PROFILES OF SERUM AMINO-ACIDS TO ASSESS CONDITION OF COTTON RATS (SIGMODON-HISPIDUS)

We investigated the use of concentrations of blood-serum amino acids t o assess status of dietary proteins of juvenile cotton rats (Sigmodon hispidus). Eighteen juvenile animals were randomly assigned to isocalo ric diets containing 4 or 16% crude protein, and serum concentrations of amino acids were determined by high-pressure liquid chromatography on days 30 and 45 of a 45-day feeding trial. Concentrations of methion ine, threonine, tryptophan, valine, hydroxyproline, and branch-chain a mino acids (BCAA) were depressed, whereas histidine and proline were e levated among low-protein-fed cotton rats. The glycine/(leucine + vali ne) and phenylalanine/tyrosine ratios were greater in serum of cotton rats fed low-protein diet, whereas the tyrosine/neutral amino acids (N AA) and tryptophan/NAA ratios were depressed. Concentration of several free amino acids in serum of juvenile cotton rats differed between 30 - and 45-day samples. Because diet x sample interactions were signific ant for only tryptophan and hydroxyproline, temporal changes probably were a reflection of age-related alterations in developmental physiolo gy and not effects of diet. Our results indicate that clinical profile s of selected amino acids in serum can provide a useful technique for assessing protein nutritional status and quality of diet in small mamm als.