Preservation of Bull Semen at Sub-Zero Temperatures — John Stuart Mill — John Shaqi
Preservation of Bull Semen at Sub-Zero Temperatures
John Stuart Mill · en
=Glycerol levels for freezing semen.= The British procedure called for
the use of 10 percent glycerol in the final mixture of semen and
extender prior to freezing. Yet, as shown in Table 6, in our laboratory
5 percent glycerol resulted in the survival of a higher percentage of
sperm than did 10 or 15 percent. In order to define more clearly the
optimum glycerol level, several ejaculates of semen were subsampled and
portions were frozen after the addition of yolk-citrate extender and
glycerol in varying quantities. From Table 9 it can be seen that
glycerol levels of 6 and 8 percent in the final mixture resulted in
maximum sperm survival during freezing. These results were confirmed in
tests on the survival of sperm at 5 deg. C. storage for 3 days following
freezing and thawing with varying glycerol levels (see Table 10).
The results shown in Tables 9 and 10 were confirmed also in later
experiments. Thirty-six samples were subjected to various levels of
glycerol and no significant difference in freezability was found between
6 and 8 percent. Based on these findings, a glycerol level of 7 percent
was adopted for use in all experiments described in this bulletin,
unless otherwise indicated. Results in a number of other laboratories
have agreed with our findings regarding the use of approximately 7
percent glycerol with the yolk-citrate diluent.[5],[6],[7],[9],[10] With
milk as the extender, 10 to 13 percent glycerol has been preferred by
some.[5],[6],[7]
Table 9.--Effect of Glycerol Level on Sperm Motility After Freezing to
-79 deg. C. and Thawing
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Glycerol Number Pre- Post- Survival
level of freezing thawing (percent)
(percent) samples motility motility
(percent) (percent)
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2 10 53 2 4
4 19 55 29 53
6 19 55 34 62
8 19 55 35 64
10 19 55 24 44
12 10 53 13 25
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Table 10.--Effect of Glycerol Level and Storage at 5 deg. C. After Thawing
on Sperm Motility
(Average of 13 ejaculates)