Effect of feeding rate on nutrient digestibility in Atlantic salmon, Salmo salar L.

A digestibility trial was conducted to examine the effect of feeding rate on dry matter, gross energy, crude protein and phosphorus digestibility in Atlantic salmon (Salmo salar). Duplicate groups of fish were fed ۰.۲۵, ۰.۵, ۰.۷۵, ۱.۰, ۱.۲۵ and ۱.۹% BW/day. The faeces were collected by Guelph-type collectors for five successive days. Dry matter, protein and phosphorus digestibility’s were all significantly (p<۰.۰۵) affected by feeding rate. Dry matter digestibility was significantly lower in fish fed ۰.۲۵% BW day in comparison with fish fed ۰.۵, ۰.۷۵ and ۱% BW day. Protein digestibility was significantly lower in fish fed ۰.۲۵% BW/day in comparison with ۱.۲۵% BW day. Phosphorus digestibility was significantly lower in fish fed ۰.۲۵% BW/day in comparison with all other treatments except for ۱%BW day. There were no significant differences for energy digestibility between fish fed with different amount of feed. The main effect was reduced digestibility at the lowest level of intake with no obvious relationship between feeding rate and digestibility above this amount. This was explained by a relatively higher loss of endogenous faecal nitrogen and phosphorus at sub-maintenance feeding.