Vle CONG. INTERN. REPROD. ANIM. INSEM. ARTIF., PARIS, 1968, VOL. Il

FREEZING OF RAM SEMEN IN STRAWS
By J.Aamdal and K.Andersen

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

A number of experiments with freezing of ram semen have

been carried out (1, 2, 3, 4, 5, 6,:7).: In all theselex=
periments the semen has been frozen in ampulles. In the
following an experiment with freezing of ram semen in straws
is reported.

Materials and Methods.

Semen was collected with artificial vagina from Gotland
breed (Swedish) and Dala breed (Norwegian). Dilution im-
mediately after collection with lactose diluent proposed
by Nagase and Graham 1964 (8): 11% lactose, L4,7% glyserol
+ 20% egg yolk. Different diluters have been tried, and we
found lactose diluent most suitable.

Our experience with insemination of sheep with fresh
semen shows that conception rate decrease if dilution
exceed 1:10, and in this experiment dilution 1l:4 - 1:6
have been used.

Aftes dilution the semen was stored in a refrigerator +4
- +5°C and filled into straws by a syringe. The straws
are of same types used for bull semen (9) 65 mm in length
and with a total amount of semen of ca. 0,3 ml. About 60
mine. after collection the straws were frozen in the va-
pour above liquid nitrogen (10) and stored in liquid
nitrogen.

Different thawing methods has been tried, and we found
fast thawing superior to slow thawing (9). Table 1 shows
the comparison of per cent unstained spermagozoa (Eosin-
nigrosin stain) (11l) in_straws thawed at 75 C in 12 sec.
and straws thawed at 35 C in 30 sec. In average the per
cent unstaingd spermatozoa are about 17% higher in semen
thawed at 75 C. The motility is not recorded in the table,
but we found about the same differences in motility
between the two thawing methods as for staining. In the
comparison of thawing at 35 C in 30 sec. or 15 sec. we
found no difference.

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