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A 48 days growth trial investigated the effects of dietary protein on growth, feed utilization in non-transgenic and GH (growth hormone gene) transgenic common carp (Cyprinus carpio L.). Transgenic common carp (TG fish) and non-transgenic (NT fish) were fed with seven diets of different protein levels (20%, 24%, 28%, 32%, 36%, 40%, 44%). The results showed that, TG fish obtained higher growth and feed utilization. NT fish showed higher whole-body protein and lipid. Compared to NT fish, the lower whole-body lipid of TG fish was mainly achieved by reducing fat synthesis and promoting fatty acid β-oxidation, including down-regulation of mRNA levels of acetyl-CoA carboxylase 1 (acc1), acyl-CoA desaturase 1 (scd1) and fatty-acid synthase (fas), upregulation of mRNA level of carnitine palmitoyl transferase 1a (cpt-1a). Plasma glucose levels were found higher in TG fish than NT fish, which might be caused by the inhibition of glycolysis (pfk, p < 0.01). With increased dietary protein, both TG fish and NT fish showed increased growth and decreased body lipid. High dietary protein levels inhibit glycolysis, fat synthesis and fatty acid β-oxidation. In conclusion, TG fish exhibited better growth performance, and lower glycolysis, lipid synthesis and better fatty acid oxidation than the NT fish.
Guo et al. (Thu,) studied this question.