Postprandial changes in serum amino acids of channel catfish fed diets containing different levels of protein and energy

Abstract

Five purified diets were utilized to investigate the effect of varying protein and energy intake on postprandial changes in systemic serum amino acid levels of channel catfish ( Ictalurus punctatus). The diets contained 25, 30 or 35% crude protein at one of three different energy levels. Systemic serum free amino acids and glucose were determined at 0, 2, 4, 8, 12 and 24 h after feeding each diet. In general, for each diet tested, most of the systemic serum free amino acid levels increased within 2 h after feeding, remained elevated for up to 12 h, and returned to fasting levels within 24 h after feeding. Varying the protein to energy ratios in the diets did not profoundly affect postprandial systemic serum free amino acid patterns. There was a significant positive correlation between the levels of systemic serum free essential amino acids and dietary levels. No such correlation was observed for non-essential amino acids. Serine and alanine were the most abundant free amino acids in catfish serum. Glutamic acid, glycine and proline remained relatively low throughout all treatments. A reciprocal relationship was observed between levels of glucose and total free amino acids in the serum.