Effect of Temperature on Growth, Feed Utilization, and Immune Status of Channel Catfish in a Recirculating System

Abstract

A feeding trial was conducted to determine growth, survival, feed utilization, nonspecific immune response, and proximate and fatty acid composition of the fillet of stocker-sized channel catfish Ictalurus punctatus reared at temperatures considered slightly below optimal (22°C), optimal (27°C), or slightly above optimal (32°C) for feed intake and growth of this species. Groups of 100 stockers initially averaging 111.4 ± 1.7 g (mean ± SE) were stocked into each of four 1,140-L tanks within each of three independent recirculating systems and were fed a 32% protein commercial floating pellet once daily to satiation for 14 weeks. Feed intake was calculated weekly. Subsamples of fish were weighed every 3 weeks to track growth. At the end of the trial, all fish were counted and weighed. Five fish per tank were bled to analyze hematology and immunological parameters. Analysis of variance and Fisher's least-significant-difference tests were used to compare differences among treatment means (P ≤ 0.05). Weight gain (252.2 ± 20.0 g) was highest and feed conversion ratio (1.3 ± 0.0) was lowest in fish held at 27°C, while survival (99 ± 0.4%) was highest in fish held at 32°C. Feed intake did not differ by temperature. When differences in final body weight were considered, the protein, dry matter, and ash in the fillet did not differ by temperature. Both temperature and final body weight affected fillet lipid. Fish reared at 32°C were smaller but had more fillet lipid than fish reared at 27°C. Hepatosomatic index did not differ by temperature. Monounsaturates in muscle lipid declined with temperature, while total n-6 highly unsaturated fatty acids and the index of fatty acid unsaturation were higher in fish held at 22°C than in those held at 32°C. Alternative complement activity was highest in fish held at 22°C, while lysozyme activity was highest at 32°C. Temperature had numerous effects on fish performance when diet was fixed. These effects must be considered when diet composition is manipulated to enhance channel catfish performance at different temperatures.