Oxygen consumption in relation to nitrogen metabolism in Black tiger shrimp, Penaeus monodon (Fabricius, 1798), fed fresh food and formulated feed

Abstract

An indoor experiment was carried out to assess the effect of various fresh foods and formulated diets on oxygen consumption in relation to nitrogen metabolism in Penaeus monodon. Seven iso-nitrogenous diets were formulated by substituting fishmeal (w/w) at 0 (control), 2.5 and 5% using groundnut oil cake (GNC-1 and GNC-2, respectively), rapeseed meal (RSM-1and RSM-2) and sesame oil cake (SOC-1 and SOC-2). Simultaneously, five different fresh foods (clam, crustaceans, fish, polychaete and squid) were also tested. Results revealed that nitrogen intake increased (p < 0.05) by 10.5%–86.6% in shrimp fed fresh food compared with control. Among the fresh food, fish meat showed the highest (p < 0.05) oxygen consumption and ammonia-N efflux. The O:N ratio decreased by 4.22–6.62 in shrimp fed on fresh food, whereas it increased by 0.91–3.28 in formulated diets. Regression analysis revealed a higher coefficient of determination for oxygen consumption (R2 = 0.9272) as well as ammonia-N excretion (R2 = 0.8778) in fresh food compared with the formulated feeds (0.3818 and 0.2187), whereas it was found to be low for O:N ratio for both the fresh food (R2 = 0.1789) and formulated feeds (R2 = 0.3260). The results confirmed that the measurement of O:N ratio can be an additional tool for assessing the nutritional quality of feed along with growth and digestibility and was more significant with the nutritional quality of formulated diets in P. monodon over fresh foods, in relation to nitrogen metabolism.