Sources and utilization of amino acids in channel catfish diets: A review

Alternatives to high-cost protein supplements in formulated diets for channel catfish Ictalurus punctatus are desirable to reduce feed costs and increase profits in modem channel catfish farming operations. Channel catfish feed manufacturers are focused on using plant proteins in least-cost diet formulations which typically contain at least 90% plant products. These diets are sometimes supplemented with purified crystalline amino acids to eliminate amino acid deficiencies associated with plant proteins, which often possess amino acid compositions that are less favorable for channel catfish than the animal products they replace. The efficiency with which channel catfish utilize these supplemented amino acids is discussed, and we describe evidence that amino acids provided in purified crystalline form are not used as effectively as the amino acids obtained from intact proteins in the feed ingredients. Because purified amino acids could be absorbed from the intestine faster than amino acids released from intact proteins, the two forms might be metabolized differently. We discuss the differences in the rates at which amino acids are released from the proteins in practical ingredients, as such differences could affect their utilization.