Dietary histidine requirement of grow-out Nile tilapia (Oreochromis niloticus), based on growth performance, muscle development, expression of muscle-growth-related genes, and blood parameters

This research was conducted to determine optimal dietary histidine requirement of grow-out Nile tilapia, Oreochromis niloticus, based on muscle development, expression of muscle-growth-related genes, and blood parameters. Fish (n = 288, initial body weight of 64.170.53 g) were fed extruded diets with graded levels of histidine (4.23, 5.44, 7.17, 8.91, and 11.57 g kg(-1)), containing approximately 289 g kg(-1) crude protein and 3565 kcal kg(-1) digestible energy. The study followed a completely randomized design with five treatments and four replicates each, for 65 days. There was a quadratic effect of dietary histidine on final body weight, feed conversion, and net protein utilization, and the best values were optimized at 8.09, 7.88, and 7.33 g kg(-1), respectively. Feed intake, hepatosomatic index, survival, body composition, and blood parameters of total protein, glucose, triglycerides, cholesterol, hematocrit, and hemoglobin were not affected by dietary treatments. Predominance of hypertrophic growth and higher mRNA levels of myogenin and MyoD were observed in fish fed histidine from 5.44 to 11.57 g kg(-1) compared with fish fed histidine at 4.23 g kg(-1). The mRNA expression of myostatin was not affected by dietary treatments. The dietary requirement of histidine for grow-out Nile tilapia was determined at 8.09 g kg(-1), considering growth performance, muscle development, and gene expression responses.