A comparison of total and digestible amino acids in diets for broilers andlayers

Eleven samples of food ingredients were analysed for their total and true d igestible amino acid content, apparent metabolisable energy and other compo nents. Large batches of these ingredients were retained for st broiler and a layer experiment. Four layer diets were formulated at 0.97 and 0.90 of to tal and digestible amino acid requirements for egg production using the ana lysed ingredients. Eight broiler diets were also formulated from 1.0 to 0.9 1 of total and digestible amino acid requirements in starter and finisher d iets. Proximate and amino acid analyses and AME values were within the norm al range for the 11 foodstuffs. Digestibility of amino acids was high with very few exceptions, e.g. cottonseed meal, meat and bone meal. Diets formul ated on a total or digestible amino acid basis gave no differences in egg p roduction parameters or broiler production parameters with no effect of lev el of inclusion. However, the main effects showed that diets formulated on a total compared to a digestible amino acid basis gave better growth rate a nd feed conversion efficiency in broilers. It was concluded that nutrient s pecifications for layers and broilers are not sufficiently precise to be ab le to differentiate between 1.97 and 0.90 of requirement for egg production or 1.0 and 0.91 for broiler growth. The use of digestible amino acids may be justified in diet formulations only when unusual protein concentrates wi th low amino acid digestibility values are used in large amounts. (C) 1999 Elsevier Science B.V. All rights reserved.