcome. Statistical analysis revealed fertility to be significantly impacted by DNA fragmentation at 0 (P = 0.00865) and 6 hours (P = 0.02676). However, these results were found to have limited biological influence due to the small group sample size, causing substantial standard error. A significant increase in DNA fragmentation by 3% at 6 hours was observed (P<.0001). A moderate correlation was also seen between morphology and DNA integrity at 0 hours (r = 0.53), suggesting morphology could predict estimated DNA fragmentation in industry semen assessment if strengthened with more data. These results infer that with more data and the inclusion of other semen quality factors, morphology and DNA integrity may serve as valuable criteria for screening sires for their fertility potential, therefore reducing pregnancy variability and improving AI outcomes to maximise genetic gain throughout the Australian sheep industry.