Causes of P deficiency

There are two major reasons for P deficiency when using a phytase in feed: low heat stability of the phytase and an overestimation of its P matrix values. In the first case, this leads to lower than expected phytase levels in final feed, reducing the P release from phytate. In the case of overestimating the P matrix values, too much inorganic P is removed from the feed, which is not compensated by sufficient P release from phytate. Both reasons will result in a P deficient diet, causing skeletal problems and reduced animal performance.

A heat stable phytase

To avoid breakdown of the added phytase during pelleting, it is required that the phytase demonstrates a high thermostability until at least 85°C. An overview of the average recovery of a novel intrinsic heat stable phytase (OptiPhos® Plus), determined in over 10 pelleting studies conducted in the EU and in the USA, is shown in Fig. 1. As the universal definition of stability stipulates that “stability is achieved when recovery of the active substance is above 80 % of the original value”, it can be seen that OptiPhos^® Plus can claim an intrinsic heat stability at 85°C when applied in the granular form (G). When a coated version (CT) is used, a stability up to 95°C is observed.

Requiring reliable P matrix values

The capacity of a phytase to replace inorganic phosphates in the feed is summarised through P matrix values for available P and/or digestible P. This can be assessed either by regular digestibility trials, or by bone ash trials, in which the response on P release from phytate is measured by adding the phytase at different doses to a P-deficient feed.

To provide reliable matrix values, multiple trials need to be conducted. For OptiPhos^® Plus for instance, 11 pig trials have already been conducted giving an average dig. P improvement for different inclusion levels (Fig. 2). Fig. 2 also shows the average of the 3 trials giving the best response of OptiPhos^® Plus on P digestibility. From both response curves, it can be deduced that an OptiPhos^® Plus dose of 500 FTU/kg provides a dig. P matrix value of 1.12 g per kg of feed when considering all trials, and a value of 1.25 g/kg when only the best 3 trials are considered.

This difference might trigger phytase suppliers to use only the best trials for establishing the P matrix values. However, this increases the risk for a nutritionist that P deficiency issues might occur, leading to lower animal performance. In that case, the financial loss will surely be much higher than the saving on the formulation cost. Therefore, it is better to rely on the average P matrix values of all conducted trials, and to not just rely on the best ones.

EU approval

Huvepharma has received the EU authorization for all pig species on December 17th 2020 at a minimum inclusion level of 250 FTU/kg. This EU registration demonstrates that OptiPhos® Plus is shown to be efficient and safe for use. Launched in March 2019 outside the EU, OptiPhos® Plus has already proven itself in the field. With this EU approval, the EU market can now also be served, and the further worldwide rollout will be continued in 2021.

Conclusion

It can be concluded that in order to avoid P deficiency in pigs, an excellent recovery of phytase in pelleted feed needs to be guaranteed. In addition, reliable P matrix values need to be provided from multiple trials. It needs to be avoided that P matrix values, calculated from only the best trials, are used during formulation as this can cause P deficiency in pigs at farm level.

For more info on OptiPhos Plus, visit https://www.huvepharma.com/news/products-in-the-picture/optiphos-plus/