This invention is an apparatus and method for automatically adjusting the moisture content of feed grains (11) to a relatively constant target level. As the grain (11) is transported into, or within the feed manufacturing process, a sample is diverted through a continuous flow moisture sensor (23). The sensor (23) generates an electronic signal proportional to the moisture content of the grain (11). This signal is used to control the application rate of a surfactant - water mixture, or of water alone. The water may be either in the form of steam or, as a hot or cold liquid. The grain (11) then enters a mixing or contact chamber (15), into which the water is metered at a rate that is proportional to the moisture content of the incoming grain (11). The treated grain will have a relatively constant moisture content, eliminating one of the largest variables in the manufacturing of livestock feeds.