Maintenance requirement for digestible energy and efficiency of utilisation of digestible energy for retention in rainbow trout, Oncorhynchus mykiss

Partitioning of digestible energy for maintenance and growth was examined in fast growing rainbow trout via multiple regression analysis. Data from 292 groups of rainbow trout fed a large variety of different diets for which digestible energy intake can be assumed as the factor limiting growth were used in the analysis. Intake of digestible energy, energy retention and protein as well as lipid gain had been quantified for each group of trout. Multiple regression suggested that maintenance requirement for digestible energy was dependent on the 0.43 power of body weight in grams. Depending on growth rate, maintenance requirement contributed to between 10 and 30% of the total digestible energy requirement. The utilisation of digestible energy that was available for retention proved to be dependent on fat concentration in the diet. Effects of dietary crude protein concentration or water temperature on digestible energy utilisation could not be determined for this data set. Daily digestible energy requirement (kJ) could be best predicted by 1.31 BW0.43 (g) + retained energy (kJ/day)/[0.66 (1 + 0.000652 g fat/kg dry diet)]. Assuming a partial efficiency of DE utilisation above maintenance for fat retention of 0.9, a partial efficiency of DE above maintenance for protein retention of 0.54 was calculated. An inter-laboratory approach is suggested to obtain a wider range of experimental data and, therefore, to improve the suitability of models for general application. (C) 1999 Elsevier Science B.V. All rights reserved.