Use of phytase to improve the digestibility of alternative feed ingredients by Amazon tambaqui, Colossoma macropomum

The study assessed the effect of phytase on the digestibility of alternative plant feed ingredients Brazil nut (Bertholletia excelsa) and leucaena (Leucaena leucocephala) leaf meal fed to tambaqui (Colossoma macropomum) and on fish growth. Five treatments were used: UPI denoted the negative control diet with unfermented plant ingredients; UPIP was positive control diet with unfermented plant ingredient supplemented with 3 g/kg phosphorus (NaH2PO4); FPI indicated diet with fermented plant ingredients; FPIPTl denoted diet with fermented plant ingredients supplemented with phytase 4000 U/kg; and FPIPT2 was diet with plant ingredients fermented together with phytase 4000 U/kg. Chromic oxide was added to the diets as inert marker for digestibility study. The diets were fed to juveniles of tambaqui (70.0±6.3 g) to satiation twice daily in recirculation systems for 56 days. Results indicated high and better digestibility of protein and lipid by fish fed diet with phytase, which resulted in a corresponding better fish growth. Growth rate of the fish was high and increased from initial weight of 70 g to 132 g almost doubling the initial weight. No significant differences were found in weight gain, specific growth rate, and feed conversion ration, but performance was better in fish fed diets with phytase. The fish grew well in low dissolved oxygen levels of 4.23-4.34 mg/1, pH of 5.80-5.91 and high ammonia concentration of 1.76-2.17 mg/1 without compromising growth and physiological functions

Optimum dietary protein requirement for Amazonian Tambaqui, Colossoma macropomum Cuvier, 1818, fed fish meal free diets Exigência protéica de juvenis de tambaqui, Colossoma macropomum Cuvier, 1818, alimentados com rações livres de farinha de peixe

Fish meal free diets were formulated to contain graded protein levels as 25% (diet 1), 30% (diet 2), 35% (diet 3) and 40% (diet 4). The diets were fed to tambaqui juveniles (Colossoma macropomum) (46.4 ± 6.3g) in randomly designed recirculating systems for 60 days, to determine the optimum protein requirement for the fish. The final weight of the fish, weight gain (28.1, 28.5, 32.2, 28.0g) and specific growth rate increased (P>0.05) consistently with increasing dietary protein up to treatment with 35% protein diet and then showed a declining trend. Feed intake followed the same trend resulting in best feed efficiency (62.5%) in fish fed diet with 35% protein. Similarly, the protein intake increased significantly with increasing dietary protein levels and reduced after the fish fed with 35% protein; while protein efficiency ratio (2.28, 1.99, 1.87, 1.74) decreased with increasing dietary protein levels. Carcass ash and protein had linear relationship with dietary protein levels while the lipid showed a decreasing trend. Ammonia content (0.68, 0.73, 0.81, 1.21 mg L-1) of the experimental waters also increased (P<0.05) with increasing protein levels while pH, dissolved oxygen and temperature remained fairly constant without any clear pattern of inclination. Broken-line estimation of the weight gain indicated 30% protein as the optimum requirement for the fish.<br>Foram formuladas quatro dietas sem a inclusão de farinha de peixes contendo os níveis crescentes de proteína de 25% (dieta 1), 30% (dieta 2), 35% (dieta 3) e 40% (dieta 4). As dietas foram fornecidas a juvenis de tambaqui (Colossoma macropomum) (46.4 ± 6.3g) distribuídos ao acaso em um sistema de recirculação durante 60 dias, para determinar o requerimento protéico ótimo para o peixe nesta faixa etária. O peso final dos peixes, o ganho de peso (28.1, 28.5, 32.2, 28.0g) e a taxa de crescimento específico tiveram um aumento não significativo (P>0,05) conforme aumentou o nível protéico das rações até o nível de 35% proteína e então uma tendência ao declínio. O consumo de alimento seguiu a mesma tendência resultando em melhor eficiência alimentar (62.5%) para os peixes alimentados com a dieta contendo 35% de proteína. Similarmente, o consume de proteína aumentou significativamente com o aumento crescente dos níveis protéicos dietários e reduziu após os peixes serem alimentados com a dieta com 35% de proteína, enquanto a taxa de eficiência protéica (2.28, 1.99, 1.87, 1.74) diminuiu com o aumento dos níveis protéicos dietários. A cinza e a proteína da carcaça apresentaram uma relação linear com os níveis protéicos dietários enquanto o lipídio mostrou uma tendência decrescente. O aumento do conteúdo da amônia (0.68, 0.73, 0.81, 1.21 mg L-1) da água dos tanques experimentais com a elevação dos níveis de proteína não foi significativo (P>0,05) enquanto o pH, oxigênio dissolvido e a temperatura permaneceram claramente constantes sem qualquer padrão claro de inclinação. O &#8220;ponto de virada&#8221; da curva de ganho de peso indicou 30% como o nível protéico ótimo para esta espécie de peixe, nesta fase de crescimento, nas condições deste experimento