The effect of fishmeal replacement with terrestrial protein sources on growth, body condition and intestinal microbiota of juvenile dusky kob <i>Argyrosomus japonicus</i>

Abstract

A balanced combination of protein sources to partially replace fishmeal in the diets of cultured carnivorous fish can promote optimal fish health and production performance. In the present study, the growth, body condition and gut microbiota of juvenile dusky kob Argyrosomus japonicus fed fishmeal-substituted diets comprising different blends of animal and plant protein sources, with crystalline amino acid supplementation, were compared. The fish (15.7 [SE 0.12] g fish⁻¹) were fed one of three isonitrogenous (41% protein) and isoenergetic (13 kJ g⁻¹) diets for 60 days. Fish fed a diet with no fishmeal (D0; blood meal and soybean protein sources only) displayed the lowest specific growth rate (p < 0.001). Longer body lengths were achieved in fish fed a 50% fishmeal diet (D50; supplemented with poultry meal, bloodmeal, canola meal and soybean) (13.2 [SE 0.4] cm) compared with those fed either a 100% fishmeal diet (D100) (12.8 [SE 0.4] cm) or a diet with no fishmeal (D0) (12.1 [SE 0.08] cm) (p < 0.001). There were no differences in condition factor, hepatosomatic index (HSI) and feed conversion ratio (FCR) between fish fed diets D50 and D100; whereas fish fed diet D0 had a lower HSI and a higher FCR when compared with the other treatments (p < 0.01). The dietary protein source did not alter the gut microbiota of these fish. In conclusion, 50% replacement of dietary fishmeal with a favourable balance of meals processed from poultry, blood, canola and soybean improved length gain in juvenile dusky kob compared with those fed a diet with no fishmeal replacement.

Keywords: blood meal, canola meal, crystalline amino acids, gut bacteria, hepatosomatic index, poultry meal, soybean meal