Start Date: Dec 15, 2012
End Date: Mar 31, 2014
Aquaculture, as in all animal agriculture, has the task of effectively removing fecal waste from the rearing environment. In water, however, the task is more difficult since many factors can affect the consistency and size of feces. Several studies and commercial trials have demonstrated that feces from fish fed plant-based diets are more diffuse and difficult to remove than feces from fish fed a standard fish-meal diet. Two aspects will be considered in this project, with the first examining the effect of diet on fecal production and the second focusing on water quality and stocking density. Aspect 1: Dietary factors causing either diffuse or large feces have not been definitively determined, but the smaller the fecal particles the more difficult to remove by filtration or sedimentation. It is known that the diet digestibility affects total fecal production, yet it is unknown how the digestibility of various soy products affects fecal size. This project consists of 4 trials focusing on dietary and management factors affecting fecal particle size, and distribution of nitrogen and phosphorus, with the goal to develop improved plant based diets. Physiological parameters and gene expression will be monitored. In the first trial, eight soy products including standard and improved meals, feed grade soy protein concentrates from various sources and food grade SPC will be evaluated for fecal size and diet digestibility. The second trial evaluates the effect of feeding plant based diets with small amounts of animal by-products, algae, guar gum, and other ingredients thought to increase fecal size. The third trial determines the effect of feeding regime on fecal size. The next study will compare fecal size of trout fed improved plant based diets to commercial trout feeds. Incorporation of plant protein sources into trout feeds can increase water-borne phosphorous and ammonia in effluent and negatively affect receiving waters. Aspect 2: The impact of plant proteins on water quality could be minimized through improved diet formulation, including incorporation of novel soy protein products and processing. Furthermore, little information is available on how density of fish fed these diets affects water quality. Baseline information is needed on water quality of rainbow trout fed diets incorporating soybean meal and soy protein products. We currently have a research tank system that is uniquely equipped to study dietary effects on water quality. The system is capable of receiving 1st, 3rd, and 5th use water from a serial-reuse trout production hatchery and is able to monitor the water quality entering and exiting the system. To our knowledge, this is the only system of its kind available for monitoring multiple-use water in a trout production hatchery.