Which amino acids are limiting in monogastrics?

Which amino acids are limiting in monogastrics?

• A. Lysine and Methionine
• B. Tryptophan and Valine
• C. Leucine and Isoleucine
• D. Threonine and Phenylalanine

Answer: (A)

In monogastrics, growth and protein synthesis are driven by the essential amino acid that is most deficient relative to the animal’s requirement. This makes certain amino acids “limiting” in a given diet. In typical cereal-based diets used for pigs and other monogastrics, lysine is the first limiting essential amino acid because cereals are relatively low in lysine. If lysine is not sufficient, the animal cannot utilize other amino acids efficiently for growth, even if they’re present in good amounts. Methionine is usually the second limiting amino acid, since plant proteins often supply less methionine (and cysteine) than the animal needs. Together, lysine and methionine set the ceiling for how efficiently protein can be synthesized on these common feeds, which is why they’re the best answer. Other pairings can be limiting in specific formulations, but lysine and methionine are the most consistently limiting in standard monogastric diets.

In monogastrics, growth and protein synthesis are driven by the essential amino acid that is most deficient relative to the animal’s requirement. This makes certain amino acids “limiting” in a given diet. In typical cereal-based diets used for pigs and other monogastrics, lysine is the first limiting essential amino acid because cereals are relatively low in lysine. If lysine is not sufficient, the animal cannot utilize other amino acids efficiently for growth, even if they’re present in good amounts. Methionine is usually the second limiting amino acid, since plant proteins often supply less methionine (and cysteine) than the animal needs. Together, lysine and methionine set the ceiling for how efficiently protein can be synthesized on these common feeds, which is why they’re the best answer. Other pairings can be limiting in specific formulations, but lysine and methionine are the most consistently limiting in standard monogastric diets.