Effects of enzyme preparations and microbial preparations on the growth and gut microbiota of juvenile Neptunea cumingii

Neptunea cumingii, a carnivorous snail renowned for its high economic value and rich nutritional content, has long been a favorite among consumers. However, the rampant overfishing of this species has caused a dramatic decline in its natural population, thereby disrupting the ecological balance of marine ecosystems. Under such circumstances, the development of artificial breeding techniques has become an urgent necessity, as it not only helps meet the market demand but also eases the pressure on wild fisheries. Currently, the artificial breeding technology for N. cumingii remains in its early stages, with the low survival rate of juvenile snails being a major bottleneck restricting its development. A critical issue is the lack of an artificial compound feed that can fully meet the nutritional requirements of juvenile snails. To address this, this study compared the effects of different additive types of artificial feed and natural feed (Sinonovacula constricta) on the growth, digestive enzyme activity, nutritional composition, and gut microbiota structure of juvenile N. cumingii.. The experiment was designed with four groups: Group A, which was fed natural shellfish bait S. constricta; Group B, which was given an artificial compound feed supplemented with pepsin; Group C, where the artificial compound feed was added with Bacillus subtilis; and Group D, which received the artificial compound feed containing Lactobacillus plantarum. After a 9-week breeding period, the results revealed that the juvenile snails in Group A exhibited the fastest growth rate, while Group C showed the best performance in terms of both growth and survival rate. In terms of digestive enzyme activities, Group A had the highest lipase activity (P<0.05), whereas Group C recorded the highest pepsin and amylase activities (P<0.05). Regarding the α-diversity of the intestinal flora, Group A had the highest Ace and Chao1 indices, Group C had the highest Shannon index, and Group D had the highest Simpson index. The number of OTUs in the gut microbiota of juvenile snails across different feeding groups, from highest to lowest was as follows: group A, group C, group D, and group B. The number of OTUs common to all four groups of juvenile snail gut samples was relatively low. Overall, although natural shellfish feed promotes the best growth of juvenile N. cumingii, artificial feed supplemented with Bacillus subtilis demonstrated relative advantages in improving survival rates, enhancing pepsin and amylase activity, and significantly regulating gut microbiota structure. Current artificial cultivation techniques for N. cumingii remain in their infancy, with one major constraint being the lack of suitable artificial feed for juveniles. This study provides a foundation for developing compound artificial feed that meets the nutritional requirements of juvenile N. cumingii, offering new feed selection approaches for the aquaculture industry.