Protein-amino nutrition of nonruminant animals with emphasis on the pig: past, present and future

During the period of 1958 to 1983, the fortified corn-soybean meal diet became standard for swine production systems. Dietary formulation changed from a protein to an amino acid basis. Amino acid requirements were established for all classes of swine. For growing swine, some of these studies led to refinements of earlier estimated requirement values, but for brood sows, both gestating and lactating, requirements for virtually all of the indispensable amino acids were established for the first time. With requirement values available, attention turned to factors affecting requirements, e.g., protein level, energy level, amino acid balance, sex and criterion of response. In addition, initial attempts were made to obtain amino acid bioavailability values for swine feedstuffs. Other nonruminant species were also represented in the dramatic changes that occurred in protein-amino acid nutrition. Improved and highly palatable purified crystalline amino acid diets were developed for rats, chicks, dogs, cats, rabbits and fish. Nitrogen nutrition and metabolism of nonruminant herbivores (e.g., rabbits and horses) likewise became better understood during the last 25 yr.