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Report no. 621

Abstract
Addition of phytase to pelleted finisher feed and a corresponding reduction in the addition of phosphorus and calcium were studied in two herds.

Two phytase products were tested: Natuphos from BASF and Ronozyme P from Roche/NOVOZYMES. Natuphos was sprayed onto the feed after pelleting, and Ronozyme was added in its dry form before pelleting. The trial comprised the following groups in herds A and B:

The analyses of the feed’s content of phosphorus, calcium and other nutrients generally showed good agreement with the planned content. The addition of phytase in the form of Natuphos was 14-37% lower than planned, while the content of Ronozyme P was 55% higher than planned.

The trial showed great variation between the feedstuff factories in how much of the natural phytase of the feed that was deactivated during pelleting (30-70%). The lowest content of natural phytase after pelleting was found in the feed for herd B, which also had lowest content of Natuphos.

In herd A there was no significant difference in the productivity between the control group and the other five groups. In herd B there was a tendency (p=0.08) to a lower productivity in the standard test group (group 2) compared with the control group, and the productivity in group 3 with phytase was significantly lower (4.4% lower) than in the control group. The reduced productivity was in particular due to a poorer feed conversion.

The results in herd A showed that it is possible to reduce the content of phosphorus from 5.2 to 4.2 g/feed unit without affecting the production results as long as the feed contains sufficient phytase. It is thereby possible to reduce the discharge of phosphorus from the basic number of 30 kg per ha to 21 kg per ha in a finisher production with 1.4 AU per ha.

Overall, the trial showed that there is no great safety margin in neither the phosphorus standard for finishers nor in the recommendation of adding phytase to pelleted feed. On the basis of this trial there is thus no grounds for changing the standard of digestible phosphorus for finishers, but the trial did show that it is important that the standard is met. This trial and a previous one found a low content of sprayed Natuphos, and it is therefore recommended to increase the dose of Natuphos from 500 to 750 phytase units per kg to avoid a deficiency of phytase if one wants to reduce the content of total phosphorus by 1 g/kg and the content of calcium by 0.5 g/feed unit compared with the standard. If the addition of Natuphos is maintained at 500 phytase units per kg, the feed should be analysed both before and after Natuphos is added to make sure that the feed contains the planned amount of phytase. As the content of Ronozyme P was higher than planned, this trial cannot say whether 750 phytase units in the form of Ronozyme P is sufficient to avoid a deficiency of phytase when the feed’s content of phosphorus and calcium is reduced by the amounts written above.

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