Characteristics of the American Polypay: A review

Abstract

SummaryThe Polypay sheep breed was developed at the U.S. Sheep Experiment Station with a reproductive capacity markedly superior to that of domestic US western range breeds. The Polypay is a four breed composite of Targhee, Rambouillet, Dorset and Finnish Landrace breeds. It is a medium-sized wool sheep (average mature ewe weight of 72 kg) with a smooth body free of excessive skin wrinkles on the neck and body and a poll head. Comparative studies with other US domestic breeds have shown the Polypay to have earlier sexual maturity higher fertility and prolificacy rates. Mature ewes give birth to an average of 2.4 lambs and wean an average total litter weight of 63.8 kg per ewe at 120 days post partum. Lamb survival rates to 21 and 120 days are greater than those of other breeds compared. Average individual lamb weaning weight at 120 days (36.1 kg) exceeded that for Rambouillet and Targhee lambs (34.5 and 33.8 kg, respectively). Polypay carcasses are similar to those of Rambouillet and Targhee for dressing percentage, body wall thickness, kidney and pelvic fat, and ribeye area. Measures of carcass fat are less in the Polypay when compared to the Rambouillet and Targhee while qualitative leg scores for the Polypay were more favorable. Productive longevity under western range herded conditions does not differ among Polypay, Rambouillet, Targhee and Columbia sheep. In a farm flock production system, the average number of productive years for Polypay ewes exceeded that of most crossbred types. Wool characteristics are defined as a coarse to medium grade wool with a fiber diameter ranging from 24 to 33 μm. Fiber staple length ranges from 7.6 to 12.7 cm with a common mean of approximately 10 cm. Raw fleece weights are considered light and range from 2.7 to 4.5 kg. Yield of clean wool is approximately 57 percent. Economic evaluations favored the Polypay in all production systems considered with 15 to 36 percent increase in sales or profits compared to other US domestic breeds. When considering the Polypay breed for importation, some prudence should be exercised because it may not be suitable to all environments and production systems in the world, especially where nutritional and management resources are not sufficient to support lactating ewes rearing twins.