Recent findings regarding calcium and phytase in poultry nutrition

Abstract

Calcium (Ca) is an essential element for poultry and even a mild deficiency can lead to significant welfare and performance issues. As a result, it is often fed at levels in excess of requirement, partly as an insurance policy and, to some degree, because of its relatively low cost compared with other feed ingredients. However, when diets meet but do not exceed the phosphorus (P) requirements of the bird, a marginal Ca excess can interfere with P digestibility. This problem is exacerbated when phytases are used to provide some of the required P because Ca decreases the efficiency of phytate (IP6) hydrolysis in a dose-dependent manner. More recently, phytases have been used at very high doses (1500 FyTase units (FTU); ‘superdosing’) in commercial diets, to improve bird performance by removing as much of the dietary IP6 and lower esters of phytate (IP5, IP4, IP3 and IP2) as possible, all of which are considered anti-nutrients, and concomitantly producing as much inositol, a nutrient, as possible. In such a regimen, the ability of the phytase to degrade the lower phytate esters, namely IP4, IP3 and IP2, takes on greater importance than does simply releasing phytate P. Calcium has recently been shown to reduce the efficacy of hydrolysis of the lower phytate esters to a greater degree than the extent to which it decreases IP6 hydrolysis. As a result, Ca concentrations in the diet should be monitored frequently if the maximum value of a phytase is to be realised.

Over-processed meat and bone meal and phytase effects on broilers challenged with subclinical necrotic enteritis: Part 2. Inositol phosphate esters hydrolysis, intestinal permeability, hematology, jejunal gene expression and intestinal morphology

“…The higher degradation in the challenged birds might have been necessitated by either the lower pH recorded in the ileum at d 29 or lower feed (phytate) intake at d 28 as reported ( Zanu et al, 2020a ). The lower the pH, the less negatively charged IP6 becomes, and its ability to chelate positively charged ions is reduced ( Bedford and Rousseau, 2017 ). This suggests that at a higher ileal pH as detected in the unchallenged birds in this study, potential chelators might have been precipitated by phytate and decreased hydrolysis by phytase.…”

Interactive effect of dietary calcium and phytase on broilers challenged with subclinical necrotic enteritis: part 2. Gut permeability, phytate ester concentrations, jejunal gene expression, and intestinal morphology

“…The findings of the current study corroborate with many reports that even in diets supplemented with phytase, the incremental concentration of Ca increases residual concentration not only of IP6 but also IP5, IP4, and IP3 as well ( Zeller et al., 2015 ; Li et al., 2016 ; Beeson et al., 2017 ). Bedford and Rousseau (2017) had argued that a severely imbalanced diet (in the case of this work, a wide Ca:P) might compromise the response of high dietary phytase because such imbalances inhibit the conversion of IP6 to the lower esters. The results therefore suggest that to dephosphorylate IP6 ultimately to inositol, high levels of phytase with a low dietary Ca level (or narrower Ca:P) is recommended.…”

“…But, the efficacy of phytases can be limited by various factors including nutritional imbalances. One such limiting factor is dietary Ca ( Bedford and Rousseau, 2017 ).…”

“…Calcium in the form of limestone or monocalcium phosphate/monodicalcium phosphate is a potent buffer, and therefore, a high concentration of Ca has a negative effect on the release of P through increased gizzard pH, precipitation of P, and interaction with phytate, rendering it less accessible. It is suggested that the addition of phytase to diets with a high Ca to P ratio may recover some of the loss in bird performance ( Bedford and Rousseau, 2017 ). The complete dephosphorylation of inositol hexaphosphate ( IP6 ) by phytase to the lower esters: inositol pentaphosphate ( IP5 ), inositol tetraphosphate ( IP4 ), inositol triphosphate ( IP3 ), inositol biphosphate ( IP2 ), and inositol monophosphate ( IP1 ) has been demonstrated to promote growth performance ( Zyła et al., 2004 ).…”

Over-processed meat and bone meal and phytase effects on broilers challenged with subclinical necrotic enteritis: Part 3. Bone mineralization and litter quality

“…In addition, a compromise in the quantity of Ca in over-processed MBM might have contributed to the higher litter score. Previous reports have suggested that feeding high Ca-diets increases the wetness of litter ( Bedford and Rousseau, 2017 ). Also, in the present study, the challenge increased DM of the litter while decreasing hock burns in the birds.…”