Manjappa K., Keshavanath P., Gangadhara B., 2002. Growth performance of common carp, Cyprinus carpio fed varying lipid levels through low protein diet, with a note on carcass composition and digestive enzyme activity. Acta Ichthyol. Piscat. 32 (2): 145-155.
Protein sparing by lipid has been demonstrated in certain cultivable species of fish. This study was carried out using four low protein isonitrogenous diets (24% crude protein) formulated by supplementing varied levels of fish oil (0, 3, 6, and 9%). The diets were fed for 120 days at 5% body weight to triplicate groups of common carp (av. wt. 2.13-2.21 g) stocked at 1 per m2 in mud bottomed cement tanks (18 m2), fertilized with poultry manure. The growth of fish was the highest (P < 0.05) with the diet containing 6% fish oil, followed by 3, 9, and 0%. Food conversion ratio and protein efficiency ratio improved with increasing dietary lipid level. Dietary lipid had a positive impact on carcass lipid level (P < 0.05). Moisture and crude protein did not vary (P > 0.05) from that of the control. Survival ranged from 96.29 (T1) to 100% (T0) without any significant (P > 0.05) difference among the treatments. While there was a general increase in amylase activity in the treated fish, protease activity showed a reduction with increase in oil supplementation. No difference (P > 0.05) in lipase activity was observed between the different treatments. The results indicate the beneficial effects of incorporating fish oil in the diet of common carp.