Forage Quality in Perspective
Forage Quality Testing or the
Forage Quality in Perspective document in Adobe PDF format.
Quality Information via the Forage
Information System (FIS)
Ranking of Major
Factors that Influence Forage Quality
Six major factors
affecting forage quality (not yield), ranked by their impact on forage
quality, include: 1) maturity, 2) crop species, 3) harvest and storage,
4) environment, 5) soil fertility, and 6) variety. The relative importance
of each of these factors, along with some exceptions to the ranking, are
- Maturity (harvest
date). Maturity is the most important factor affecting forage quality.
Forage quality is never static; plants continually change in forage
quality as they mature. As plant cell wall content increases, indigestible
lignin accumulates. In fact, forage plant maturity changes so rapidly
that it is possible to measure significant declines in forage quality
every two or three days.
- Crop species.
Differences in forage quality between grasses and legumes can be very
large. The protein content of legumes is typically much higher than
that of grasses, and legume fiber tends to digest faster than grass
fiber, allowing the ruminant to eat more of the legume.
- Harvest and
storage. Improper harvest techniques can seriously reduce forage
quality, primarily through the loss of leaves. Storing a hay crop at
an incorrect moisture content, or improper ensiling of a forage crop,
can dramatically lower its quality.
(climate). Moisture, temperature, and the amount of sunlight influence
forage quality. Rain damage is very destructive to forage quality. When
bad weather delays harvesting, the forage crop becomes more mature and
hence lower in quality. High temperatures may increase lignin accumulation
and decrease quality, but drought stress may actually benefit quality
by delaying maturity.
- Soil fertility.
Soil fertility affects forage yield much more than it does quality.
While it is possible to produce high quality forage on poor, unproductive
soils, it is generally very difficult to produce high yields of high
quality forage with an unproductive soil resource. Proper soil phosphorus
(P) and potassium (K) levels help to keep desirable legumes in a mixed
seeding and also reduce weed problems. It is necessary to balance soil
fertility to avoid mineral imbalances in ruminants. Low soil fertility,
as well as very high fertility, has resulted in reduced forage quality.
- Variety (cultivar).
After decades of breeding foraged for yield and persistence, attention
has recently been focused on developing or identifying varieties with
improved quality. 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
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.
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. Harvest and
storage of a forage crop at a moisture content leading to spontaneous
combustion would plainly become a most important factor. Or, if prolonged
flooding or drought threatens a forage crop, environment becomes as important
as any of the other factors. Certain soil fertility conditions, such as
a very low pH, could eliminate alfalfa from a mixed seeding, thereby changing
the species composition of the stand and greatly diminishing its quality.