50 Comparing different semen extenders based on post-thaw sperm motility, kinetics, and quality of caprine semen

Semen cryopreservation and artificial insemination allow for flocks to incorporate genetics from all over the world. This research aimed to compare post-thaw caprine semen characteristics based on the type of extender used during preservation. The hypothesis was that the different extenders would have comparable post-thaw results. Osmolarity and pH of the extenders used were determined before the study (Table 1). Glycerol was used at the cryoprotectant in all recipes and extenders were made in the laboratory the morning of collections. Both meat and dairy breeds were used, including Boer (n = 3), Nigerian Dwarf (n = 3), and Saanen (n = 2), three collections were used for each buck. Bucks were collected by artificial vagina; ejaculates were assessed using iSperm (Initial) before processing to determine entry into the study. Each ejaculate was divided into three equal portions, and each was diluted using a different extender (EGG: egg yolk-based; SOY: soymilk-based; and UHT: ultra-high temperature milk-based). Post-thaw sperm parameters were evaluated across treatments at hours 0 (PT0h) and 2 (PT2h) and were compared to Initial characteristics and other treatments. Characteristics evaluated included motility, sperm kinetics, and proportion of samples above 30% motility at PT0h (quality). Data were analysed using the GLIMMIX procedure in SAS 9.4. Significance was considered at P ≤ 0.05. For motility there were effects of extender, breed, time, breed by extender, breed by time, and time by extender. There was no difference in Initial motility across the different extenders (72.3 ± 2.63%, 72.0 ± 2.65%, and 71.5 ± 2.64% for EGG, SOY, and UHT, respectively). For all breeds EGG had the greatest motility at both timepoints PT0h and PT2h. For all breeds initial motility was greater than both PT0h and PT2h. The EGG portion had 51.1 ± 7.30% mean motility and was greater than UHT, which had 30.1 ± 9.04% mean motility, and both EGG and UHT had greater motility than SOY (22.3 ± 10.99%). The Saanen buck mean motility was 45.0 ± 7.56% and was greater than both Boer (31.1 ± 10.15%) and Nigerian Dwarf (25.9 ± 9.49%) which were not different. Main effects of extender, breed, time, and the interactions between were evaluated for sperm kinetics. For average path velocity, straight-line velocity all effects except for breed were significant. For curvilinear velocity, all effects except for breed and the three-way interaction were significant. For linearity, all effects except for breed and breed by time were significant. For straightness, all effects except breed, extender, breed by extender, and breed by time were significant. For quality, there were effects of extender and breed. The EGG extender had greater quality (80% of samples having >30% motility at PT0h) than both SOY and UHT, which were not different (13% and 25% of samples having >30% motility at PT0h, respectively). Although EGG extender resulted in more samples of greater quality and greater post-thaw motility, UHT extender is a valid option for caprine semen resulting in acceptable motility and quality post-thaw characteristics. The SOY extender needs to be reevaluated before it can be used with caprine semen.