Performance, carcass characteristics and coefficients of apparent digestibility of Nile tilapia fingerlings (Oreochromis niloticus) fed diets with increasing levels of poultry by-product meal (PM) were evaluated. Three hundred fingerlings with average initial weight of 0.35±0.01 g were placed in thirty 120 L net ponds in five cement 1000 L tanks. Six levels of PM inclusion (0.00, 4.00, 8.00, 12.00, 16.00 and 20.00%) were used in the diets, in an experimental randomized blocks desing with six treatments and three replicates. An experiment of diet digestibility was undertaken with 0.00 and 20.00% PM diets on fish of average weight 47.81±9.97 g. A linear improvement was observed at PM inclusion levels with regard to final weight, percentage of weight gain, protein efficiency rate, nitrogen retention and quadratic effect for food conversion, ether extract retention and percentages of crude protein and carcass ethereal extract. Concerning to the digestibility experiment, the 20.00% PM diet showed lower coefficients of apparent digestibility for dry matter, crude protein, crude energy and higher coefficients for ether extract. However, higher values of digestible ether extract and energy were obtained with 20.00% PM diet, even though digestible protein was lower than the 0.00% PP diet. Apparent digestibility coefficients of the ether extract, crude protein and crude energy of PM for the Nile tilapia were 70.45, 63.93 and 55.89% respectively. Thus, the inclusion of 20.00% PM in diet improved performance, however increased ether extract content and decreased crude protein levels in carcass and dry matter, crude protein and energy digestibility coefficients of the diets.
apparent digestibility; carcass composition; Nile tilapia; Oreochromis niloticus; performance; poultry by-product meal
