A simple model for the determination of the relative utilization efficiency of protein by blacklip abalone (Haliotis rubra Leach)

A 6-week growth rate trial of 6.7 mm ± 1.35 SD long blacklip abalone ( Haliotis rubra ) fed one of four graded protein feeds (26%, 32%, 37%, 45% crude protein, CP) resulted in a maximum average growth rate of 81 μm day⁻¹ (percentage daily weight gain of 5.2% day⁻¹) with the 45% CP diet. Based on the results, a new, simple, non-destructive method to calculate the relative utilization efficiencies (RUE) of nutrients is presented to estimate the relative contributions of a nutrient to growth, body maintenance and the excess used for energy. Calculations of RUE of protein estimated that at the maximum growth rate, 59% of the CP was responsible for growth, while 31% was used for body maintenance and an excess of 10% was lost and presumably catabolized for energy and carbohydrate anabolism. At the %CP where the highest proportion of CP was used for growth, i.e. the maximum RUE of protein for growth (slightly higher at 62%), 35% was used for body maintenance and only 3% of the excess was lost to energy.