Phosphorus forms in animal manure

Abstract

The proportion of inorganic (P_i) and organic (P_o) P in animal feces is affected by rearing conditions. This study was conducted to evaluate the P status of farm animal wastes and the effects of some management factors. Total (P_t), P_i, residual (P_r), acid-soluble organic (P_aso), and lipid (P_l) P were determined in freeze-dried, ground (2 mm screen) samples of fresh, uncontaminated dairy (Bos taurus L.), beef (Bos taurus L.), hog (Sus scrofa domestica L.), and poultry (Gallus gallus domesticus L.) feces from commercial farms collected during the winter. Additionally, feces from calves (Bos taurus L.) fed cut-1 and cut-2 of three cultivars of reed canarygrass (Phalaris arundinacea L.) and one cultivar of timothy (Phleum pratense L.) were analysed. Total P varied from 6·7 g kg⁻¹ for feeder cattle feces to 29·1 g kg⁻¹ for hog feces on a dry-matter basis. Of P_t, P_i ranged from 34·8 (broilers) to 63·2% (dairy), P_r from 11·0 (broiler) to 40·8% (finisher beef), P_aso from 7·8 (dairy) to 53·4% (broilers), and P_l from 0·4 (hog) to 2·1% (feeders). Dry matter ranged from 14·3 (dairy) to 67·5% (broilers). Ruminant feces varied more in P_t, P_aso, and P_l but less in P_i and P_r than non-ruminant fecal material. Total P and P_i were closely related. Fecal P_i and P_l were higher in cut-2 hay than in cut-1. Calves fed timothy forage produced feces with less P_i than those fed reed canarygrass. Some calves on cut-2 forage produced feces with lower P_i and less P_r on cut-1 material than other animals. Published values were found to be unreliable indicators of fecal P status.