Interaction between genotype and dietary concentrations of methionine for immune function in commercial broilers

Area of Science:

• Animal Science
• Poultry Nutrition
• Immunology

Background:

• Methionine is an essential amino acid crucial for poultry growth and health.
• Understanding methionine requirements for both growth and immunity is vital for broiler production.
• Genotype differences may influence nutrient requirements and immune responses in broilers.

Purpose of the Study:

• To investigate the impact of varying methionine concentrations on growth, antibody response to sheep red blood cells (SRBC), and Escherichia coli resistance in broiler chicks.
• To assess potential genotype-by-methionine interactions on these parameters.
• To determine if methionine requirements differ for optimal growth versus optimal immune function.

Main Methods:

• Broiler chicks from four commercial genotypes were fed diets with four methionine concentrations (3.91-5.54 g/kg) from 1 to 49 days of age.
• Growth performance, antibody titers to SRBC, and resistance to E. coli challenge were measured.
• Cell-mediated immunity was assessed using phytohaemagglutinin-P (PHA-P) skin tests.

Main Results:

• Methionine concentration did not significantly affect overall body weight gain, except at 28 days where the lowest level resulted in lower weight.
• Higher methionine levels increased antibody titers to SRBC and enhanced the cutaneous basophilic hypersensitivity (CBH) response.
• Genotype influenced weight gain, and CBH response to PHA-P varied among genotypes, but genotype-methionine interactions were not significant for most immune parameters.

Conclusions:

• Broiler chicks may achieve optimal growth and food efficiency with 3.91 g/kg methionine.
• Immune functions, such as antibody production and CBH response, benefit from higher methionine concentrations.
• The methionine requirement for optimal immunity appears higher than that for growth in most broiler genotypes.