Effect of digestible protein on intermediate metabolism, hepatic enzyme activities, energy reserves and growth performance of pacu (Piaractus mesopotamicus) in the finishing growth phase

Abstract

Abstract This research aimed to determine the effect of digestible protein (DP) on blood metabolites, hepatic enzyme activities, energy reserves and production characteristics of pacu (Piaractus mesopotamicus) in the finishing growth phase. For this purpose, six semi-purified and isoenergetic diets containing graded levels (16.3, 20.1, 23.8, 27.2, 31.5 and 34.8%) of DP were fed to finishing pacu (1,100.0 ± 10.3 g, initial weight) three times daily for seven weeks. The experiment consisted of six treatments with three randomly arranged replicates (tanks) per treatment. At the end of the experimental period, the data obtained were analyzed through the one-way analysis of variance (ANOVA) and the significant difference (p < 0.05) among treatments was determined by the Tukey’s test. The blood metabolites including glucose, triglycerides, total protein and total cholesterol were significantly (p < 0.05) affected by DP while the serum ammonia concentration did not show any significant (p > 0.05) difference among the treatments. The hepatic enzyme activities including glucokinase, pyruvate kinase, alanine aminotransferase and aspartate aminotransferase, with the exception of hexokinase, as well as the energy reserves including hepatosomatic index and viscerosomatic fat index, except the hepatic total lipid content, were significantly (p < 0.05) associated with DP. The growth performance parameteres including food intake, feeding rate and weight gain were significantly (p < 0.05) increased by DP. This study show that overall the pacu in the finishing growth phase fed on the relatively intermediate level of DP (23.8%) with digestible energy of 17.95 MJ kg− 1 promoted better physio-biochemical health status and production characteristics.