Blood glucose and ammonia excretion rate as metabolitics indicators of the activity of exotic enzymes in Nile tilapia

Abstract

The glycemic curve and the excretion of ammonia rate are methods used to assess the variation in glucose and the excretion of the nitrogen compound ammonia due to changes in the amount of carbohydrates and proteins, respectively, available in the diets. However, reports are scarce regarding its use in research related to the use of exogenous enzymes in fish feeding. Therefore, the objective of this study was to evaluate blood glucose levels and ammonia excretion as metabolites indicators of the efficiency of the activity of exogenous enzymes in diets for Nile tilapia. Therefore, two tests were performed, where the composition and concentration of phytase, alpha-amylase and protease enzymes were tested. The treatments were composed of a control diet (DC), which was later supplemented with a blend 1 containing 100ppm phytase + 200ppm protease, a blend 2 composed of 100ppm phytase + 400ppm protease, then blend 3 containing 200ppm phytase + 200ppm protease + 133ppm alpha-amylase, and blend 4 with 200ppm phytase + 400ppm protease + 200ppm alpha-amylase. The blood glycemia peak of the Nile tilapia occurred in the first 4 hours post tilapia feeding in all treatments evaluated. The diets supplemented with phytase, protease and alpha-amylase promoted higher levels of blood glucose, whereas peaks of ammonia excretion occurred at 2h, 4h and 8h after fish feed, which may be related to increased protein availability by supplementing the diets with the protease. Blood glucose concentrations and ammonia excretion rate can be indirect indicators of the efficiency of digestive enzyme activity in Nile tilapia.

Keywords

• blend enzimático. curva glicêmica. tilapicultura.