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Comparison of the Yields of Side Samples from Weanling and Yearling Sheep¹

United States Departments of Agriculture and the Interior

Abstract

Data on the clean wool yields of side samples collected at weanling and yearling ages from 461 crossbred ewe lambs raised at the Southwestern Range and Sheep Breeding Laboratory, Ft. Wingate, N. Mex. during a 5-year period were analyzed.

Average yields at yearling age were from 6.5 to 22.8 percent lower and much more variable than the weanling yields for the same sheep.

Approximately 5 percent of the total variance in yield at both weanling and yearling ages was due to the effect of rams used within years. Differences between years were responsible for about 2 percent of the weanling variance, and 41 percent of the yearling variance. Thus, differences between lambs represented about 93 percent of the total variance in the weanling yields and only 54 percent at yearling age.

The relation between the weanling and yearling yields for individual years and progeny groups varied greatly, ranging from non-significant to highly significant correlations. The correlation between the yields of weanling and yearling samples, independent of the effect of years and rams used within years, was 0.45, a highly significant value. The regression equation calculated from these data, however, was found to have little practical value for estimating yearling yields from weanling data because of the extreme variations resulting from environmental conditions.

Further long-time studies are needed to determine the relationship between yield, other fleece characters, and environmental factors.

¹ This study was conducted under authority of the Bankhead-Jones Act, by the Bureau of Animal Industry, U. S. Department of Agriculture, in cooperation with the Office of Indian Affairs, U. S. Department of the Interior, at the Southwestern Range and Sheep Breeding Laboratory, Ft. Wingate, N. Mex.