Research Note: Effect of Crystalline Lysine and Methionine Intake on Amino Acid Excretion by Precision-Fed Cockerels

Abstract

A study was conducted to investigate the relationship between increasing intake of crystalline lysine and methionine and excretion of these amino acids in a precision-fed cockerel assay. Birds were deprived of feed for 24h and then given increasing amounts of crystalline L-Lysine-HCl or DL-methionine via crop intubation. The amino acids were given with either 30 g of sucrose or with 30 g of an intact protein diet deficient in the test amino acid. The supplemental dietary levels (percentage of diet) were 0, 1.0, 2.4, and 9.1% for lysine and 0, .2, .45, 1.6, and 7.1% for methionine. Excreta (feces plus urine) were quantitatively collected for 48h postfeeding. The results showed that lysine and methionine excretion were significantly increased (P < .05) only at the highest dietary level. The effect of supplemental dietary lysine on lysine excretion was greater for the sucrose diet than the intact protein diet. Relative lysine balance (intake minus excretion expressed as a percentage of intake) decreased at the 2.4 and 9.1% levels in the sucrose diet and at the 9.1% level in the intact protein diet. Relative methionine balance was high at all intake levels. The results of the present study indicate that crop intubation of moderate levels of crystalline amino acids has little or no effect on amino acid excretion in the precision-fed cockerel assay.