Effect of phytase on growth performance, phytate degradation and gene expression of myo-inositol transporters in the small intestine, liver and kidney of 21 day old broilers
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An experiment was conducted to evaluate phytase on growth performance, phytate degradation and the gene expression of myo-inositol transporters in 21-day old broilers. Ross 308, male broilers (n = 240) were obtained and assigned to one of four diets, 10 with pens/diet and six birds/pen from day one to 21. The diets consisted of a negative control (NC) formulated to meet or exceed Ross 308 nutrient requirements, with the exception of calcium (Ca) and available P (avP), which was reduced by 0.16 and 0.15%, respectively. The NC diet was supplemented with 0, 500, 1,500 or 4,500 FTU/kg of phytase to create four experimental diets. On day 21, all birds per pen were euthanized to obtain digesta and tissue samples for phytate degradation and gene expression. Data were analysed as an analysis of variance using the fit model platform in JMP v 13.0. The model included phytase and significant means were separated using orthogonal linear and quadratic contrasts. Phytase supplementation increased gain (linear, P < 0.05) but had no effect on feed intake or feed conversion ratio. Phytate (IP6; quadratic, P < 0.05), phytate ester (IP5, IP4, IP3; quadratic, P < 0.05) and inositol (linear, P < 0.05) concentration in the gizzard was influenced by phytase supplementation. Phytase supplementation decreased IP6 (linear, P <0.05) and IP5, IP4, IP3 (linear or quadratic, P < 0.05) and increased inositol (quadratic, P < 0.05) concentration in the ileal digesta. The expression of the H+-dependent myo-inositol transporter, HMIT, was decreased (linear, P < 0.05) in the kidney and increased (linear, P < 0.05) in the ileum as phytase dose increased. Expression of the sodium-dependent myo-inositol transporter, SMIT2, increased in the liver (quadratic, P < 0.10) and the jejunum (quadratic, P < 0.05) as phytase dose increased. Intestinal alkaline phosphatase expression increased in the ileum (linear, P < 0.05) as phytase dose increased. The influence of phytase on phytate, phytate esters and inositol may influence intestinal alkaline phosphatase activity and the expression of myo-inositol transporters in the small intestine and kidney.
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