Níveis de proteína na nutrição do surubim (Pseudoplatystoma spp.)

Abstract

An experiment accomplished at the aquaculture laboratory of the Minas Gerais Federal University during sixty-six days, had the purpose to evaluate the effects of different gross protein concentrations on juveniles of surubim (Pseudoplatystoma reticulatum x P. corruscans) diets. One hundred and twelve animals, with initial weight of 468 ± 90,21g, were distributed in complete random design with four treatments (gross proteins level: 36, 38, 40 and 42%) and four repetitions, in recirculation water systems. Each tank with seven animals was an experimental unit. The fishes received cooked-extruded isoenergetics diets, with 3954 kcal/kg of gross energy, supplied three times a day until apparent satiety. The water quality parameters were maintained appropriate to tropical fishes. The results were submitted to variance analysis and regression studies. There were no observed differences in the daily food consumption (3,04 g per fish), the daily average of weight gains (3,2g per fish), feed conversion (2,28), protein efficiency rate (1,2) and survival (100%). Likewise, differences were not observed for the fillets (P>0,05), neither about the chemical-bromatologic composition in the dry material: gross protein (85,63%), ether extract (8,68%), ashes (5,59%); nor in the corporal reserves forms: viscerosomatic (6,77) and hepatosomatic(1,45) indexes. The blood parameters, glucose (46,32 mg/dL), hematocrit (13,28%), total protein (4,97 g/dL), creatinine (0,23 mg/dL) and the aspartate aminotransferase (28,49 U/L) and alanine aminotransferase (20,75 U/L) enzymes were not affected by the diets (P>0,05). The results showed that different protein levels of the diets did not lead to any difference in the evaluated parameters. Then, is indicated to use lower gross protein level diets (36%), which results in a gross energy/gross protein relation of 10,98 kcal/g (gross energy = 3654 kcal/kg with 36% of gross protein) for surubins (Pseudoplatystoma spp.) which weight between 378 and 839g.