DS-lancaster Farming. Saturday, October 30, 1993
FORAGE QUALITY IN
PERSPECTIVE: FACTORS
INFLUENCING QUALITY
Dr. Marvin Hall
Penn State University
Fluctuations in milk prices,
feed costs, and government prog
rams are forcing dairy farmers to
become more efficient with their
farm operation.
Since feed accounts for approx
imately one-half of the total cost
of producing milk, and high qual
ity forage optimizes the productiv
ity of the animals, increasing the
quality of forage available is one
of the best methods of improving
overall feeding efficiency.
To effectively produce high
quality forage, it is necessary to
understand what forage quality is
and to keep the factors influencing
forage quality in perspective.
Forage quality is defined as the
sum total of the plant constituents
that influence an animal’s use of
the feed. Along with its quality,
the overall potential feeding value
of a forage feed is influenced by
the form in which it is fed (e.g.,
particle size), the palatability of
the forage, and by the quality of
other feeds in the ration (associa
tive feed effects).
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Six major factors affecting for
age quality (not yield), ranked by
their impact on forage quality,
include maturity, crop species,
harvest and storage, environment,
soil fertility, and variety. The rela
tive importance of each of these
factors, along with some excep
tions 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 for
age quality as they mature (Figure
1). As plant cell wall content
increases, indigestible lignin accu
mulates. 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. Impro
per harvest techniques can seri-
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ously reduce forage quality, pri
marily through the loss of leaves.
Storing a hay crop at an incorrect
moisture content, or improper
ensiling of a forage crop, can dra
matically lower its quality. Esti
mated averaged economic losses
during harvest and storage are
shown in Figure 2.
• Environment (climate).
Moisture, temperature, and the
amount of sunlight influence for
age quality. Rain damage is very
destructive to forage quality.
When bad weather delays harvest
ing, 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 delay
ing maturity.
• Soil fertility. Soil fertility
affects forage yield much more
than it docs 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 unproduc
tive soil resource. Proper soil pho
Table 1. Relationship between net energy of lactation (NEI) and relative maturity (mean
stage by count, MSC) for several alfalfa varieties.
Variety**
Vernal
Multileaf-A
Multileaf-B
High quality-A
High yield-A
High yield-B
• The higher the maturity stage number, the more mature the alfalfa. A stage reading of 3.0 is at an carl
flower stage.
•* Multilcaf-A and -B were selected for the multilcaf trait. High quality-A was selected for high quality.
High yicld-A and -B produced two of the highest yields of 44 varieties tested in the trial.
sphorus (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.
iER’S
WE,
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V'-.'ftS.v ‘"“ ■ , '•‘J-'wS’
y.H.rii'j:’.'. -v cv*'-',' -”■ -'i
ffesaSji-Jr:* V . ,
Figure 1. Maturation of plant cell walls.
NEi Maturity’*
Meal! lb stage
0.71
0.75
0.75
0.77
0.70
0.70
t LEBANON N
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322 W
Timber
• Variety (cultivar). After
decades of breeding foraged for
yield and 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
(Turn to Pago D 7)
Young Plant Cell
Proteins