Ram seminal plasma improves pregnancy rates in ewes cervically inseminated with ram semen stored at 5 °C for 24 hours

In this study, we compared pregnancy rates obtained using ram semen stored at 5 °C for 24 h, with ram or bull seminal plasma (SP) added to TRIS-egg yolk extender. During the breeding period, 670 adult Corriedale ewes were cervically inseminated with semen (2 × 10⁸ sperm in a volume of 0.2 mL) from eight adult Corriedale rams. Ejaculates, obtained using an artificial vagina, were split into three aliquots and diluted with the following: TRIS-egg yolk based extender (T), T + 30% ram SP (R), or T + 30% bull SP (B). Samples were refrigerated and stored at 5 °C for 24 h until used for AI. Pregnancy was assessed by ultrasonography 35 to 40 d after AI. Pregnancy rate was not affected by ram (P = 0.77) or breeding period (P = 0.43), and there were no interactions between extender and ram (P = 0.94), or extender and breeding period (P = 0.24). However, there was an effect of extender (P = 0.0009) on pregnancy rates; ram SP, but not bull SP, increased pregnancy rates compared with extender without SP (49.7, 38.1, and 31.1%, for R, B, and T respectively). In conclusion, ram SP added to TRIS-egg yolk extender had a beneficial effect on the pregnancy rate of ram sperm stored at 5 °C for 24 h and used for cervical insemination of ewes.     

Artificial insemination of sheep: Effects on fertility of number of spermatozoa inseminated and of storage of diluted semen for up to 18 hours at 5°C

Ram semen was prepared in a buffered glucose-saline solution containing 3% (v/v) egg yolk so that insemination doses of 25 or 100 million spermatozoa in volumes of 50 or 250 μl could be given per ewe at artificial insemination (AI). Fertility was significantly reduced by dilution and, within the treatments of diluted semen, significantly higher lambing rates followed the use of doses of 100 million spermatozoa. The volume of the AI dose had no significant effect on fertility.Of 945 inseminations performed using diluted semen, 388 were with samples that had been cooled to 5°C and stored chilled for 5 or 18 hr. The mean lambing result of 40% for freshly diluted semen was significantly higher than 31.6% and 30.2% for samples stored chilled for 5 and 18 hr respectively. Ewes inseminated with doses of chilled semen containing 25 million spermatozoa had a low lambing rate of 21.3%. The presence of 7.5% glycerol (v/v) in the diluent did not significantly affect the fertility of chilled semen.