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Four diets (T0–T3) were formulated reducing the fishmeal (Indian) component by 100 g kg–1 from 300 to 0 g kg–1 and including proportionately increasing quantities of maize. Diets were fed for 120 days at 50 g kg–1 body weight to triplicate groups of common carp (av. wt. 2.11–2.18 g) stocked at 1 m–2 in mud bottomed cement tanks (18 m2), fertilized with poultry manure. Fish growth, SGR and FCR in the different treatments were statistically not significantly different (P > 0.05). PER was lowest for the 300 g fishmeal kg–1 diet treatment (diet T0), increasing with decrease in dietary fishmeal content (diets T1–T3). Fish survival ranged from 96.29 to 100%. Diets influenced carcass composition and digestive enzyme activity. A significant increase in lipid deposition was recorded with increasing dietary carbohydrate content. Amylase, protease and lipase activities were higher in fish fed with diets T2 and T3. The protein sparing effect of dietary carbohydrate and the economic implication of eliminating fishmeal from the diet are discussed.

A growth trial was conducted on common carp Cyprinus carpio (L.) fry in cement tanks for 100 days in order to test the efficacy of mixed feeding schedules. The diets tested were a fishmeal-based diet (diet D with 30.9% protein) and three Colocasia esculenta-based diets (diet A with 16.7% protein, diet B with 19.7% protein and diet C with 25.8% protein) separately and in three mixed feeding combinations of diet A, B and C with D on alternate 2 days (2A/2D, 2B/2D and 2C/2D, where the numeral indicates the number of days that the particular diet was offered continuously). The results revealed no difference in growth of common carp fed the plant protein-based diets A and B (P > 0.05). Although the fish fed on diets C and D and mixed feeding combinations 2A/2D and 2B/2D performed comparably and higher than those on diets A and B, the schedule 2C/2D resulted in the highest final weight. Specific growth rate, feed conversion ratio and RNA/DNA ratios were the highest in the 2C/2D schedule. Among the mixed feeding schedules, the highest saving in protein and cost was recorded with the 2A/2D schedule, followed by 2B/2D and 2C/2D. An increase in dietary protein led to decreased protein and increased fat deposition in the carcass. An increasing trend in the protease and amylase activities was recorded with increased dietary protein level. The study highlighted the efficient utilization of plant proteins by common carp under mixed feeding schedules.

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 m 2 in mud bottomed cement tanks (18 m 2 ), 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 (T 1 ) to 100% (T 0 ) 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.

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