A casein-based coating, Nutri-Shield, was uniformly sprayed onto alfalfa hay cubes to determine its effectiveness in protecting cubes subjected to an environment of 38° C (100° F) and 80% relative humidity. Rate of moisture vapor absorption for cubes treated at the manufacturer's recommended application rate was 50% less than that of untreated cubes. The treatment delayed mold development on cube surfaces without adversely affecting measures of forage quality. INTRODUCTION Quality control of alfalfa hay cubes shipped overseas is becoming an increasing concern for exporters. Measures of quality include color, nutritional parameters, such as crude protein, and the presence of mold. Buyers have rejected cargos due to inferior cube quality at the destination. Factors contributing to mold development in alfalfa cubes shipped overseas include: • excessive moisture content at harvest • exposure to precipitation prior to placement in overseas transport containers • adverse environmental conditions during overseas transport • exposure to precipitation while stored on shipping docks prior to delivery