Evaluation of some plant ingredients as dietary protein sources for common carp ( Cyprinus carpio L.) fry

Abstract

A laboratory growth trial was conducted to evaluate the suitability of various oilseed cakes and leucaena leaf meal as dietary protein sources for common carp fry (mean ± SE weight, 50 ± 1.6 mg). Eleven experimental diets were formulated containing different levels of mustard, sesame, linseed, copra and groundnut oil cakes and leucaena leaf meal to substitute for fish meal protein up to a maximum of 75% of the total protein content. Sesame oil cake was tested at three inclusion levels (25, 50 and 75% of total protein), whereas mustard (25 and 50%), linseed (25 and 50%) and groundnut (25 and 75%) oil cakes were each tested at two levels. Copra and leucaena were tested at one inclusion level (25% of total protein) only. The control diet was prepared with fish meal as the sole source of protein. All diets were isonitrogenous and contained about 40% protein. The experiment was conducted in a laboratory recirculation system with three replications for each treatment. The performances of the diets were evaluated on the basis of feed acceptability, survival, growth, feed conversion, protein utilisation, protein digestibility, body composition and histopathological changes. The results of the study showed that growth and performance were significantly affected by the type of plant protein as well as level of inclusion. There was no significant ( p > 0.05) variation in the observed growth responses and feed conversion ratios among the control diet and the diets containing 25% linseed and 25% groundnut oil cakes. The diet containing 25% leucaena meal showed the poorest performance. Similar trends were also observed for protein efficiency ratio and apparent net protein utilisation. Apparent protein digestibilities were broadly similar (78–90%) for all diets except the diet containing 25% leucaena meal which showed the poorest value (63%). With the exception of the control and 25% leucaena diets, the carcass composition of experimental fish was relatively unaffected by different dietary treatments. Histopathological examination of liver revealed higher levels of intracellular lipid deposition in fish fed diet containing mustard cake. A large proportion of fish fed the 75% groundnut diet showed severe deformations of the body. Based on these results, the possibility of using plant ingredients as a partial replacement for fish meal in diets for the common carp fry is discussed.