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Estimating Solids-not-fat Content of Herd Milk Samples¹

Department of Animal Sciences, Washington State University, Pullman 99163
and Mayflower Farms, Inc., Portland, Oregon 97200

ABSTRACT

Various regression equations for estimating solids-not-fat in herd milk samples were calculated from 12,826 samples from 300 herds in one data source and 356 samples from 29 herds in another. Accuracy of estimating solids-not-fat is about the same when any two of the three independent variables (number of beads down, milk fat per cent, and per cent protein) are part of the regression equation. Little increase in accuracy was obtained when quadratic independent variables were included in the equations. Equations involving beads and protein per cent were slightly more accurate than equations involving beads and milk fat per cent. Fitting separate equations to different milk fat percentages appreciably improved the accuracy of estimating solids-not-fat only when the equation did not include the milk fat per cent as an independent variable. These results indicate the choice of the equation among those used in this study to estimate solids-not-fat in milk could be made by weighing the operational costs of the various equations rather than the predictive accuracy of the equation.

¹ Scientific Paper no. 3338. College of Agriculture Research Center Projects Numbers 1766 and 1868.

² Present address: Fred Meyer, Inc., 3800 S.E. 22nd Ave., Portland, Oregon 97200.