Title: Nitrogen utilization from diets with refined and blended poultry by-products as partial fish meal replacements in diets for low-salinity cultured Florida pompano, Trachinotus carolinus Author
Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 19, 2014
Publication Date: N/A
Interpretive Summary: Feeds are the major production cost of farmed fish accounting for approximately 50% of the cost of production. Fish meals continue to be the preferred protein source for fish feeds for marine fish like Florida pompano as they are highly digestible and palatable to fish. However, fish meal proteins are expensive and experience periodic fluctuations in pricing and availability. This has prompted considerable effort towards the search for suitable alternatives. One particularly attractive alternative because of its lower cost and high availability is meals rendered from poultry by-products from processing plants. Five differently processed types of poultry by-products were substituted for 2/3 of the fish meal protein in a fish meal diet and evaluated for their suitability as partial replacements. Three trials were conducted to: 1) evaluate growth and efficiency; 2) determine how digestible the products are; and 3) determine if there are differences in the amount of waste produced measured as ammonia and urea. Relative to fish meal there were no difference in growth and efficiency. All but one of the poultry by-product diets were as digestible as the fish meal diet. Similarly, all the poultry by-product diets except one resulted in the same amount, or even less ammonia production, whereas all resulted in the same amount of urea production as the fish meal diet. The results suggest poultry by-products are a very good alternative as partial fish meal replacements in Florida pompano diets.
Technical Abstract: Three trials were performed to evaluate partial fish meal (FM) replacement with poultry by-products in a practical-type diet for Florida pompano, Trachinotus carolinus reared in low-salinity. Two refined and blended meals (BP67, BP70), two chicken concentrates (CC66, CC70) and one standard pet-food grade by-product meal (E150) were evaluated. Diets were formulated to contain 48% crude protein (CP) and 21 MJ/kg. Poultry by-products replaced 67% of the FM protein on an isonitrogenous basis. Trial 1 was a 10 week growth trial. No differences were detected in growth, efficiency, feed intake, protein productive value, or body composition between the by-product diets and FM. Trial 2 examined protein, energy, dry matter, and organic matter digestibility. Apparent CP digestibility (65.6-72.9%) was significantly lower (P<0.05) in the BP67 diet than the others, except BP70. No other differences were detected. In trial 3, fish were fed a morning meal, and postprandial ammonia (TAN) and urea excretion measured at 8 hourly increments. Ammonia increased 3.1-3.4 fold within 1 h. Rate of TAN excretion (mg TAN/kg•hr) did not significantly decrease until 4-5 h postprandially. No differences in TAN accumulation were observed until 4 h when accumulation was significantly higher (P<0.05) in CC66, and at 5 h lower in CC7 relative to the FM diet. Rate of urea excretion was constant. A slope ratio analysis indicated urea excretion was significantly lower (P<0.05) in CC70 and E150 relative to FM and CC66. Stepwise regression suggested Methionine and Lysine were likely limiting explaining 90% of the variability in weight gain. Methionine and Threonine accounted for 90% of the variability in ammonia excretion, and Threonine 70% of the variability in urea excretion. Ammonia accounted for 94-95 % of the total N (TAN + urea-N) excreted. The results suggest poultry by-products are suitable partial replacements for FM in Florida pompano diets.