Inositol phosphates in the digestive tract and phosphate utilisation of farm animals fed maize
From the total P contained in maize kernels, 60 to 80 % occur as phytate, which is the main storage form of phosphate in plants. Phytate must be degraded enzymatically via phytases in order for the contained phosphate to be utilised by animals. In general, endogenous mucosal phytase activity of non-ruminants such as pigs and chickens is considered insufficient. Additionally, the intrinsic phytase activity of most maize genotypes is very low. Thus feeds for pigs and poultry contain microbial phytase and/or feed phosphate produced from mined rock phosphate. The inclusion of the former is not possible for organic farming operations and the inclusion of the latter is not sustainable, since rock phosphate is a finite resource. It also leads to a higher concentration of phosphate in the manure. This can contribute to environmental problems such as the eutrophication of sensitive ecosystems. Thus the utilisation of phosphate derived from phytate needs to be improved and the inclusion of feed phosphate in feed mixes reduced.
This research subject explores in a large number of maize genotypes the variation in phytate content and the effect of phosphate fertilization. It also investigates phosphate utilisation and phytate breakdown in the digestive tract of non-ruminants fed maize with different intrinsic phytase activities or phytate content by mainly using established in vitro assays.
