Growth and energy utilization of juvenile pink abalone Haliotis corrugata fed diets containing different levels of protein and two starch : lipid ratios

Abstract

Juvenile pink abalone Hahotis corrugata (initial mean length = 10.7 +/- 0.3 mm

initial mean weight = 0.15 g) were Brown under laboratory conditions in an aerated flow-through seawater system at 21 +/- 1 degrees C. For 131 days, abalone were fed diets containing three different levels of protein (42%, 36% and 32%), each level containing two ranges of starch:lipid ratios (1.5-1.8 or 3.2-3.6). The gross energy content of the diets ranged from 4.26-3.68 kcal/g. Within a particular protein level, growth did not differ significantly. When dietary protein levels exceeded 32%, a trend of higher growth of abalone was observed for dietary treatments that contained lower levels of lipid (higher starch to lipid ratios). The amount of protein consumed daily for the 32%a dietary protein is apparently insufficient to meet requirements for energy and maximum growth. No notable diet-dependent differences in the proportional composition (dry weight) of the shell and the soft tissue, and the energy content of the soft tissue were observed. Daily food intake and consumed energy were significantly different among treatments, being inversely related to the calculated P:E ratios. The increased consumption may have been somewhat overestimated because of loss arising from lower water stability of the diets. Ammonia excretion ranged from 7.9-4.8 mu g NH4+/h /g abalone but was not significantly different among treatments except for the treatment containing 32% crude protein and a low carbohydrate: lipid ratio. Specific Dynamic Action (SDA) comprised nearly 50% of measured oxygen consumption and did not significantly differ among treatments. Respiration increased during the night showing a typical circadian pattern reported in Haliotis genera. Measured mucus production (lid not vary among treatments. Carbohydrate preferentially serves as the principal energy source and a consistent amount of dietary protein is also used as an energy source, regardless of dietary protein content. Within a developed energy budget, approximately 70% of the ingested energy was lost through feces. and approximately 25% of the ingested energy was metabolized, with 7% to 10% channeled to growth. A direct determination of available digestible energy was not possible because of the inability to collect sufficient feces to estimate fecal energy. The results suggest that practical diets should include levels of dietary protein that are approximately 35% protein to meet requirements for energy and maximum growth. In addition, carbohydrates seem to be the preferred energy source and lipid levels should be minimized to the extent that essential fatty acids requirements are met.