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

STUDIES ON SYNCHRONIZATION OF ESTRUS |
IN PIGS WITH METHALLIBURE IN JAPAN |

Y. NISHIKAWA (Faculty of Agr. Kyoto Univ., Kyoto, Japan)
T. NIWA (Faculty of Agr. Iwate Univ., Morioka, Japan)
Y. SAKAI (Nat. Inste Anim. Indust., Nasu, Japan)

Establishment of a practical technique for synchronization |
of estrus will be of great significance industrially as well as }
scientifically. Methods using progesterone or synthetic pro- ‘
gestins have been reported as being effective for cattle and |
sheep. In pigs, however, means of treatment with steroids are
known to be quite impracticable as they induce cystic follicles
(1). Since the distinct effectiveness of methallibure, a non-
steroid drug, in synchronizing estrus in pigs was reported, this
drug has drawm attention both in practical and scientific fields
(2),(3),(4). Thnis investigation was conducted to find out how
effective methallibure is in synchronizing estrus in pigs under
conditions in Japan.

MATERTALS AND METHODS. The experiments were conducted by three
groups, using 79 gilts and 70 sows, 149 pigs in total. The
breeds involved were Large White, Middle :White, Landrace, Birk-
shire and their cross-breds. The daily dose of methallibure
was ordinarily 100 mg per gilt and 150 to 200 mg per sow.
Animals were dosed for 15 to 20 days with the drug mixed in a
small amount of féod, 4 to 19 days (mostly 8 to 10 days) after
estrus was over. Furthermore, 6 gilts out of 79 and 11 sows
out of 70 were given injections of PMS at 1,000 IU per head one
day after the withdrawal of methallibure, and 500 MU of HCG

L days later.

RESULTS AND DISCUSSION. 1. Suppression of estrus: The rate of
suppression of estrus was 96 % in total. There was no notable
difference between gilts and sows. Oyt of 9 pigs in which ad-
ministration of methallibure was started in their late folli-
cular stage (16 to 19 days following estrus), the effect was
negative in two out of four cases in which treatment was started
on the 19th day. Besides the above 149 pigs, methallibure was
given to four pigs that had lacked estrus over a long period.
Dosage per animal of 100 mg a day for 20 days, failed to recure

(1) P.J. DZIUK & C. POLGE, 1962, J. Reprod. & Fertil.,
4 : 207-208.
(2) C. POLGE, 1964, Proc. Vth Inter. Congr. Anim. Reprod. &
A.I., 2 : 388-392.
(3) R.J. GERRITS & L.A. JOHNSON, 1964, ibid., 3 : 455-459.
(4) T.W. GROVES, 1967, Vet. Rec.,, 80 : 470-475.

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