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Relative Accuracies of Several Methods of Estimating Clean Fleece Weight

U. S. Department of Agriculture ¹

Abstract

Relative accuracies of several methods of estimating clean fleece weight were tested on whole, clean fleece data from 418 Rambouillet, Targhee and Columbia sheep at the U. S. Sheep Experiment Station, Dubois, Idaho.

In most instances the correlations between regression equation estimates of clean fleece weight and actual whole, clean fleece weight were higher than correlations between estimates obtained by any other method and whole, clean fleece weight. The most accurate regression equation in this study reduced the standard error of estimate by an average (over all grades) of 2.4% under that obtained using the side sample estimate, 13.3% under grease fleece weight, and 20.1% for machine reading.

The regression equations presented were derived from data which were entirely independent of the data on which they were evaluated and included information on six fleece and body traits.

The side sample method was generally superior in accuracy of estimating clean fleece when compared to methods based on single trait observations (grease weight, machine reading, staple length, body weight, number of crimps per inch or visual fleece grade in spinning counts). Although the side sample was superior in a few instances to regression equation methods, its modest superiority appears not to justify the greater time, special equipment and high costs associated with its use.

The machine reading was more accurate than grease weight for estimating clean fleece weight in the fine wool grade, while grease weight was superior in estimating clean weight in the remaining blood grades of wool.

Other methods were invariably less accurate than those mentioned above for estimating clean fleece weight.

¹ From the U. S. Sheep Experiment Station and Western Sheep Breeding Laboratory, Sheep and Fur Animal Research Branch, Animal Husbandry Research Division, ARS, Dubois, Idaho, in cooperation with the University of Idaho. Published with the approval of the Director of the Idaho Agricultural Experiment Station, Moscow, as Research Paper No. 588.