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Characteristics of the American Polypay: A review

Published online by Cambridge University Press:  01 August 2011

G.D. Snowder
G.D. Snowder
Affiliation:
USDA, ARS, U.S. Sheep Experiment Station, Dubois, Idaho 83423, USA
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Summary

The 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.

Resumen

La raza ovina Polypay fue desarrollada en la Estación Experimental Ovina de EE.UU. con una capacidad de reproducción claramente superior a la media de las razas locales de la zona oeste de EE.UU. La raza Polypay está compuesta por cuatro razas: la Targhee, la Rambouillet, la Dorset y la Finnish Landrace. Se trata de una raza de lana de mediana estatura (el peso medio de la oveja en edad madura es de 72 kg), con un cuerpo suave sin exceso de piel arrugada en la nuca y en el cuerpo y ausencia de cuernos. Estudios comparativos con otras razas locales estaduinenses han mostrado que la Polypay posee una madurez sexual precoz, y mayor grado de fertilidad y prolificidad. Las ovejas maduras paren una media de 2,4 corderos y los crian hasta un peso medio de 63,8 kg a los 120 días del parto. La supervivencia de los corderos de 21 a 120 días es superior a la de otras razas comparadas. La media individual de peso al destete a los 120 días (36,1 kg) es mayor que para la raza Rambouillet y Targhee (34,5 y 33,8 kg, respectivamente). Las canales de Polypay son semejantes a las de Rambouillet y Targhee en cuanto al porcentaje de manto, espesor corporal, grasa entorno a riñones y zona pélvica, y área del músculo dorsal. Las cantidades de graso de la canal son inferiores en la Polypay comparadas con la Rambouillet y la Targhee, mientras que los índices cualitativos de las patas son más favorables en la Polypay. La longevidad productiva en condiciones de rebaño en las regiones del oeste no es diferente entre la Polypay y las razas Rambouillet, Targhee y Columbia. En un sistema de producción en granja la media de años productivos en las ovejas Polypay no excede la media de la mayor parte de tipos de razas cruzadas. Las características de la lana vienen definidas de gruesa a media con un diámetro de fibra que va de 24 a 33 μm. La longitud de la fibra a la raíz va de 7,6 a 12,7 cm con una media aproximada de 10 cm. Los pesos de vellón crudo están considerados como bajos y van de 2,7 a 4,5 kg. La superficie de lana limpia representa aproximadamente el 57%. Las evaluaciones económicas favorecen a la raza Polypay en todos los sistemas de producción considerados, con un porcentaje de 15 a 30% de aumento en la venta o en las ganancias en comparación con las demás razas locales en EE.UU. Si consideramos la raza Polypay para la importación debemos tener cierta prudencia, ya que no resulta adecuada a todos los medios y a todos los sistemas de producción en el mundo, en particular allí donde los recursos nutricionales y de manejo son insuficientes para consentir la lactación de ovejas con partos gemelares.

Keywords

Polypay sheepReproductionGeneticsWoolLamb
Type
Research Articles
Information
Animal Genetic Resources/Resources génétiques animales/Recursos genéticos animales , Volume 29 , April 2001 , pp. 19 - 30
Copyright
Copyright © Food and Agriculture Organization of the United Nations 2001

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