Estimating Solids-Not-Fat in Herd Milk Using the Plastic Bead Method of Golding

Abstract

This study was made to derive and compare equations for estimating solids-not-fat (SNF) in herd milk using the plastic bead method of Golding. Milk was sampled from farm bulk tanks at delivery on alternate days from 64 herds for 1 yr. In all, 1,423 herd samples were analyzed for per cent milk fat, per cent protein (dye-binding), specific gravity (plastic bead method), and per cent total solids by oven-drying. Percentage SNF was estimated by difference (per cent total solids-per cent milk fat).Multiple regression equations were calculated and compared for estimating per cent SNF from density. Single equations were unsatisfactory, because of significant differences between the partial regressions for breeds. The most efficient equations were those including density and per cent milk fat or per cent protein within six milk fat intervals. For these, the standard errors of estimate ranged from 0.11 to 0.14% SNF, and fractions due to regression ranged from 0.60 to 0.77. The average deviations for annual herd averages among herds was 0.04% SNF, with 95% confidence limits of 0.10% SNF. For months the average deviation was 0.05% SNF with 95% confidence limits of 0.14% SNF.