Real-time measurement of protein leaching from micro-particulate larval fish feeds

The small size and high surface area to volume ratio of larval fish feed presents challenges for nutrient retention in micro-particulate diets. A method for the accurate and rapid measurement of nutrient retention or loss from micro-particulate feed in water is needed to help develop micro-particulate feeds with good nutrient retention characteristics. The present study developed and validated an instrument method using fibre optic technology that measures protein leaching in real time. Larval fish feed particles of different sizes (100-500 mu m) and formulations were measured. Under consistent experimental conditions, a feed could be assayed for the rate of mass loss and the half-life or time of 50% total soluble mass loss. The results closely approximated natural decay models with coefficients of determination (r(2)) > 0.95. The end result is a fast and accurate method to quantify and provide solid reference data for a feed formulation or particle size. Using this method allows different feeds to be compared and conclusions drawn for relative performance.