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Wool Fiber Density of Shropshire Lambs

United States Department of Agriculture¹

Abstract

Wool fiber densities are discussed, results being obtained from 10 Shropshire lambs, sampled at 20 and 52 weeks of age. Seven body regions were considered: neck, back, dock, shoulder, side, hip, and belly. Fiber measurements were made near the base end of each lock by the method proposed by Hardy and Wolf (1942).

The average fiber density at 20 weeks of age was 2517 fibers per square centimeter compared with 1970 fibers per square centimeter at 52 weeks of age. The high and low density regions when the lambs were 20 weeks of age were also high and low regions at the age of 52 weeks. The density at 20 weeks was highly correlated with density at 52 weeks. However, certain individual regions were not significantly correlated at the two periods. The dock, back, and shoulder fiber densities at 20 weeks are significantly correlated with the fiber density at 52 weeks for the same locations. From all considerations, analysis was to be limited to only one region.

From weight of clean wool and body measurements, it was possible to estimate the fiber density of the sheep at 52 weeks of age. The estimated value ranked the sheep in practically the same order as did the measured fiber density. The wool producing area upon which the fiber density was estimated was based on a formula developed from sheep volume measurements.

Differences between sheep, body regions, locks and ages are all highly significant. The differences within the regions may be due to order of sampling or more likely to gradients within the 16 square inch area sampled. The fiber density moreover changed during the growth period from 20 to 52 weeks. Indications were that the number of wool producing follicles remained constant but that they were spread out by the skin growth.

A method for early selection of sheep for wool production has been developed, use being made of fiber density, fiber diameter, fiber length, body weight and body size. The correlations between the estimates and scoured value of clean wool at 52 weeks were highly significant. A significant regression relationship existed between these estimates and clean wool at 52 weeks. This provides a method of estimating from weanling measurements the clean wool content of a fleece at 52 weeks.

¹ Agricultural Research Center, Beltsville, Maryland.