We report performance of rainbow trout (Oncorhynchus mykiss) fed a balanced dietary mix of plant proteins supplemented with either fish bone meal (FBM) derived from Alaskan seafood processing byproducts or dicalcium phosphate.
Seven experimental diets were formulated to contain two levels of dicalcium phosphate or two levels of two different kinds of FBM in all plant-protein (APP) based diets as follows: Diet 1, FM based; Diets 2 and 3, APP diets with low or high dicalcium phosphate; Diets 4 and 5, APP diets with 4% or 8% low phosphorus FBM; and Diets 6 and 7, APP diets with 2.7% or 5.4% high phosphorus FBM. The limiting amino acids methionine and lysine, as well as the amino sulfonic acid taurine, were added to the APP diets at appropriate concentrations. Triplicate groups of juvenile rainbow trout (average weight 31.5g) were fed one of the seven experimental diets for 12 weeks. Negative effects on growth performance and feed utilization were observed in the fish fed both kinds of FBM or the low level of dicalcium phosphate supplemented to APP diets. Fish fed high levels of dicalcium phosphate showed growth performance and feed utilization that was not significantly different from the control group indicating that FM may be completely replaced by plant proteins with appropriate dietary supplements. Significantly decreased ash levels and increased lipid content were observed in fish fed diets supplemented with FBM or dicalcium phosphate at low levels. Whole-body phosphorus level was not significantly different between controls and fish fed APP diets supplemented with dicalcium phosphate whereas phosphorus levels were significantly lower in FBM fed fish. The apparent digestibility coefficients (ADC) of protein and phosphorus were lower in the control diet than diet 3. The digestibility of the two kinds of FBM was not different. Therefore, the results indicate that total replacement of dietary FM solely by plant proteins could be possible in rainbow trout with no apparent reduction in growth performance or feed utilization when a balanced mix of plant protein ingredients is properly supplemented with highly available inorganic phosphate, limiting amino acids and taurine. Maintenance of the body Ca/P ratio close to 1 was also found in rainbow trout although the differences in diets were considerable. Alaskan FBM could be used in fish feeds as a supplemental calcium source but not as the primary source of phosphorus because of the low bioavailability of phosphorus to fish in these diets.
Publication: Aquaculture, Volume 302 , Issue 3