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Estimation of the Mean Fiber Length of Individual Grease Fleeces

U. S. Department of Agriculture

Abstract

This study was designed to evaluate the importance of variation due to individual fibers, location on the lock from which the fibers are drawn, randomly selected locks, ram or animal effects and technicians in the estimation of average fiber length of individual fleeces. A total of 15,200 fibers were measured both stretched and unstretched from 38 ram fleeces with 50 locks chosen at random from each fleece.

Variance due to rams, technicians, locks and the ram-by-technician interaction accounted for 12.1, 2.1, 18.5 and 2.1% of the variation in unstretched fiber length; whereas, the variance due to the same sources accounted for 9.2, 12.0, 14.4 and 1.8% of the variation in stretched fiber length, respectively. The regression of fiber length on location on the lock (from tip to base) was –.08 and –.12 for unstretched and stretched fiber lengths. This regression differed significantly between technicians for both measures. The results therefore indicate that more objective procedures of selecting and measuring fiber length are needed and particularly if stretched fiber length is to be used.

The regression of "true" phenotype for average unstretched fiber length on estimated phenotype is expected to be .97 if eight fibers from each of 60 randomly selected locks are measured per fleece and .92 for four fibers from each of 30 locks assuming that the animal by technician interaction is eliminated. The expected standard error of the ram or fleece mean in these two cases is 1.6 and 2.6% of the mean, respectively.

From the results of this study it appears that a satisfactory method for determining individual fiber length from individual fleeces consists of measuring unstretched length of eight fibers from each of 50 locks obtained at random over the entire fleece. Two technicians, fixed for a particular study, would measure four fibers obtained at random from the base of each lock.

¹ Formerly Biometrician, Livestock Research Staff, A.R.S., U.S.D.A., Beltsville, Maryland. Present address, Department of Dairy Science, Ohio State University, Columbus.

² Sheep and Fur Animal Research Branch, Animal Husbandry Research Division, A.R.S., U.S.D.A., Beltsville, Maryland.

³ The assistance of Benjamin F. Gadsden and John T. Larsen in measuring fiber length is appreciated.