An appraisal of current and potential replacement agricultural feeds for rainbow trout culture

Abstract

The objective of this thesis is to explore means by which feeding costs incurred in the culture of rainbow trout (Salmo gairdneri) may be stabilised or reduced, This is achieved by considering novel and traditional feed types and ingredients with regard to their economic potential, comparing performance with that expected using conventional commercially prepared dry compound pellets whose price is linked particularly to fishmeal supplies and which is therefore subject to the upward cost pressures on industrial fisheries worldwide. Attention is focussed on the scope for developing suitable and more price stable alternatives to fishmeal as a basis for trout diets. Materials are examined individually with regard to price and/or estimated production costs, handling costs and nutritional value to the fish, this latter being determined either on the basis of performance as recorded in the literature or by linear programming analysis of nutrient composition and digestibility. Use of the materials under varying circumstances are discussed and costed and are illustrated by a number of specific examples. Certain materials appear potentially useful as novel protein substitutes in the manufacture of standard compound pellets, while others would seem to be more economically attractive if used in an alternative fashion, either as a wet diet or as an ingredient in the formulation of a farm-prepared moist diet, for which examples are costed. Projections are made as to the costs and benefits of the various alternatives discussed and recommendations made as to suitable areas of future study.