Comparative Efficacy of Three Semen Extenders for Preserving Bunaji and Friesian-Bunaji Cross Bull Semen during Cooled Storage

Abstract

Artificial insemination (AI) underpins genetic improvement and productivity in livestock, yet its success depends on semen extenders that reliably preserve sperm viability during cooled storage. This study compared the efficacy of three extenders: Tris–egg yolk (TEY), egg-yolk sodium citrate (EYS), and a novel coconut water–egg yolk blend (CWE) in preserving semen quality from indigenous Bunaji and Friesian–Bunaji crossbred bulls. The CWE formulation consisted of 68ml boiled fresh coconut water, 28ml egg yolk, 1.2g Sulphanilamide, 0.24g penicillin, 0.54g Streptomycin, 300ml distilled water. Ejaculates were collected using artificial vagina, extended at a 1:10 semen-to-extender ratio in triplicate, and stored at 4 °C. Samples were evaluated daily for six days, measuring progressive motility, viability (live/dead ratio), morphological abnormalities (coiled and bent tails) and pH stability. Two-way ANOVA with repeated measures were used to analysed data while significant differences were considered at p < 0.05. TEY maintained the highest motility (66.7%) and lowest proportions of dead spermatozoa (33.3%), coiled tails (0%), and bent tails (3.0%) over six days, outperforming EYS (motility 60.0%, dead 40.0%) and CWE (motility 62.5%, dead 37.5%). Crossbred bulls displayed slightly higher baseline motility (80% vs. 75%) than indigenous Bunaji. TEY was recommended for extended cooled storage in AI programmes, while CWE offers a cost-effective, locally available option for same-day inseminations in resource-limited contexts. Three ejaculates were collected on same day from each bull.