The utilization of selected organically certified ingredients in rainbow trout (Oncorhynchus mykiss Walbaum, 1792) nutrition

This thesis summarizes research pertaining to usefulness in rainbow trout diets with organically certifiable alternate protein and carbohydrate sources. Four different fish nutrition trials were carried out in this thesis. Trial I aimed to evaluate the dietary organically certified yeast (NuPro?) on growth performance, nutrient utilization and whole-body composition in juvenile rainbow trout, Oncorhynchus mykiss under organic production conditions. Two reference diets (CR: conventional reference and OR: organic reference) and three experimental diets including different levels of NuPro? [10% (N10); 20% (N20) or 30% (N30)] as partial replacements for fish meal protein were formulated. Diets were assigned to triplicate groups of 20 fish (initial body weight: 4.0 g) for 12 weeks. The use of conventional or organic wheat meal in reference diets did not result in any difference in growth performance or Feed Conversion Ratio (FCR) of rainbow trout in control groups (CR and OR) (p> 0.05). Similar growth responses were observed in the experimental groups except CR and N20 groups which were significantly different in terms of final body weight. FCR of CR and OR groups were slightly lower than other treatments. Parameters of nutrient utilization and body composition did not reveal any significant difference (p> 0.05).Trial II designed to assess the dietary organic lentil meal on growth performance, nutrient utilization and whole-body composition in juvenile rainbow trout, Oncorhynchus mykiss. Two reference diets (CR: conventional reference and OR: organic reference) and two experimental diets including organic lentil meal as partial (9.45%-low level) or totally (18.9%-high level) replacements for organic wheat meal were formulated. Diets were assigned to triplicate groups of 20 fish (initial body weight: 4.0 g) for 12 weeks. The data showed no difference in final weight, specific growth rate, and feed utilization by the supplementation of the reference fish meal basal diet with organic lentil meal (p> 0.05).In trial III, triplicate groups of rainbow trout with initial weight of 134 g were fed with either a fish meal based control diets or diets containing 10, 20 or 30% NuPro? for 8 weeks. Rainbow trout fed with 30% yeast diet showed the best growth performance and feed utilization (p< 0.05). No significant effects of dietary NuPro? inclusion on body composition were noted, though some alterations in organ somatic indices such as condition factor and hepatosomatic index were identified. Fish fed N30 diet had significantly higher hematocrit levels than control groups (p< 0.05).In the last trial, an 8-week feeding trial was conducted to evaluate the use of organic lentil meal as a dietary carbohydrate source for large rainbow trout. Two reference diets (CR: conventional reference and OR: organic reference) and two experimental diets including organic lentil meal as partial (18.55%-low level) or totally (37.10%-high level) replacements for wheat meal were formulated. Lentil meal diet at a low level had beneficial effects on growth parameters when compared to the lentil meal at a high level diet. Fish fed low level lentil meal diet had increased hematocrit than other treatments. No significant treatment effects were found on condition factor, hepatosomatic index, viscerosomatic index and dress-out. Whole body composition, except ash, of trout fed the various test diets was not significantly different.Results showed that organically certified yeast can contribute to organic feed formulations with an effective biological support to fish meal instead of organic plant proteins in the diets of juvenile rainbow trout. Organic lentil meal proved to have potential as feed ingredients for rainbow trout, mainly as carbohydrate replace for wheat.