The effect of increasing inclusion rates of soybean, pea and canola meals and their protein concentrates on the growth of rainbow trout: Concepts in diet formulation and experimental design for ingredient evaluation

Abstract

A series of six growth experiments were conducted to assess the effects of feeding pea meal (PM), pea protein concentrate (PPC), soybean meal (SBM), soy protein concentrate (SPC), canola meal (CM) and canola protein concentrate (CPC) on the growth of rainbow trout. The nutrient digestibility of the experimental ingredients was determined prior to commencement of this experiment. Based on these digestibility values, diets containing 0, 75, 150, 225 or 300g/kg of each test ingredient were formulated. All diets contained 17.6MJ/kg digestible energy, 386.2g/kg digestible crude protein and were balanced for digestible essential amino acids to meet or exceed the requirements of rainbow trout. The inclusion of fish meal in the diets was kept as constant as possible within the constraints of balancing digestible nutrients. Experiments for each ingredient were conducted consecutively over a 361-day period. During each growth experiment, three tanks of rainbow trout per treatment were fed twice daily to apparent satiety for 56days. Fish were weighed on days 0 and 56 and total feed intake was measured. Linear and quadratic regression equations of the growth parameters on ingredient inclusion rate were calculated. The calculated regression equations for inclusion rate on average daily feed intake (ADFI), specific growth rate (SGR), feed conversion ratio (FCR) and protein efficiency ratio (PER) were not significant for PM, SPC or CPC (P>0.05). PPC inclusion had a positive linear relationship with ADFI (P<0.05). SBM inclusion had a significantly negative quadratic relationship with SGR and FCR, while for PER, both the linear and quadratic regressions were negative (P<0.05). CM inclusion rate had a significantly negative linear and quadratic relationship with specific growth rate and feed conversion ratio. The P-value for the linear regression was lower than for the quadratic regression. CM also had a negative linear relationship with PER (P<0.05). The results suggest there are no significant negative ingredient effects of PM, PPC, SPC and CPC on rainbow trout growth. Thus, growth can be predicted on the basis of digestible nutrients for these ingredients, provided the nutritional standards set for this experiment are followed. SBM and CM have significantly negative ingredient effects, which must be taken into account when using these ingredients in rainbow trout diets.