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Forage Quality
Jim Morrison
Extension Educator
Crop Systems
Forage quality can be defined as the extent to which a forage has the potential to produce a desired animal
response or level of performance (for example, daily gain or milk production).
Forage quality is a function of voluntary intake and nutritive value. The forage quality need of an animal
depends upon its age, sex, and production status. It is a simple concept, but yet encompasses much
complexity.
Let’s take a quick look at the major factors that influence forage quality.
Species differences. Legumes generally produce higher quality forage than grasses. This is the result of
less fiber in legumes and thus intake will be higher when legumes are consumed. Cool-season grass
species (orchardgrass, bromegrass, perennial ryegrass, etc.) are generally higher in quality than warmseason grasses (bermudagrass, switchgrass, corn, etc.). Digestibility and crude protein are typically
higher in cool-season grasses than in warm-season grasses. Warm-season grasses convert sunlight into
forage more efficiently than cool-season grasses, but their leaves contain a higher proportion of highly
lignified, less digestible tissues.
Maturity stage. Maturity stage at harvest is the most important factor determining forage quality of a
given species. Forage quality declines with advancing maturity. Reduced leaf-to-stem ratio is a major
cause of the decline in quality with maturity. Leaves are higher in quality than stems, and the proportion
of leaves in forage declines as the plant matures. Maturity at harvest also influences forage consumption
by livestock. As plants mature and become more fibrous, forage intake drops dramatically. The intake
potential decreases and neutral detergent fiber (NDF) concentration increases as plants mature. This is
because NDF is more difficult to digest than the non-fiber components, thus digestion slows greatly as
forage becomes more mature.
Harvesting and storage effects. Leaf shatter, plant respiration, and leaching by rainfall during field drying
of hay can significantly reduce forage quality, especially with legumes. Rainfall during curing damages
legume leaves the most. Damage from rain increases as forage becomes dryer, and is especially severe
when rain occurs after the hay is ready to bale. Quality losses also occur due to weathering, plant
respiration, and microbial activity during storage. In high rainfall areas, losses can be large for round
bales stored outside, due to the weathering of the outer layers.
University of Illinois/U.S. Department of Agriculture/Local Extension Councils Cooperating
University of Illinois Extension provides equal opportunities in programs and employment.
Secondary factors that affect forage quality include soil fertility and fertilization, temperatures during
forage growth, and variety.
The ultimate measure of forage quality is animal performance. This winter, plan your strategies for
producing the forage quality needed in your operation. Additional information is found in the publication
entitled “Understanding Forage Quality”, available at Extension offices.
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Jim Morrison, (815) 397-7714, [email protected]
Date: 1/09/2005
University of Illinois/U.S. Department of Agriculture/Local Extension Councils Cooperating
University of Illinois Extension provides equal opportunities in programs and employment.