Dried duckweed and commercial feed promote adequate growth performance of tilapia fingerlings

Abstract

The present study evaluated Nile tilapia when fed on dried duckweed in combination with commercial feed, aiming at reducing production costs. Three diets, which consisted of commercial feed (40% crude protein), dried duckweed or a combination of commercial feed and dried duckweed were fed to triplicate groups of 20 tilapia (Oreochromis niloticus) fi ngerlings. Fish weighing 3.2 ± 0.94g were stocked in nine 1-m 3 net cages and fed twice a day for 50 days. The fi nal average weights of fi ngerlings fed commercial feed (21.67g) and 50% feed + 50% dried duckweed (19.53g) were not different (p<0.05). Likewise, the specifi c growth rate did not differ between fi sh receiving these dietary treatments. Weight gain decreased as water temperature decreased along the experimental period, increasing feed conversion mainly for fi ngerlings fed on dried duckweed only. Also, when fed alone dried duckweed promoted the lowest weight gain and specifi c growth rate. It was confi rmed that dried duckweed can replace 50% (1:1 dry weight) tilapia fi ngerling 40% crude protein feed for a period of at least 50 days, without reducing growth. Resumo Desempenho de alevinos de tilapia nilótica alimentados com uma combinação de lemnas secas e ração comercial. O presente estudo avaliou a utilização de ração comercial e lemna seca no cultivo de alevinos de tilápias nilóticas com o objetivo de reduzir os custos de produção. Três dietas representadas por lemna seca, ração comercial (40% proteína bruta) e uma combinação de lemna seca e ração comercial foram fornecidas a um grupo de 20 alevinos de tilápia (Oreochromis niloticus) em triplicata. Peixes com peso médio 3,2 ± 0,94 g foram estocados em nove tanques-rede com volume de 1-m 3 e alimentados duas vezes ao dia durante um período de 50 dias. O peso médio fi nal dos alevinos alimentados com ração comercial (21,67 g) e 50% ração + Biotemas, 21 (3): 91-97, setembro de 2008