Total number of fibres on sheep. II. Estimation by greasy fleece and fibre weights

Abstract

The total number of fibres on a sheep (N_T) was calculated by the formula N_T = G_T/g, where G_T is the greasy fleece weight and g the mean greasy fibre weight. The variation over the sheep's body of the mean greasy fibre weight and the accuracy of estimation of N_T by the above formula were investigated. The latter accuracy was compared with that obtained by means of the formula N_T = W_T/w, where W_T is the clean fleece weight and w the mean clean fibre weight. It was found that the standard error of the estimate based on greasy fleece weight was not much larger than that based on clean fleece weight. (For about 2000 counted fibres, the standard error was of the order of 4.5 per cent. for clean and 6 per cent. for greasy wool.) Moreover, good agreement was found between the number N'_T based on the formula N_T = W_T/w and the number N"_T, based on the formula N_T = G_T/g, which suggests that no appreciable bias is introduced when estimating N_T by greasy instead of clean fibres.