Growth and Nutrition of Carp in Heated Effluents

Abstract

The growth responses and food utilization of mirror carp were investigated under varied dietary and environmental conditions. Studies showed that growth rate was least at 35°C intermediate at 20°C and greatest at 25 & 30°C. Food conversion ratio increased with increasing level of feeding at each temperature. Temperature and feeding rate influenced the proximate body composition of carp. Feeding trials showed that the protein level, of diets containing 18% lipid, could be reduced from 45 to 30% with no diminution of weight gain and with improved protein utilization. Varying the dietary lipid and protein levels influenced the proximate body composition of carp and the apparent digestibilities of protein and energy. Further feeding trials showed that a methanophilic bacterium and a petroprotein yeast have potential a fish meal replacements in carp diets, These protein sources were well digested and assimilated when used as the sole protein sources in 30% protein rations. Soyabean and algal protein, although well digested, were poorly assimilated in similar feeds. When one third of the protein, in a 30% fishmeal protein diet, was replaced by soyabean protein concentrate there was a significant decrease in growth rate and food utilization. Temperature did not have a profound effect on the protein requirement of carp although it did influence growth, body composition and food utilization. Growth of carp in a thermal effluent showed no depression compared to that in laboratory recycling systems and the optimum protein content of carp diets under these conditions was 35%. It was concluded that carp is a suitable species, both nutritionally and in terms of its temperature requirements, for intensive culture in heated effluents.