Effects of Non-Starch Polysaccharide Enzymes in Diets with Seaweed Ulva pertusa on Growth, Dietary Apparent Digestibility and Flesh Nutrition Composition of Siganus canaliculatus

Abstract:

In order to evaluate the effects of non-starch polysaccharide (NSP) enzymes in the seaweed Ulva pertusa-containing diets on the feed utilization of Siganus canaliculatus, we prepared six isonitrogenous and isolipid compound diets with 32% crude protein and 8% lipid. Diets without seaweed were used as control diet 1 (C1); diets that contained 15% seaweed powder were used as control diet 2 (C2); four other diets that contained 15% seaweed powder together with different levels of non-starch polysaccharide enzyme were used as experimental diets (T1−T4). S. canaliculatus juveniles were fed with these six diets for 8 weeks. We then compared their growth performance, the activities of digestive enzymes, and the apparent digestibility of nutrients, in order to determine the effects NSP and its optimal amount in the diet. The results showed that the weight gain rate, specific growth rate and protein efficiency rate in Groups T1−T4 were higher than those in Group C2, but displayed no significant difference from Group C1 (except for the protein efficiency in Group T4) (P>0.05). All six groups showed no significant differences in the body biochemical composition and activities of digestive enzymes in stomach, foregut and liver that included protease, amylase and lipase (P>0.05). The apparent digestibility coefficient of protein and the digestibility of dry matter in Groups T1−T4 were significantly higher than those in Group C2 (P<0.05). The whole body composition was similar between the seaweed groups and the control group. In terms of the amino acid and fatty acid composition in the dorsal muscles, seaweed groups showed no significant differences from the control, except that the levels of ALA, EPA, DPA, Tyr and Met in flesh were reduced in the seaweed groups, and the level of His was increased. These results indicated that the addition of NSP enzyme in seaweed-containing diets could improve the growth performance and feed utilization efficiency, and seaweeds in diet have little impact on the nutrition composition in the flesh.