Effect of dietary protein‐to‐energy ratios on growth performance, body composition, feed utilization and nitrogen metabolism enzyme of Cirrhinus mrigala

Abstract

The present study was conducted to encompass the effect of dietary protein‐to‐energy ratios on growth performance, feed utilization, body composition and nitrogen metabolism enzymes of Cirrhinus mrigala. Five Iso‐energetic diets (16 kJ/g) with graded levels of P/E ratios (17.84, 19.79, 22.19, 24.46 and 26.50 mg/kJ) named as A, B, C, D and E were formulated. A total of 300 C. mrigala fingerlings (initial body weight 17.8 ± 0.12 g) were equally distributed into five groups (in triplicate). Each group was fed twice a day at 4% wet body weight with respective P/E ratio diets for 8 weeks. Highest weight gain, specific growth rate, protein efficiency ratio and protein retention efficiency were observed in group C with the lowest, feed conversion ratio, Hepatosomatic index and Viscerosomatic index as compared to other groups. Furthermore, the whole‐body and muscle tissue composition were also significantly (p < .05) influenced by the P/E ratios in diets. Among all groups, group C was significantly higher in crude protein and ash contents, with comparatively low lipids level and moisture contents compared to other groups. Additionally, the activities of nitrogen metabolism enzymes, Aspartate amino transferase, Alkaline amino transaminase, Glutamate dehydrogenase and Adenosine 5′‐monophosphate deaminase (AST, ALT, GDH and AMPD) were significantly (p < .05) increased with the increasing of P/E ratios in diets. Our results showed that on the basis of second‐order polynomial regression analysis of feed conversion ratio, the optimal dietary P/E ratio of C. mrigala (fingerlings) was 22.61 mg/kJ.