Metabolic and Intestinal Morphometric Responses of Nile Tilapia Fed Diets Containing Soybean and Protease

Proteases facilitate the breakdown of components associated with antinutritional factors. This study evaluated the effects of protease supplementation in Nile tilapia diets on metabolic and intestinal responses. Three diets were tested: soybean meal SM1 (fish meal FM:SM = 1:1), SM2 (1:2), and SM3 (1:3), based on the protein content. All the diets were without or with protease (0.44 g/kg). The fish were randomly allocated to 18 tanks/49 days. In SM3 without protease, an increase in the villus height and width, as well as the number of goblet cells, was observed. Protease supplementation increased the villus height compared to diets without the enzyme. The SM1 with protease resulted in a reduction in the digestive somatic index, but significantly increased the hepatosomatic and intestinal quotient indices. In SM2 with protease, reductions in the amino acid (AA) content and aspartate aminotransferase activity in the liver were observed. In the muscles, supplementation increased the AA concentrations. Higher plasma AA and albumin concentrations were detected in the SM2 and SM3 groups with protease. A significant interaction was found, with SM3 without protease showing lower plasma protein and AA concentrations. In SM2 with protease, higher levels of albumin and globulin were recorded. Protease in soybean meal diets improved the intestinal health and metabolism in tilapia.