Effect of dietary protein level on growth, survival, feed utilisation and body composition of hybrid Clarias catfish (Clarias batrachus × Clarias gariepinus)

A feeding trial was conducted to study the effect of iso-energetic diets containing 250 (D1), 300 (D2), 350 (D3) and 400 g (D4) crude protein (CP) kg−1 dry matter (DM), in hybrid post-larvae of Clarias batrachus ♀ × Clarias gariepinus ♂. Triplicate groups of post-larvae with mean initial body weight 67±6 mg were reared in cement tanks (4 m×1 m), in outdoor rearing system and fed diets at 10% of body weight for 30 days. Performance was judged on the basis of growth (specific growth rate, SGR), percent survival, feed conversion ratio (FCR) and protein efficiency ratio (PER), which were influenced both linearly and quadratically. An increase in body weight gain, SGR, PER and decreased FCR was observed with increasing dietary protein. The percent survival was increased linearly (P<0.01) as well as quadratically (P<0.05) among fish fed increased levels of protein. Both amylolytic and proteolytic enzymes in the intestine of hybrid Clarias catfish were studied. The α-amylase activity decreased linearly (P<0.05) with increased dietary protein level and protease activity increased. sh accumulated increasing (linear component, P<0.05) protein as well as ash and decreasing lipid in the whole body with increasing dietary protein. The broken-line regression analysis indicated that for maximal growth, hybrid Clarias catfish post-larvae require 365 g dietary crude protein kg−1 diet.