Quantifying Nutrient Requirements of Fish

TLDR

Accurate use of these techniques can yield reliable conclusions about dietary protein requirements. The study used 350 rainbow trout across seven protein diets (30–60%) and analyzed 10‑week weight gains with ANOVA, broken‑line, and polynomial regression methods. Polynomial regression, being continuous, offers greater accuracy over other methods for wide nutrient intervals and supports economic decisions on protein levels for maximum returns.

Abstract

Four replicates of 50 rainbow trout (Salmo gairdneri) fingerlings each were assigned to each of seven dietary protein levels from 30 to 60% in 5% increments. Percentage weight gains for 10 wk were related to dietary protein levels using an analysis of variance and multiple comparisons of the means, a "broken line" analysis, and a polynomial regression analysis. When correctly used, one of these techniques should lead to a reasonable conclusion concerning dietary protein requirements. However, the polynomial regression analysis has the advantage of being continuous, like the relation of growth to dose, and should be more accurate than the other methods when the intervals between experimental dietary nutrient concentrations are wide. The polynomial regression analysis also provides the basis for making economic decisions relative to protein requirements for maximum economic returns.