B. SEMEN EVALUATION

Semen evaluation involving the motility, type of
activity, sperm count, and volume, gives a basis for
prefreezing dilution. Any semen not meeting the
following standards should be discarded: 1) _if the
total sperm concentration per ml. is 60 X 106 or less,
2) if the sample is rated less than 40 percent motil-
e RS ) if there are feeble motile cells or a lack
of progressive activity, 4) if there is a high level
of abnormal sperm or 5) 1if the semen contains an
excessive amount of dirt. Usually semen of low qual-
ity was high in seminal-plasma and ranged higher in
pH (7.5 to 7.9). Acceptable semen normally reads
between 6.9 and 7.2 pH. After many trial and error
experiences, it was discovered that spermatozoa were
usually sensitive to rough handling (trauma) and possi-
bly intense light. Unprocessed semen (fresh) must be
protected from temperature shock (optimum RIS L

C. PROCESSING

Extensive work with normal semen shows that the
recovery of motile cells after freezing will range
from 50 to 70 percent. On this basis, a method of
extending semen can be estimgted pre-freezing. Field
trials indicate-that 40 X 10° to 80 X 10° motile sper-
matozoa are required per insemination. The opinion of
breeders is that the volume of the insemination should
be 8 to 10 ml.

After many experiments, the following diluent and

method of diluting stallion semen were developed.
Length of time from collection to freezing is a

factor to be considered for maximum recovery of motile
cells. Acceptable evaluated semen should be mixed
with this high sugar-low glycerine diluent at the same
temperature as the semen. Cooling can begin immedi-
ately in air at 5°C. 1In fact, printed ampules can be
filled and sealed prior to cooling with no apparent
damage to the sperm. Holding the diluted or ampuled
semen 3% to 4 hours permits antibiotic bacterial con-
trol in the semen.

D. TEMPERATURE TAKE-DOWN
Extending semen with this diluent, because of its

high sugar, low glycerine and salt content, permits
the rapid temperature drop as illustrated in Figure 1.

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