Optimising the nutrient specifications of manufactured feeds for farmed juvenile greenlip abalone (Haliotis laevigata Donovan)

A series of experiments were conducted to investigate the protein, energy and lysine requirements of greenlip abalone Haliotis laevigata. An initial experiment estimated the optimal crude protein requirement. Digestibility coefficients of the protein and energy components of feed ingredients were then estimated and used to formulate diets to investigate the optimal dietary ratio of digestible protein to digestible energy and the effect these parameters have on tissue quality in abalone. Finally, the lysine requirement of greenlip abalone was estimated using two methods of lysine supplementation. The first experiment involved feeding a series of semi-purified diets in which the essential amino acid profile was similar to that of the soft tissue of abalone. Abalone grew fastest at a crude protein level of 20.1%. Excess dietary protein reduced the growth rate. The optimal digestible protein:digestible energy ratio was estimated at 14.4 gDP.M.VDE. Leaching of essential amino acids over 24 hours immersion ranged from 26-54%. The apparent and true digestibility coefficients of the protein and energy components of five feedstuffs were estimated. Defatted soyflour provided the most digestible protein (96.7% digestible). Pre-gelled starch provided the most digestible energy (80.6%). Cost analysis indicated that defatted soyflour was the most costeffective source of protein and energy of the feedstuffs studied. In a factorial experiment, abalone were fed diets at ten levels of protein and two levels of energy. The optimal dietary digestible protein level was estimated at only 13%, and the optimal ratio of digestible protein:digestible energy between `12.3-17.9 g.M.J^-1`. Abalone grew poorly on diets with fish oil levels of 6.0 - 9.0%, although their growth rate increased when returned to a commercial diet containing less oil. The composition of abalone foot muscle and, to a lesser extent, viscera, was affected by dietary protein level and, in some cases, by dietary energy level. Carcass partitioning revealed that meat yield was also affected by dietary protein level. The lysine requirement of greenlip abalone was determined using two methods of lysine supplementation; the addition of free L-lysine-hydrochloride to diets and the use of gluten enriched with covalently-bound lysine. Abalone showed a linear response to free-lysine, and a curvilinear response to covalently-bound lysine. The former method was therefore unable to produce an estimate of dietary lysine requirement. Use of covalently-bound lysine predicted that maximal growth occurred when lysine accounted for 3.9% of crude protein.