Gamma ray irradiation improves feather meal as a fish meal alternate in largemouth bass Micropterus salmoides diet

An 8-week feeding trial was conducted to evaluate the potential of replacing fish meal with feather meal in largemouth bass Micropterus salmoides diet. The reference diet (R) contained 300 g/kg fish meal, and 20 % and 40 % of the fish meal in diet R was replaced by either gamma ray (gamma) irradiated feather meal (IF20 and IF40) or non gamma-irradiated feather meal (F20 and F40). Contents of fish meal and feather meal (gamma-irradiated or non gamma-irradiated) were 240 g/kg and 53 g/kg in diets F20 and IF20, respectively, and were 180 g/kg and 106 g/kg in diets F40 and IF40. The weight gain of fish fed diet R did not significantly differ from that of fish fed diets F20, IF20 and IF40, but was higher than that of fish fed diet F40. The feed intake and feed conversion ratio were lower in fish fed diets F20 and F40 than in fish fed diets IF20 and IF40. No significant differences were found in retention efficiencies of carbon and nitrogen, condition factor, body contents of moisture, protein and lipid, and wastes outputs of carbon and nitrogen among fish fed diets R, F20, F40, IF20 and IF40. This study reveals that gamma-irradiated feather meal could replace more fish meal in largemouth bass diet than that replaced by non gamma-irradiated feather meal, and the dietary fish meal content could be reduced to 180 g/kg when gamma-irradiated feather meal was used as a fish meal alternate.