38 QUAIL EGG YOLK IN CITRATE EXTENDER IS SUITABLE FOR CRYOPRESERVATION OF NGUNI BULL SEMEN

Traditionally, commercial hen egg yolk has been used in extenders or freezing media because of its easy availability. However, the use of quail egg yolk has not been used for preserving Nguni bull semen. The aim of the study was to compare the suitability of different quail egg yolk concentrations (5, 10, 15, and 20%) for cryopreserving Nguni bull semen. Semen was collected from 14 stud Nguni bulls with the aid of electro ejaculator. Collected semen samples were kept in a thermos-flask containing warm water at a temperature of 37°C and transported to the laboratory for further analyses. The sperm motility traits were evaluated using computer-aided sperm analysis prior extension. Semen samples were then randomly allocated into 5, 10, 15, and 20% of quail egg yolk and 20% concentration of chicken egg yolk (control) in citrate extender. The extender was supplemented with 12% of glycerol (Seshoka et al. 2012) as a cryoprotectant, and semen samples were diluted (1 : 2) and equilibrated for a period of 4 h at 5°C. After equilibration, semen samples were loaded into 0.25-mL straws, placed into a controlled rate programmable freezer, and stored in a LN tank (–196°C) until thawing. Frozen semen straws were thawed in a water bath at 37°C for 1 min. Thawed semen was evaluated for sperm motility traits using a computer-aided sperm analysis system. Data were analysed with ANOVA. A significant difference was recorded between fresh total sperm motility rate (99%) and frozen-thawed semen samples with either 5% (87.3%) quail or 20% (87.6%) chicken egg yolk citrate extender compared with 10% (92.6%), 15% (91.2%), or 20% (89.9%) quail egg yolk citrate extender. Moreover, fresh semen also resulted in a significantly higher progressive sperm motility rate (39.3%) as compared with frozen-thawed with 5% (26.2%) or 20% quail (28.5%) or 20% chicken (22.7%) egg yolk citrate extender. The results also demonstrated that the use of 10, 15, and 20% quail egg yolk in citrate extender yielded comparable results on total sperm motility with fresh semen as compared with 5% quail and 20% chicken egg yolk. In conclusion, quail egg yolk extender provided sufficient cryo-effectiveness to cryopreservation of Nguni bull semen.