Influence of Sugars with Glycerol on Post-thaw Motility of Bovine Spermatozoa in Straws

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Abstract
Semen from each of 7 bulls was diluted in egg yolk-citrate extender containing 0, 60, 120, or 180 mM fructose, lactose or raffinose in every possible combination with 0, 3, 6, 9 and 12% (vol/vol) glycerol, to establish if these sugars were cryoprotective for spermatozoa in straws. Fructose was not beneficial to post-thaw motility in the absence of glycerol and became increasingly detrimental as glycerol concentration was increased. Although lactose was beneficial when glycerol was absent or present at low concentration, no combination of glycerol and lactose was superior to glycerol alone. The response to raffinose and to lactose was similar. In all 3 experiments, post-thaw motility was as good or better with 6% glycerol than with any of the other glycerol percents. Also, motility was generally greater for spermatozoa frozen in French straws than for those in Continental straws frozen by the same procedure. Cryoprotective effects of lactose and raffinose, used singly and in combinations with each other, were examined further in a 4th experiment. All extenders contained a final 7% glycerol. Motility of spermatozoa frozen in the absence of lactose and raffinose did not differ from that with any combination of these sugars. Motility averaged 22 and 18% for spermatozoa in French or Continental straws and declined more rapidly during post-thaw incubation for spermatozoa in Continental straws.