Sequence in Which Essential Amino Acids Become Limiting for Growth of Chicks Fed Rations Containing Cottonseed Meal

LIMITED amounts of meal prepared from glanded cottonseed are used in poultry rations. It has generally been recognized, however, that the protein in that meal is too deficient in lysine for large amounts to be included in commercial broiler rations. Grau (1946) found that lysine is the most limiting amino acid in cottonseed meal protein; additional methionine was also needed to allow the most rapid growth rate. Further supplementation with threonine or tryptophan did not increase growth rate. Jonston and Watts (1964) have reported that lysine and methionine are also limiting in meals prepared from glandless cottonseed. Lysine was found to be more limiting in the glanded than in the glandless meal. This paper reports the results of experiments conducted to determine the sequence in which the essential amino acids become limiting for growth of chicks in semi-purified rations based on five different cottonseed meals. The experiments are similar to …