Strategies to Modify Phosphorus (P) in Poultry Manure and Litter

Dietary strategies Meet but do not exceed bird P requirements. Dietary P originates primarily from plant and animal feedstuffs and from inorganic P supplements. Formulating nutritionists can make considerable impact when they provide enough available P to meet bird requirements yet control the urge to add significant amounts as an extra margin of safety. For example, the National Research Council (NRC) (1994) recommends 250 mg available nonphytate P (nPP) per hen per day, while Leghorn breeder guides advise producers to provide 450 to 460 mg per hen per day early in lay, and 288 to 390 mg late in the hen’s cycle. While a small margin of safety is advisable for a commercial flock, the literature supports the NRC recommendation. An experiment evaluating two levels of available P (0.2% and 0.4%), two levels of calcium (Ca), and three levels of phytase for commercial White Leghorn hens was carried out in two phases from 18 to 55 weeks and 55 to 67 weeks (Scott et al. 1999). In the period before 55 weeks of age, the lower level of available P was adequate for maximum production regardless of Ca or phytase levels. Boling et al. (2000) reported similar findings indicating that 0.15% available P supported optimum egg production from 20 to 70 weeks on corn and soybean meal (CSM) diets, while 0.20% maintained body weight and tibia ash equal to higher NRC (0.25%) and breeder recommendations (0.45%). The opportunity to reduce fecal P is quickly realized when a large complex of hens is involved. In a four-week period, 1.2 million hens in a large complex consume 7.4 million lbs of feed (3,696 tons). If dietary available P were reduced from 450 to 250 mg per hen per day, it represents a $4.82 per ton cost savings in dietary dicalcium phosphate totaling $17,814 in feed costs. With such a formulation, fecal P2O5 is reduced approximately 35,000 lbs in one month. According to Angel (2000), NRC (1994) broiler recommendations for nPP from hatch to 3 weeks appears to be well supported both under controlled experimental conditions and commercial conditions. However, in the grower and finisher phases, NRC (1994) recommendations for nPP (0.35% and 0.30%) exceed those used successfully in the field and proven to be adequate under experimental conditions. Waldroup (1999) indicated that after 3 to 4 weeks of age the P needs of commercial broilers are greatly reduced and that when birds consume a significant amount of feed there is little need for supplemental P in a typical CSM broiler diet. Similarly, commercial dietary recommendations for finishing turkeys fall between 0.45% and 0.57% available P, while the NRC (1994) recommends 0.28% nPP. Select feed ingredients with readily available P. While strategies for minimizing P levels in manure are numerous, a major impact can be made by selecting ingredients with highly available P. Phytic acid or phytate P (Figure 11-4) found in many cereal grains and plant byproducts is in a form that birds do not absorb well. The P in corn and SBM, for example, has a biological value of only 30 and 25, respectively, and is only 19% and 20% available because of the large phytate P content (Table 11-5). Compared with the P in animal meals and fishmeal, which are almost 100% bioavailable, feeding cereals can contribute to manure P. However, feeding low-phytate grains offers opportunities to reduce fecal P. New highly available P (HAP) corn Meet but do not exceed bird P requirements.