Variety or cultivar can affect forage quality, but not as greatly as the other five factors. In alfalfa, selection for improved quality is underway by most commercial companies, and several U.S. firms have initiated selection in corn silage hybrids for improved forage quality. Other factors affecting forage quality. Several lesser factors also can influence forage quality. Weeds can negatively affect quality, especially in the case of noxious weeds.
Insect pests can lower forage quality, particularly if they cause significant leaf loss.
Plant diseases can affect quality when they result in a shift in the species present in the field and when they promote leaf senescence. Insects and diseases generally have their greatest impact on yield and persistence of forages. Exceptions to the ranking Forage crops that accumulate a significant quantity of grain may increase slightly in overall quality with maturity as grain content increases in the plant. Some species contain antiquality factors that can lower animal performance. Variety can become the most important forage quality factor in cases where varieties are developed to significantly reduce or eliminate species antiquality factors, as in low-alkaloid varieties of reed canarygrass.