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

FERTILITY OF BULL SEMEN
FROZEN FOR TWELVE YEARS

iRl MIXNER2
Department of Animal Sciences,
Rutgers-The State University,
New Brunswick, New Jersey, U.S.A.

The effect of length of storage period on the
motility and fertility of frozen bull semen has not
been reported to any large extent. 1In experiments
designed to determine this effect on semen stored
for various periods up to twelve years, semen
ejaculates were collected from five bulls in the
stud of Sussex County Cooperative Breeding Associa-
tion, Inc., Sussex, New Jersey (now a part of the
Cooperative Northeastern Breeders Association, Tunk-
hannock, Pennsylvania). Part of each ejaculate was
used fresh as unfrozen control semen and part was
used as frozen experimental semen. The experimental
semen was processed and frozen by the procedures
outlined by Mixner (1955). The composition of the
diluent for the frozen semen was as follows: 20%
egg yolk, 2.175% sodium citrate dihydrate, 7% gly-
cerol and 0.5 mg. of streptomycin sulfate per ml.
The diluent for the fresh unfrozen semen was the
same except that the glycerol was omitted.

The fresh semen was used for insemination on
the day of collection and the day following; the
experimental fgozen semen was inseminated after
storage at -79 C for 7-14 days, 6 months, one year,
two years, four years and eight years. At eight
years the semen was transferred to liquid nitrogen
(=196 C) and stored for an additional four years
(total of 12 years) at which time it was used for
breeding. The percent of first service cows which
did not return for a second service during a period
of 60 to 90 days after breeding was used as the
measure of fertility.

A preliminary report on the results of these trials
through eight years of storage was made by Mixner and
Wiggin (1964).

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