Much of the phosphorus in feed ingredients is unavailable to the pig because it is locked up in phytic acid and phytates, which the pig cannot digest. Raw ingredients that have not been heat-treated contain endogenous phytases which can be activated by steeping in water prior to inclusion in liquid feed for pigs. This results in an increase in soluble phosphorus due to the hydrolysis of phytic acid and phytates, and hence an increase in the phosphorus available to the pig. However, with heat-treated ingredients such as soyabean meal (SBM) endogenous enzymes are destroyed during processing. In liquid feed systems steeping combinations of raw materials may have an advantageous affect on the availability of phosphorus as the endogenous phytases of the cereal component of the diet may hyrolyse phytates present in SBM. In wheat the phytate phosphorus and phytase is concentrated in the aleurone layer of the grain (Eeckhout and De Paepe 1994). Therefore, the addition of wheatfeed to liquid feed may increase the amount of endogenous wheat phytase present and hence the amount of soluble P released during steeping. The amount of phosphorus that is available to the pig from these raw ingredients is 30%, 42% and 66% of the total phosphorus for SBM, wheat and wheatfeed respectively (Ewing 1997). The objective of this study was to determine the effect of steeping SBM with wheat, wheatfeed or a combination of the two on the release of soluble phosphorus.
Effect of Dietary Non-phytate Phosphorus Levels on the Diversity and Structure of Cecal Microbiota in Meat Duck from 1 to 21 d of age
