76 the effect of glycerol concentrations in egg-yolk citrate extender on the quality of cryopreserved nguni bull semen.
ABSTRACT There are bull shortages in South African poor rural areas. Artificial-insemination technology could play a significant role on breeding emerging farmer's cattle. The objective of this study was to compare glycerol concentrations (0, 4, 8, or 12%) during freezing of Nguni bull semen to conduct AI in different villages. Semen was collected by electro ejaculator from 2 Nguni bulls of known and proven fertility. Collected semen samples were kept in a thermo flask (37°C) and transported to the laboratories within 10min after collections. Semen samples were pooled and evaluated by Sperm Class Analyser(®) and allocated randomly per treatment. Semen was then diluted (1:2 v:v) with egg-yolk citrate extender supplemented with either 0% (negative control), 4, 8, and 12% of glycerol concentration or AndroMed(®) (positive control). Semen samples were equilibrated for 4h at 5°C. After equilibration period, samples were loaded into 0.5-mL straws and placed horizontally into the controlled rate (-5, -8, -10, -12, -15, -25, -35°Cmin(-1)) from 5°C until target temperature of -80°C is reached. The frozen semen straws were stored in a liquid nitrogen tank (-196°C) until thawing. Treatment means were separated using Fisher's protected t-test least, and data are presented as mean ± SD. There was a significant differences (P<0.05) between raw total sperm motility (83.3±19.3) and frozen-thawed sperm with either 0% (0.0±0.0), 4% (30.2±13.4), 8% (47.9±12.5), or 12% (61.5±4.7) of glycerol and on AndroMed(®) (27.7±17.8) group. Regardless of the glycerol concentrations used, the freezing-thawing process reduced (P<0.05) the Nguni total sperm motility rate compared to uncryopreserved sperm (83.3±19.3). In conclusion, egg-yolk citrate extender supplemented with 12% glycerol yielded a better (P<0.05) total sperm motility rate (61.5±4.7) as compared with the 0% (0.0±0.0), 4% (30.2±13.4), 8% (47.9±12.5), and AndroMed(®) (27.7±17.8) group. Further studies are required to test other levels of glycerol concentrations (>12%) on freezing Nguni semen and conducting AI.