Could an extra long-term boar semen extender be successfully used during liquid storage of ram semen at 15°C?

The aim of the present study, was to verify, whether, a commercial diluent (Duragen: an extra long-term boar semen extender) could be a good alternative to skim milk (SM) and Tris-egg yolk (TEY) to store ram semen at 15°C. Ejaculates were collected once a week during 6 weeks from two different local Moroccan breeds (Boujaad a nonprolific and INRA180 a prolific sheep) using an artificial vagina. The ejaculates containing spermatozoa with >80 % total motility and concentrations higher than 3 x 109 spermatozoa/ml were pooled. The pool was divided to three parts and each part was extended in TEY, SM or Duragen (Duragen; Magapor S.L.; Zaragoza, Spain) to reach a final concentration of 0.8 × 109 spermatozoa/ml. The Sperm motility (proportion of total and progressive motile sperm) was assessed by means of a computer-assisted semen analysis (CASA) (ISAS, version 1.0.17, Proiser, Valencia, Spain) at different periods (0, 8, 24h). The sperm viability (VIA), the morphology of abnormal spermatozoa (ABN); the hypoosmotic swelling test (HOST); the spontaneous lipid peroxidation (thiobarbituric acid reactive substance: TBARS) and DNA fragmentation tests are in progress to complete the evaluation of semen quality. All data were analyzed using the Statistical Analysis System software JMP (SAS version 10) and expressed as the mean ± SEM. Differences with values of P < 0.05 were considered to be statistically significant. The results of progressive motility (PM) showed that at 0h, there was no different between SM (66.12 ± 0.89%) and Duragen (66.52 ± 0.85%) while the TEY showed the lowest value (54.06 ± 1.71%). At 8h of storage, the best PM was recorded with SM (63.57 ± 0.93%), while Duragen showed 58.90 ± 1.19% and TEY 35.69 ± 1.63%. After 24h of storage, the same tendency was recorded. The SM showed 59.53 ± 1.63% of PM while Duragen gave 48.89 ± 1.51% and TEY showed 34.06 ± 2.05%. Similarly, even at 24h of storage, the SM and TEY gave the best results on terms of total motility (TM) (78.48 ± 1.48%, 76.97 ± 1.44% respectively) while Duragen showed the lowest value (68.41 ± 1.47%). In conclusion, Duragen could be a good alternative to TEY and SM regarding the PM. However, it will not be a good one regarding the TM for both extenders (SM and TEY). Additional tests such as VIA, ABN, HOST, TBARS and DNA fragmentation are in progress to complete the evaluation of semen quality.