Lipid and protein quality of poultry by-products preserved by phosphoric acid stabilization

The increase in intensive poultry productions has raised the public concern about poultry waste disposal and its efficiency of nutrient utilization. When properly handled, nutrients from poultry mortality and poultry processing waste can be recovered and recycled into nutritionally valuable and biologically safe 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, 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 derived from processed DAF sludge, in broiler diets. Results showed that both feed-grade and food-grade phosphoric acid were more effective than lactic acid fermentation in preserving protein and lipid quality of silages for a short term storage (15 days), while food-grade phosphoric acid was found to be the most effective preservative for long term storage (45 days). Food-grade phosphoric acid was a more effective preservative of protein and lipid quality than feed-grade at 2.76% acidification. Regardless of acid sources, the inclusion of 5.52% phosphoric acid significantly improved protein quality of poultry mortality silages. Similar effects were observed when phosphoric acid was used to preserve nutrient quality of DAF sludge. However, phosphoric acid stabilization did not improve the lipid quality of DAF silages because extensive lipid oxidation occurred prior to acid preservation. Apparent nutrient digestibilities of SPN, including apparent metabolizable energy corrected for nitrogen retention (AMEn), apparent nitrogen retention (ANR, %) and apparent fat digestibility (AFD, %), was evaluated in broilers using acid insoluble ash (Celite(TM) and titanium dioxide as digestibility markers. Results indicated that the acid insoluble ash method had higher accuracy and preciseness in measuring nutrient digestibility of the diets. The calculated AMEn, %ANR and %AFD of dietary SPN estimated by the use of Celite(TM) was 1650.37 kcal/kg, 23.66%, and 12.60%, respectively. These values were then used in the formulation of experimental diets containing increasing levels of SPN and growth performance and nutrient digestibility of broilers were observed. AMEn, ANR, AFD, and broiler performance decreased as the levels of SPN increased. At 14 days of age, birds fed the diet containing 20% SPN had significantly higher incidence of rickets due to vitamin D deficiency, and this led to a significantly higher mortality from 14 to 21 days of age. (Abstract shortened by UMI.)...