|What is forage quality?|
by Don Ball
Within the next two or three months, a lack of available forage in pastures will require most Alabama livestock producers to begin providing hay or some other stored feed to their animals. Therefore, forage quality should be a topic worthy of some thought at this time of year. Some concepts associated with forage quality include the following.
Palatability- Will the animals eat the forage? Animals select one forage over another based on smell, feel, and taste. Palatability may therefore be influenced by texture, leafiness, fertilization, dung or urine patches, moisture content, a pest infestation, or compounds that cause a forage to taste sweet, sour, or salty. High-quality forages are generally highly palatable.
Intake- How much will they eat? Animals must consume adequate quantities of forage to perform well. Typically, the higher palatability and forage quality are, the higher intake will be. As compared to good quality forage, poor quality forage hurts animal performance in two ways. It supplies fewer nutrients per pound of material consumed, and it also moves through an animal’s digestive system more slowly, which means the animal cannot eat as much of it in a given period of time.
Digestibility- How much of the forage will be digested? Digestibility (the extent to which forage is absorbed as it passes through an animal’s digestive tract) varies greatly. Immature, leafy plant tissues may be 80 to 90% digested, while less than 50% of mature, stemmy material is digested.
Nutrient content- Once digested, will the forage provide an adequate level of nutrients? Living forage plants usually contain 70 to 90% water. To standardize analyses, forage yield and nutrient content are usually expressed on a dry matter basis. Forage dry matter can be divided into two main categories: (1) cell contents (the non-structural parts of the plant tissue such as protein, sugar, and starch) that supply good levels of nutrients; and (2) structural components of the cell wall (cellulose, hemicellulose, and lignin) that supply few nutrients.
Anti-quality factors- Various compounds may be present in forage that can lower animal performance, cause sickness, or even result in death. Such compounds include tannins, nitrates, alkaloids, cyanoglycosides, estrogens, and mycotoxins. The presence and/or severity of these elements depend on the plant species present (including weeds), time of year, environmental conditions, and animal sensitivity. High-quality forages do not contain harmful levels of anti-quality components.
Animal performance- The ultimate test of forage quality is how the animals perform, especially when forages are fed alone and free choice. Forage quality encompasses “nutritive value” (the potential for supplying nutrients, i.e., digestibility and nutrient content), how much of the forage animals will consume, and any anti-quality factors present. The best concise definition of forage quality is the extent to which forage has the potential to result in a desired animal response.