Replacement of fish meal with a matrix of organic plant proteins in organic trout (Oncorhynchus mykiss) feed, and the effects on nutrient utilization and fish performance

Abstract

This study examined the effects on nutrient utilization and fish performance when replacing 16, 31, and 47% of fish meal protein (corresponding to replacing 15, 29 and 44%, respectively, of total dietary protein) with a fixed matrix of organic pea, horsebean and rapeseed plant protein concentrates (PPC) in a ratio of 1.07:1.00:0.66. Four iso-energetic and iso-nitrogenous diets were produced to include 0, 136, 274 or 410 g kg − 1 of the organic PPC matrix, respectively. The organic protein ingredients were chosen based on their high protein content, and the matrix was established to mirror the amino acid composition of fish meal. The plant ingredients were dried, dehulled, grinded and air classified in accordance with the European Union Commission Regulation on organic aquaculture production, increasing the protein concentrations up to 577 g kg − 1 dry matter. Two experiments were carried out using juvenile rainbow trout (Oncorhynchus mykiss): 1) a digestibility study to examine the apparent digestibility of protein, lipid, nitrogen-free extract (NFE), total phosphorus and phytate-phosphorus, followed by a water sampling period to determine the output of nitrogen and phosphorus and enabling the setup of nitrogen and phosphorus mass-balances; and 2) a 57 day growth study including 3 growth periods each of 19 days and using pit-tagged fish. Substituting fish meal with organic PPC significantly increased the apparent digestibility coefficient (ADC) of protein and lipid (P b 0.008) at the highest PPC inclusion level, while there was a significant (P b 0.044) decrease in the ADC of NFE with increasing PPC inclusion level. The apparent digestibility coefficient of phytate-phosphorus was significantly lower (P b 0.005) at the highest PPC inclusion level compared to the fish meal control diet. The mass-balances revealed a significant increase in the excretion of ammonium-nitrogen (NH 4 N, P b 0.017) at the two highest PPC inclusion levels and a decrease in phosphorus (P b 0.009) excretion at the highest organic PPC inclusion level. There was no overall effect on the specific growth rates (SGRs) or feed conversion ratios (FCRs). The study thus demonstrated that it is possible to replace fish meal by 47% organic PPC without compromising rainbow trout performance. However, the results also indicated that it will be difficult to replace much more than this as long as supplementation with synthetic amino acids and exogenous phytase is not allowed in organic feed.

Evaluation of Locally-available Agroindustrial Byproducts as Partial Replacements to Fishmeal in Diets for Nile Tilapia (Oreochromis niloticus) Production in Ghana

“…At the global level, alternative protein sources for fish culture have been studied intensively during the last few decades because of the declining availability and high cost of fish meal [3][4][5]. A large number of plant products have been evaluated as potential protein sources in the diets for fish including cottonseed meal, sunflower meal and corn meal [6], soybean meal, cassava leaf meal, sweet potato leaf meal, groundnut cake [7], pea, horsebean and rapeseed plant protein concentrates [8], Jatropha kernel meal [9], cowpea [10] and lupin meal [11]. Despite the abundance of a large number agro-industrial by-product in Ghana, their potential as cheap ingredients for fish feed formulation remains to be fully exploited.…”

Effects of organic plant oils and role of oxidation on nutrient utilization in juvenile rainbow trout (Oncorhynchus mykiss)

“…The digestibility of NFE was low for all diets, presumably because of the high plant concentrate inclusion level (see also Lund et al 2011). It was significantly lower for the LO than for the SO diet (P , 0.005).…”

“…1.5% to 2.5%) to support a measurable effect on growth in the growth study or masked by the formulation of diets optimal in dietary protein content. Dietary methionine level was slightly lower than recommended for rainbow trout (Lund et al, 2011), which may also negatively have affected additional protein synthesis and growth in diets with an improved lipid digestibility. Metabolic energy expenditures in fish may increase by elongating and desaturating 18 carbon n-3 and n-6 PUFAs from plant oils to long-chain LC PUFAs such as EPA and DHA (Geurden et al, 2005).…”

“…Diet preparation and force-oxidation Five iso-energetic and iso-nitrogenous diets were formulated by BioMar Ltd, substituting 47% fishmeal protein by a fixed matrix of three organic plant protein concentrates as described in Lund et al (2011; Table 1). The diets were coated with either commercial fish oil (FO; serving as control diet), or one of the following four cold-pressed organic oils: LO, SO, RO and GO.…”

“…The objectives of this study were therefore twofold: first to test the influence of complete substitution of FO with either organic rapeseed oil (RO), LO, SO or grapeseed oil (GO) on nutrient digestibility and growth evaluated against FO as lipid source in diets in which 47% fishmeal protein was replaced by a matrix of organic plant proteins (Lund et al, 2011). Second, to investigate the susceptibility of moderate oxidation of these oils and how this affects the dietary plant oil FA composition, diet palatability (feed intake), as well as lipid digestibility and utilization in juvenile rainbow trout (Onchorhynchus mykiss).…”