Blends de proteases em dietas para tilápias (Oreochromis niloticus)

Abstract

The objective of the study was to evaluate the inclusion of different levels of acid and alkaline protease blends in diets for Nile tilapia (Orechromis niloticus), from the aspects of productive performance, fillet yield and histological and enzymatic responses. The experiment was conducted in the Aquaculture laboratory of the Aquaculture Studies and Management Group (GEMAq) at the State University of Western Paraná (UNIOESTE), Toledo/PR campus, for 71 days. 300 fish with an initial average weight of 117.89 ± 5.69 g were distributed completely at random in 20 conical-cylindrical aquariums, totaling five treatments and four replications with 15 animals per experimental unit. Five experimental diets were formulated with different inclusion levels of acid and alkaline proteases, being a positive control diet (CP) with supplementary conditions of higher amino acids, a negative control (CN) with supplementary conditions of normal amino acids and protease enhancement, and three test rations containing 100, 200 and 400 grams/tons of acid and alkaline protease. The animals were fed four times a day (7:40 am, 11:40 am, 2:40 pm and 5:00 pm) and during the experimental period the physical-chemical variables of the water were monitored (temperature, dissolved oxygen, pH, total ammonia, toxic ammonia, hardness and nitrite). At the end of the experimental trial, productive performance, fillet yield and viscerosomatic indices were evaluated. Proximate analyzes of the fish and experimental diets, the histology of the organs and tissues collected (liver and muscle) and the analysis of digestive enzymes and amino acid metabolism in the intestine and muscle of the fish were also carried out. The protease blend influenced apparent feed conversion, protein efficiency rate and muscle fibers. The other parameters evaluated had no effect of the protease blend. It is recommended to include 200 to 400 g/t of acid and alkaline protease blend in diets for tilapia in the final stage of development.