Which AEA Curve Should I Use?
CMC includes several equations for predicting the Apparent Efficiency of Absorption (AEA) of immunoglobulin G (IgG). These equations were developed during the construction of the CMC model to evaluate different mathematical descriptions of how AEA changes with calf age.
The available curves are:
- Linear
- Quadratic
- Cubic
- Exponential
Each curve uses the same biological variables but describes the decline in AEA with age using a different mathematical function.
Why are there multiple curves?
During model development, several candidate equations were evaluated to determine which best described the published research data. Each equation was fitted to the same dataset and compared using standard statistical measures of model fit.
Although all four equations describe the same general biological relationship—a decline in IgG absorption with increasing calf age—they differ slightly in how rapidly AEA declines during the first day of life.
Which curve is recommended?
For most users, the Exponential curve is recommended.
The exponential model provided the best overall balance between biological realism and statistical performance during model development. It describes the rapid decline in intestinal IgG absorption during the first 24 hours of life while maintaining biologically reasonable predictions at both early and later feeding ages.
The exponential equation is also the model used throughout the accompanying CMC manuscripts and validation studies.
When might another curve be useful?
The remaining equations are included primarily for research purposes.
Researchers may wish to compare predictions among different mathematical models or evaluate how sensitive a particular analysis is to the choice of equation. Because all models were developed from the same dataset, their predictions are generally similar over the range of ages commonly encountered in commercial dairy production.
Our recommendation
For routine farm simulations, educational use, and most research applications, select the Exponential curve unless you have a specific reason to evaluate one of the alternative equations.
