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
=Effect of freezing procedures on oxygen utilization by sperm.= Limited
data have been obtained on the effects of some of the freezing
procedures on the oxygen utilization of bull sperm. The results obtained
in these experiments confirmed the earlier findings that tipping
glycerol directly into the diluted semen at 37 deg. C. caused an increase in
oxygen consumption (Table 16). All other steps in the freezing procedure
had little effect on oxygen consumption by the sperm. Except where
glycerol was added during the determination, the rate of oxygen
utilization was lower the second hour than during the first. The oxygen
uptake of semen that had been frozen and thawed seemed to drop faster
than that of unfrozen samples.
=Effect of freezing procedures on methylene-blue reduction time.= The
methylene-blue reduction test has been used as a means of measuring
semen quality and is dependent on the metabolic activity of the sperm.
The effects of various freezing procedures on the ability of samples to
decolorize methylene blue were determined with 10 semen samples. Sperm
numbers were standardized to 300 x 10^{6} cells per milliliter and the
time required for these cells to reduce a 1:40,000 solution of methylene
blue was determined on freshly diluted semen, after the addition of
glycerol, after equilibration, and after freezing and thawing. Portions
of each diluted sample were tested at these stages of the procedure with
glycerol alone added and with glycerol and various sugars added.
A marked increase in the time required for the sperm to reduce methylene
blue occurred when the glycerol was added (Table 17). This increase was
greatest in the portions with glycerol alone and with glycerol and
glucose. The time increase was less pronounced in the presence of the
three pentose sugars used. Following equilibration, the samples regained
the ability to reduce methylene blue at a rate only slightly slower than
when they were fresh. Freezing and storage of semen resulted in slower
reduction of the methylene blue than was shown after equilibration with
glycerol. Since freezing usually kills some of the sperm, a slowing of
the reduction time after freezing would be expected.
Table 17.--Effect of Freezing Procedures on the Methylene-Blue Reduction
Time of Bull Semen With and Without the Addition of Sugars[M]
(Average of 10 ejaculates)