SS-AGR-93
Factors Affecting Forage Quality1
M.O. Wallau, A. T. Adesogan, L. E. Sollenberger, J. M. B. Vendramini, and J. C. B. Dubeux, Jr.2
What Is Forage Quality? the animal and offered without quantity restrictions (ad
libitum). It is also dependent on animal species and class,
Forage quality, the degree to which a forage meets animal
in the sense that the same forage can have higher value for
nutritional needs, is expressed in terms of animal produc-
one type of herbivore than to another. Animal performance,
tion, such as growth, milk, or wool production. Forage
whether growth or milk production, depends upon the
quality is affected by forage nutritive value(i.e., chemical
animal’s potential for production, as well as on how much
composition and digestibility) and intake, and it can be
dry matter (DM) the animal eats and the nutritive value of
estimated when forage is the sole source of nutrients to
the DM the animal consumes. Therefore, the two forage-
related factors that determine animal performance are (1)
forage intake and (2) forage nutritive value. Collectively,
these factors determine the quality of the forage.
Factors Affecting Forage Intake
Forage intake is affected by a range of pasture, animal,
environmental and management factors. Herbage allow-
ance (amount of forage available per animal) and canopy
structure, composition and arrangement are primary plant
determinants of intake. Nutritive value, especially crude
protein and digestibility are associated with the passage
rate of the forage through the gastrointestinal tract. Forages
of low digestibility and protein have slower passage rate,
physically limiting intake (gut fill). Intake is also affected by
Figure 1. Over-mature bermudagrass hay field. Both an increase in animal body size, performance level, health, genotype, and
fiber and senescent material decrease the forage quality. social hierarchy. Environmental aspects that affect intake
Credits: Marcelo Wallau
1. This document is SS-AGR-93, one of a series of the Agronomy Department, UF/IFAS Extension. Original publication date April 2002. Revised July 2015
and June 2018. Original authors were A. T. Adesogan, professor, Department of Animal Sciences; L. E. Sollenberger, distinguished professor, Agronomy
Department; and J. E. Moore, professor emeritus, Department of Animal Sciences. This publication is a part of the Florida Forage Handbook, an
electronic publication of the Agronomy Department. Visit the EDIS website at http://edis.ifas.ufl.edu.
2. M.O. Wallau, assistant professor, Agronomy Department, Gainesville, Fl 32611; T. Adesogan, professor, Department of Animal Sciences; L. E.
Sollenberger, distinguished professor, Agronomy Department; J. M. B. Vendramini, associate professor, Agronomy Department, UF/IFAS Range Cattle
Research and Education Center, Ona, FL; J. C. B. Dubeux, Jr., associate professor, Agronomy Department, UF/IFAS North Florida Research and Education
Center, Marianna, FL; UF/IFAS Extension, Gainesville, FL 32611.
The use of trade names in this publication is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the
products named, and references to them in this publication do not signify our approval to the exclusion of other products of suitable composition.
The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services
only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status,
national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county’s UF/IFAS Extension office.
U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County
Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.
, include temperature, humidity, and rainfall. Animals out of within and among grass genera, and between varieties of
their comfort zone tend to reduce time grazing. Manage- the same species.
ment factors — such as stocking rate, type, and level of
supplementation, feeding frequency, and availability of 2. Maturity
water and feed — also affect forage intake. Additionally, for The stage of forage regrowth at the time of utilization—
stored forage intake is affected by the type of conservation whether as hay, haylage, or grazed forage—has a major
process (i.e., hay or silage), particle size and nutritive value influence on forage nutritive value. Forage-regrowth stage is
(e.g., fiber, protein, digestibility) and mold contamination, determined by the number of days between harvests for hay
poor fermentation, or any substances that make the forage or haylage and by the rest period in rotational grazing.
less acceptable.
There is always a compromise between forage quantity
“Voluntary forage intake” is used to describe how much for- and nutritive value. Forage nutritive value begins to decline
age DM an animal will consume when adequate amounts during the regrowth period due to the accumulation of
of forage are available, when no supplements of protein and stems and deposition of poorly digested lignin in both
energy are fed to the animal, and when adequate minerals leaves and stems.
are available —either in the forage or as supplements.
Energy and protein supplements may either increase or Maturity of legumes and cool-season grasses can be as-
decrease livestock forage intake, depending upon the sessed by determining the physiological stage of growth.
composition of the forage and the composition and amount For warm-season grasses, however, weeks of regrowth are
of supplement being fed to the livestock. a better indicator of maturity because flowering may begin
shortly after regrowth begins. Table 1 shows a decline in
Factors Affecting Forage Nutritive the digestibility and crude protein of Coastal bermudagrass
after week five (day 35) of regrowth. The information in
Value this table indicates that harvesting Coastal bermudagrass
Forage nutritive value is primarily determined by concen- at intervals greater than five weeks will reduce the nutritive
trations of crude protein (CP) and “available” energy in the value of this forage. Table 2 provides examples of the effects
forage. For many years, total digestible nutrients (TDN) of forage genotype and maturity on the nutritive value of
has been used as an overall measure of available energy in typical forage grasses in Florida. Each value represents
forages. In the past 20 years, however, measurements of several cuttings made from different varieties in different
digestible energy, metabolizable energy, and net energy of years. These values are a general reference point. These data
forage have increasingly been used, especially for more fine- suggest that digitgrass and limpograss tend to have higher
tuned diets. However, TDN is still an acceptable and easily nutritive value than bahiagrass, bermudagrass, and star-
understood measure of nutritive value, particularly for beef grass, especially at later stages of maturity. These differences
cattle. Forage nutritive value is affected most by variations often affect voluntary intake as well.
in forage genotype, maturity, season, and management, and
presence of “anti-quality” factors. With respect to maturity effects on perennial grasses, the
most dramatic difference is the decrease in voluntary intake
1. Genotype between six and eight weeks. These data and others show
Legumes generally have a higher nutritive value than that after eight weeks of regrowth, forage nutritive value
grasses because of higher CP and TDN concentrations at will generally be less than needed for livestock mainte-
a given age of regrowth. This results in greater intake by nance. Exceptions are digitgrass and limpograss, which
livestock, particularly when compared with warm-season maintain a somewhat higher TDN when mature than do
(C4) grasses. The TDN concentrations of legumes and the other grasses. Consequently, limpograss and digitgrass
cool-season grasses are similar because legumes typically are excellent forages for fall stockpiling. However, those
have higher lignin and cool-season grasses are generally are often are low in CP when mature, and require protein
low in fiber and high non-structural carbohydrates. Gener- supplementation for optimum utilization.
alizations about the nutritive value of grasses are risky, but
temperate or cool-season grasses, such as rye and ryegrass, 3. Season
are nearly always higher in nutritive value than tropical or Seasonal effects on forage nutritive value have been noted
warm-season grasses such as bermudagrass and bahiagrass. in grazing trials in Florida where forage regrowth intervals
However, there is much variation in forage nutritive value were kept constant. Gains of grazing cattle have been less
Factors Affecting Forage Quality 2
Factors Affecting Forage Quality1
M.O. Wallau, A. T. Adesogan, L. E. Sollenberger, J. M. B. Vendramini, and J. C. B. Dubeux, Jr.2
What Is Forage Quality? the animal and offered without quantity restrictions (ad
libitum). It is also dependent on animal species and class,
Forage quality, the degree to which a forage meets animal
in the sense that the same forage can have higher value for
nutritional needs, is expressed in terms of animal produc-
one type of herbivore than to another. Animal performance,
tion, such as growth, milk, or wool production. Forage
whether growth or milk production, depends upon the
quality is affected by forage nutritive value(i.e., chemical
animal’s potential for production, as well as on how much
composition and digestibility) and intake, and it can be
dry matter (DM) the animal eats and the nutritive value of
estimated when forage is the sole source of nutrients to
the DM the animal consumes. Therefore, the two forage-
related factors that determine animal performance are (1)
forage intake and (2) forage nutritive value. Collectively,
these factors determine the quality of the forage.
Factors Affecting Forage Intake
Forage intake is affected by a range of pasture, animal,
environmental and management factors. Herbage allow-
ance (amount of forage available per animal) and canopy
structure, composition and arrangement are primary plant
determinants of intake. Nutritive value, especially crude
protein and digestibility are associated with the passage
rate of the forage through the gastrointestinal tract. Forages
of low digestibility and protein have slower passage rate,
physically limiting intake (gut fill). Intake is also affected by
Figure 1. Over-mature bermudagrass hay field. Both an increase in animal body size, performance level, health, genotype, and
fiber and senescent material decrease the forage quality. social hierarchy. Environmental aspects that affect intake
Credits: Marcelo Wallau
1. This document is SS-AGR-93, one of a series of the Agronomy Department, UF/IFAS Extension. Original publication date April 2002. Revised July 2015
and June 2018. Original authors were A. T. Adesogan, professor, Department of Animal Sciences; L. E. Sollenberger, distinguished professor, Agronomy
Department; and J. E. Moore, professor emeritus, Department of Animal Sciences. This publication is a part of the Florida Forage Handbook, an
electronic publication of the Agronomy Department. Visit the EDIS website at http://edis.ifas.ufl.edu.
2. M.O. Wallau, assistant professor, Agronomy Department, Gainesville, Fl 32611; T. Adesogan, professor, Department of Animal Sciences; L. E.
Sollenberger, distinguished professor, Agronomy Department; J. M. B. Vendramini, associate professor, Agronomy Department, UF/IFAS Range Cattle
Research and Education Center, Ona, FL; J. C. B. Dubeux, Jr., associate professor, Agronomy Department, UF/IFAS North Florida Research and Education
Center, Marianna, FL; UF/IFAS Extension, Gainesville, FL 32611.
The use of trade names in this publication is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the
products named, and references to them in this publication do not signify our approval to the exclusion of other products of suitable composition.
The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services
only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status,
national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county’s UF/IFAS Extension office.
U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County
Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.
, include temperature, humidity, and rainfall. Animals out of within and among grass genera, and between varieties of
their comfort zone tend to reduce time grazing. Manage- the same species.
ment factors — such as stocking rate, type, and level of
supplementation, feeding frequency, and availability of 2. Maturity
water and feed — also affect forage intake. Additionally, for The stage of forage regrowth at the time of utilization—
stored forage intake is affected by the type of conservation whether as hay, haylage, or grazed forage—has a major
process (i.e., hay or silage), particle size and nutritive value influence on forage nutritive value. Forage-regrowth stage is
(e.g., fiber, protein, digestibility) and mold contamination, determined by the number of days between harvests for hay
poor fermentation, or any substances that make the forage or haylage and by the rest period in rotational grazing.
less acceptable.
There is always a compromise between forage quantity
“Voluntary forage intake” is used to describe how much for- and nutritive value. Forage nutritive value begins to decline
age DM an animal will consume when adequate amounts during the regrowth period due to the accumulation of
of forage are available, when no supplements of protein and stems and deposition of poorly digested lignin in both
energy are fed to the animal, and when adequate minerals leaves and stems.
are available —either in the forage or as supplements.
Energy and protein supplements may either increase or Maturity of legumes and cool-season grasses can be as-
decrease livestock forage intake, depending upon the sessed by determining the physiological stage of growth.
composition of the forage and the composition and amount For warm-season grasses, however, weeks of regrowth are
of supplement being fed to the livestock. a better indicator of maturity because flowering may begin
shortly after regrowth begins. Table 1 shows a decline in
Factors Affecting Forage Nutritive the digestibility and crude protein of Coastal bermudagrass
after week five (day 35) of regrowth. The information in
Value this table indicates that harvesting Coastal bermudagrass
Forage nutritive value is primarily determined by concen- at intervals greater than five weeks will reduce the nutritive
trations of crude protein (CP) and “available” energy in the value of this forage. Table 2 provides examples of the effects
forage. For many years, total digestible nutrients (TDN) of forage genotype and maturity on the nutritive value of
has been used as an overall measure of available energy in typical forage grasses in Florida. Each value represents
forages. In the past 20 years, however, measurements of several cuttings made from different varieties in different
digestible energy, metabolizable energy, and net energy of years. These values are a general reference point. These data
forage have increasingly been used, especially for more fine- suggest that digitgrass and limpograss tend to have higher
tuned diets. However, TDN is still an acceptable and easily nutritive value than bahiagrass, bermudagrass, and star-
understood measure of nutritive value, particularly for beef grass, especially at later stages of maturity. These differences
cattle. Forage nutritive value is affected most by variations often affect voluntary intake as well.
in forage genotype, maturity, season, and management, and
presence of “anti-quality” factors. With respect to maturity effects on perennial grasses, the
most dramatic difference is the decrease in voluntary intake
1. Genotype between six and eight weeks. These data and others show
Legumes generally have a higher nutritive value than that after eight weeks of regrowth, forage nutritive value
grasses because of higher CP and TDN concentrations at will generally be less than needed for livestock mainte-
a given age of regrowth. This results in greater intake by nance. Exceptions are digitgrass and limpograss, which
livestock, particularly when compared with warm-season maintain a somewhat higher TDN when mature than do
(C4) grasses. The TDN concentrations of legumes and the other grasses. Consequently, limpograss and digitgrass
cool-season grasses are similar because legumes typically are excellent forages for fall stockpiling. However, those
have higher lignin and cool-season grasses are generally are often are low in CP when mature, and require protein
low in fiber and high non-structural carbohydrates. Gener- supplementation for optimum utilization.
alizations about the nutritive value of grasses are risky, but
temperate or cool-season grasses, such as rye and ryegrass, 3. Season
are nearly always higher in nutritive value than tropical or Seasonal effects on forage nutritive value have been noted
warm-season grasses such as bermudagrass and bahiagrass. in grazing trials in Florida where forage regrowth intervals
However, there is much variation in forage nutritive value were kept constant. Gains of grazing cattle have been less
Factors Affecting Forage Quality 2
