Lipid and Protein Quality of Poultry By-Products Preserved by Phosphoric Acid Stabilization

Abstract

The increase in intensive poultry productions has raised the public concern about poultry waste disposal. When properly handled, nutrients from poultry mortality and poultry processing waste can be recycled into valuable animal feed ingredients. There were two general objectives included in this dissertation. 1) to evaluate the effectiveness of different sources and levels of phosphoric acid (H₃PO₄), and lactic acid fermentation in preserving protein and lipid quality of poultry mortality and poultry processing waste (dissolved air floatation sludge, DAF), and 2) to evaluate the nutritional value of secondary protein nutrients (SPN), a product meal produced from DAF sludge, in broiler diets. Both feed- and food-grade H₃PO₄ were more effective than lactic acid fermentation in preserving protein and lipid quality of silages following 15 d of storage, while food-grade H₃PO₄ was the most effective preservative for 45 d of storage. Food-grade H₃PO₄ was more effective than feed-grade in preserving nutrient quality of silages at 2.76% acidification. Regardless of acid sources, using 5.52% H₃PO₄ significantly improved protein quality of silages. Phosphoric acid stabilization was found to improved only protein quality of DAF silages. Nutrient digestibility of SPN was evaluated in broilers using acid insoluble ash (Celite™) and titanium dioxide as digestibility markers. The acid insoluble ash method had higher accuracy and preciseness in measuring nutrient digestibility of the diets. The calculated apparent metabolizable energy (AMEn), apparent nitrogen retention (ANR, %) and apparent fat digestibility (AFD, %) of SPN estimated by the use of Celite™ were used to formulate the experimental diets containing various levels of SPN. AMEn, ANR, AFD, and broiler performance decreased as the levels of SPN increased. At 14 d of age, birds fed the diet containing 20% SPN had significantly higher incidence of rickets due to vitamin D deficiency, which caused a significantly higher mortality from 14 to 21 d of age. The reduction in bird performance demonstrated the adverse effects of including a high level (> 7.5%) of SPN on nutrient availability of broiler diets.