Submitted to: Aquaculture
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/22/2014
Publication Date: 5/4/2014
Citation: Read, E.S., Barrows, F., Gaylord, G.T., Paterson, J., Petersen, M.K., Sealey, W.M. 2014. Investigation of the effects of dietary protein source on copper and zinc bioavailability in rainbow trout. Aquaculture. 432:97-105. Interpretive Summary: The development of plant-based feeds that support rapid growth of trout has demonstrated that trout require nutrients in the proper proportion not specific ingredients like fishmeal. The nutrients, however, must be available to the digestive process of fish. Plant protein products contain a substance called phytate that can bind minerals and other nutrients. This study was conducted to determine if the level of copper and zinc that is added to trout diets needs to be altered when the protein comes primarily from plant sources. After 12 weeks of feeding both fishmeal and plant based diets supplemented with different levels of copper and zinc, it was observed that to maximize growth when feeding plant-based diets the level of both copper and zinc added to the diet should be increased.
Technical Abstract: Limited research has examined the effects that dietary protein sources have on copper (Cu) and Zinc (Zn) absorption, interactions and utilization in rainbow trout. Therefore, the objective of the first trial was to determine what effect protein source (plant vs. animal based), Cu source (complex vs. inorganic) and concentrations of Cu (0, 5, 10, 15, 20 ppm) in the diet had on rate and efficiency of gain and Cu tissue levels in rainbow trout. The second trial then examined if interactions occur due to increasing dietary content of Zn (0, 30, 300, 1500 ppm) in rainbow trout fed a plant-based diet. Results from the first trial demonstrated differences in growth and tissue mineral levels due to Cu level but not source. Trout fed plant-based diet had higher weight gain, improved FCR and higher hepatic Cu concentrations when compared to fishmeal-fed trout. Results from the second trial show that increasing dietary Zn supplementation increased whole body Zn and Cu at 12 wks. No significant antagonism between Cu and Zn was observed in rainbow trout fed plant-based diets. Zn deficiency signs including mortality, cataracts and caudal fin erosion were observed in trout fed the Cu and Zn deficient diet at 12 wks. Results of these studies indicate rainbow trout fed plant-based diets require both Cu and Zn supplementation at levels higher than those previously reported to maximize growth.