Effects of dietary protein and lipid level, and water temperature, on the post-feeding oxygen consumption of Atlantic cod and haddock

Tank respirometry was used to study the interactive effects of protein: lipid level (55%:11% vs. 42%:16%; both diets isoenergetic) and temperature (11, 6 and 2 degrees C) on the magnitude and duration of specific dynamic action (SDA) in juvenile Atlantic cod and haddock. The protein: lipid level did not affect any measured variable. However, numerous temperature and species effects were observed. For example, although the maximum post-feeding oxygen consumption (30-50% above routine metabolic rate; RMR) and SDA duration (similar to 55-85 h; SDA(DUR)) were not affected by temperature, SDA(DUR) g(-1) of food increased from 11 to 2 degrees C (from similar to 3 to 12 hg food(-1)). While absolute SDA (mg O-2) decreased by similar to 60-65% in cod and similar to 75% in haddock from 11 to 2 degrees C, due to a concomitant decrease in food consumption from similar to 2.0% to 0.6% body mass, SDA comprised between 3.3% and 5.2% of the dietary energy content at all temperatures. Finally, RMR at 11 and 2 degrees C and SDA(DUR) at 2 degrees C were 25-35% and 25% greater in cod, respectively, as compared with haddock. These results suggest that feeding reduced protein diets at low water temperatures is unlikely to improve the growth of these species.