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US Department of Agriculture2, Dubois, ID 83423
Abstract
Development of the Polypay breed was undertaken to combine into a composite breed the potential for greatly increased reproductive capacity along with desirable growth rate and carcass quality. Four breeds were selected for the foundation of the new breed-the Ram-bouillet and the Targhee for hardiness, large body size, long breeding season, herding instinct and fleece characteristics; the Dorset for carcass quality, milking ability and long breeding season and the Finnsheep for early puberty, early postpartum fertility and high lambing rate. Dorset X Targhee and Finnsheep X Rambouillet matings were first made in 1968, and reciprocal Dorset-Targhee X Finn-Ram-bouillet matings were initiated in 1969. Beginning in 1970, the respective two-breed crosses and the four-breed cross (Polypay) were each mated inter se and selected, along with straight-bred Rambouillets and Targhees, for lamb production when given two opportunities to lamb/year. Initial comparisons among straightbreds and inter se mated groups showed few important differences in meat-type body conformation, body condition or growth rate, but superior annual reproductive performance by Polypays. Fertility of Polypays at 1 yr of age was high and comparable to that of the Finn-Rambouillets. Response of Polypays to twice-a-year lambing was superior to responses of Rambouillets, Targhees, Dorset-Targhees or Finn-Rambouillets. The 1974 to 1975 annual production of young Polypays was about 13% more lambs weaned than from Finn-Rambouillets and 18% more weight of lamb weaned than from Dorset-Targhees, the best of the other groups for these traits. The current (1979 to 1981) reproductive performance of Polypay ewes selected for high once-a-year lambing rate under typical range management conditions is very competitive with that of 
Finn cross-breds. Annual production of mature Polypays on the twice-a-year lambing schedule was 1.78 lambs weaned and 58.6 kg of lamb weaned/ewe put into fall breeding.
1 Present address: Jornada Experimental Range, Box 3JER, New Mexico State Univ., Las Cruces, NM 88003.
2 Agr. Res. Service, U.S. Sheep Exp. Sta., Dubois, ID 83423, in cooperation with the Univ. of Idaho, Moscow.
This article has been cited by other articles:
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  R. C. Borg, D. R. Notter, L. A. Kuehn, and R. W. Kott Breeding objectives for Targhee sheep J Anim Sci, November 1, 2007; 85(11): 2815 - 2829. [Abstract] [Full Text] [PDF]
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