Effects of different feeds on growth performance, body biochemical composition and digestive enzyme activity in ivory shell Babylonia areolata

The ivory shell Babylonia areolate a gastropod of the class Gastropoda, the order Stenoglossa, family Buccinidae, is distributed in tropical and subtropical sea areas of the Indo-Pacific Ocean. In China, the southeastern coastal provinces, such as Hainan, Guangdong and Fujian are the main cultural areas of this species. Until now, trash fish are the main feed in ivory shell culture, which often cause water pollution and pathogenic microbial infection. One way to solve this problem is to study new suitable artificial compound feed for ivory shells. In this study, in order to obtain suitable feed for this species, the effects of five types of feed, including chilled round scad meat (A, control group), steamed round scad meat (B), high temperature formed soft feed (C), low temperature formed soft feed (D) and commercially available puffed pellet feed (E), on the growth performance, muscle nutritional composition and intestinal digestive enzyme activity of ivory shell juveniles body weight (2.92±0.06) g were investigated over an 8-week feeding period. The survival rate was the highest in ivory shells fed with group C diet 97.14%±2.86%, and its weight specific growth rate was significantly higher than other feed groups (P<0.05), but less than the control group (A) (P<0.05). The food conversion ratio of ivory shells fed with group C diet was 1.98±0.12, showed significantly lower than those of A, B and D groups (P<0.05), but significantly higher than that of E group (P<0.05). In this study, the essential amino acid (EAA) contents of ivory shell muscle ranged from 7.55-8.58 g/100 g. Significantly lower EAA levels were found in group C and D treatments, compared to other groups (P<0.05). C22:6n-3 (docosahexaenoic acid, DHA), C20:4n-6 (arachidonic acid, ARA) and C18:0 were the top three fatty acids in ivory shell muscle. There was no significant difference in these three fatty acid profiles among different treatments (P>0.05), except of significant lower C22:6n-3 content in group E (P<0.05). The amylase and lipase activities in group C and D were significantly higher than those in control group (P<0.05), while the opposite results were observed in pepsin activity, when compared to control and E groups. In summary, ivory shells fed with high temperature formed soft feed (C) showed relatively higher survival rate and growth performance, and reasonable fatty acid composition in muscle, which meant this type of artificial compound feed was suitable for ivory shell culture.