This study compared growth performance between female and male transgenic channel catfish, Ictalurus punctatus, containing channel catfish growth hormone full-length cDNA driven by the ocean pout antifreeze protein promoter, opAFP-ccGH, the rainbow trout metallothionein promoter, rtMT-ccGH, or both constructs, and their non-transgenic siblings in earthen ponds at 16 and 48months of age. Body weight between the transgenic and their non-transgenicsiblings differed (P < 0.001) at all ages. Transgenic F2 opAFP-ccGH grew 1.51- to 2.58-, F2 rtMT-ccGH grew 1.44- to 2.99- and F1fish transgenic for both constructs grew 1.36- to 2.92- fold larger than their non-transgenicsibling controls, depending upon age and sex. Body weight of the transgenic GH males was significantly higher than those of the transgenic GH females at 16months of age (P < 0.001). However, body weight of the transgenic GH females was significantly higher (P < 0.001) compared with those of the transgenic GH males at 48months of age, but not for the double transgenics (P > 0.05). In the case of non-transgenic GH siblings, males were larger than females at both 16 and 48months of age (P < 0.001). Sexually dimorphic responses to GH transgenes were the opposite after sexual maturation. When critically low dissolved oxygen levels were encountered, survival of transgenic male and female opAFP-ccGH channel catfish was lower than that of controls (P = 0.004), as well as rtMT-ccGH females (P = 0.11), which is not surprising since the largest fish are most likely to succumb during an oxygen depletion.
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