Exogenous phytase and xylanase exhibit opposing effects on real-time gizzard pH in broiler chickens

Sophie A. Lee (Lead Author), Jenny Dunne, Erica Febery, Charles A. Brearley, Toby Mottram, Michael R. Bedford

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1. The current study was conducted to evaluate the influence of high phytase doses and xylanase, individually and in combination, on performance, blood inositol and real time gastric pH in broilers fed wheat-based diets. 
2. In a 42 d experiment, a total of 576 male Ross 308 broiler chicks were allocated to four dietary treatments. Treatments consisted of a 2 × 2 factorial arrangement, with 500 or 2500 FTU/kg phytase and 0 or 16000 BXU/kg xylanase, fed in two phases (starter 0–21; grower 21–42 d). Heidelberg pH capsules were administered to eight birds from each treatment group, pre and post diet phase change, with readings captured over a 5.5 h period. 
3. At 21 and 42 d, birds fed 500 FTU/kg phytase without xylanase had on average 127g and 223 g lower weight gain than all other treatments, respectively (P<0.05). At 21 d, FCR was reduced (P<0.01) by 2500 FTU/kg phytase or xylanase, however, 42 d FCR was unaffected by enzyme treatment. Inositol content of plasma was twice that of the erythrocyte (P<0.001), with 2500 FTU/kg phytase tending to increase (P=0.07) inositol content in both blood fractions. 
4. Across all treatments, capsule readings ranged from pH 0.54 to 4.84 in the gizzard of broilers. Addition of 2500 FTU/kg phytase to the grower diet reduced (P<0.05) average gizzard pH from 2.89 to 1.69, whilst feeding xylanase increased (P<0.001)gizzard pH from 2.04 to 2.40. In contrast, digital probe measurements showed no effect of xylanase on gizzard pH, while addition of 2500 FTU/kg phytase increased (P=0.05) pH compared to 500 FTU/kg phytase with or without xylanase. 
5. These findings suggested that xylanase and high phytase doses have opposite effects on real-time gastric pH, while similarly improving performance of broilers.
Original languageEnglish
Pages (from-to)568-578
Number of pages11
JournalBritish Poultry Science
Issue number5
Early online date6 Jul 2018
Publication statusPublished - Oct 2018


  • Gizzard
  • pH
  • Capsule
  • Phytase
  • Xylanase

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