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

SYNCHRONIZATION OF ESTRUS AND SUPEROVULATION %N SWINE
WITH ICI 33828 AND PREGNANT MARE SERUM

B. N. Day and D. E. Longenecker
University of Missouri, Columbia, Missouri, U.S.A.

The occurrence of estrus and ovulation in swine can be prevented
by feeding a ration containing ICI 33828 (2,3). Following the with-
drawal of ICI 33828, estrus will occur with the majority of the animals
showing sexual receptivity 5 to 7 days after the last feeding of ICI
33828. Fertility level at the first post-treatment estrus is normal.

More precise control of the time of ovulation can be obtained in
gilts by the administration of pregnant mare serum (PMS) and human
chorionic gonadotrophin (HCG) following the withdrawal of ICI 33828
(4). This treatment sequence provides a method for the insemination of
a group of gilts on one day without adverse effects on fertility or
fecundity.

Superovulation can be induced in gilts with PMS (5,6) and it has
been shown that the average number of embryos present on the 25th day
of gestation is increased in sows superovulated with PMS at the first
post-weaning estrus (7).

The purpose of the present experiment was to determine the time of
estrus and the fertility level in gilts superovulated with PMS follow-
ing the suppression of estrus with ICI 33828.

Materials and Methods. The experimental animals were 93 cross-bred
gilts 7 to 9 months of age and weighed between 100 and 125 kg. A1l
animals had exhibited at least one estrus prior to treatment.

A11 gilts were fed ICI compound 33828 (1- -methyallythiocarbamoyl-
2-methythiocarbamoylhydrazine) for a period of 20 days. The gilts were
fed once daily in individual stalls (41 gilts) or as groups of 10 to 15
animals (52 gilts). Each gilt was offered daily 1.82 kg. of a
complete-mixed feed containing 100 mg. of ICI 33828.

Gilts selected at random within treatment pens were injected
subcutaneously with 1500 i.u. of PMS* in 5 ml. of sterile saline 24 hr.
after the last feeding of ICI 33828. A total of 38 gilts was treated
only with ICI 33828 (Group I) and 55 gilts received ICI 33828 and PMS
(Group II).

(1) Contribution from the Missouri Agricultural Experiment Station.
Journal Series Number 5439. Approved by the Director.

(2) C. Polge, 1964. Proc. 5th. Int. Cong. Anim. Reprod. 2:388-392.

(3) R. Gerrits & L. A. Johnson, 1964. Proc. 5th. Int. Cong. Anim.
Reprod. 3:455-459.

4) C. Polge, B. N. Day & T. W. Groves, 1968. Vet. Rec. (In press).

5) R. H. F. Hunter, 1964. Anim. Prod. 6:189-194.

6) B. N. Day, D. E. Longenecker, S. C. Jaffe, E. W. Gibson & J. F.
Lasley, 1967. J. Anim. Sci. 26:777-780.

7) D. E. Longenecker & B. N. Day, 1968. J. Anim. Sci. 27:709-711.

Equinex, Ayerst Laboratories.

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