RESULTS AND DISCUSSION.

Table 1 presents the characteristics of the
semen initially and at intervals of storage up to
twelve years. The mean percent of motile sperm
initially was 63; immediately after freezing, 44;
after storage for four years, 36; after storage for
eight years, 28; and after storage for twelve years, 9.

Table 2 presents the fertility results on these
semen samples. A total of 24 cows was bred to semen
from four bulls stored for twelve years. Ten of these
cows did not return to service (mean fertility of
41.7%) and five cows were diagnosed pregnant by rectal
palpation. Fertility of the semen at 12 years was
significantly lower than the fertility of the semen
stored for four and eight years (56.1% and 59.2%,
respectively) which in turn was lower than the fertil-
ity of semen stored for periods up to two years.

We can not be positive that the semen storage tem-
peratures were exactly as stated during the entire
twelve years of this experiment although they were
believed to be so. The results of these trials do
indicate that satisfactory fertility can be obtained
witg bull semen stored for twelve years (eight years at
-79 C and four additional years at -196 C.

REFERENCES.

MIXNER, J.P., 1955. Processing, Storing and Shipping
Frozen Bull Semen. New Jersey Agr. Exp. Sta.,
Cilrecular. 573

MIXNER, J.P. and WIGGIN, S.H., 1964. The effects of
ageing on the motility and fertility of frozen
bull semen. Proceedings Vth International Con-
gress On Animal Reproduction And Artificial
Insemination, 4:264-268.

1 ! :
Paper of the Journal Series, New Jersey Agri-
cultural Experiment Station, Rutgers-The State
University, New Brunswick, New Jersey, U.S.A.

2
Professor of Animal Physiology

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