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The Effect of Dietary Phosphorus Level and Phytase Supplementation on Growth Performance, Bone-Breaking Strength, and Litter Phosphorus Concentration in Broilers¹

S. Powell^*, S. Johnston^*, L. Gaston and L. L. Southern^*,2

^* School of Animal Sciences, and School of Plant, Environmental, and Soil Sciences, Louisiana State University Agricultural Center, Baton Rouge 70803

² Corresponding author: lsouthern{at}agcenter.lsu.edu

This research was conducted to determine the effects of feeding different P levels with and without phytase supplementation on broiler growth performance, bone-breaking strength (BBS), and litter P concentration. An experiment with 4 trials was conducted with 7,840 Ross x Ross straight-run broilers. For each trial, 1,960 broilers were allotted on d 0 to treatments, with 7 replications each and with 70 broilers per replication. The broilers were fed a 4-period feeding program consisting of starter (0 to 14 d), grower (14 to 32 d), finisher (32 to 41 d), and withdrawal (41 to 50 d) periods. For each trial, the same pen was used continuously for each treatment-replication combination, and the litter was not removed between trials. Broilers were fed a control diet [0.43, 0.40, 0.36, or 0.32% nonphytate P (nPP)] in the starter, grower, finisher, and withdrawal periods, respectively, a low Ca and P (LCaP) diet with a 0.05% reduction in nPP in each period, and these 2 diets supplemented with phytase at 600 phytase units/kg (nPP and Ca were reduced by 0.094% in diets with phytase). Diet did not affect (P > 0.10) broiler performance in the starter or withdrawal periods. Generally, both phytase addition and the LCaP diet decreased some aspects of growth performance during the grower and finisher periods. There was no main effect of phytase on BBS, but BBS was decreased in the broilers fed the LCaP diet with phytase addition (nPP x phytase, P < 0.01) in the grower period, and BBS was decreased in the finisher (P < 0.02) and withdrawal (P < 0.01) periods for broilers fed the LCaP diet. Total P, soluble P (SP), and reactive soluble P (RSP) were decreased (P < 0.04) in the litter of broilers fed the LCaP diets. Total P, SP, and RSP were decreased (P < 0.01) in the litter of broilers fed phytase. These data indicate that phytase supplementation at 600 phytase units/kg reduces growth in some periods, has no effect on BBS, and reduces total P, SP, and RSP in the litter.

Key Words: broiler • phosphorus • phytase • litter phosphorus

¹ Approved for publication by the Director of the Louisiana Agricultural Experiment Station as manuscript number 07-18-0285.