Effect of the response interval of self-feeders on the self-regulation of feed demand by rainbow trout (Oncorhynchus mykiss) fry
2003
Shima, T. | Yamamoto, T. | Furuita, H. | Suzuki, N.
We studied the effect of varying response intervals of a self-feeding system on growth and feeding profiles of rainbow trout (Oncorhynchus mykiss) fry (1.53±0.55 g, mean±S.D.). Triplicate groups of 40 fish were fed a commercial trout feed for 49 days via self-feeders with response intervals adjusted to 2, 4, 15, or 60 s and a fixed reward level of 0.03 g (0.05% of initial biomass) per activation. In all groups, feeder activation occurred exclusively during the light period (07:00-19:25) with marked peaks at the artificially induced dawn and dusk. As the experiment progressed, the number of feeder activations during peak periods significantly increased in the 2 and 4 s response interval groups, but not the 15 and 60 s groups. Throughout the experiment, the amount of feed dispensed daily increased in all response interval groups. However, as the experiment progressed, the amount of feed dispensed in the 15 and 60 s groups gradually became less than the 2 and 4 s groups. There were significant negative relationships between the response interval and the feeding rate, final body weight (BWf), specific growth rate (SGR), and condition factor (CF) (P<0.05). Coefficients of variation of BWf and feed efficiency were not affected by the response interval. Results of this study indicate that the long response intervals (> or = 15 s) of the present self-feeder with a fixed reward level significantly restrict the ability of fish to increase the number of feeder activations to satisfy their energy requirements.
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