Effects of ammonia on growth, digestion and antioxidant capacity in juvenile yellow catfish Pelteobagrus fulvidraco (Richardson, 1846)

Abstract

Effects of ammonia stress on food ingestion, growth, digestion and antioxidant capacity were investigated in juvenile yellow catfish Pelteobagrus fulvidraco (Richardson) with initial body weights of 20.24 ± 0.18 g. The fish were reared in triplicate in 15 experimental tanks at a rate of 30 fish per tank for 56 days. Water was maintained at a dissolved oxygen (DO) level of over 6.2 mg L−1, pH 7.2–7.6, and temperature of 29.0 ± 1.5°C under a natural 12L: 12D photoperiod. Survival, food ingestion (FI), specific growth rate (SGR), food conversion efficiency (FCE), apparent digestibility coefficient (ADC), total antioxidant capacity (T-AOC), levels of glutathione (GSH) and malonaldehyde (MDA), and activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-PX) of the juveniles were determined in total ammonia nitrogen (NH3-N+NH4-N) levels of 0 (control group), 3.36, 6.72, 13.44 and 26.88 mg L−1. The results show that the survival, FI, SGR, FCE, and ADC decreased significantly with an increase in total ammonia nitrogen (p < .05), and a significantly negative correlation between SGR and total ammonia nitrogen levels (p < .05). T-AOC, SOD, CAT, GSH-PX and GSH in the blood, liver and gills were found to decline significantly with an increase in the total ammonia nitrogen level (p < .05), while the MDA in the blood, liver and gills was elevated significantly with the increase in total ammonia nitrogen (p < .05). The results indicate a threshold in the induction of the T-AOC and activities of antioxidant enzymes in yellow catfish tissues with a total ammonia nitrogen increase. In the present study the total ammonia nitrogen threshold thus changed from 6.72 mg L−1 in the juvenile yellow catfish.