Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/24/2003
Publication Date: 4/1/2004
Citation: Riche, M.A., Haley, D., Ortkrt, M., Garbrecht, S., Garling, D. 2004. Effect of feeding frequency on gastric evacuation and the return of appetite in tilapia oreochromis niloticus (L.). Aquaculture. 234:657-673. Interpretive Summary: The rate at which food is consumed, and the efficiency with which it is utilized are prime factors in determining growth rate. How often fish are fed can effect how efficiently they utilize the feed. Additionally making food available as soon as appetite has returned can maximize intake, and increase efficiency. Demonstrating a consistent relationship between stomach fullness and the return of appetite will allow an optimal feeding interval to be predicted. Tilapia were fed to satiation at 2, 3, 4, and 5 hour intervals. The rate at which the feed left the stomach and traversed the gastrointestinal tract was measured by following a marker. The data was used to generate a mathematical model describing food passage in Nile tilapia. The feeding interval did not affect the rate of movement. However, fish fed at 2 and 3 hour intervals ate more feed than their stomachs could efficiently digest. The optimal feeding interval for Nile tilapia at 28oC, as predicted from the model, is 4 hours.
Technical Abstract: The rate at which food is consumed, and the efficiency with which it is utilized are prime factors in determining growth rate. There is a positive relation between growth and feeding frequency. Additionally, feeding frequency is strongly correlated with gastric evacuation time. Nile tilapia O. niloticus were fed to satiation with a pelleted diet at two different feeding frequencies (three meals day -1 and five meals day -1) to evaluate the effects of feeding frequency on gastric evacuation and the return of appetite. Ferric oxide was used as an inert indicator to follow gastric evacuation and gastrointestinal transit. Following an initial meal to satiation with the ferric oxide containing diet fish were serially dissected at 0, 0.5, 1, 2, 4, 6, 8, 12, and 24 h post-prandially. The fish remaining in the treatments receiving three meals day -1 were fed to satiation again at 1200 hr and 1700 hr. The fish remaining in the treatments receiving five meals day -1 were fed to satiation again at 1000, 1200, 1500, and 1700 hr. Gastric evacuation rates (GER) for both treatments were curvilinear and were best described by a surface-area dependent model. The equation describing GER for fish fed three meals day -1 was VT = 67.0 e -0.153(x) and for fish fed five meals day -1 was VT = 85.0 e -0.149(x) . The instantaneous evacuation rates obtained by linearizing the data were not significantly different and suggest gastric evacuation is independent of feeding frequency. Fish fed at 4 - 5 hr intervals consume as much as they have evacuated. Fish receiving meals at 2 -3 hr intervals exhibit gastric overload. The return of appetite following a satiation meal is approximately 4 hr in Nile tilapia held at 28oC.