Ideal amino acid profile for chicks during the first three weeks posthatching

Area of Science:

• Animal Nutrition
• Poultry Science
• Biochemistry

Background:

• Amino acid (AA) profiles are crucial for optimal chick growth and feed efficiency.
• Established profiles like NRC 1984, NRC 1994, and Illinois Ideal Chick Protein (IICP) guide nutritional formulations.
• Understanding the precise AA ratios relative to lysine is essential for refining these profiles.

Purpose of the Study:

• To compare the efficacy of three distinct amino acid profiles (NRC 1984, NRC 1994, and IICP) in chick bioassays.
• To evaluate the impact of varying digestible lysine levels on chick performance with different AA profiles.
• To determine the optimal indispensable amino acid ratios for poultry nutrition.

Main Methods:

• Two chick bioassays utilizing chemically defined amino acid diets.
• Chicks were fed diets based on NRC 1984, NRC 1994, and IICP profiles during the 2nd and 3rd weeks post-hatching.
• Diets were isonitrogenous, with digestible lysine levels set at deficient (0.80% or 0.90%) or superadequate (1.12%) concentrations.

Main Results:

• Chicks fed the NRC 1994 profile exhibited significantly greater weight gain than those fed the NRC 1984 profile at both deficient and superadequate lysine levels.
• When compared to the IICP profile at a deficient lysine level, the NRC 1994 profile resulted in similar weight gain and feed efficiency.
• The findings suggest that the NRC 1994 profile may contain higher levels of indispensable amino acids relative to lysine than optimal.

Conclusions:

• The NRC 1994 amino acid profile demonstrates superior performance over the NRC 1984 profile in young chicks.
• The IICP profile provides comparable results to NRC 1994, indicating potential overestimation of certain indispensable amino acids in the NRC 1994 profile relative to lysine.
• Further refinement of indispensable amino acid ratios, particularly concerning lysine, is warranted for poultry nutrition guidelines.