Feeding strategies and energy to protein ratio on tambaqui performance and physiology

The objective of this work was to evaluate the effect of feed deprivation and refeeding with diets containing different energy to protein ratios (E/P) on the performance and physiology of juvenile tambaqui (Colossoma macropomum). A 4x2 factorial arrangement with three replicates was used, with four E/P ratios (11.5, 10.5, 9.5, and 8.5 kcal g-1 digestible energy per protein) and two feeding regimens (with and without deprivation), during 60 days. Fish from the food-deprived group were fasted for 14 days and refed from the fifteenth to the sixtieth day, whereas the remaining fish were fed for 60 days. At the end of the experimental period, weight of fish subjected to food deprivation was lower than that of those continuously fed; however, this condition did not influence the physiological parameters analyzed. Tambaqui fed 11.5 kcal g-1 achieved lower final weight than those fed with the other diets, in both regimens. Among the physiological parameters, only plasma protein presented significant increase in fish fed 8.5 kcal g-1, in both feeding regimens, probably due to the higher dietary protein concentration. These results indicate that fish show a partial compensatory growth, and that 10.5 kcal g-1 can be recommended for the diet of juvenile tambaqui

Optimum dietary crude protein requirement for juvenile cachama Piaractus brachypomus Exigência ótima de proteína bruta para juvenis de pirapitinga, Piaractus brachypomus

A growth experiment was conducted to determine the optimal dietary protein requirement for juvenile cachama, Piaractus brachypomus. Six semi-purified isoenergetic experimental diets using casein and gelatin as protein sources were formulated to contain graded levels of protein (16, 20, 24, 28, 32 and 36%). Fish initially averaging 15.52&plusmn;0.33g (mean&plusmn;SD) were randomly distributed into the tanks (500L) as groups of 20 fish and fed to apparent satiation twice daily for 60 days. The results showed that feed consumption, feed conversion ratio, fish weight gain, specific growth rate, protein efficiency ratio and protein productive value were affected by dietary protein level (P<0.05) . No significant differences were observed in proximal composition of carcass (P<0.05) in response to dietary protein. Analysis of dietary protein level x WG with a second order polynomial regression suggested a requirement of 31.6% CP for optimum growth.<br>O presente experimento foi realizado para determinar o requerimento ótimo de proteína em dietas para juvenis de pirapitinga, Piaractus brachypomus. Foram formuladas seis dietas experimentais semi-purificadas, iso-energéticas e com diferentes níveis de proteína (16, 20, 24, 28, 32 e 36% de PB) usando caseína e gelatina como fontes de proteína. Os peixes com peso inicial 15,52&plusmn;0,33g (média&plusmn;SD) foram distribuídos aleatoriamente em grupos de 20 animais por tanque; foram alimentados durante 60 dias, duas vezes/dia até aparente saciedade. Os resultados mostraram que o consumo de alimento, taxa de conversão de alimento, ganho de peso, taxa de crescimento específico, taxa de eficiência de proteína e valores produtivos da proteína e da energia foram significativamente afetados pelos níveis de proteína das dietas (P<0,05). Não foram observadas diferenças significativas na composição proximal da carcaça (P<0,05) entre tratamentos. A análise do ganho de peso em função dos níveis de proteína da dieta, realizada utilizando regressão polinomial de segundo grau, deu um requerimento de 31,6% de proteína para ótimo crescimento de juvenis de pirapitinga