Effects of different feeding rates of extruded and pelleted feeds on growth and nutrient retention in channel catfish (Ictalurus punctatus)

Abstract

Extruded and pelleted feeds were fed with different amounts (100, 90, 80, and 70% of satiation) to channel catfish (42 g initial weight) and the effects on growth, nutrient retention, and serum biochemistry were examined. The two feeds were designed with the same formula (containing 308 g kg−1 crude protein and 53 g kg−1 crude lipid), and were fed to eight treatments of fish (pelleted feed with a satiation of 100, 90, 80, 70% and extruded feed with a satiation of 100, 90, 80, 70%) with triplicate cage per treatment (20 fish per cage) for 10 weeks. The results indicated that weight gain (WG) of the eight groups were 371.1, 328.1, 302.1, 281.1 and 370.5, 334.0, 311.0, 285.3%, respectively. The fish fed extruded and pelleted feed at the same feeding rate showed no significant differences in growth performance, whole-body composition, and nutrient retention (P > 0.05). In both extruded and pelleted feeds, WG, feed conversion ratio (FCR), intraperitoneal fat ratio (IFR), whole-body lipid content, lipid retention (LR), and serum triglyceride (TG) content decreased (P < 0.05), but protein retention (PR) increased from 35.3 to 39.4% in pelleted feeds and from 35.9 to 39.7% in extruded feeds with the decrease of feeding rate from satiation (100%) to 70% of satiation (P < 0.05). The above results demonstrated that channel catfish fed extruded feed had the similar growth to that fed pelleted feed with the same formula. The utilization of protein and feed could be improved by the reduced feeding rate from satiation (100%) to 70% of satiation.