Griffin, Erin Michelle (2006-04). Development of an extender protocol to enhance the viability of frozen-thawed bovine spermatozoa. Master's Thesis.
Thesis
Determination of an extender protocol which will enhance the viability of frozenthawed bovine spermatozoa will allow producers to obtain higher conception rates due to the increased survival rate of the spermatozoa. Ejaculates of six Brangus bulls (age=18 months) were evaluated for spermatozoal motility, acrosomal integrity, and morphological characteristics (collectively called spermatozoal viability) in two experiments to test our hypotheses that (1) the treatment combination of a 4 hr cooling duration and a 2 hr equilibration with glycerol will result in optimum spermatozoal characteristics after freezing and thawing and (2) rank of three selected extenders relative to their effects on spermatozoal viability after freezing and thawing will be egg yolk-citrate (EC), egg yolk-tris (IMV), and skim milk (milk). In experiment 1, an ejaculate from each bull was partially extended and cooled to 4 AoC for either 2 or 4 hr and then allowed to equilibrate with the glycerolated extender for 2, 4, or 6 hr. Spermatozoal viability was assessed at 0, 3, 6, and 9 hr after thawing. In experiment 1, 4 hr of cooling resulted in a higher percentage of motile spermatozoa than did 2 hr of cooling. The 2 hr equilibration with glycerol yielded lower percentages of motile spermatozoa, acrosomal integrity, and morphologically normal spermatozoa than 4 and 6 hr equilibration durations with glycerol. In experiment 2, we observed a decrease in spermatozoal viability for all three extenders upon freezing and thawing. Viability of frozen-thawed spermatozoa extended in the milk was reduced for all incubation durations, and the IMV extender had a higher percentage of motile spermatozoa than the EC extender at 6 hr of incubation. A higher percentage of intact acrosomes was observed with the IMV extender; however, the EC extender had a higher percentage of morphologically normal spermatozoa than the IMV extender. Our results indicate that at cooling duration of 4 hr and a 4 hr equilibration with glycerol provide the highest level of spermatozoal viability post-thaw of the treatments evaluated and that the IMV extender enhances the percentage of spermatozoa with an intact acrosome for frozenthawed spermatozoa over the EC and skim milk extenders.
