caa a22 4500 397569114 CHVBK 20180308164836.0 cr unu---uuuuu 161202e199601 xx s 000 0 eng 10.3382/ps.0750069 doi (NATIONALLICENCE)oxford-10.3382/ps.0750069 Phosphorus Equivalence of Microbial Phytase in Turkey Diets as Influenced by Calcium to Phosphorus Ratios and Phosphorus Levels [Elektronische Daten] [H. QIAN, E. T. KORNEGAY, D. M. DENBOW] Male day-old turkey poults (n = 768) were fed 0, 300, 600, or 900 U of phytase/kg of a corn-soybean diet in combination with four Ca:total P (tP) ratios of 1.1, 1.4, 1.7, and 2.0:1, and two levels of nonphytate P (nP) of 0.27 and 0.36% in a 21-d trial. Dietary Ca:tP ratios were obtained by varying defluorinated phosphate and limestone at the expense of cornstarch. The calculated dietary percentage of phytate P was 0.266 for all diets. Phytase additions linearly increased (P < 0.05) BW gain, feed intake, gain:feed, toe ash content, and apparent retentions of Ca and P at each Ca:tP ratio and nP level, but the response was influenced by dietary Ca:tP ratios and P levels. The detrimental effect (P < 0.02) of widening the Ca:tP ratio was observed for all measurements at each phytase and P level, and was greatest at lower phytase and P levels. Widening the Ca:tP ratio from 1.4 to 2.0 decreased the phytase efficacy by 7.4 and 4.9%, respectively, for 0.27 and 0.36% nP diets, which was close to the decrease in the phytase activity in vitro by 7.5 and 6.7%, respectively. The largest responses to supplemental phytase were achieved when poults were fed diets with 600 and 900 U of phytase/kg diet, respectively, for 0.36 and 0.27% nP, and for Ca:tP ratios ranging from 1.1 to 1.4:1. Second-order translog equations were generated for the phytase, Ca:tP ratio, and P effect, and nonlinear and linear equations for the phytase and Ca:tP ratio effect. Based on an assessment for the R2 and P values of equations, BW gain, feed intake, toe ash content, and P retention were sensitive measurements of the response to phytase addition. Equivalent equations were developed to determine the P equivalency of supplemental phytase. About 652 and 963 U of phytase were equivalent to 1 g nP, respectively, for 0.27 and 0.36% nP diets in turkey poults from hatch to 21 d of age. © 1996 Poultry Science Association, Inc. Metabolism and Nutrition nationallicence phytase nationallicence calcium nationallicence phosphorus nationallicence turkey nationallicence equivalent nationallicence QIAN H. aut KORNEGAY E. T. 1To whom correspondence should be addressed. aut DENBOW D. M. aut Poultry Science Oxford University Press 75/1(1996-01), 69-81 0032-5791 75:1<69 1996 75 ps https://doi.org/10.3382/ps.0750069 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.3382/ps.0750069 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- QIAN H. aut NATIONALLICENCE 700 1- KORNEGAY E. T. 1To whom correspondence should be addressed aut NATIONALLICENCE 700 1- DENBOW D. M. aut NATIONALLICENCE 773 0- Poultry Science Oxford University Press 75/1(1996-01), 69-81 0032-5791 75:1<69 1996 75 ps Metadata rights reserved CC BY-NC-4.0 http://creativecommons.org/licenses/by-nc/4.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-oxford