Nutritional strategies to reduce phosphorus excretion by broilers.

摘要

Several experiments were conducted to determine the extent phosphorus (P) excretion could be reduced by taking nutritional approaches while maintaining performance of broilers and to evaluate the P requirement during the entire growth period of broilers as influenced by these approaches. Supplementation of feed with microbial phytase, introduction of high available phosphorus corn (HAP corn), use of 25-OH-D3, and reduction of dietary P levels were evaluated in a unified nutritional program.; The greatest need for P was to maximize tibia ash. The requirements for P of broilers 0 to 7 wks of age to maximize tibia ash were in close agreement with the current NRC (1994) recommendations and the P requirement 8 to 9 wks was no more than 0.23% nonphytate P (npP). With phytase supplementation, the npP requirements for maximum tibia ash were 0.30, 0.25, and 0.15% for 0–3, 3–6, and 6–9 wk, respectively and fecal P content could be reduced by 25-35% with these P levels, compared with the birds on the current NRC recommendations. The use of starter diets with adequate npP levels (0.50% without phytase, 0.40% with phytase), followed by markedly reduced levels in grower and finisher periods (0.25% and 0.15% without phytase, 0.20% and 0.10% with phytase) with and without phytase was examined. Fecal P content of birds during the grower and finisher periods were reduced by 21 to 44% (without phytase) and 31 to 56% (with phytase) without negative effects on live performance and skeletal integrity. Broilers utilized the npP in HAP corn as well as inorganic P. Fecal P levels of broilers at day 56 were reduced by 20.5 and 58.2% through use of HAP corn alone and coupled with phytase supplementation, respectively. Addition of 25-OH-D₃ significantly increased tibia ash of 21-day-old broilers fed normal corn diets, but not HAP corn diets, and it worked additively with phytase supplementation. The addition of 25-OH-D ₃ and phytase reduced fecal P content by 6.72 and 17.6%, and the combination by 34%. In conclusion, fecal P levels could be markedly reduced by nutritional strategies without sacrificing performance of broilers.