Igo Gomes Guimarães

Apparent nutrient digestibility and mineral availability of protein-rich ingredients in extruded diets for Nile tilapia

Apparent digestibility coefficients (ADC) of gross energy and dry matter (DM) and mineral availability were evaluated for eight protein-rich ingredients (corn gluten meal, soybean meal, cottonseed meal at 280.0 and 380.0 g/kg, poultry by-product meal, meat meal, fish meal and feather meal) in compound diets for Nile tilapia. Chromic oxide was used as inert digestibility marker. Higher ADC values of DM and energy were, respectively, 0.862 and 0.881 for corn gluten meal, 0.811 and 0.888 for poultry by-product meal; 0.729 and 0.731 for feather meal; 0.666 and 0.754 for fish meal; 0.578 and 0.642 for soybean meal; 0.476 and 0.652 for meat meal at 450.0 g/kg; 0.352 and 0.449 for cottonseed meal at 380 g/kg; and 0.251 and 0.324 for cottonseed meal at 280.0 g/kg. The highest average mineral availability was for poultry by-product meal (0.582), and the lowest calcium and phosphorus availability were recorded for cottonseed meal at 280.0 g/kg. Therefore, poultry by-product meal appears to be the best ingredient for using in Nile tilapia diets.

Effects of digestible protein to energy ratios on growth and carcass chemical composition of siamese fighting fish (Betta splendens)

The expansion in the market of ornamental fish depends on the intensification of production systems and the generation of appropriate technologies. Therefore, it is necessary to know the nutritional requirements of each species for the formulation of nutritionally balanced diets. A 30-day feeding trial was undertaken to evaluate the effects of different dietary digestible protein to energy ratio in diets for Betta splendens fingerlings. Fifty-six all-male B. splendens with 1.03 ± 0.11 g average weight were randomly stocked into 56 1L-aquaria in a completely randomized design with a 2 x 4 factorial arrangement, comprising eight treatments and seven replication. Each fish was considered an experimental unit. Diets were formulated to contain 28.0, 35.0, 42.0 and 49.0% DP and 3,600 and 3,200 kcal/kg DE. The growth parameters evaluated in this trial were weight gain (WG), feed intake (FI), feed conversion ratio (FCR), protein efficiency ratio (PER) and specific growth rate (SGR). No difference (P > 0.05) was observed for WG, FCR and SGR. However, a higher FI was observed for fish fed diets containing 42.0% DP (P < 0.05). A positive effect of DP and DE on PER was observed in this study. Generally, according to the increase of DE levels, a reduction on PER was observed. Based on this experimental condition, we recommend the use of 28.0% DP and 3,200 kcal/kg DE in diets for B. splendens.

Protein to energy ratios in goldfish (Carassius auratus) diets

The optimal dietary digestible protein to energy ratio is critical for the success of fish farming. Considering that it provides the proper development of the animals, this study was undertaken to evaluate the effects of different dietary digestible protein to energy ratio in diets for goldfish fingerlings. Diets were formulated to contain 28.0, 35.0, 42.0 and 49.0% DP and 3,600 and 3,200 kcal/kg. The growth parameters evaluated were daily weight gain (DWG), feed intake (FI), feed conversion ratio (FCR), protein efficiency ratio (PER), protein productive value (PPV) and energy retention ratio (ERR) and specific growth rate (SGR). Regardless FI, all the parameters were affected by protein and energy levels and interaction between both factors was observed. The second-order polynomial equation best fitted to the DWG, SGR, FCR, PER and ERR with estimated requirement values of 38.81, 38.85, 41.05, 41.80 and 39.39% DP, respectively, at the 3,200 kcal/kg. A second-order polynomial model was significant only for the ERR data at the 3,600 kcal/kg with an estimated requirement value of 36.45% DP. Generally, fish fed diets containing 3,200 kcal/kg had better growth performance than fish fed 3,600 kcal/kg (P<0.01), indicating a higher feed efficiency. A 3,200 kcal/kg diet seems to be the proper DE level for meeting goldfish requirement for highest weight gain. Based on this experimental condition, we recommend the use of DP levels between 38.0-40.0% in diets for goldfish with 3,200 kcal/kg or a dietary protein to energy ratio between 119-125 mg/kcal DE.