Comparison of two processing systems for bull semen with regard to post-thaw motility and nonreturn rates

Two semen processing systems based on either skim milk-yolk extender or Biladyl(R) were compared with regard to post-thaw motility and nonreturn rates. The skim milk-yolk extender contained penicillin and streptomycin, while Biladyl(R) consisted of tylosin, gentamycin, spectinomycin and lincomycin. The dilution of semen involved a 2-step procedure for both extenders. The second dilution with the skim milk-yolk extender took place at 5 degrees C, while the Biladyl(R) extender was processed at room temperature. In this study 197 ejaculates from 45 Norwegian Cattle bulls were used. The ejaculates were split-sampled and diluted with the 2 extenders. A total of 41,445 first inseminations was recorded, 21,035 with semen diluted with skim milk-yolk and 20,410 with Biladyl(R). The 60-d nonreturn rates were 73.1 and 71.9% for skim milk-yolk and Biladyl(R), respectively. The results for skim milk-yolk were significantly better than for Biladyl(R) (P<0.01). No difference in post-thaw motility for these extenders was found.