Effect of replacing fish meal with simple or complex mixtures of vegetable ingredients in diets fed to Nile tilapia (Oreochromis niloticus)
Borgeson, Tracy L
The effect of fractionating flax, peas and canola on the digestibility of these ingredients in Nile tilapia was determined. Dehulling of flax, and processing peas and canola to pea protein concentrate and canola protein concentrate, resulted in significant increases in the energy and dry matter digestibilities of these products (P < 0.05). Protein digestibility was significantly improved by dehulling flax but there were no differences in the protein digestibilities of pea, canola and their protein concentrates. The ability of the most digestible ingredients from Experiment 1 to replace fish meal in tilapia diets was examined in a 9 week growth trial. The diet formulations were arranged in a 2 x 4 factorial design with 2 types of plant protein mixtures used to replace fish meal (simple: soyabean meal and maize gluten meal or complex: soyabean meal, maize gluten meal, dehulled flax, pea protein concentrate and canola protein concentrate) and 4 levels of protein originating from fish meal (100%, 67%, 33% and 0%). Diets were formulated to contain equal digestible protein (380 g kg-1) and digestible energy (17.63 MJ kg-1). Fifty six tanks containing 10 male Nile tilapia were used in this experiment. Fish were fed to apparent satiation twice daily for a total of 63 days and growth and feed intake was measured for the entire experimental period. On day 64 of the experiment, one fish per tank was euthanized and a 1 cm segment of small intestine was prepared for measurement of villus length. The average daily gains, specific growth rates and feed efficiencies of fish fed diets with 0% fish meal were significantly lower than fish fed diets with the 33, 67 or 100% fish meal levels. Fish fed the complex diets had significantly higher average daily gains, specific growth rates, feed:gain ratios and protein efficiency ratios than those fed the simple diets. Villus length decreased with decreasing levels of fish meal and increased with increased diet complexity but the effects were not significant. The results indicated that replacement of fish meal with a complex mixture of plant ingredients may allow a greater replacement of fish meal in diets fed to Nile tilapia.
DegreeMaster of Science (M.Sc.)
DepartmentAnimal and Poultry Science
ProgramAnimal and Poultry Science
SupervisorDrew, Murray D.
CommitteeZello, Gordon A.; Thacker, Philip A.; Christensen, David A.; Buchanan, Fiona C.
Copyright DateJanuary 2005