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Grazing Alfalfa Successfully
Carefully balance the needs of the stock and the needs of
By Jim Gerrish
Research Center, University of Missouri
Grazing alfalfa requires top-notch management to ensure optimal
stand persistence and animal
performance. As with any high-value crop, greater economic return is
generally achieved with a higher level of management. With the development of
alfalfa cultivars selected specifically for grazing tolerance, some of the
management emphasis on stand persistence is diminished, but persistence must
remain a prime concern.
Management for Stand Persistence
Several factors affect stand
persistence in grazed alfalfa. While some of these factors are similar to
mechanically harvested fields, others are unique to grazing. These management
Management for Animal Performance
- Proper soil site selection. As with alfalfa
hay production, selecting well-drained, naturally fertile fields will produce
the best alfalfa grazing opportunities. Aside from the well-documented disease
problems associated with wetter soils, the potential for stand damage through
animal treading is greatly increased on soggy soils. Physical damage to both
the roots and crowns may occur
when stock graze alfalfa fields on saturated soils.
Soil compaction resulting from grazing when too wet also reduces regrowth
potential and stand longevity.
stock to grass-sodded paddocks when alfalfa paddocks are too wet to graze.
Build flexibility into grazing systems
to allow removal of the animals to grass-sodded paddocks when the alfalfa
paddocks become too wet to graze. On most farms, not every acre is suited to
growing alfalfa. Plan to take advantage of that site limitation to provide
buffer areas for wet-weather grazing. Including a grass with the alfalfa
seeding will produce a more stable soil surface and reduce the risk of trampling
damage. Open stand bunch grasses such as orchardgrass or timothy do not provide
the same degree of sod support as grasses such as tall fescue, reed canarygrass,
or perennial ryegrass, where adapted. On sandy, well-drained soils, the need
for the companion grass is reduced.
- Fertility management. Soil pH,
phosphorus, and potassium levels all affect alfalfa establishment and
persistence. Having proper soil nutrition at time of establishment and early
stand development is equally important for hay production and grazing. Once the
field is in production, fertility management of the two systems becomes very
When hay is harvested from the field, many pounds of soil
nutrients are removed from the field. Typical figures reported include 10 to 15
lb of P2O5 and 40 to 60 lb of K2O equivalent per ton of hay. While a six-ton hay yield might
remove 60 to 90 lb. P2O5/acre
and 240 to 360 lb. K2O/acre, a comparable dry matter
yield in pasture may produce
800 lbs of beef
per acre containing only 15 to 20 lb. P2O5
and 5 to 10 lb K2O. It is very evident that the
removal of mineral nutrients from the field is relatively quite small in a
grazing situation compared to hay removal.
with hay, stock remove very little P & K, but they can transfer large
quantities to shade and water sites.|
The livestock do, however,
have the capability of moving large quantities of nutrients around the field
through uneven manure redistribution. Generally, greater than 90 percent of the
minerals an animal consumes are excreted back to the soil. The redistribution
is not uniform and tends to be concentrated around water, shade, and other
preferred lounging areas. The lower the stock density, the farther the animals
must travel to water, and the more isolated the shade locations, the more uneven
the distribution becomes.
Research at the Forage Systems Research
Center has shown that manure distribution is greatly enhanced when travel
distance to water is limited to 600 to 800 feet and when stock density exceeds
about 10,000 lb. animal-liveweight/acre (Peterson and
Gerrish, 1995; Gerrish et al, 1995). Designing
systems with these parameters in mind will minimize the need for maintenance
fertilizer in alfalfa grazing systems. Soils should be tested about every 3
years to ensure that target soil test levels are being maintained.
- Insect pests. One of the greatest advantages
that grazing alfalfa holds over hay harvest systems is the virtual elimination
of alfalfa weevil as a significant pest. Grazing first growth alfalfa in the
late vegetative and early bud stage
animals to consume nearly all weevil larvae before significant economic damage
first growth can prevent weevil damage.|
Combining grazing of first growth alfalfa with hay harvest of
later crops is a very sound IPM strategy. Damage by potato leafhoppers and
several other lesser insect pests can be greatly reduced with timely grazing.
Short grazing periods and high stock density may be even more beneficial in
leafhopper control than it is for weevil control.
- Season of use. The season of use for grazing
alfalfa can be longer than that for hay harvest, if properly managed. In an
area where September 15 is the last recommended hay harvest date, alfalfa may be
grazed considerably later. The key difference is that whereas hay harvest
removes all the leaf growth and regrowth energy must come from stored
carbohydrates, grazing can be managed to remove only a portion of the leaf area.
If adequate leaf growth is left below the grazing height, stress of fall
harvest is minimal. To accomplish this strategy, a six to
eight inch stubble height should be
maintained. After killing frosts occur, the alfalfa may be grazed to a lower
can graze alfalfa later |
than you can
hay it without damaging the
During dry periods, alfalfa often does not regrow to an
economically harvestable yield level as hay and part of the growing season is
effectively wasted. Grazing can be used to salvage the value of that crop and
can also stimulate new crown regrowth when moisture becomes available. Having
the flexibility of grazing alfalfa fields greatly increases the utility of
- Appropriate grazing management. Grazing
management for alfalfa persistence can take two distinctively different avenues.
The first is based on continuous stocking with a flexible stocking rate and is
more appropriate for grazing tolerant cultivars. With this approach, the
manager's goal is to maintain an appropriate level of leaf growth to maintain
plant vigor. As growth rate varies through the season, it is necessary to vary
stocking rate to maintain desired grazing pressure. This may be achieved by
increasing or decreasing animal number on the pasture or using a buffer fence to
hold out some of the area for mechanical harvest.
approach is to use rotational stocking to regulate extent of defoliation and
length of rest period. Management flexibility is also required in this system
to allow different degrees of defoliation and regrowth depending upon
performance objectives. With optimal growing conditions, alfalfa may be
re-grazed with only 20 to 25 days of rest while environmentally stressful
conditions may require rest period of 40 days or more. Typical mid-season rest
period are in 28 to 35 day range.
While alfalfa is recognized
as a high quality forage, there are situations where alfalfa fails to produce
the expected animal performance. Understanding the morphology and growth habit
of alfalfa is one of the keys to grazing it successfully. Using alfalfa in
combination with other forages can result in better performance than either crop
gives alone. There are several areas of concern regarding animal performance
Paying attention to the details is what makes successful alfalfa grazers
successful. Both plant and animal management need to be given balanced
consideration in designing alfalfa based grazing systems. Many more
opportunities exist for the alfalfa grazier compared to the producer limited to
mechanical harvest systems.
- Bloat potential. Bloat is probably the
greatest single fear that livestock producers have about grazing alfalfa, as
well as other legumes. This particular topic is dealt with extensively in
another chapter of the proceedings of the Second National Alfalfa Grazing
Conference (Aug. '97, Omaha, Neb.), so it is
only briefly here. This is not to diminish the seriousness of the problem, but
only to avoid redundancy. (See also Manage
Grazing to Beat Bloat.)
stock often forces them to eat stems as well |
Successful alfalfa graziers have reported
several strategies for reducing bloat losses. Probably the most common
recommendation is to seed a grass with the alfalfa to provide some other forage
entering the rumen. Unfortunately we know very little about how much grass is
necessary and if one species or variety is more effective than another in bloat
A second common recommendation is to never allow the
animals to stand hungry before turning them to a new paddock. From this
perspective, set stocking alfalfa may be much safer than rotational stocking.
Using multiple moves each day with a high stock density forces the stock to
consume stems and leaves together which minimizes bloat occurrence. Avoiding
moving stock when heavy dew or rainfall is fresh on the alfalfa has also been
recommended. Many graziers do not rotate alfalfa paddocks until midday to avoid
morning dews. On any given farm, on any given day, these strategies may or may
- Seasonal variance in quality. Alfalfa is
of highest quality in the cooler times of the year including both spring and
fall. With increasing summer temperatures, lignin content will increase and
animal performance will decline. Keeping rest periods to the shortest
acceptable length will help limit lignification. Seasonal variances in quality
will be most pronounced in continuously stocked pastures while quality may be
more readily controlled in a rotational system through regulation of the rest
- Day-to-day variance in quality. In
continuously stocked pastures, forage quality is fairly similar from one day to
the next while seasonal variances may be prominent. In rotational systems,
seasonal variance is reduced, but daily variance may be very significant. If
stock are rotated on a daily basis, the
from one day to the next may be very uniform. As the length of the grazing
period increases, the daily variance in nutrient intake also increases.
grazing periods reduce daily quality variations .|
Livestock typically graze alfalfa from the top down. The first bite
may be almost entirely leaf material and be exceptionally high in crude protein
and low in ADF. Using rumen cannulated heifers to collect forage samples, it
is not uncommon to measure protein levels higher than ADF levels. As the
animals remain on a particular paddock for several days, the nutrient intake
declines each day until on the final day the intake may be less than maintenance
requirement (Morrow, et al., 1991).
- Complementary forages. Alfalfa in the
vegetative stage may be very high in degradable protein and low in fiber. Even
though we may consider this to be very high quality forage, it may actually
produce disappointing animal performance. Including grasses with the alfalfa in
the pasture may enhance livestock performance. While pure alfalfa hay may
produce better results than alfalfa-grass hay mixtures, the alfalfa-grass
mixtures often produce better animal performance than pure alfalfa. This basic
difference may be due to grasses in a pasture being grazed at much less mature
stages than the same grass as a hay crop. Grasses with rapid
potential such as orchardgrass, fescue, or ryegrass are better suited for
pasture mixes with alfalfa than are slower regrowth grasses such as timothy or
often perform better grazing alfalfa-grass mixes than on pure stands.|
Companion grasses also benefit the animal through
reduction of bloat potential and reducing potential mud problems. Some
non-traditional forages such as crabgrass and quackgrass which are not popular
as companion grasses in hay systems work well with alfalfa in grazing
situations. Grazing alfalfa greatly increases the flexibility of management and
opens broader horizons for livestock producers.
- Appropriate supplementation. As with
bloat, supplementation is discussed in detail in another chapter of these
proceedings. While much research has focused on supplementation of low quality
pastures, little work has been done on supplementation of high quality pastures.
Due to the high crude protein, low fiber nature of vegetative alfalfa, the most
appropriate supplements are likely to be high energy materials based on
digestible fiber. (See also Better Balancing.)
- Morrow, R.E., V.G. Schulze-Tate, J.R. Gerrish, and
C.A. Roberts. 1991. Implications of daily quality changes in rotationally grazed
pastures. Proc. Amer. Forage and Grassl. Coun. Columbia MO April 1-4, 1991.
- Peterson, P.R. and J.R. Gerrish. 1995. Grazing
management affects manure distribution by beef cattle. Proc. Amer. Forage and
Grassl. Coun. Lexington, KY March 12-14, 1995. pp 170-174.
- Gerrish, J.R., P.R. Peterson, and J.R. Brown. 1995
Grazing management affects soil phosphorus and potassium levels. Proc. Amer.
Forage and Grassl. Coun. Lexington, KY March 12-14, 1995. pp 175-179.
©1997 Committee for Sustainable
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