Abstract:
The influence of dietary protein content on some nutritional parameters of Clarias gariepinus fry was studied. Seven diets were formulated to yield 28, 31, 34, 37, 40, 43, and 46% crude protein (CP) while the 8th 48.8% CP diet was prepared from microencapsulated whole egg and preserved in a refrigerator at 7º C. The diets were fed to advanced fry of C. garepinus (mean initial weight, 1.6 ± 0.24 g) in triplicate 25 L plastic baths per treatment at 5% body weight per day in three portions for 56 days. The mean weight gain (MWG), daily rate of growth (DRG) increased as the dietary protein level increased up to 40% but gradually declined as CP level increased while increase in CP did not significantly affect daily rate of feeding (P > 0.05). The best response of fish to gross efficiency of food conversion was within 37 - 40% dietary CP and thus reflected the best mean weight gain (0.86 - 1.93g), DRG (0.17 – 20 g), and nitrogen metabolism (12.62 - 13.43 mg/100g) respectively. There was a relatively high metabolizable energy: protein ratio for the 48.80% CP diet (9.88 KJ/mg) compared to 40% CP diet (7.60 mg/kg). Similarly, the low net protein utilization (NPU) value recorded with diets of between 31% to 40% CP compared to the NPU value of higher CP level (43% to48.8%) suggests that despite the apparently better utility of protein by fish fed the higher CP diets, much of the ingested protein might have been affected by endogenous nitrogen losses resulting in its unavailability for productive use by the fish.
