In vivo rat assay for true protein digestibility: collaborative study.

Area of Science:

• Animal Nutrition
• Food Science
• Analytical Chemistry

Background:

• Accurate determination of true protein digestibility is crucial for evaluating protein quality in animal feed and human food ingredients.
• Standardized assays are needed to ensure reliable and reproducible measurements across different laboratories.
• Previous methods may lack the precision required for consistent protein quality assessment.

Purpose of the Study:

• To estimate the precision and reproducibility of a standardized rat assay for true protein digestibility.
• To evaluate the assay's performance across a range of protein sources including animal, fish, and cereal products.
• To provide data supporting the official adoption of the assay for food and ingredient analysis.

Main Methods:

• Eight laboratories participated in a collaborative study using a standardized rat assay.
• Seven protein sources (casein, tuna fish, macaroni/cheese, pea protein concentrate, rolled oats, pinto beans, nonfat dried milk) were tested.
• Rats were fed diets containing 10% protein from a single source for acclimation and balance periods.

Main Results:

• Mean true protein digestibilities ranged from 72.6% (pinto beans) to 98.6% (casein).
• Repeatability relative standard deviations averaged 0.9% (range 0.5-2.8%).
• Reproducibility relative standard deviations averaged 2.4% (range 1.3-4.4%).

Conclusions:

• The standardized rat assay demonstrates acceptable precision and reproducibility for determining true protein digestibility.
• The method is suitable for a variety of food and ingredient protein sources.
• The assay has been approved as interim official first action for protein digestibility analysis.