An ammonia treatment system for cereal straws has been recently developed in Japan. The new method is based on a contractor system and is referred to as the “HOKUNOU-S” system. Ammoniation can be used for all types of silos, including, stack, bag, tube and bunker silos as well as wrapped bales. In addition, this technique is suitable for use where a safe, economical, laborsaving treatment with ammonia can be applied. The injection system consists of a large-sized high-pressure vessel, a volume and pressure regulator, lead hose, an injection pipe and nozzle; the durability of this equipment and the safety of its handling comply with Japanese industrial stan dards. For one treatment, normally 8 kg of ammonia is injected into a round bale 1.2 m in diameter within 1-2 min, About 10 t or 40 round bales of cercal straw can be treated by a contractor within 1 h. By treating rice straw with ammonia, the TDN content of rice straw increased from 40 to 60%. As a result, treated rice straw was similar to good quality grass hay while treated barley and wheat straws were similar to grass hay harvested at a slightly later stage. An adequate level of breeding efficiency in yearly calving was obtained in the 3-year reproduction test using a total of 96 breeding cattle. The cost varied with the supply and demand of straw, the length of the actual working time of the wrapping machine, and field conditions (wet conditions cause an increase in time and therefore an increase in harvesting expenses).