Vie CONG. INTERN. REPROD. ANIM. INSEM. ARTIF., PARIS, 1968, VOL. I

FAST THAWING OF BULL SEMEN FROZEN IN STRAWS.
By J.Aamdal and K.Andersen

Inst. of Reproductive Physiology and -Pathology
Veterinary College of Norway, Oslo, Norway.

In the first experiments on freezing Bull spermatozoa
Smith & Polge (1950) (1) thawed at 40 C. Since then a
number of investigations concerning semen frozen in
ampulles have been carried out, comparing thawing at
temperatures ranging from O C. A short review was given
in 1965 by Pickett et al (2) who came to the conclusion
in their own experiments that thaw%ng in ice-water was
superior to thawing in water at 15 C.

In experiments concerning bull spermatozoa frozen in
straws Jondet in 1964 (3) used thawing in water at 5 C.-
Cassou quoted by Dyrepdahl in .1966 (4) recommended thaw-
ing in water at 30-35C in 30 sec.

Materials and Methods.

In this experiment Norwegian-made straws of polyvinyl-
chloride are used (length 65 mm, diameter 3 mm). Semen
is filled into the straws with a syringe and stoppered
by a plastic plug at each end. Two different diluents
are used:

l. 114 lactose - 20% eggyolk - 4,7% glycerol (5).

2. 11% skimmed-milkpowder - 2% fructose - 5% eggyolk (6).
Dilution rate is 1:10 to 1:25, and the semen is equili-
brated in 3 hours and frozen in the vapour above liquid
nitrogen (3).

The straws are thawed by immersion in water, and semen
quality is measured by counting the percentage of unstain-
ed spermatozoa after staining with eosin-nigrosin (7).
We found thawing at +4 C inferior to thawing at 35 C.
Also thawing at room temperature (20 °C) in air or in
water gave lower percentage of unstained spermatozoa
than at +35 C. By increasing the temperature of the
thawingwater, a further increase of unstained spermato-
zoa was seen. For example, thawing of the straws in
boiling water in 6 sec. gave a considgrably higher per-
centage of unstained sperm than at 35 C. A more conveni-
ent temperature to work with is 75 C, and table 1 shows

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