Comparison of fasting plasma amino acid patterns in the pig, rat, and chicken

Abstract

Comparison of free amino acid levels in plasma (PAA) at 8, 12, 16, 20, and 24 h postprandial in pigs, rats, and chickens revealed differences between mammalian and avian species in the fasting metabolism of amino acids. PAA patterns during fasting were more variable for chickens than for either rats or pigs. There was a marked increase in the plasma lysine level in chickens (27.5 to 115.8 μg/ml) as fasting was extended from 8 to 24 h. Plasma lysine levels in pigs and rats, by contrast, increased from 14.2 to 19.5 μg/ml and 39.8 to 63.7 μg/ml respectively during the same period of fast. Plasma threonine and methionine levels also increased in chickens during fasting whereas the levels of these amino acids in pigs and rats decreased or remained unchanged during a 24-h fast. Extending the period of fast to 36 h in chickens and 48 h in pigs resulted in further small increases in the plasma lysine concentration.