citric acid monohydrate medium. The thawing medium was heated
at 80-90°C repeatedly in ampoules in boiling water and stored
in a refrigerator or at room temperature until use.

Periods of semen storage in this trial were 5-397 days with
liquid nitrogen.

RESULTS and DISCUSSION. Fertility of the trials is given in
Table 1.

The fertility of all stallions was 34.7% (34/98) based on
the rectal palpation. Conception races for each stallion varied
from 11s1% E1/9)5t 0/:66/5670(8 [12)s3e The Fertildity -t omthe - trial
this year was 127 less than in 1966. It may be due to
insemination less fertile mares.

Relationship between fertility, number of spermatozoa
inseminated, and post-thaw motilities are given in Fig. 1 and 2.

Although the number of cases was too small to investigate
conclusively, it may be that 7-8 (108) of sperm and 207 or more
at post-thaw motility are sufficient to achieve good fertility.

REFERENCES.

(1) H. NAGASE, S. SOEJIMA, T. NIWA, H. OSHIDA, Y. SAGARA,
N. ISHIZAKI and S. HOSHI, 1966, Jap. J. Anim. Reprod.
12, 48 (with English summary)

(2)5 SH. NAGASE S SOEIIMA, T. TOMLZUKA, ‘H: OSHEDA;. T.
MIKAWA, Y. SAGARA, S. HOSHI and T. NIWA, 1966 Jap. J.
Anim. Reprod. 12, 52 (with English Summary)

(3) H. OSHIDA, T. MIKAWA, S. HORIUCHI, H. TAKAHASHI, T.
TOMIZUKA and H. NAGASE, 1967, Jap. J. Anim. Reprod.
1355136

(4) D. KRAUS and D. GROVE, 1967, J. Reprod. Fertility,
1967 Sd:4 3 139

(5) H. WIBLINGS, 1966, Personel Communication
¢ AT iDdiges B5119/65 $1'3'; INo T 1:2
(7) Y. NISHIKAWA, S. SHINOMIYA, T. KOMATSU, N. NISHIO,

Y. TAKUTO and Y. WAIDE, 1967, Jap. J. Frozen Semen
Res. Soci. No. 23, 17

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