Assessing changes in the composition of broiler litters from commercial poultry units in Northern Ireland following the adoption of phytase in diets
2014
Foy, R.H. | Ball, M.E.E. | George, J.
Microbial phytases increase the bioavailability of phytate P in poultry diets, and a survey was undertaken to determine if their use had lowered the P composition of broiler litter in Northern Ireland compared with standard values of litter composition listed in the current United Kingdom fertilizer recommendations. Litter samples were collected from a total of 20 units across Northern Ireland in 2010 and analyzed for DM, N, phosphate (P₂ O₅), potash (K₂ O), magnesium oxide (MgO), water-soluble P (WSP), ammonium N (NH₄ N), and uric acid N. Dry matter of litter was positively correlated (P < 0.001) with N (r² = 0.65), P₂ O₅ (r² = 0.63), K₂ O (r² = 0.56), and MgO (r² = 0.58). Negative correlations were observed between litter DM and WSP (r² = 0.45, P < 0.001) and NH₄ N (r² = 0.22, P = 0.038) contents. A standardized litter composition with a 60% DM gave a phosphate content of 13.7 kg/t that was 45% lower than the fertilizer book value (RB209), but there were only slight differences (<3%) between book values and DM standardized values for N and potash contents. Uric acid and NH₄ contents were similar to published values. Mean N:P ratio (by weight) of litter increased from 3.7 in 2004 to 5.0 in 2010, lowering the risk of oversupply of P if land applications are targeted to meet N supply. Using the standard RB209 values to plan land applications of broiler litter to meet crop P demands risks undersupplying P, and there is a need for the regulatory values to be modified in light of the changing composition of broiler litter.
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