Replacement of fish meal with fish processing by-product silage in diets for the rainbow trout,Oncorhynchus mykiss

This study evaluated the effects of the dietary fish silage (fs) used as a replacement for fish meal (fm),on growth performance,fatty acid composition and serum variables of rainbow trout,oncorhynchus mykiss. four experimental diets,including 0% (fs0),20% (fs20),40% (fs40) and 60% (fs60) of fish silage,were formulated. diets were given to triplicate groups of 40 fish/cage (average weight 52.90±1.88 g) for 8 weeks. the results showed that there were no significant differences in growth performance and nutrient utilization between control and fs20 group (p>0.05). fish fed with the fs20 diet grew significantly better than others (p<0.05). fillet protein and lipid content decreased with increasing of fish silage addition (p<0.05). fm replacement by fs did not affect the serum glucose level,but significantly increased total protein,triglyceride and total cholesterol levels (p<0.05). fatty acid composition of fish fillet was no significantly different between groups (p>0.05). results showed that fish processing by-product silage has potential to replace fish meal up to 20% in rainbow trout diets without adverse effects on growth performance,fatty acid composition and serum biochemical variables. copyright 2014 zoological society of pakistan.