Two experiments were carried out with 348 White Leghorn male chicks on the effect of pre-feeding programs, length of pre-feeding and experimental periods and type of protein source to linearity of dose-response curve of growth response of chicks against dietary protein level.
By using standard protein well balanced in amino acid composition and by applying the restricted pre-feeding program with the chick starter diet well balanced in nutrients, linear growth response of the chicks was obtained within the range of dietary protein level 4 times as wide as that HEIMAN et al.¹⁾ originally advocated. This means that error variance of gross protein value estimated by the procedure proposed in this paper is about 1/16 of that by the procedure of HEIMAN et al.¹⁾.
Besides the wider range of protein level in assay diets, the restricted pre-feeding program is superior from several viewpoints to the 8% protein diet pre-feeding program originally proposed by HEIMAN et al.¹⁾. Physiological activity of the chicks on the former program is uniform on all of the assay diets while that on the latter program is not. The chicks on the former program are more quiet and easier to handle than those on the latter program.