Growth Performance and Nutrient Utilization of Hormonal Sex-reversed Male and Mixed Sex <i>Oreochromis niloticus</i> under Outdoor Rearing Condition

Abstract

This study investigates the performance of all male and mixed sex tilapia ( Oreochromis niloticus ) raised in outdoor rearing conditions. All male tilapia were obtained by hormonal administration of 17 α-methyltestosterone (30 µg) into the diet of hatchlings of O. niloticus and fed them for 28 days. Both sex-reversed male and mixed sex O. niloticus were fed with coppens ® commercial diet and replicated thrice at 45% crude protein for 24 weeks Biological evaluation such as Mean Weight Gain (MWG), Specific Growth Rate (SGR) and Feed Conversion Ratio (FCR) were determined. Temperature, pH, conductivity and total dissolved solids were measured using standard methods. Data were analyzed using descriptive statistics and ANOVA at P=0.05. Result revealed that all male tilapia had significant weight gain (p<0.05) (5.93 ± 0.13 g) compared to the mixed sexes (2.19 ± 0.09 g). However, breeding activity was not noticed within the mixed sex tilapia population after a culture period of six months. Hence, poor performance could not be directly linked to spawning activity. The value of temperature, pH, conductivity and total dissolved solids were closely related and were within recommended range for the culture of tropical fishes. It was therefore hypothesized that 17 α-methyltestosterone besides achieving masculation, may have growth promoting characteristic. The detail mechanism responsible for this better performance could be the focus of future research.