Growth, nutrient utilization, haematology and biochemical parameters of African catfish (Clarias gariepinus, Burchell, 1822) fed with varying levels of Bacillus subtilis

This study examined the growth response, nutrient utilization, biochemical and haematological properties of Clarias gariepinus juveniles, fed with graded levels of Bacillus subtilis. Five diets were formulated (35% crude protein; 3127 kCal/kg energy), comprising 0 (T1), 20 mg/100g oxytetracycline (T2), 105 (T3), 107 (T4) and 109 (T5) B. subtilis CFU/ml. African catfish, C. gariepinus (n=150; mean weight =94.33±0.67g) were allotted to 15 rectangular tanks and fed experimental diets apparently to satiation for 8 weeks. Growth performance, nutrient utilization, haematological and biochemical parameters were examined using standard methods. The results showed that fish fed with Diet T5 recorded significantly high values for mean weight gain (MWG) (116.67±5.70g), specific growth rate (SGR) (1.58±0.07%) and percentage weight gain (PWG) (133.62±7.47%), while Diet T1 had least values for MWG (89.00±0.58g), SGR (1.36±0.01%) and PWG (94.35±0.91g). Feed conversion ratio (FCR) and protein efficiency ratio (PER) were significantly different (p<0.05) across the test diets, with Diet T5 having the best values for FCR (1.17±0.04) and PER (3.27±0.18). No significant differences (p>0.05) were observed in the haematological, AST, ALP and GSH indices between the fish fed graded levels of probiotic and control diets. The excellent growth performance recorded at the highest inclusion level (T5) of B. subtilis showed that the probiotic could be favourably incorporated into the diet of C. gariepinus juveniles.Keywords: Growth, Nutrient Utilization, Blood Parameters, Clarias gariepinus, Bacillus subtili