Influence of Freezing Methods, Extenders, and Storage Temperatures on Motility and pH of Frozen Bovine Semen

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Abstract
Fourteen ejaculates, two from each of seven bulls, were extended in heated, whole homogenized milk and egg yolk citrate(EYC) frozen with either dry ice-alcohol(DI) or liquid nitrogen(LN), then divided for storage at -79C(DI), -92C (Mechanical) and -196C(LN). Samples from each ejaculate and each treatment were evaluated for pH and percent progressive motility at pre-freeze, post-freeze, one day, ten days, one, three, six and nine months. EYC extender maintained significantly higher (P<0.001) motility values than milk extender when averaged across all other treatments. However, there was no significant difference between the motility values obtained for these extenders when DI freezing was used for DI and LN storage. Motility of semen frozen with DI was significantly higher (P<0.001) for all treatments than samples frozen with LN. Motility values of semen extended to EYC and stored at -92 and-196C were approximately equal and in all instances higher than comparable samples stored at -79C. After three months'' storage the samples extended in milk exhibited higher motility values when stored at -196C than when stored at -92 or -79C. There was little variation in mean pH values within extenders due to freezing methods or storage temperatures.