Effect of supplemented fungal phytase on performance and phosphorus availability by phosphorus-depleted juvenile rainbow trout (Oncorhynchus mykiss), and on the magnitude and composition of phosphorus waste output |
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| Authors: | Johanne Dalsgaard Kim Schøn Ekmann Per Bovbjerg Pedersen Viviane Verlhac |
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| Institution: | 1. Technical University of Denmark, DTU Aqua, Section for Aquaculture, The North Sea Research Centre, P.O. Box 101, 9850 Hirtshals, Denmark;2. Kwame Nkrumah University of Science and Technology, Department of Fisheries and Watershed Management, Faculty of Renewable Natural Resources, Kumasi, Ghana;1. US Fish and Wildlife Service, Bozeman Fish Technology Center, Bozeman, MT 59715, USA;2. Montana State University, Department of Animal and Range Sciences, Bozeman, MT 59715, USA;3. USDA-ARS, Trout Grains Project, Bozeman Fish Technology Center, Bozeman, MT 59715, USA;4. ADM Research, 1001 N Brush College Road, Decatur, IL 62521, USA;5. USDA-ARS, Harry K. Dupree Stuttgart National Aquaculture Research Center, 130 East, Stuttgart, AR 72160, USA;1. Aquaculture and Fisheries Group, Wageningen Institute of Animal Sciences (WIAS), Wageningen University, Wageningen, The Netherlands;2. Danisco Animal Nutrition, DuPont Industrial Biosciences, Marlborough, UK;1. Wageningen Institute of Animal Sciences, Aquaculture and Fisheries Group, Wageningen University and Research, Wageningen, the Netherlands;2. Sustainable Aquaculture Program, WorldFish, Bangladesh;3. WorldFish Head quarters, Penang, Malaysia |
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| Abstract: | The effect of a supplemental fungal phytase on performance and phosphorus availability by juvenile rainbow trout fed diets with a high inclusion of plant based protein and on the magnitude and composition of the waste phosphorus production was tested in a 2 × 3 factorial design at a temperature of 11 °C. Two factors comprised of two dietary fungal phytase levels (0 or 1400 U kg? 1 feed? 1), and three dietary total phosphorus levels (0.89, 0.97 or 1.12%). All fish were acclimated to the lowest total phosphorus diet for 16 days, which included 0.29% phytate-phosphorus and no supplemental fungal phytase, to ensure that they were depleted of phosphorus prior to the feeding trial.Growth and feed conversion ratios were not significantly affected by the increasing dietary phosphorus level or supplemental fungal phytase. Phosphorus availability increased significantly as a result of phytase supplementation, reaching an upper level of 74% at an available dietary phosphorus concentration of 0.71%. Adding fungal phytase to the diets improved the availability of phytate-phosphorus from an average of 6 to 64%. The fish retained 53–79% of the ingested phosphorus, while 24–44% was recovered in the faeces. The particulate phosphorus waste output was significantly higher in faeces from fish fed diets without fungal phytase compared to fish fed phytase supplemented diets. The dissolved/suspended phosphorus waste output represented 2–13% of the ingested phosphorus, and there was a significant increase in the dissolved/suspended phosphorus waste output from fish fed the phytase supplemented diet containing 0.71% available phosphorus, suggesting that the phosphorus requirement was reached at this phosphorus level. Consistent with this, there was a substantial increase in the dissolved/suspended phosphorus waste output from fish fed the phytase supplemented diet containing 0.81% available phosphorus, suggesting that the phosphorus requirement was exceeded in this group.This study demonstrated that phytase supplementation will be advantageous to the fish and the environment if supplemented to low-phosphorus diets containing a large share of plant-derived protein. Conversely, the results demonstrated that fungal phytase should not be supplemented to diets in which the available phosphorus level already meets the requirement of the fish, as this will lead to a significant increase in the dissolved/suspended phosphorus waste output. |
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