Abstract
The growth and energy budget for F 2 ‘all‐fish’ growth hormone gene transgenic common carp Cyprinus carpio of two body sizes were investigated at 29·2° C for 21 days. Specific growth rate, feed intake, feed efficiency, digestibility coefficients of dry matter and protein, gross energy intake ( I E ), and the proportion of I E utilized for heat production ( H E ) were significantly higher in the transgenics than in the controls. The proportion of I E directed to waste products [faecal energy ( F E ) and excretory energy loss ( Z E + U E ) where Z E is through the gills and U E through the kidney], and the proportion of metabolizable energy ( M E ) for recovered energy ( R E ) were significantly lower in the transgenics than in the controls. The average energy budget equation of transgenic fish was as follows: 100 I E = 19·3 F E + 6·0 ( Z E + U E ) + 45·2 H E + 29·5 R E or 100 M E = 60·5 H E + 39·5 R E . The average energy budget equation of the controls was: 100 I E = 25·2 F E + 7·4 ( Z E + U E ) + 35·5 H E + 31·9 R E or 100 M E = 52·7 H E + 47·3 R E . These findings indicate that the high growth rate of ‘all‐fish’ transgenic common carp relative to their non‐transgenic counterparts was due to their increased feed intake, reduced lose of waste productions and improved feed efficiency. The benefit of the increased energy intake by transgenic fish, however, was diminished by their increased metabolism.