The variation in the concentration of plasma amino acids and blood urea in pregnant sows

Two pregnant sows were fed on a basal diet consisting of equal amounts of ground barley and ground wheat with or without addition of L-lysine hydrochloride. Plasma amino acid and blood urea levels varied according to the time after feeding. Almost all the essential amino acids reached a maximum level after one hour and then declined at four hours after feeding. The results suggested that samples taken at between one and four hours after feeding were responsive to changes in dietary composition and could provide a measure to evaluate the amino acid pattern in relation to feeding. Both plasma amino acid and blood urea data suggested that lysine was the first limiting amino acid in the basal diet.