Effect of feeding frequency on growth performance, antioxidant status, immune response and resistance to hypoxia stress challenge on juvenile dolly varden char Salvelinus malma

This study aimed to evaluate the effects of feeding frequency on growth, antioxidant status, immune response and resistance to hypoxia stress challenge on juvenile dolly varden char Salvelinus malma (average weight: 9.40 ± 0.30 g). Fish were randomly assigned to one of six feeding frequencies (1, 2, 3, 4, 5 and 6 times/day) following the same ration size for 8 weeks. Weight gain increased significantly as feeding frequency increased from 1 to 5 times/day, but decreased with further increasing feeding frequency. Feed intake, whole body crude lipid content, serum aspartate transaminase, alanine transaminase and malondialdehyde content increased significantly as feeding frequency increased. Serum total antioxidant capacity increased significantly as feeding frequency increased from 1 to 5 times/day. Hepatosomatic index, serum lysozyme activity and 50% haemolytic complement content of fish fed 1-2 times/day were lower than those of fish fed 3-6 times/day. During the hypoxia challenge, cumulative mortality increased significantly as feeding frequency or hypoxia time increased. This study indicates that lower and higher feeding frequencies had a negative influence on growth of dolly varden char; the optimal feeding frequency to enhance growth and boost immunity of this species at juvenile stage is 4 times/day.