The nutritive value of boiled full-fat soybean in pelleted feed for Nile tilapia

Abstract

The utilization of boiled full-fat soybean as a dietary protein source in pelleted feed for Nile tilapia, Oreochromis niloticus L., was studied. Boiling for 1 h at 100°C inactivated 80% of the trypsin inhibitor (TI) activity. Isonitrogenous (30% crude protein) and isocaloric (338 kcal/100 g diet) diets were formulated to contain graded levels of trypsin inhibitor activity by using various combinations of boiled and unboiled soybean. Fish were cultured for 70 days in a recirculating water system housed under a covered shelter. An increase in the level of unboiled soybean resulted in an increase in trypsin inhibitor activity which reduced fish growth. Nile tilapia grew well at low levels of trypsin inhibitor (<0.09% TI). The best growth and feed conversion efficiency were obtained with a diet containing boiled soybean meal (58 g/100 g diet) as the sole source of plant protein, although there was a significant increase in the lipid content of the fish.