Ruguang Chen

Evaluation of a Dietary Dairy―Yeast Prebiotic in Juvenile Golden Shiners in Ponds

Abstract We evaluated the performance in ponds of juvenile golden shiners Notemigonus crysoleucas fed a control diet or a diet with 2% dairy–yeast prebiotic. Fish weighing 0.1 ± 0.001 g (mean ± SD) were initially stocked into five 0.04-ha earthen ponds per diet at 21.9 kg/ha and fed extruded 35%-protein pellets to satiation twice daily. Subsamples of fish were weighed at 2-week intervals for 6 weeks; the fish were harvested at 7 weeks to avoid reproduction. For golden shiners fed the control and prebiotic diets, the mean individual weight gain (2.93 and 2.89 g, respectively), net yield (214.0 and 198.8 kg/ha), feed conversion ratio (1.34 and 1.47), and survival (61.5% and 64.2%) did not differ. Condition index (Fultons K) was higher in fish fed the control (1.15) rather than the prebiotic diet (1.08). After harvest, 100 fish per pond were acclimated to tanks before being subjected to a bacterial challenge with Flavobacterium columnare. Each pond replicate received one of three experimental treatments: co...

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 Fishers least-significant-difference tests were used to compare differences among treatment means (P ≤ 0.05). W...

Effect of Diets Supplemented with Soybean, Flaxseed, or Menhaden Fish Oil on the Growth, Feed Utilization, Immune Status, and Sensory Properties of Channel Catfish in a Recirculating System at 22°C

Channel catfish feed intake and growth decline with temperature, but different dietary lipids might sustain performance during cool weather. Catfish at a suboptimal temperature (22°C) were fed 32% protein commercial floating pellets supplemented with 2% soybean oil (SBO), menhaden oil (MFO), or flaxseed oil (FLX). After 12 weeks, fish were counted and weighed, then health assays and proximate and fatty acid analysis of fillets were conducted. Weight gain, feed conversion ratio, and survival were similar among treatments, indicating limited potential of different lipids to improve growth at low temperatures. However, the favorable feed conversion ratios (FCRs; ≤1.6) indicated that feeding at 22°C was worthwhile to maintain good condition of catfish. Across diets, the unsaturated fatty acids in muscle lipids increased. The FLX and MFO both increased the n-3 HUFA in the fillet, but FLX was less effective. Unfortunately, both FLX and MFO reduced sensory properties of the fillet relative to the SBO control.