Manipulation of growth of the Amazonian fish tambaqui, Colossoma macropomum (Characiformes: Serrasalmidae): analysis of physiological and zootechnical aspects

ABSTRACT Colossoma macropomum, known locally as tambaqui, is the native fish most farmed in Brazil, however, technological advances are needed to reach efficient production rates. Modulating growth factors, such as growth hormone, may be associated with improved growth rate and feed efficiency. The use of exogenous hormone for fish rearing is prohibited in Brazil, yet the experimental use of bovine hormone can be useful in research aimed at understanding how to stimulate endogenous growth hormones in fish. Therefore, the present study had the strict objective of understanding the effects of growth hormone on the physiology and zootechnical parameters of C. macropomum under experimental conditions. The animals were intraperitoneally injected every fifteen days with 1, 10 and 100 μg g-1 of bGH using 0.9% NaCl saline as diluent. The 10 and 100 μg g-1 bolus had a positive effect on the performance indexes of C. macropomum: weight gain (g), growing length (cm), daily weight gain (g), feed conversion and specific growth rate (% per day). The bGH promoted a greater increase in length than in mass, which caused a reduction in condition factor of the individuals receiving a bolus of 10 and 100 μg g-1. Furthermore, bGH caused no changes in glucose levels, cortisol, hematological parameters, plasma levels of Na+ and K+, and activity of gill’s H+-ATPase and Na+, K+-ATPase, at least during the experimental period considered in the present study.