This experiment evaluated soy protein concentrate (SPC) and meat and bone meal as a replacement for fish meal protein (FP) in the diet of Nile tilapia fingerlings. Five diets were evaluated including a control diet (50.0% crude protein [CP], of which half the protein came from fish meal [FM]), and four diets in which FM was replaced by increasing amounts of SPC (25.5, 50.0, 75.5, and 100.0%) in combination with meat and bone meal. At the conclusion of a 60-d growth trial, the following parameters were determined: final weight (FW), final length (FL), weight gain (WG), feed intake (FI), apparent feed conversion (AFC), survival (SUR), and production cost. The estimate of the best replacement value was determined by polynomial regression and the linear response plateau. The results showed significant (P < 0.05) improvement for WG and AFC ratio as FM was gradually replaced by SPC. The parameters FL and FI reached their optimum value at a replacement level of 100% SPC. These results show that it is feasible to use a combination of SPC and meat and bone meal in a balanced feed formulation as an alternative protein source in the diets of Nile tilapia fingerlings.

The effect of different levels of crude protein (32A, 32B, 36, 38, 44 and 50% CP; 3,500 kcal digestible energy) on Nile tilapia broodstock was assessed. After 30 experimental weeks (Sept./14 to Mar./15), 91.0% of eggs from fish fed 44% CP hatched and produced 16.4% more viable larvae than the treatment with 32% CP. Egg production and absolute fecundity were similar between treatments (p>0.05). Sperm motility, average path, straight line and curvilinear velocities showed satisfactory values with 44% CP, unlike 36% CP. Lower profitability was observed with 32% CP; profit increased as protein level upped. Statistically significant responses were not found for reproductive performance of females. Results were satisfactory for commercial-scale production as crude protein increased. The initial hypothesis was demonstrated for most parameters assessed in males, larvae growth and economic viability. Therefore, it is recommend the use of diets with 44% CP for Nile tilapia brood fish.