Effect of dietary pH on amino acid utilization and the lysine requirement of fingerling channel catfish.

The pH of amino acid test diets has been shown to be of major importance in dietary amino acid studies in the channel catfish (Ictalurus punctatus). Maximum growth rate and feed conversion was observed when the test diet was adjusted to pH 7. Growth studies, utilizing a 24% crude protein diet containing an amino acid pattern similar to whole egg protein, indicate that the lysine requirement for fingerling channel catfish is about 1.23% of the diet (dry weight basis) or 5.1% of the dietary protein. The dietary requirement was confirmed by serum free lysine analysis. A marked increase in serum free lysine occurred at a dietary lysine level of approximately 1.2% of the diet.