level. The response observed in sows was in agreement with
the earlier finding reported (4) and suggested that synchro-
nization of estrus with ICI 33,828 was not as effective in
sows as it was in gilts. No differences were noted in the
average weight gains between replicates or between years of
the gilts that had been treated with the compound. The aver-
age weight gain of the sows was different from that of the
gilts while on treatment. There were no differences in aver-
age litter size of gilts between replicates within year or
between years. Sows had larger litters than gilts. No
adverse side effects were noted in the course of the study.
Although specific measurements were not taken, it was noted
that water intake of the animals was increased and they uri-
nated more frequently. No feed intake problems were encoun-
tered. On day three or four after the start of treatment,
it was also noted that the animals were less aggressive in
their eating habits. When the animals had been off the
treatment for a period of three or four days, they returned
to their normal behavior eating habits. The data show that
ICI 33,828 is effective in altering the estrous cycle and
synchronizing estrus in gilts and sows, can be recommended
for use in regular swine production units, and results in
normal reproductive performance.

(1) C. POLGE, 1964. Proc. 5th Int. Cong. Anim. Reprod. and
AJT., Trento, Ttaly;-T1:388.

E2) R IS SGERRTTS tand =l L AR=IJOHNSONS 964" “Proc s 5EhInt.
Cong. Anim. Reprod. and A.I., Trento, Italy, III:455.

(3) R. J. GERRITS, E. V. KREHBIEL, and C. M. KINCAID, 1966.
J. Animal Sci. 25:923.
R. J. GERRITS and L. A. JOHNSON, 1965. J. Animal Sci.
24:918.
R EGERRITS fand cL 2 A= JOENSON S =196 55 vdi. #Animaid ~Sci-
24:917.