Diurnal ammonia and urea excretion rates in European sea bass, Dicentrarchus labrax fed diets containing mixtures of canola and cotton seed oil at two different ambient temperature

Abstract The knowledge about the combined effects of higher temperature and dietary nutrient quality on the diurnal nitrogenous excretion rates is very limited in farmed fish species including European sea bass. Therefore this study investigated the combined effects of increasing levels (30 vs. 60 %) of dietary fish oil replacement by equal mixture of cotton seed oil (CSO) and canola oils (CO) and two different ambient temperature (24 vs. 30 °C) on diurnal total ammonia and Urea–N excretion rates in European sea bass ( Dicentrarchus labrax ). Experimental diets were fed to fish three times (08:30–13:30–18:30 h) at a fixed rate of 3 % BW.d −1 . The daily consumed nitrogen and energy intake of fish were similar during the investigation in different dietary treatments. However, the daily excretion rates of TAN, total nitrogen (TAN+Urea–N) and total nitrogen expressed as a proportion of consumed nitrogen by the European sea bass maintained at 30 °C were found to be significantly ( P P