Replacement of Fish Meal by a Mixture of Animal By-Products in Juvenile Rainbow Trout Diets

A mixture of animal by-products (MAB) was tested to replace fish meal (FM) in diets for juvenile rainbow trout Oncorhynchus mykiss. Fish averaging (±SD) 0.96 ± 0.07 g were divided into 15 groups, and 3 groups were fed one of five isonitrogenous diets replacing 0, 20, 40, 60, or 100% of FM protein with similar percentages of MAB (control, MAB20, MAB40, MAB60, or MAB100, respectively). The MAB consisted of 25% meat and bone meal, 24.5% leather meal, 20% squid liver powder, 15% feather meal, 7.5% blood meal (spray-dried), 7.5% poultry by-product meal, and 0.25% each methionine and lysine. After 16 weeks of feeding, fish fed diets MAB40, MAB60, and MAB100 exhibited significantly lower growth performance than the fish fed the control and MAB20 diets. Apparent digestibility estimates of protein with different collection times (every 40 min and after 12 and 48 h) did not show, in a feces collection system, protein leaching into the water for up to 48 h. The MAB substitution of up to 60% of FM protein in...