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Effects of Pregnancy, Parturition, and Lactation Upon Wool Production of Range Ewes

Agricultural Research Service, U. S. Department of Agriculture and New Mexico Agricultural Experiment Station, University Park

Abstract

The effects of breeding group, age of ewe, year, weight of ewe, staple length, type of parturition, lactation, and subsequent pregnancy on grease and clean wool production were studied on 2424 records of grease and 1451 clean fleece weights. The ewes were classified according to the type of parturition, lactation and subsequent pregnancy. The grease and clean fleece weights used in this study were taken just prior to lambing. This allowed most of the effects due to the three factors under study to be reflected in the wool yield.

The average grease fleece weight was 7.07 lb., and the average clean fleece weight was 3.60 lb. Partial regressions of clean fleece weight on staple length, body weight of ewe, and grease fleece were 0.09 lb., 0.02 lb., and 0.32 lb., respectively. The regressions of grease fleece weight on staple length and body weight of ewe were 0.20 lb. and 0.04 lb., respectively.

The effects of parturition and lactation on wool production were very pronounced, with ewes giving birth and nursing twin or single lambs producing significantly less clean and grease wool than ewes producing no lambs. The effects of pregnancy were less pronounced than those of parturition and lactation. Ewes pregnant with a single lamb did not produce significantly less grease wool than ewes which failed to lamb; however, the difference in clean wool yield was significant. These results indicate that wool records should be adjusted for the effects of lactation and pregnancy before the records are used in a selection program.

¹ Present address: Department of Animal Husbandry, New Mexico State University, University Park, New Mexico.

² Present address: Sheep and Fur Animal Research Branch, Animal Husbandry Research Division, ARC, U.S.D.A., Beltsville, Maryland.

³ Southwestern Range and Sheep Breeding Laboratory, Sheep and Fur Animal Research Branch, Animal Husbandry Research Division, Fort Wingate, New Mexico, and Computing Laboratory, Biometrical Services, ARC, Beltsville, Maryland.