The protein and energy requirements of farmed South African abalone Haliotis midae L. cultured at optimal and elevated water temperatures

Abstract

Formulated abalone feeds used by the culture industry are believed to be unsuitable for use at elevated water temperatures (>20 °C). The aim of this study was to develop a feed that could safely be fed to abalone cultured at elevated water temperatures by optimizing dietary protein/energy levels. Abalone (54.90 ± 0.08 mm; 28.99 ± 0.16 g) were cultured at either 18, 22 or 24 °C, and fed diets containing graded levels of protein (18–26%) and energy (11.6–16.2 MJ kg−1). Abalone growth was temperature dependent, declining from 4.33 g month−1 at 18 °C to 0.77 g month−1 at 24 °C. Shell length and weight gain were independent of dietary protein, provided that the digestible energy content of the diet was not lower than 13.5 MJ kg−1. Dietary energy levels below 13.5MJ kg-1 resulted in significant reductions in shell growth, weight gain and increased mortality from 5% to 27%. Feed consumption of the 22% and 26% protein diets with 11.6 MJ kg−1 was significantly higher (0.53 ± 0.04 and 0.55 ± 0.04% bd. wt. day−1 respectively) compared with abalone fed the 16.2 MJ kg−1 diets at the same protein levels (combined mean of 0.45 ± 0.04% bd. wt. day−1) indicating that consumption was linked to energy requirement. The growth and mortality results suggest that abalone cultured at these temperatures have a dietary digestible energy requirement of at least 13.5 MJ kg−1.