Effects of Cu2+-exchanged montmorillonite on intestinal microflora, digestibility and digestive enzyme activities of Nile tilapia

A total of 360 Nile tilapia at an average initial body weight of 3.9 g were randomly allocated to four treatments, each of which had three replicates of 30 fish per tank and used to investigate the effects of Cu2+-exchanged montmorillonite (Cu-MMT) on intestinal microflora, digestibility and digestive enzyme activities. The dietary treatments were: (i) basal diet, (ii) basal diet + 1.5 g kg(-1) MMT; (iii) basal diet + 30 mg kg(-1) copper as CuSO4 (equivalent to the copper in the Cu-MMT treatment group), or (iv) basal diet + 1.5 g kg(-1) Cu-MMT. The results showed that supplementation with Cu-MMT significantly improved growth performance as compared with the control and fish fed with Cu-MMT had higher growth performance than those fed with MMT or CuSO4. Supplementation with Cu-MMT reduced (P < 0.05) the total intestinal aerobic bacterial counts and affected the composition of intestinal microflora with Aeromonas, Vibrio, Pseudomonas, Flavobacterium, Acinetobacter, Alcaligence, Enterobacteriaceae decreasing as compared with the control. Addition of MMT improved (P < 0.05) the apparent digestibility of dry matter and crude protein, and the activities of intestinal amylase, lipase, and alkaline phosphatase as compared with the control. Addition of Cu-MMT improved (P < 0.05) the apparent digestibilities of dry matter, crude protein, ether extract, and crude ash, and the activities of total protease, amylase, lipase, and alkaline phosphatase as compared with the control. While supplementation with CuSO4 had no (P > 0.05) effect on intestinal microflora, digestibility, and digestive enzyme activities the results showed that Cu-MMT exhibited antibacterial activity in vivo resulting in a positive effect on digestive enzyme activities, and then promoted the digestion and absorption of dietary nutrition.