Resumo:
This study evaluated the production performance of Nile tilapia (Oreochromis niloticus) in cage culture systems, comparing the zootechnical performance and environmental impacts of fish fed a commercial control diet (31% crude protein) and three isoproteic test diets (28.4% crude protein), formulated with predominantly plant-based ingredients and different mineral supplements. The experimental diets included one formulation with inorganic minerals and two with organic mineral supplements: CrZn – chromium chelated to methionine (0.8 mg·kg⁻¹) and zinc chelated to amino acids (60 mg·kg⁻¹); and CrFe – chromium chelated to methionine (0.8 mg·kg⁻¹) and iron chelated to amino acids (62.5 mg·kg⁻¹). The experiment was conducted over a 96-day period. In addition to productive performance, a Life Cycle Assessment (LCA) was carried out to estimate the environmental impacts associated with each feeding strategy. Fish fed the control diet showed the best zootechnical indices (weight gain per fish: 0.65 kg; biomass gain per cage: 92.5 kg; apparent feed intake: 1.53). However, due to the higher inclusion of animal-based ingredients in the control diet, its environmental performance resulted in greater impacts across all assessed categories. Fish fed the experimental diets showed higher survival rates — particularly in the CrZn (99%) and CrFe (91%) treatments.
Results of energy and nutrient retention and excretion indicated that the CrZn treatment achieved higher retention of nitrogen (31%), phosphorus (25%), and energy (27%), along with lower nitrogen (46 kg·t⁻¹) and energy (4,555 Mcal·t⁻¹) excretion values, supporting the lower environmental impacts associated with this diet. In all evaluated categories, the experimental diets led to reduced environmental contributions, with reductions ranging from 36% to 67%. The results suggest that the use of plant-based proteins combined with organic mineral supplementation contributes to improved energy and nutrient utilization, even under protein-restricted conditions, and provides environmental benefits through the reduction of nitrogen and phosphorus waste in the environment. They also highlight the potential of alternative diets formulated with plant ingredients and organic minerals as a strategy to enhance the efficiency and sustainability of intensive aquaculture systems, such as cage farming.
