Dietary protein requirement of fingerlings of the herbivorous carp tawes, Pontius gonionotus (Bleaker)

Abstract. The dietary protein requirement of fingerlings of Pontius gonionotus (Bleaker) was investigated by feeding five isoenergetic semi-purified diets containing varying levels of dietary protein within a range of 15%–557% by weight over a 70-day feeding period. On the basis of percentage weight gain, daily weight gain, specific growth rate and daily tissue protein deposition the dietary protein requirement of fingerlings of P. gonionotus was approximately 35% when fish meal, blood meal and casein were used as the dietary protein source. Feed conversion ratio, protein efficiency ratio and apparent net protein utilization all decreased with increasing dietary protein levels while apparent protein digestibility was not significantly affected. There was a significant increase in carcass moisture and a decrease in carcass lipid content with progressive dietary protein substitution whilst carcass protein and ash were relatively unaffected.