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    The effect of macro nutrients and phytase on mineral digestibility and immunity in weaned pigs


    The aim of this project is to assess the effects of supra levels of the enzyme phytase on the digestibility of other mineral elements and the possible impacts on gut health and immunity in relation to other micro and macro nutrients.


    The food we eat provides us with a range of nutrients that keeps us healthy and active. It is therefore very important that this food forms a balanced diet that includes the right amounts of carbohydrates, proteins, fats, vitamins and minerals that our bodies need, in the right forms to be digested and used. Those nutrients that are needed in relatively large quantities are termed macro nutrients and generally include carbohydrates, proteins, fats and some minerals such as phosphorus (P) and calcium (Ca). Other nutrients such as zinc (Zn) and iron (Fe) are also needed for body processes such as immunity and play vital roles as components of cellular signalling pathways. In comparison to the macro nutrients, the latter are only needed in much smaller amounts and so are named micro nutrients.    

    Phosphorus (P) is generally regarded as one of six unconditional ingredients for life on earth, the others being oxygen, carbon, nitrogen, hydrogen and sulphur. In plants it tends to be found in groups of six attached to a carbohydrate ring called myo-inositol. When joined in this way we call the chemical myo-inositol hexakisphosphate (IP6) or phytic acid for short. The highly reactive molecule likes to form a salt with minerals such as Ca, Zn, Fe and magnesium (Mg) which we then refer to as phytate. Because phytate accounts for the vast majority of phosphorus found in plant seeds it inevitably ends up being fed to humans and animals in the form of cereals and other grains. This is not a problem for ruminant animals such as cows and sheep because they have plenty of microorganisms living in their digestive tract that release an enzyme called phytase. This enzyme shears phosphate molecules off the phytate complexes to release the minerals and make them available for the animal to use.

    Unfortunately, animals that do not have a rumen stomach (monogastrics) such as pigs, chickens and humans do not naturally produce such effective phytase enzymes and have to rely on those added to or found naturally in their food. In pig nutrition, these phytases have been added for several decades and are well documented to improve pig growth rates and performance. This is largely due to them shearing IP6 down to its lower esters of IP5, IP4, IP3, IP2 and IP1 in the stomach before it has had a chance to bind with proteins and other nutrients. The challenge, which this project aims to address is based on the principle that we know normal doses of phytase, added to pig feed, breaks down phytate complexes to release nutrients.

    What we don't know is why super doses of phytase seem to give above expected improvements in pig performance or what happens to the lower esters of inositol phosphates once they have been absorbed through the intestines into cells and the blood. There is evidence to suggest that IP1 may reform to higher esters such as IP3 and IP6 inside of cells and affect certain cellular functions. Some human researchers have suggested that IP6 might actually be very beneficial as a cancer fighting agent. Research is therefore needed to determine how minerals, other nutrients and inositol phosphates affect gene expression, immunity and physiology in monogastic animals at normal and super doses. This will allow us to formulate the best diets for farmers to produce healthy food from healthy animals.

    Funding Body

    The Silcock Fellowship for Livestock Research, Primary Diets & AB Vista

    Lead Organisation

    Harper Adams University


    Click the file name to download the project file:


    Mansbridge, S.C. and Stewart, A.H. 2012. An assessment of straw intake by acid insoluble markers in commercial pigs housed in straw based systems. Advances in Animal Biosciences, 3 (1), P. 56

    Mansbridge, S.C., Atkins, N. and Mackenzie, A.M. 2014. Blood collection methods: Vacutainer selection for serum or plasma mineral analysis (pigs). Advances in Animal Biosciences, 5 (1), P. 142. 

    Mansbridge, S.C., Mackenzie, A.M., Pirgozliev, V., Skinner, L.S., Evans, N., Walk, C.L. and Stewart, A.H. 2014. Selection of reference genes suitable for normalisation of IFN-gamma and TNF mRNA expression by real time SYBR Green polymerase chain reaction in porcine duodenum tissue. Proceedings of the 2nd Annual International Conference on Veterinary Science Research, 24th November, Singapore.

    Mansbridge, S.C., Mackenzie, A.M., Pirgozliev, V., Walk, C.L., Bedford, M.R., Wellock, I. and Stewart, A.H. 2015. The effects of dietary digestible phosphorous, phytase and zinc oxide on the growth performance of weaner pigs. Advances in Animal Biosciences, 6 (2), P. 234 (ISSN 2040-4700).

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