Effect of the response
interval of self-feeders on the self-regulation of feed demand by rainbow
trout (Oncorhynchus mykiss) fry
T. Shima, T. Yamamoto, H. Furuita, N. Suzuki-2003
Aquaculture, 224(1-4): 181-191
Abstract:
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
(>/=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.