SLU news

Heat treatment and tannins may increase ruminants’ protein utilization

Published: 13 March 2013

The interest in using locally produced ruminant feed is large, especially in organic production where there are demands for a high degree of self-sufficiency. Unlike the commonly used imported soybean meal, Swedish protein feed and protein in forages contain a relatively low proportion of protein that is stable in the rumen. This means that the protein is decomposed rapidly in the rumen and the utilization of protein is less than if it is digested in the gut.

A common method to protect proteins from degradation in the rumen is heat treatment of feed ingredients. The heat treatment is made industrially and both the temperature and the duration of the treatment are important to avoid that the protein binds so tightly that it instead becomes indigestible.

Fredrik Fogelberg, at JTI – Swedish Institute of Agricultural and Environmental Engineering, has equipment for roasting or heat treatment that can be used at home on the farm. Rolf Spörndly, SLU, has in trials tested the protein degradation in the rumen for faba beans which were roasted at JTI at 165 °, 185 ° and 205 °C in approximately 5.5 minutes. For each temperature increase the protein was slightly more stable in the rumen. Compared with untreated dried bean, about 13 percent higher protein value is reached. The same method was also tested on crushed and ensiled faba bean, but then it received instead about 7 percent lower protein value compared to traditional drying. Crushed and ensiled faba bean may therefor be a good alternative to dried beans, if it is bad harvesting conditions.

Another method to reduce the degradation of the protein in the rumen is to feed ruminants with so-called condensed tannins found naturally in some feeds. Tannins bind the protein to form complexes that are protected from degradation in the rumen. Most of the complexes are then dissolved in the abomasum. The binding can occur both in silage in the silo and when the ruminant chews the feed.

Torsten Eriksson at SLU has studied the feasibility of improving Swedish dairy cows protein supply with birdsfoot trefoil in the ley. Birdsfoot trefoil has relatively low tannin content, which may be positive since too high tannin content can cause more nitrogen to leave with the dung. In the two-year feeding trial birdsfoot trefoil was compared with white clover and there was a certain effect from the tannin that reduced the degradability of protein in the rumen and a yield increase (milk protein and a tendency to more quantity of milk). Torsten also found a reduced fibre digestibility and higher milk urea with birdsfoot trefoil in the ration. Torsten eventually conclude that it is possible to improve dairy cow protein supply with birdsfoot trefoil in the ley.