Effects of four sugars as carbon sources on intestinal digestive enzymes and intestinal flora of Litopenaeus vannamei

The purpose of this study was to investigate the effects of four common sugar sources on the growth, digestive enzymes and intestinal flora of Litopenaeus vannamei. The selected initial weight of L.vannamei was (0.36±0.02)g. Four kinds of common sugars (glucose, fructose, starch and sucrose) were selected from a variety of sugars as the sugar source to prepare the feed. Four treatments were carried out in total, three replicates for each treatment, 40 prawns for each replicate. The breeding period was 56 days, and the added amount of each sugar source was 20%. The test results show that, ① The specific growth rate and protein efficiency of L.vannamei were significantly different, the starch group was significantly higher than the other three groups, but there was no significant difference in the liver body ratio and the meat content rate between the groups. The whole body nutrition of shrimp, the crude fat of sucrose group was significantly lower than the other three groups, the ash of glucose group was significantly higher than the other three groups, and there was no significant difference between crude protein and moisture. ② There were significant differences in digestive enzyme activities among different groups of L.vannamei, the activity of lipase in starch group and sucrose group was significantly higher than that in glucose group and fructose group. There was no significant difference between starch group and sucrose group, while the activity of pepsin in starch group was significantly higher than that in other three groups. ③ There was no significant difference in OTU, Ace and Chao indexes among the groups; Shannon index in starch group and sucrose group were significantly higher than glucose group; Simpson index starch group was significantly lower than sucrose group, and sucrose group was significantly lower than glucose group. At the level of phylum, the relative abundance of Proteobacteria in sucrose group was significantly higher than that in glucose group, while that in Bacteroidetes and Actinobacteria in starch group was significantly higher than that in glucose group, but there was no significant difference between the groups. At the class level, there was significant difference in the intestinal microflora of L. vannamei between the treatment groups. The Flavobacteriia, Gammaproteobacteria, Actinobacteria, Cytophagia in the intestinal tract of L. vannamei in starch group were significantly higher than those in sucrose group and glucose group.In summary, the absorption and utilization of starch and sucrose by L.vannamei is better than that of glucose and fructose. Meanwhile, starch and sucrose have certain influence on the diversity of intestinal flora of L.vannamei. Starch and sucrose are the suitable sugar sources in L.vannamei feed.