Sequence in which essential amino acids become limiting for growth of rats fed rations containing cottonseed meal.

Two studies were made to determine the sequence in which essential amino acids become limiting for
growth of rats fed rations containing 10% protein from cottonseed meal. In the first study, a mixture of
six essential amino acids in which cottonseed proteins are deficient, as compared with human milk
proteins, was added to the meal. Each of the amino acids was omitted sequentially and the effect on protein
efficiency ratio (PER) and growth was studied. In the second study, the amino acids were added to
the meal singly and in combinations. Data regarding PER and net protein utilisation (NPU) obtained
in the two studies show that lysine is the first limiting amino acid in cottonseed proteins, followed by
threonine, isoleucine and sulphur amino acids.