Published 06.01.2023

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Phytase in winter crops: Content is higher in population varieties than in hybrid rye varieties

Organic farmers are not allowed to add synthetic phytase to feed and must therefore rely on the natural phytase content of the feed grain or add mineral phosphorus to feed.

The enzyme phytase is crucial for the livestock's utilization of phosphorus bound in the feed and the enzyme thus has both an impact on feed utilization and the environment, due to the impact of surplus phosphorus. 

Large variation between varieties

Rye is the best source of natural phytase, followed by triticale and wheat, but there are also varietal differences within species. This is shown by the results of organic national trials in 2020 and 2021 with winter rye, winter triticale and winter wheat.

In winter rye, the highest content was measured in the varieties Inspector and Dukato. These are both population varieties, and the phytase content is about 80-90 per cent higher than in the hybrid varieties. The yields are lower in the population varieties, but they are apparently the best source of phytase.

Variation in phytase content in three winter cereal species.
Source: National Field Trials® 2021

•    Wheat: 631-931 FTU/kg
•    Triticale: 642-1566 FTU/kg
•    Rye: 2466-4429 FTU/kg

Enzymes could be a solution in poultry feed

Unfortunately, rye is not suitable as feed material for poultry due to harmful fibers, and organic poultry production is therefore particularly challenged by the lack of natural phytase in the feed. In addition to wheat, oats and maize are widely used as poultry feed, but none of these contain phytase of significant importance for phosphorus utilization. Adding extra phosphorus of mineral origin is therefore necessary, leaving poultry producers in a situation where they risk reaching the maximum phosphorus limit in the manure, and therefore cannot fertilize the fields with optimal nitrogen-levels.

The high phytase level in rye makes it interesting to investigate whether rye can somehow be included in the poultry feed after all. This could be in the form of small amounts of the most suitable varieties for poultry nutrition, or with the addition of enzymes such as xylanases to improve digestion, xylanases are available for use in organic production.

Rye also has the useful property that it does not lose phytase when heated to the same extent as wheat and barley, which is an advantage due to the demand for heating of poultry feed to avoid infectious diseases as Salmonella.