Location: Warmwater Aquaculture Research Unit
2012 Annual Report
1)Digestibility trials were conducted to determine apparent digestibility coefficients (ADCs) for several alternative protein sources including corn gluten feed, distillers dried grains with soluble, canola meal, poultry by-product meal, and hydrolyzed feather meal as compared with that of soybean meal. ADCs for protein ranged from 70 to 87%, lower than 94% for soybean meal. ADCs for energy ranged 52–59% for plant feedstuffs and 79–82% for animal feedstuffs as compared with 79% for soybean meal. Lysine in plant feedstuffs was 67–79% available and that in animal feedstuffs was 61–72% available to catfish, lower than 94% for soybean meal. These ADC values can be useful in formulating cost-effective feeds using these feedstuffs..
2)A pond study was conducted to evaluate the use of corn gluten feed and cottonseed meal to replace 25, 50, 75 and 100% soybean meal in the control diet. Levels of corn in the diets also decreased as corn gluten feed and cottonseed meal levels increased. Net yield, carcass and fillet yield, and fillet protein and fat levels decreased and feed conversion ratio increased linearly as soybean meal replacement levels increased. Results demonstrate that a maximum of 50% of the soybean meal in channel catfish diets may be replaced (soybean meal was reduced from 51.4% to 25.7%) by a combination of corn gluten feed and cottonseed meal (up to 20% of each in the diet) without markedly affecting physical quality of feed pellets, fish growth, processed yield, and body composition. The poor performance of diets containing high levels of corn gluten feed and cottonseed meal are likely a result of high fiber and/or low digestible energy of the diet. At current feedstuff prices, the use of a combination of corn gluten feed and cottonseed meal to partially replace soybean meal and corn reduces feed cost for catfish producers..
3)A second pond study was conducted to examine the use of distillers dried grains with solubles (DDGS) in catfish feeds. Results showed no significant differences in production characteristics among fish fed DDGS at levels up to 20%. No obvious yellow pigmentation was observed in fillets of fish fed the DDGS diets. However, processed yield significantly decreased with increasing levels of DDGS, which is likely caused by reduced digestible protein, an imbalance in essential amino acids, or high fat content in DDGS. Improved Culture Methods: Studies on stocking different ages of fry have been completed. Stocking hatchery-fed fry resulted in 41.6% survival, stocking swim-up fry resulted in 7.1% survival, and stocking sac fry resulted in 4.5% survival. The final recommendation is to continue feeding fry in the hatchery before stocking to improve survival rates. New Production Strategies for Large Catfish:.
1)In forage fish studies, the addition of threadfin shad to catfish ponds did not improve catfish growth or feed conversion. Threadfin shad did reduce algae-caused off-flavor in summer but caused fishy flavors in the winter. Presence of fathead minnows had no effect on production or fillet quality. Overall the use of forage fish to increase production efficiency does not appear effective. While threadfin shad did reduce algal derived off-flavors during the summer, fishy flavors were noted during the winter which could present processing issues during winter harvest. .
2)Recirculation flow rates and aeration requirements have been established for the split pond systems based on desired minimum dissolved oxygen concentration, maximum fish biomass, and water temperature. Daytime flow rate through the system (gallons per minute) = [(maximum pounds)(0.8)] ÷ (lowest desired DO). Nighttime aeration requirement (using standard paddlewheel aerators, in horsepower) = (maximum pounds of fish)(0.0002).