Abstract
Feeding trials were conducted with yellowtail and red sea bream to examine effects of partial or complete replacement of fish meal in their diets. Experimental diets were formulated to replace fish meal with various combination of plant and animal protein meals (dietary fish meal: 40, 30, 20, 10, and 0%). Commercial dry pellets containing 65% fish meal was used as a control diet. These experimental diets were fed to yellowtail, Seriola quinqueradiata, weighing 140 or 105 g on average for 101 or 97 days in net cages, respectively, and to red sea bream, Pagrus major, of 30 g for 70 days in aquaria.
In both species, palatability of diets was not affected by inclusion of alternate proteins. Growth rate and feed gain ratio of yellowtail were proportional to the fish meal content in diets and were especially low in fish fed diets containing fish meal below 20%. However, performance parameters of fish on diets containing 40 and 30% fish meal were nearly comparable to those of the control. A similar tendency was also observed in hemochemical constituents. The poor feed performances due to high inclusion levels of alternate proteins might result from the deficiency of essential amino acids such as lysine and methionine in diets. In red sea bream, there was no marked difference in growth and feed performance, and health status among dietary treatments.
Thus the alternate protein ingredients can be effectively included to reduce fish meal content to 30% (replacing around 50% of fish meal) in yellowtail diets. On the other hand, fish meal could be completely replaced by a suitable combination of substitutive proteins in red sea bream diets without ill effects.
