Among the cereal grains, winter rye has one of the fastest growth rates, quickly moving from the vegetative stage to stem elongation and head emergence in the blink of an eye. That impressive growth rate makes winter rye difficult to manage if the goal is to harvest for high-quality forage, said James Rogers, North Dakota State University-Extension forage-crops production specialist.According to Rogers, there are three major factors that affect plant forage quality.plant speciesplant part -- leaves vs. stemsplant maturityWithin a single plant species, plant maturity is the most important factor influencing forage nutrient content. All forage plants will go from a leafy vegetative stage that is high in protein and low in fiber to a reproductive stage that is low in protein and high in fiber. As the plant moves from vegetative high-quality to reproductive low-quality, plant yield increases. The rate at which plants progress from the vegetative stage to reproductive stage depends on species, with some plants, such as legumes, declining in quality at a much slower rate than a grass.