Protein replacement in practical diets altered gut allochthonous bacteria of cultured cyprinid species with different food habits

As the cheap and sustainable recycled natural resources, intestinal casing meal (ICM) and yeast of monosodium glutamate (YMG) might be alternative protein sources in aquaculture diets. To determine the effects of dietary ICM and YMG on fish growth, feed utilization and gut allochthonous bacteria, 8-week feeding trials were conducted with blunt snout bream (Megalobrama amblycephala, MA; a typical herbivorous cultured fish species in China), black carp (Mylopharyngodon piceus, MP; a typical carnivorous species in China) and gibel carp (Carassius gibelio, CG; a typical omnivorous species in China) with partial or complete replacement of soybean meal by ICM or ICM and YMG mixture. The results indicated that ICM and YMG incorporation had positive effects (P value >0.05) on weight gain and feed conversion rate. The complete replacement altered the gut allochthonous microbiota of gibel carp and black carp (Cs < 0.70). Proteobacteria, Fusobacteria, Firmicutes and uncultured bacteria were predominant bacteria in these fish intestine by DGGE detection. Compared with the control diet group with SBM, intestinal allochthonous bacteria of fishes fed with ICM and YMG were significantly stimulated, such as proteobacterium clone (EF707282.1), Cetobacterium somerae (AB353124) and some Bacillus subtilis dependent on fish species. Based on these results, ICM and YMG have the potential to replace SBM in aqua feed, and altered gut allochthonous bacteria variedly as fish food habitats.