INTERVIEW ▶▶▶ Jan Dijkstra


Feed strategies designed to reduce emissions


Jan Dijkstra, animal feed expert at Wageningen University & Research (WUR), sees many opportunities to reduce nitrogen, ammonia, phosphate and methane through the proper use of feed.


BY HANS SIEMES, FREELANCE JOURNALIST C


attle farmers (supported by consultants) often play it too safe when it comes to feed concentrates, says Jan Dijkstra. They’re afraid of lower milk production, so they tend to over-feed their cows. The surplus protein finds


its way into the animal’s urine in the form of nitrogen where it evaporates as ammonia. “On average, farmers feed 16.5% raw protein in the dairy ration. This can be brought down to 15.5% without any loss of milk production, which leads to a reduction in ammonia emissions of nearly 10%. That’s a huge difference.” He takes the Irish approach as an example. This country’s law dictates that derogation participants can only use feed concentrates with less than 15% raw protein next year. with no exceptions. Dijkstra: “This is not possible in the Netherlands, unfortunately. We do not have a government agency like the Irish one that checks the max- imum amount of protein or can make exceptions to this rule.”


What role can the compound industry play? “There are opportunities for feed concentrates. Low-protein feed concentrate is an option, but you should always look at it in con- nection with protein from grass (silage). The quality of feed con- centrates will become a focal point, especially the protein quality. Durability and quickly or slowly degradable fibres come into view here. In the future, using specific amino acids in protein may also come into play.”


Can the problems with nitrogen/ammonia, phosphate and methane be solved by adopting an ideal feed strategy? “That would be fantastic, but it mostly just creates conflicts. A measure that does work is feeding a silage maize ration. This is low in protein, has better nitrogen efficiency, with less nitrogen and ammonia emissions and less phosphate. It also has lower methane emissions than grass.”


A silage maize ration is favourable, but the exemption ac- tually curbs silage maize cultivation by increasing the grassland cultivation norm from 70% to 80%. “This is a shame, but the exemption exists because of the amount of nitrate in groundwater. The nitrate concentration under maize land on sandy soil is twice as high as on grassland. You must then consider the best option. Nitrogen efficiency has deteriorated in the last four years due to a reduction in maize cultivation because of exemption and drought. The increase to 80% should be re- versed or it should become even lower than 70%. A combination of protein from grass and starch from maize delivers higher nitro- gen efficiency and is better for the environment. When you culti- vate the soil properly and cultivate a good catch crop, you can achieve a lot with modern silage maize cultivation.”


You also recommend mowing grass early with a dry matter yield between 2,000 and 2,500 kilograms per hectare. That solves two problems, right: optimal feed and less methane? “Young grass goes hand in hand with low-protein feed. Protein from young grass is by far the cheapest and its quality comes close to the protein quality of feed concentrates. Mowing and feeding every day is ideal, optionally adding silage maize. The grass should not grow above 15 centimeters for a pasture cut. Take your grass level meter into the field several times a week. That way you can achieve a reduction in methane emissions of 30%, which is a big step for the environment. However you do it, do not let the grass grow for too long, because this leads to a reduction in feed quality. Roughage quality is the foundation for feeding well.”


Shouldn’t the government reward such a decrease in methane? “That will be the case some day, but reducing nitrogen is the first point on the government’s agenda. This can be done through compound feed or roughage (or both) to get a ration that is lower


▶ ALL ABOUT FEED | Volume 28, No. 6, 2020 21


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