Urease activity in soybean meal: effect on its nutritional quality and on growth and survival of Penaeus monodon juveniles.

Abstract

Based on the results of a survey conducted on the urease activity (UA) in commercial shrimp feed containing soybean meal (SBM) (0.00-29. 70 ppm UA), a study was carried out to determine the effects of different heat treatments on the UA, and on the nutritional quality of SBM. The effect of these heat treated SBMs when incorporated into shrimp diet on the growth and survival of Penaeus monodon juveniles was likewise tested. Various levels of UA in SBM were obtained with different heat treatments. Six practical diets were formulated and contained 0.00 (SBM heated at !20°C for 20 min); 0.50 (SBM heated at 60°C for 160 min); 4.0 (SBM heated at 60°C for 80 min); 8.0 (SBM heated at 60°C for 40 min); 11.0 (SBM heated at 60°C for 20 min) and 22.0 ppm UA (without heating). These diets were fed to P. monodon (average weight = 4.24±0.10 g) juveniles for a period of 60 days. Results showed that protein quality in terms of amino acid content of SBM was not significantly affected by the different heat treatments. Weight gains of shrimps fed diets with 8.0, 11.0, 25.0 ppm UA were significantly lower than those fed other diets. Survival of shrimps was lowest with diets containing unheated SBM, but this was not significalltly different from those heated at 60°C. Heat treatment of SBM at 120°C is adequate to be an effective ingredient in shrimp diets.