Effect of phytase supplementation on plasma and organ myo-inositol content and erythrocyte inositol phosphates as pertaining to breast meat quality issues in chickens

Abstract

‘Woody breast’ (WB) and ‘white striping’ in broiler meat is a global problem. With unknown etiology, WB negatively impacts bird health, welfare and is a significant economic burden to the poultry industry. New evidence has shown that WB is associated with dysregulation in systemic and breast muscle-oxygen homeostasis, resulting in hypoxia and anaemia. However, it has been observed that phytase (Quantum Blue (QB) a modified, E. coli-derived 6-phytase) super dosing can reverse dysregulation of muscle-oxygen homeostasis and reduces WB severity by ~5%. The objective of this study was to assess whether levels of Ins(1,3,4,5,6)P5, the main allosteric regulator of haemoglobin, are influenced by changes in plasma myo-inositol arising from super dosing with phytase. To enable this, methods suitable for measurement of myo-inositol in tissues and inositol phosphates in blood were developed. Data were collected from independent trials, including male Ross 308 broilers fed low and adequate calcium/available phosphate (Ca/AvP) diets supplemented with QB at 1,500 phytase units (FTU)/kg, which simultaneously decreased gizzard InsP6 (P<0.001) and increased gizzard myo-inositol (P<0.001). Similarly, male Cobb 500 broiler chicks fed a negative control (NC) diet deficient in AvP, Ca and sodium or diet supplemented with the QB phytase at 500, 1000 or 2,000 FTU/kg increased plasma (P<0.001) and liver (P=0.007) myo-inositol of 18d-old birds at 2,000 FTU/kg. Finally, QB supplementation of Cobb 500 breeder flock diet at 1,250 FTU/kg increased blood myo-inositol (P<0.001) and erythrocyte Ins(1,3,4,5,6)P5 (P=0.011) of their 1d-old hatchlings. These data confirmed the ability of phytase to modulate inositol phosphate pathways by provision of metabolic precursors of important signalling molecules. The ameliorations of WB afforded by super doses of phytase may include modulation of hypoxia pathways that also involve inositol signalling molecules. Elevations of erythrocyte Ins(1,3,4,5,6)P5 by phytase supplementation may enhance systemic oxygen carrying capacity, an important factor in the amelioration of WB and WS myopathy.

Phytase dose-dependent response of kidney inositol phosphate levels in poultry

“…The tissue inositol phosphates ( Fig 1A and 1B ) are similar to those identified in avian erythrocytes [ 20 , 41 , 42 ]. Thus, despite clear impact of dietary phytase on inositol phosphates in gizzard and ileal content, and on tissue inositol phosphates, the tissue isomers (of inositol phosphates) are phosphorylated in positions not expected from phytate degradation by Quantum Blue or endogenous feed phytase.…”

“…One objective of this study was to investigate the effect of the addition of dietary phytase on the inositol phosphate levels observed in poultry tissues. Previous studies have identified changes in plasma inositol levels in relation to changes in gizzard and ileal phytate hydrolysis [ 9 , 20 , 27 ], but have been unable to access tissue inositol phosphates by commonly used analytical methods. Consequently, the inositol phosphate profile of different tissues is undefined.…”

“…The peaks identified in Fig 1B for kidney tissue samples are also the isomers present in liver tissue samples ( Fig 1A ). The identities of peaks in the set of standards ( Fig 1C ) have been described [ 20 , 36 , 39 ]. The isomers detected in tissues, D-and/or L-Ins(3,4,5,6)P 4 and Ins(1,3,4,5,6)P 5 , differ from the known products of phytate degradation in Quantum Blue-supplemented diets, D-and/or L-Ins(1,2,3,4)P 4 , D-and/or L-Ins(1,2,5,6)P 4 , Ins(1,2,3,4,6)P 5 , D-and/or L-Ins(1,2,3,4,5)P 5 and D-and/or L-Ins(1,2,4,5,6)P 5 [ 40 ] ( Fig 1D and 1E ).…”

“…The ground samples were stored at 4°C until analysis. Diets, gizzard and ileal digesta were extracted as described in Whitfield et al [ 20 ].…”

“…Both approaches have been complemented by Western blot of transporters or signalling components in tissues such as intestinal mucosa, liver and muscle [ 6 , 19 , 20 ]. Remarkably, given the importance of inositol phosphates and phosphatidylinositol phosphates to intracellular signalling, the study of effect of phytase has not extended to measurement of these molecules in tissues, except for blood [ 20 ].…”