Abstract
This study was conducted to examine the effect of supplementing chitin, chitosan, and cellulose in the diet on the growth of red sea bream, Japanese eel, and yellowtail. The growth rate of all fishes fed with the 10% chitin supplemented diet recorded the highest value indicating diet super-iority. The feed efficiency in the red sea bream and Japanese eel which were fed with the 10 chitin supplemented diet also recorded the highest values. All fishes fed with the chitosan sup-plemented diet had the lowest growth rates and feed efficiencies indicating that the inclusion of 10% chitosan in the diet must have inhibited the processes involved with the digestion, absorption, and assimilation of the basal diet. The growth rates and feed efficiencies of red sea bream and yellowtail fed with the 10% cellulose supplemented diet were slightly higher than the values recorded for the control diet.
Chitinase, chitosanase, and cellulase activity in the stomach of the three types of fishes which were fed with the aforesaid diet were measured and only chitinase activity was detected. The level of chitinase activity in the stomach of these three fishes were in proportion to the rate of growth when fed with the chitin supplemented diet. These results suggested that in fishes which possess high activity of chitinase in their digestive gland, chitin is digested and utilized.
