Metabolism traits of 'all-fish' growth hormone transgenic common carp (Cyprinus carpio L.)

Transgenic animals with improved qualities have the potential to upset the ecological balance of a natural environment. We investigated metabolic rates of 'all-fish' growth hormone (GH) transgenic common carp under routine conditions and during starvation periods to determine whether energy stores in transgenic fish would deplete faster than controls during natural periods of starvation. Before the oxygen uptake was measured, the mean daily feed intake of transgenic carp was 2.12 times greater than control fish during 4 days of feeding. The average oxygen uptake of GH transgenic fish was 1.32 times greater than control fish within 96 h of starvation, but was not significantly different from controls between 96 and 144 h of starvation. At the same time, GH transgenic fish did not deplete energy reserves at a faster rate than did the controls, as the carcass energy contents of the two groups following a 60-d starvation period were not significantly different. Consequently, we suggest that increased routine oxygen uptake in GH transgenic common carp over that of control fish may be mainly due to the effects of feeding, and not to an increase in basal metabolism. GH transgenic fish are similar to controls in the regulation of metabolism to normally distribute energy reserves during starvation. (c) 2008 Published by Elsevier B.V.

Feeding level-scaled retention efficiency, growth and energy partitioning of a marine detritivorous fish, redlip mullet (Liza haematocheila T. & S.)

The effects of feeding level on growth, retention efficiency, faeces production and energy partitioning of redlip mullet were studied. A practical diet was used and fed at six levels from starvation, 1%, 2%, 3%, 4% of body weight (BW) to satiation for 3 weeks. The temperature was kept at 24 +/- 1 degrees C. Reducing the feeding amount resulted in significantly lower weight gain, and retention efficiency was significantly affected by feeding levels and attained the maximum at maximum feeding intake. Feeding 2% BW was the minimum required for fish to maintain growth. Fish carcass composition under different feeding levels could be divided into three groups: (1) starvation and FL1; (2) FL2 and FL3 and (3) FL4 and satiation, with significant differences among the groups but no differences in the groups except that ash content remained at constant value. Body composition of fish of group 2 was close to initial fish. The thermal-unit coefficient was 0.0381 at satiation, and significantly increased with increasing feeding levels. In order to accurately estimate basal metabolism (HeE), another trial on the relationship between HeE (kJ) and BW (g) was carried out. An exponential curve as HeE=0.1255BW(0.8386) explained this relationship. Intake energy (IE) increased from 11.30 to 63.08 kJ per fish, matching with different feeding levels. Energy allocated to growth of IE decreased with reducing feeding amount. There was a linear relationship between metabolism energy and retention energy in percentage.