The invention relates to a method for the improvement of the feed value of especially plant stems, i.e. straw, through influence by ammonia vapours and means for the performance of the method. The object of the invention is to obtain a large percentage of nitrogen by treatment of the straw and thus a large percentage of total protein and with the possibility of supplying much ammonia to the feeding stuff. This gives a uniform feeding stuff with a low percentage of ash and without a residual lye which would be noxious to the animals. For the performance of the method the plant stems are confined in an airtight bag which is them evacuated of air, whereafter a suitable amount of ammonia is supplied. After a suitable time the stems are removed and can them be used as feeding stuff, if necessary, after a mechanical comminution. Further the invention relates to some advantageous mans for use in connection with the application of a plastic bag as a container for the straw during the treatment. Finally the inven
