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

SYNCHRONIZATION OF ESTRUS
AND REPRODUCTIVE PERFORMANCE
OF GILTS AND SOWS
EED GICT 535828

R JSGERRITS R 05 HETZER rand R T “KOUBA
USDA, ARS, Animal Husbandry Research Division
Beltsville, Maryland, USA

SUMMARY .

The study was conducted in the same swine herd in two
successive years. Two hundred and eighty-nine gilts and
sows were group—-fed a daily ration of 2.27 kg. containing
125 mg. of l-a-methylallylthiocarbamoyl-2-methylthiocarbamoyl-
hydrazine (ICI 33,828). Six replicates were treated the
first year, and five were treated the second year. Treat-
ment was initiated at unknown stages of the estrous cycle
and continued for 20 days. All animals were bred by natural
service. Eighty-one percent of the animals expressed estrus
on the fifth, sixth, or seventh day after the end of treat-
ment. The mean number of days required to return to estrus
was 5.5. The conception rate after first service was 89.6%.
The farrowing rate of the first service animals was 867%.
Litters averaged 9.5 pigs born alive. No significant differ-
ence in reproductive performance was noted between replicates
within year or between years.

RESUME.

L'étude fut conduite sur un méme troupeau de cochons
pendant deux années consécutives. Deux cent quatre-vingt-
neuf truies adultes et jeunes furent nourries en groupe d'une
ration journaliére de 2.27 kg. contenant 125 mg. de l-a-
methylallylthiocarbamoyl-2-methylthiocarbamoylhydrazine
(ICI 33,828). Six répliques de truies furent traités
pendant la premidre année, et cinq pendant 1'année suivante.
Le traitement fut commencé lors d'étapes inconnues du cycle
oestral et continué pendant vingt jours. Tous les animaux

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