Increasing nutrient availability of feather meal for ruminants and non-ruminants using an ammonia pressurisation/depressurisation process

An ammonia pressurisation/depressurisation process (PDA) was evaluated for efficacy in enhancing solubility and digestibility of feather meal (FM) pro tein. Commercial FM was processed for 5 min with variable ammonia loadings (0.5-2 g g(-1) DM), moisture contents (10-50%) and temperatures (75-90 degr ees C). Dry matter and protein solubility were determined in a 0.15 M NaCl solution (6h, 39 degrees C) and soluble protein content was determined by t he Lowry method. Ruminal solubility was determined by the Kjeldahl method a s protein lost in the rumen (1 min) of a cannulated steer. Protein digestib ility (crude protein by Kjeldahl analysis) was determined using the in situ dacron bag and pepsin techniques. Protein solubility in the untreated FM w as low (13.3 and 7.2%, in NaCl and in rumen fluid, respectively) and increa sed (p < 0.05) to 39.4 and 23.0%, respectively, in the treated FM at the op timal conditions (50% moisture, 2g ammonia g(-1) dry FM and 90 degrees C). Ruminal and pepsin protein digestibilities increased (p < 0.05) with increa sing moisture content, ammonia loading and temperature. Protein digested in the rumen at 12h increased from 21.9 (untreated) to 43.0%. Highest digesti bility value at 48h was 54.8%. Pepsin protein digestibility increased (p < 0.05) from 35.4% in the untreated FM to 89.3% in the optimal treatment. Pro tein solubility in NaCl correlated very well (0.98) with pepsin digestibili ty. The 3-fold increase in solubility and 2-fold increase in digestibility could improve nutrient availability of FM and increase its value as a prote in source for both ruminants and non-ruminants. (C) 1999 Society of Chemica l industry.