A note on the method of calculating digestibility coefficients of nutrients provided by single ingredients to feeds of aquatic animals

A commonly used equation for the calculation of the apparent digestibility coefficients of feedstuffs for fish and crustaceans is shown to be incorrect. The correct (but rarely used) equation is presented and contrasted with the previous equation. Data from a previously published trial is used to illustrate the differences between these equations. In many cases, the values obtained using the two equations is very similar. Larger differences are found, however, when the level and digestibility of the nutrient in the test ingredient are greatly different from those in the reference diet.