Modeling immunocompetence development and immunoresponsiveness to challenge in chicks

Area of Science:

• Animal Immunology
• Mathematical Modeling
• Avian Health

Background:

• Evaluating immunological variables in young chicks is complex due to developing immune systems and maternal immunity.
• Accurate assessment of immunocompetence and immunoresponsiveness is crucial for improving animal health via genetic selection.
• Mathematical models can aid in defining optimal challenge and measurement strategies for immunological evaluations.

Purpose of the Study:

• To develop a deterministic model of immunocompetence and immunoresponsiveness kinetics in chicks challenged with pathogens.
• To utilize the model to demonstrate the impact of experimental design factors on immunological assessments.

Main Methods:

• A deterministic model was created, incorporating four components: maternal immunity, baseline immunity, acute phase response, and antibody response.
• The model describes immune system development and response kinetics from 0 to 56 days of age in chicks.
• Simulations explored four scenarios varying challenge age and measurement timing across three broiler genotypes with different baseline immunity levels.

Main Results:

• Model component equations generally provided adequate fits to published data.
• Simulations showed that experimental design significantly influences the ranking of genotypes, groups, or individuals based on immunoresponsiveness.
• The choice of measured variable, timing of measurement, and age at challenge critically affect the reliability of extrapolations.

Conclusions:

• The developed model serves as a valuable tool for designing effective challenge and measurement strategies in immunocompetence and immunoresponsiveness studies.
• The model can generate hypotheses regarding immunological relationships for subsequent experimental testing.
• This approach aids in optimizing experimental designs for more reliable immunological evaluations in poultry.