| dc.description.abstract | 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 ºC 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. | en |
