Everglades Station Mimeo Report EES67-10 May 1967
THE PRESENT STATUS OF FORAGE EVALUATION TESTS AND THEIR VALUE FOR CATTLEMEN
D. W. Beardsley-'
Everyone is familiar with soil testing to obtain a fertilizer recommendation
for producing a vegetable crop, a grain crop, or the forage needed for cattle.
In a sense, testing the forage to determine its content of certain nutrients, and
getting a feeding recommendation to utilize those nutrients most efficiently, is
like soil testing for proper soil treatment to obtain maximum production.
Generally, when we are thinking of forage evaluation tests what we have in
mind are some means of estimating the nutritive value by chemical analysis. In
actual practice, the content of certain nutrients is determined and digestion
factors are applied to estimate the digestible protein content and the energy
value. These digestion factors are derived from closely controlled experiments
in which nutrient intake and output are measured. Digestion coefficients such
as these may be found in the literature, e.g., the appendix taples in Morrison's
Feeds and Feeding.
The objectives of the tests now used are to provide a simple means by which
the farmer can determine how good or bad is the forage produced and to provide a
basis for feeding recommendations that will utilize the forage most efficiently.
The scheme shown in figure 1 outlines the relationship of the various factors
involved in the utilization of forages by the animal. Some investigators feel
that of the two factors most closely related to animal performance, intake and
digestibility, the ratio of importance is approximately 70 percent versus 30
percent, respectively. Most everyone agrees that the best single measure or index
of the value of a forage to an animal is its intake on a voluntary, unrestricted
STalk presented at the Sixteenth Annual Beef Cattle Short Course, University
of Florida, Gainesville, Florida, May 4, 1967.
2/ Animal Nutritionist, Everglades Experiment Station, Belle Glade, Florida.
(C.P., C.F., E.E.,
N.F.E., energy, ash)
Digestibility and nature
of digested products
Acceptability Output per animal
Rate of passage
Forage available per -> Rate of intake
animal per unit time
on the animal
Figure 1.--Relationship of plant and animal factors to animal output.
(Mott, 1962. In Forages, The Iowa State University Press, Ames, Iowa, p. 109.)
Two other factors which should be considered are level of the animals being
fed, i.e., maintenance or full feed, and the ratio of concentrates to forages in
the daily ration. In addition there are many factors which influence the pro-
portion of the various plant constituents and consequently the value of the
forages. These include species of plant, stage of growth, nutrient supply, and
certain environmental factors such as temperature, moisture, time and length of
It should be apparent from figure 1 that determining the chemical composition
of a forage provides only a limited amount of information needed to predict animal
performance. This should be kept in mind when considering what forage tests can
or can not do.
The usual laboratory analysis--proximate analysis--for most feeds and forages
includes determination of moisture or dry matter (DM), crude protein (CP), crude
fiber (CF), ether extract (EE), and ash. Nitrogen-free extract (NFE) is calculated
by difference. Individual minerals or vitamins are determined as needed. Most
forage evaluation tests are concerned only with moisture, crude protein, and
crude fiber on hay and these plus pH on silage samples.
The nutritive content of forages can be estimated from factors which depend
on relationships between crude protein and digestible protein and between crude
protein, crude fiber and total digestible nutrients (TDN). Examples of some of
the equations used by the Penn State Forage Testing Service are:
TDN = 74.43 + 0.35 CP 0.73 CF
TDN = 50.41 + 1.04 CP 0.07 CF
TDN = 77.07 0.75 CP 0.07 CF
Digestible protein for all forages
DP = CP x 0.929 3.48
Obviously these equations would not fit.forages grown in Florida because of
differences in kind and growing conditions. The accuracy with which such equations
can predict forage value would depend a great deal on the forage used and the
digestion trials from which the factors were developed.
An example of the information needed on the forage sample and the kind of
analyses recorded is given on the next page. This information sheet is the one
used in Georgia.
To get an idea of the practices and problems involved in other areas, a
survey was conducted to determine the extent of forage testing services available
to the farmer and rancher in the United States. The land grant colleges in all
50 states were sent a questionnaire to provide whatever information they could
about the service. Of 42 replies received, 20 states indicated that some type
of forage testing service supervised.by.the university is available for farmers
and ranchers. Of the 22 states with no forage testing service, two indicated a
service had been started but was terminated and two others stated that some type
of service would soon be offered. In the nine southeastern states only Florida
Sand Mississippi have no organized program.
Six states have had a service in effect for eight or more years, while
three have had the service two years or less. Four states maintain a large
program, processing more than 1,000 samples per year. Six states handle less
than 200 samples per year. '~hen asked if the number of samples analyzed had
increased or decreased the past year, 50% indicated the number had increased,
25% observed a decrease, and 25% did not change. Eight states -indicated forage
quality had definitely improved since beginning the program; six others noted
slight improvement and three found none .
The basic analyses conducted are moisture determination and crude protein.
In addition most states include crude fiber determination. A few run a complete
proximate analysis. The charge ranges from 2 to 10 dollars per sample depending
on the analyses performed and whether commercial or university laboratory. The
usual fee is around five dollars per sample. Four states charge nothing for the
In most states the program is supervised by the Extension Service and the
analysis of the forage sample is used as a basis 'for feeding recommendations.
In more than half of the states these recommendations are sent to the farmer
..along with analytical results. Six states provide feeding recommendations only
on request. Usually the recommendations are made by the Extension Dairy Specialist
or Extension Beef Cattle Specialist depending on whether the sample is from a
dairyman or a rancher.
In 11 states analyses are performed by university laboratories. Seven states
use commercial laboratories, while in the other two states the samples are
analyzed by laboratories of the state Department of Agriculture.
GEORGIA FORAGE TESTING INFORMATION SHEET
COOPERATIVE EXTENSION SERVICE
University of Georgia College of Agriculture
Georgia Department of Agriculture Cooperating
Will be fed to
Analysis Report (Reported on as fed basis)
Moisture J pH of Silage__
Dry Matter (DM)
Estimated Digestible Protein (EDP) _
Crude Protein i
Crude Fiber (CF)
Estimated Total Digestible Nutrients (TDN) Y%
Estimated Net Energy (ENE) Therms NE per 100 lbs.
For DHIA Supervisors
Date Chemical Analysis
Date Quality Analysis
HAY: Crop (s)
% of each
Description of Sample
Stage of growth at cutting caring method
Hay conditioner used_ Odor Color
Cutting Height or age of Coastal Bermuda hay
Fertilization: Lb3. mixed goods per acre Analysis Applied
Actual nitrogen per acre applied days after last cutting.
Estimated yield per acre tons. Rained on
SILAGE: Crop(s) Variety(ies)
% of each Date cut
Stage of growth at cutting Cutting method
Type of harvester used Row spacing_ Seeding rate
Preservative Kind Amount lbs. per ton
Days required to fill silo Packing method
Type of silo Cover Odor Color
Fertilization: Lbs. mixed goods per acre Analysis
Lbs. actual nitrogen per acre
Estimated yield per acre tons.
Analysis Report (Reported on aB fed basis )
By far the greatest use of the service is made by dairymen. In 11 states
more than 90 percent of the samples come from dairymen, In only two states are
more than fifty percent of the samples submitted by ranchers and cattle feeders.
Two major advantages were cited to point out the value of the service:
1. An excellent educational tool; helps farmers decide what management
practices are desirable.
2. Provides basis for feeding recommendations.
As with any program of this type, there are also certain problems involved.
Some of the disadvantages pointed out in the survey by people who are directly
involved in the conduct of the program include:
1. Intake, a very important factor, is not determined by chemical analysis;
there is no way to measure palatability.
2. The chemical analysis of a forage may suggest that the forage is better
quality than it really is.
3. Chemical tests are not completely accurate; it is difficult to maintain
adequate supervision of laboratory procedures, particularly when using
4. The validity of the results is particularly dependent on obtaining a
representative sample, a sometimes difficult task.
5. The time necessary to complete the analysis and provide feeding
recommendations is usually 10 to 14 days or longer.
It appears that where the service is now used the advantages outweigh
the disadvantages. Whether the interest of the farmer and rancher can be .
maintained or increased remains to be seen. One university professor commented
on the program in his state, "This is the best program we have ever started.
We couldn't do without it."
When pushed by the farmer and rancher and promoted by the Extension
Service such programs appear to be very helpful. It is apparent that there
is much more interest from,dairymen than beef cattlemen. This may be simply
a reflection of the ease with which the dairyman can observe the effect of
feeding an excellent forage or a poor one on his pocketbook.
What is the potential of this type service for Florida cattlemen? No
doubt all the advantages and disadvantages noted in other areas would apply
to Florida conditions plus some problems peculiar to Florida. Pasture is all
or a major portion of the feed supply for cattle in Florida. It is difficult
to maintain uniform forage quality since pastures can change considerably
from one week to the next. There may be wide variations in chemical analyses
from one type of forage grown under one set of conditions to another type of
forage grown under a different set of conditions. This is illustrated by data
shown in table 1 from samples analyzed by the Everglades Station laboratory.
If these two samples were submitted for analysis and feeding recommendations,
it would probably be safe to say the rye grass could be utilized most efficiently
by feeding corn or citrus pulp along with it, whereas the pangola grass could
best be sold as mulch and good hay purchased in its place.
Table 1.--Chemical analysis of two forage samples (oven-dry basis).
Component Rye grass Pangola
...-------------............-Percent-- ----- ---
Crude protein 31.6 2.9
Crude fiber 18.6 37.7
Ether extract 5.0 1.2
Ash 14.3 5.7
Nitrogen-free extract 30.5 52.6
There is no question that good cattle and good forage go together. It seems
to me that any program which would help cattlemen produce good forage and utilize
it to best advantage should be considered. Every progressive cattleman can
benefit by some testing service which will provide him a yardstick to measure
whether or not the forage he is producing is excellent or poor. Even with its
obvious drawbacks a forage testing program sponsored by the University or
associated industry, e.g., feed dealers, fertilizer companies, etc. could be of
considerable benefit to cattlemen.
Forage evaluation tests based on chemical analyses can be used to estimate
the nutritive value of forage. Such tests attempt to provide a simple means by
which the farmer can determine the quality of forage produced and a basis for
feeding recommendation for efficient forage utilization. The forage value can
be predicted from crude protein and crude fiber content. It should be kept in
mind, however, that chemical composition is only one of many plant and animal
factors related to animal performance.
A survey of the land grant colleges in the United States revealed that 20
states have some type of forage testing service available for farmers and ranch-
ers. -'In most states the program is supervised by the Extension Service. The
primary advantage of such a service is its value as an excellent educational tool.
In Florida where pasture is all or a major portion of the feed supply for cattle,
poor quality forage is a real problem. Any program which would help the cattle-
man produce and utilize good forage efficiently should be considered.