Hamilton Hisano

Níveis de vitamina C e ferro para tilápia do nilo (Oreochromis niloticus)

The effects of different levels of vitamin C and iron on growth performance and physiological parameters on Nile tilapia (Oreochromis niloticus) were evaluated for 73 days. A factorial experiment with three levels of vitamin C (125; 375 e 1115 mg/kg) and three levels of iron (30, 90 e 270 mg/kg), plus an additional treatment (with 0 mg/kg of vitamin C and iron), was considered on a completely randomized design, with four replicates for each experimental group. It was randomly stocked 240 reverted fingerlings, an average weight of 7.46 ± 0.49 g, into 40, 250L, aquaria at a density of 6 fish/aquarium. A albumin-gelatin-diet was formulated to contain 32.0% of crude protein and 3,300 kcal/kg of digestible energy. Fingerlings of Nile tilapia fed diet without supplemental vitamin C and iron developed hypochromic microcytic anemia and the supplemental vitamin C determined the presence of immature erythrocytes on blood. It was also determined that iron serum concentration was influenced by vitamin C and iron supplied on diets, and that levels above to nutritional requirements for the specie did not determined detrimental effect on growth performance, plasmatic protein or morphologic characteristics of liver.

Níveis de proteína digestível e energia digestível em dietas para tilápias-do-nilo formuladas com base no conceito de proteína ideal

This study was carried out to determine the best digestible energy and digestible protein ratio in feeds for Nile tilapia (Oreochromis niloticus) juveniles 30.0 ± 4.21 g) based on digestible amino acids and the ideal protein concept). Twelve rations were formulated with protein levels 22.0; 26.0; 30.0 and 34.0% of digestible protein and levels 3,000, 3,300 and 3,600 kcal/kg digestible energy. The digestible energy/digestible protein ratio was between 8.94 and 15.19 kcal/g. Three hundred and twenty four tilapias were randomly distributed in thirty six 250 L circular tanks at a density of 9 fish/tank, a total of 12 treatments with three replications. After 60 days, there was no significant difference in weight gain, daily weight gain and feed conversion ratio among the studied treatments. A linear increase was observed in fillet yield with increasing digestible protein. With respect to feed cost/kg weight gain, the treatment with 30.0% DP and 3,000 kcal/kg DE presented low cost and better cost effectiveness index. Therefore, it was concluded that digestible energy did not influence the productive performance parameters and that effective feeds can be formulated with DP levels lower than 34% when feeding juvenile tilapias. The ration should be formulated based on the concept of ideal protein.