The primary criterion when judging hay for horses is not its energy value but its condition. Hay for horses should be free of dust, mold, and weeds. Factors Affecting Quality Numerous factors, both controllable management factors and uncontrollable environmental factors, influence hay quality. Unfortunately, quality and yield are usually inversely related. Harvest management and variety selection Stage of maturity at the time of cutting is the most important controllable factor.
Quality declines with advancing maturity.
However, yields increase with advancing maturity, so harvest management is a compromise between maximum yields and maximum quality. Hay variety selection influences forage quality, as do hay-making practices. Raking or baling when the hay is too dry results in excessive leaf shatter and reduced quality. Heating and mold growth occurs in hay that is baled too wet. Although quality differences among hay varieties are not great compared with differences in other characteristics, most hay seed companies are making a major effort to improve forage quality through breeding.