Effect of Extender, Storage Time and Temperature on Kinetic Parameters (CASA) on Bull Semen Samples

SIMPLE SUMMARY: The bull accounts for a great part of the economic value of beef herds managed with natural mating, with the Bull Breeding Soundness Evaluation (BBSE) performed in the field becoming essential. Part of the BBSE is the semen-quality evaluation (classical and kinetic parameters) that can be performed in situ (by trained practitioners) or at laboratories, with semen being short-term stored and shipped. The extender used as well as the storage temperature and duration may affect its quality. Thus, our aim was to explore the best conditions to preserve CASA kinetic parameters, to be reliably assessed afterwards. CASA parameters were preserved for up to 4–6 h post-ejaculation, except for AndroMed(®) in most of the parameters. Motility decreased from 4–6 h up to 24 h, with the best values obtained with BIOXcell(®) at 5 °C. The rest of kinetic parameters worsened when analyses were performed at 24 h. Therefore, we suggest evaluating seminal quality as soon as possible. However, using BIOXcell(®), either at 5 °C or room temperature, and INRA96(®) at room temperature, sperm motility can be reliably evaluated for up to 6 h. These results help to fix adequate protocols for the short-term storage and shipment of bovine semen collected under field conditions. ABSTRACT: CASA kinetic parameters are often evaluated in a diagnostic centre. How storage conditions affect ejaculates up to evaluation is unclear. We assessed, in 25 commercial bulls electroejaculated in the field, the impact of time until evaluation (0–2 h, 4–6 h, and 24 h post-ejaculation), holding temperature (5 °C vs. room temperature), and extender (AndroMed(®), BIOXcell(®) or INRA96(®)) on CASA kinetic parameters. Total and progressive motility, VCL, VAP, VCL, ALH, BCF, STR, LIN, and WOB were assessed. CASA kinetic parameters were preserved for up to 4–6 h post-ejaculation, except for AndroMed(®). Regardless of extender or temperature, motility decreased from 4–6 h up to 24 h, with the best values obtained with BIOXcell(®) at 5 °C. Our results suggest that BIOXcell(®) can preserve sperm motility for up to 6 h, either at 5 °C or room temperature, and also INRA96(®) at room temperature, with motility assessments and the percentage of the most rapid sperms being the lowest with INRA96(®) at 5 °C. The kinetic parameters decreased when analyses were performed at 24 h. Therefore, we suggest evaluating seminal quality as soon as possible, before 6 h after collection. These results help to fix adequate protocols for the short-term storage and shipment of bovine semen collected under field conditions.