Effect of graded levels of phosphorus on growth and mineral concentration in giant African catfish Heterobranchus bidorsalis

Abstract

Eleven diets (D1 - D11), designated as treatments (T1 - T11), supplemented with different levels of inorganic phosphorus (P) (CaHPO

4) were fed to Heterobranchus bidorsalis (10.8 4) were fed to Heterobranchus bidorsalis (10.8

4) were fed to Heterobranchus bidorsalis (10.8

± 0.02 g) to determine the optimum P requirement. D1 - D11 contained total P of 10.2, 10.4, 11.0, 11.9, 12.3, 12.6, 13.4, 13.9, 14.2 14.7 and 15.4 g kg-1 respectively. After 84 days of feeding trial, there was increase in fish growth up to T5 with 12.3 g P kg-1 diet, followed by consistent decline in growth towards T11 with the highest P content. However, fish in T5 had the best (P < 0.05) growth performance and feed conversion ratio (FCR). Fish in T1 and T2 had the highest (P < 0.05) FCR. Carcass protein was the same in T5, T6, T7, T8, T9 and T10, which was higher (P < 0.05) than in T1, T2, T3 and T4. Carcass fat content was highest in fish in T1 which also had the lowest water content. P and Ca concentration in fish carcass increased linearly and was highest (P < 0.05) in fish in T11, while Mg and Zn were highest (P < 0.05) in fish in T5. Data from the study suggest 12.3 g P kg-1 diet as optimum requirement for the growth of Heterobranchus bidorsalis.