Modeling digestibility of dietary phosphorus in growing and finish pigs.
Low P digestibility combined with intensive pig production can lead to water pollution. The aim of this paper was to develop a model able to represent P digestion in pigs across diets and contribute towards the reduction of P excretion. Phosphorus in plant feedstuffs includes some nonphytate P (NPP) that is readily digested but is mostly as organic phytate P (oP) that is indigestible unless it is dephosphorylated. The ability of pigs to dephosphorylate oP using endogenous phytase enzymes is limited and is a function of Ca intake. The effect of Ca (g/kg diet) on the proportion of oP dephosphorylated (kg/kg) in the small intestine (SI) and large intestine (LI) was determined as 0.26 - (0.015 × dietary Ca) and 0.69 - (0.059 × dietary Ca), respectively. The dephosphorylated oP in the LI was assumed to be indigestible and was excreted. Proportion of oP dephosphosphorylation (kg/kg) by microbial and plant phytase activity (FTU) in the stomach was estimated to be 0.56 × [1 - exp(-0.001 × FTU)] and 0.38 × [1 - exp(-0.002 × FTU)], respectively. Phosphorus digestibility (kg/kg) of NPP and dephosphorylated oP in the SI was assumed to be constant at 0.8. The model was used to predict P digestibility in 2 experiments by Stein et al. (2011) and Poulsen et al. (2010) and compare the predictions with experimental outcomes. The model successfully predicted the P digestibility to a range of dietary Ca concentrations and for 2 levels of supplementation with microbial phytase. However, the predictions overestimated P digestion systematically but always within a 10% margin of the observed values. The model could be a useful tool for formulating strategies to improve the efficiency of P digestion and reduce soluble P excretion in pigs.
School of Agriculture Food and Rural Development, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK. v.symeou@ncl.ac.uk
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Symeou
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Edwards
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Kyriazakis
D000821:Animal Feed / Q000032:analysis; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D019587:Dietary Supplements; D008954:Models, Biological; D016226:Phosphorus, Dietary / Q000378:metabolism*; D013552:Swine / Q000254:growth & development* / Q000502:physiology*
D016226:Phosphorus, Dietary