Growth and production of the African catfish, Clarias lazera (C. & V.) : III. Bioenergetic relations of body weight and feeding level

Abstract

Bioenergetic relations of body weight and feeding level in C. lazera were studied in open circuit balance respirometers to elucidate the physiological background of the highly efficient feed conversion in this fish. It was found that changes in proximate body composition that occurred at different feeding levels were largely attributable to concurrent changes in weight. The various body components were allometrically related to body weight. The same was true for the daily oxygen consumption where the weight exponent equalled 0.86 ± 0.02 (S.E.) for fasting fish and 0.75 ± 0.01 (S.E.) for feeding fish. The primary effect of feeding level was in the overall level of metabolism, which increased more than 3-fold from fasting to satiation feeding. The metabolic “scope for growth” was 0.346· W 0.75−0.145· W 0.83(kJ/day). The metabolizability of the feed energy was about 70% decreasing with the feeding level. ME utilization for energy gain above maintenance was 80% efficient, independent of body weight and feeding level. The intake of ME for gain was calculated to decrease from 6.9 to 2.8 times the maintenance requirement for fish of 1 to 200 g. This high ME p ME m ratio largely explains C. lazera's efficient utilization of the feed for growth.