Effects of poultry by-product meal replacing fish meal on growth performance, feed utilization, intestinal morphology and microbiota communities in juvenile large yellow croaker (Larimichthys crocea)

Abstract

An 8 weeks feeding trail was conducted to evaluate the potential of poultry by-product meal (PBM) replacing fish meal (FM) in the diet of juvenile large yellow croaker (Larimichthys crocea). Five iso-nitrogenous (45% crude protein), iso-lipidic (10% crude lipid) and iso-energetic (about kcal 400 g diet −1) diets were formulated with 0, 25%, 50% 75% and 100% FM being replaced by PBM (marked as FM, PBM25, PBM50, PBM75 and PBM100). Crystal methionine and lysine were added into PBM-containing diets to match its concentration in FM diet. Each diet was randomly assigned to triplicate groups of 30 fish (initial weight 18.43 ± 1.28 g) in floating sea cages. The weight gain, specific growth rate and feed efficiency of L. crocea decreased significantly when the replacement level of FM was higher than 25%. The feed intake of fish fed PBM100 was significantly lower than those fed FM, PBM25 and PBM50. Juveniles fed PBM-containing diets showed significantly lower value of muscular thickness in intestine when compared to those fed FM. Villi length decreased significantly when the replacement of FM in diets was more than 50%. Fish fed FM diet had the relative higher abundances of Exiguobacterium (from order to genus), Bacillus (from order to genus), Pseudomonadales (from order to genus) and Acinetobacter genus, those fed PBM25, PBM50 and/or PBM75 showed higher abundance of Peptostreptococcaceae and Vibrio. Overall, PBM replacing dietary FM may inhibit growth performance of L. crocea through reducing digestibility via declining the abundance of intestinal bacteria that producing digestive enzyme, and improving the abundance of pathogen. Peptostreptococcaceae and Vibrio could be the indicator in the intestinal of L. crocea fed high PBM diets. The optimum dietary FM replacement level by PBM was 25% for L. crocea.