Abstract
Simple SummaryDietary amino acid concentration should closely meet the quantitative requirement of animals dependent on genotype, gender, age, aimed performance and housing conditions. Both under- and over-supply yield impaired efficacy of individual amino acid utilization and increase the nitrogen excretion. Hence, for optimal feed formulation, a validated knowledge about adequacy of dietary amino acid balance is necessary. Present studies contribute toward ensuring ideal amino acid ratios in diets for growing broiler chicken making use of a new amino acid efficiency-based procedure.Three consecutive nitrogen balance experiments with fast-growing male broiler chickens (ROSS 308), both during starter and grower periods, were conducted to determine the ideal ratios of several indispensable amino acids relative to lysine. The control diets based on corn, wheat, fishmeal, field peas, wheat gluten and soybean oil were formulated by computer optimizing to meet the assumed ideal amino acid ratios and to fulfill both the energy and nutrient requirements of growing chicken. According to principles of the diet dilution technique, balanced control diets were diluted by wheat starch and refilled by crystalline amino acids and remaining feed ingredients, except the amino acid under study. The lysine, threonine, tryptophan, arginine, isoleucine and valine diluted diets resulted in significantly lower protein quality as compared to control diet, especially following increased dietary lysine supply (experiments II and III) and stronger amino acid dilution (experiment III). Accordingly, the limiting position of individual amino acids was confirmed, and the derived amino acid efficiency data were utilized to derive ideal amino acid ratios for the starter period: Lys (100): Thr (60): Trp (19): Arg (105): Ile (55): Val (63); and the grower period: Lys (100): Thr (62): Trp (17): Arg (105): Ile (65): Val (79).
Highlights
According to physiological needs, absorbed amino acids (AA) should be available for tissue protein synthesis in time and in a ratio that matches the AA requirement of individual tissues
In most experimental periods, lower N balance data were obtained with AA diluted diets as compared to the balanced control diet (CD), resulting from both reduced supply of individual AA and total
A more specific evaluation of the responses due to individual AA dilution was obtained by applying the model parameter, b
Summary
According to physiological needs, absorbed amino acids (AA) should be available for tissue protein synthesis in time and in a ratio that matches the AA requirement of individual tissues. A maximized correspondence between dietary supply and physiological requirements is the tool to improve metabolic efficacy within the physiological possibilities and sustainability of nutrient conversion in systems for food producing animals. Both improved AA requirement data and procedures to evaluate the feed potential are needed. A controversy exists according to the procedures, which are mostly adapted to the physiological conditions in the animal Such procedures utilize dose response studies making use of graded AA supplementation [7,8] or derive optimal ratios from AA response due to individual AA deletion from an AA complete diet [9]. Estimates of the AA requirement are conducted in terms of “subjective” and “objective”
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