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A Rapid Method for the Estimation of Clean Fleece Weight with the Aid of a New Wool Density Device¹

New Mexico Agricultural Experiment Station

Abstract

A new device for the measurement of the relative density called the Neale Density Meter was described.

Regression equations were constructed for the prediction of the clean fleece weight (CFW) of range yearling and mature fine wool Rambouillet rams. Body weight (BW), staple length (SL) and density (D) were used in the prediction equations. There were available 110 yearling and 57 mature rams for this analysis. The prediction method was designed to be rapid so that selection on the basis of CFW may be made directly in the field. Grease fleece weight (GFW) also entered the analysis to investigate its relationships to the other variables and to be used in the prediction whenever it was available. The following highly significant correlations between CFW and the other variables were obtained (within age groups): BW=.4O, SL=.41, D=.32, and GFW=.63. The correlation of GFW with each of the other variables was smaller in each case than the correlation of that variable with CFW. There was no significant correlation between any two of the three variables: BW, SL and D. The multiple correlation coefficient (R) of CFW with BW, SL, D and GFW was .81 for the yearlings and .75 for the matures. When GFW was eliminated the corresponding R's were .70 and .71, respectively.

Measured in terms of the net variation in CFW associated with each of the other variables, their order of importance in prediction is:yearling—1st SL, 2nd GFW, 3rd BW, 4th D; mature 1st SL, 2nd D, 3rd BW and 4th GFW.

In the case of yearlings the standard deviation of CFW was .57 pounds. When BW alone was used in prediction the S.E. of estimate became .52, when SL was added it became .43, and when D was added it became .41, and when GFW was added it became .34 pounds. The corresponding figures for the mature group are: .82, .76, .67, .59 and .56.

It was concluded that the method of prediction should prove useful in selecting breeding animals. Certain suggestions thought to further increase the accuracy of prediction, without interfering with the practicability of the method, were made.

¹ Journal Series No. 75, New Mexico Agricultural Experiment Station, State College, New Mexico.

² Agricultural Specialist, Dept. of Agriculture, Baghdad, Iraq; Animal Husbandman, New Mexico Agricultural Experiment Station; and Assistant in Agricultural Economics, New Mexico Agricultural Experiment Station, respectively.