Swimming respirometry was employed to compare inactive metabolic rate (Rr), maximum metabolic rate (Rmax), resultant aerobic scope and maximum sustainable (critical) swimming speed (Ucrit), in growth hormone transgenic (GHT) and wild‐type (W) tilapia Oreochromis sp. hybrids. Although the Rr of GHT tilapia was significantly (58%) higher than their W conspecifics, there were no significant differences in their net aerobic scope because GHT tilapia exhibited a compensatory increase in Rmax that was equal to their net increase in Rr. As a consequence, the two groups had the same Ucrit. The GHT and W tilapia also exhibited the same capacity to regulate oxygen uptake during progressive hypoxia, despite the fact that the GHT fish were defending a higher demand for O2. The results indicate that ectopic expression of GH raises metabolic rate in tilapia, but the fish compensate for this metabolic load and preserve such physiological determinants of fitness as aerobic scope, swimming performance and tolerance of hypoxia.

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The administration of secretin improves visualization of the pancreatic ducts and helps in the evaluation of remnant pancreatic function after pancreatoduodenectomy.

Recent advances in modern marine biotechnology have permitted the generation of new strains of economically important fish species through the transfer of growth hormone genes. These transgenic fish strains show improved growth performance and therefore constitute a better alternative for aquaculture programs. Recently, we have obtained a transgenic tilapia line with accelerated growth. However, before introducing this line into Cuban aquaculture, environmental and food safety assessment was required by national authorities. Experiments were performed to evaluate the behavior of transgenic tilapia in comparison to wild tilapia as a way to assess the environmental impact of introducing transgenic tilapia into Cuban aquaculture. Studies were also conducted to evaluate, according to the principle of substantial equivalence, the safety of consuming transgenic tilapia as food. Behavior studies showed that transgenic tilapia had a lower feeding motivation and dominance status than controls. Food safety assessment indicated that tilapia growth hormone has no biological activity when administered to nonhuman primates. Furthermore, no effects were detected in human healthy volunteers after the consumption of transgenic tilapia. These results showed, at least under the conditions found in Cuba, no environmental implications for the introduction of this transgenic tilapia line and the safety in the consumption of tiGH-transgenic tilapia as an alternative feeding source for humans. These results support the culture and consumption of these transgenic tilapia.

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Growth manipulation of fish is an important task in aquatic biotechnology. The growth promoting effect of recombinant Pichia pastoris expressing tilapia growth hormone was demonstrated in red tilapia fry (Oreochromis sp.), which were immersed into water containing intact cells of the recombinant yeast. The weight increase of the treated group was 171% relative to the control group after 6 weeks.