Metabolic availability of threonine in common foodstuffs in pigs

Abstract

Availability of amino acids (AA) in foodstuffs must be known to ensure adequate dietary supply. Ileal digestibility and protein digestibility amino acid score do not account for the true metabolic utilization of absorbed AA. Availability of AA in adult animals may be different from growing pigs. The metabolic availability (MA) of threonine (THR) in corn and barley was determined in 8 pregnant sows and 8 growing pigs using the indicator amino acid oxidation method ([1‐*C] phenylalanine). Reference diets provided 40 – 80% of the THR requirement; other nutrients were set at 120% of requirement, and test diets provided THR at 80% of requirement. Tracer phenylalanine was given orally in 8 ½‐hourly meals and expired 13CO2 and 14CO2 was quantified. The MA of THR in corn and barley in sows was 88.0 and 89.3%, respectively. The MA of corn in growing pigs was 82.2%, similar to the published true ileal digestibility of THR in corn (82.0%). Metabolic availability is therefore, a good estimate of the true availability of AA in foodstuffs. Pregnant mature animals have a greater capacity to digest and utilize AA in common ingredients than growing animals. Funding: AB Pork, ON Pork, ALIDF, ACAAF, Ajinomoto.