Reduced sperm DNA longevity is associated with an increased incidence of still born; evidence from a multi-ovulating sequential artificial insemination animal model

Stephen D. Johnston, Carmen López-Fernández, Francisca Arroyo, Altea Gosálbez, Elva I. Cortés Gutiérrez, Jose-Luis Fernández, Jaime Gosálvez

Using a rabbit model, we assessed the influence of sperm DNA longevity on female reproductive outcomes. Semen was collected from 40 bucks, incubated at 38 °C for 24 h, and the rate of sperm DNA fragmentation (rSDF) was determined using the sperm chromatin dispersion assay. Males were allocated into high rSDF (>0.5 units of increase per hour) or low rSDF (<0.5 units of increase per hour) groups. High and low rSDF semen samples were sequentially artificially inseminated into the same doe to reduce female factor variability, and pregnancy outcomes were recorded. While there was no difference in SDFs between rSDF groups immediately after collection (T0), differences were significant after 2 h of incubation; SDFs determined at collection and rSDF behaved as independent characters (Pearson correlation = 0.099; P = 0.542). Following artificial insemination, the rate of stillborn pups was significantly higher in does inseminated by males with a high rSDF (14/21) compared to those with low rSDF (15/6); (contingency χ(2) 5.19; p = 0.022). The risk of stillborn when low rSDF rabbits were used for insemination was 0.16, but increased to 0.36 when high rSDF animals were used (odds ratio = 2.85; 95 % confidence interval = 1.4-2.7). Dynamic assessment of SDF coupled with natural multiple ovulation, high fecundity of the rabbit and control over female factor influence, provided a useful experimental model to demonstrate the adverse effect of reduced sperm DNA longevity on reproductive outcome.