Estimating Optimum Levels of Dietary Histidine Needed to Attain Improved Performance of Juvenile Nile tilapia

Abstract

Background: Optimum levels of essential amino acids in the diet have a  critical role in fish growth and health. This study investigated the effects of  dietary histidine levels on the growth performance, and whole-body 
composition of Nile tilapia (Oreochromis niloticus) juveniles. Methodology:  The experimental design included six diets with varying histidine levels  (0.56%, 0.68%, 0.81%, 0.96%, 1.09%, and 1.25%), with five replicates  consisting of 17 Nile tilapia juveniles per tank. The fish were fed twice a day  until satiety for 55 days. Data were analysed by one-way ANOVA using the  SAS GLM procedure, and differences among dietary treatments were compared using Tukey’s multiple comparison test. Results: Growth performance data showed that fish fed with 0.56% dietary histidine exhibited  the highest body weight gain compared to other treatments, with the 1.09%  histidine diet showing the lowest body weight gain (p < 0.05). A similar pattern was observed for the thermal growth coefficient and feed intake, where values decreased as dietary histidine level increased  (p < 0.05). Feed conversion ratio and protein retention did not differ significantly across the varying histidine levels (p > 0.05). Results indicated that only the body protein content was significantly affected by dietary histidine levels, increasing proportionally with higher histidine concentrations (p < 0.05). Conclusion: The study recommended the dietary histidine supplementation of 0.56% for Nile tilapia, as this level yielded the best growth performance under the tested conditions. This finding can guide the formulation of more cost-effective and nutritionally balanced diets, optimising tilapia nutrition and enhancing the sustainability of 
aquaculture production.