There was no indication that conception rate or number of
lambs was in any way affected by repeated treatments.
Because treatments were imposed at less than yearly inter-
vals, matings occurred and lambs were produced throughout
the year.

There was no indication that any one progestogen
treatment was superior to the others. All treatments were
equally effective.

SUMMARY. Estrus and mating was controlled in 57 Rambouillet
cwues at 8 to 12 month intervals over a 53 month period.
Estrus was controlled by a 14 day treatment of either an
orally administered progestogen or by subcutaneous silicone
rubber implant impregnated with a progestogen.

After a progestogen treatment during the anestrous
season from January to July each ewe was given 500 IU of
pregnant mare's serum gonadotrophin (PMS). PMS was not
given during the estrous season from August to December.
Lambs were produced in each month following 243 of 260
treatments. Lambing rate was 1.5 lambs/lambing. Because
lambings occurred at 8 to 10 month intervals, the yearly
rate was 1.9 lambs/ewe/year. Fertility was maintained at
a normal level throughout the 53 month period.

(1) E. M. Roberts and D. G. Edgar, 1966. J. Reprod. Fert.
12:561-564.

(2) C. V. Hulet and W, C. Foote, 1967. J. Animal Sci.
26:545-548.

(3) F. C. Hinds, P. J. Dziuk and J. M. Lewis, 1964.
FesAnimalesSoils. 235782 -7 86%

(4) P. J. Dziuk and B. Cook, 1966. Endocrinology.
78:208-211.

 

 

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