One of the keys to a successful livestock operation
is the proper use of pasture, either native rangeland
or tame forages. To properly manage the land, a
producer must be familiar with the amount of dry
matter forage the pasture can produce and the amount
of forage required over the grazing season by each
animal and the herd as a whole.
With this knowledge, the proper combination of
land, time and number of animals may be chosen
to ensure the sustained, long-term productivity
of the pasture. The optimum number of animals on
the pasture makes efficient use of the forage without
waste, but still leaves enough forage to allow
quick and complete recovery.
There has often been confusion among producers
when discussing carrying capacity and stocking
rates. In order to benefit from your pasture management
practices an understanding of the terms and the
factors that influence them should be reviewed.
Carrying capacity is considered to be the measurement
for the average number of animals that a particular
pasture or range can sustain over a grazing season.
Carrying capacity is primarily determined by four
factors: 1) annual forage production, 2) seasonal
utilization rate, 3) average daily intake, and
4) length of the grazing season.
Carrying capacity does not fluctuate yearly in
response to forage production. Stocking rates,
however, do fluctuate with weather conditions.
Stocking rates are often expressed as the number
of animal unit months (AUM) supplied by one acre
of land. Keep in mind that stocking rate and average
daily gain (ADG) are negatively related therefore
we need to find the balance and manage accordingly.
Determining the appropriate stocking rate for
a particular grazing unit is a key decision affecting
the profitability and viability of any grazing
operation. Livestock intake and subsequent performance
is very dependent upon forage availability to the
animal on a daily basis. One can not stress enough
the importance of monitoring and management of
the three variables of intake; amount, quality
and composition. These three factors will determine
the profitability of your pastures. Setting the
stocking rate too low will result in wasted forage
and lost profit potential. Setting the stocking
rate too high will result in lowered intake and
animal output and often times, diminished profits.
If a producer has been fairly successful in a traditional
grazing system then an understanding of an appropriate
stocking rate is already available. While in the
long term carrying capacity will be increased with
improved grazing management. However, do not expect
to increase stocking rate substantially in the
first year of a more intensive managed grazing
system (eg. rotational).
There are several factors that can influence the
stocking rate, but I wanted to briefly cover some
of them including grazing management, plant vigor,
livestock distribution, and forage intake.
Continuous, season long grazing can be an inefficient
way to harvest plant growth. Losses due to trampling,
plant maturation and leaf death, wastage, consumption
by insects, diseases, and other herbivores, and
improper season and degree of use are all higher
with continuous grazing than with rotational
grazing. In addition, rotational grazing provides
times when plants are not being grazed in each
area. Thus, plant vigor and growth remain the
same or increase compared to continuous grazing,
even when a greater proportion of the forage
is consumed by livestock.
A simple rotation involves
two or more separate pastures that are grazed
only once during the growing season. Such systems
can provide 20 percent higher grazing capacity
than a continuous grazing system. More intensive
short duration or time-controlled grazing systems
that involve numerous areas that are grazed
several times each season may allow up to 30-50
percent higher stocking rates than a continuous
grazing system. However, these are usually not
recommended on native pastures or rangeland.
These rotational grazing systems improve livestock
distribution, reduce waste, allow longer periods
of no grazing, and maintain plants in a more
nutritious vegetative growth stage for longer
periods of time. However, as grazing intensity
increases, so does the risk of weakening the
forage stand. High stocking rates require higher
levels of management skill and frequent monitoring
to maintain plant vigor. One should keep in mind
the availability and flexibility to use alternative
feedstuffs to adjust stocking rates whenever
forage availability and forage demand are not
Suggested initial stocking rate assumes “normal” weather,
good plant vigor, uniform grazing patterns, and
level consumption. These assumptions are often
incorrect so stocking rate must be changed to
fit each situation. Weather variation most frequently
dictates stocking rate adjustments. Drought,
floods, late spring or early fall frost, hail,
or very cool or very hot temperatures may lower
forage production or deay growth. Raid forage
growth and high yields are often encouraged by
abundant soil moisture tiely rains, warm springs,
and moderate summer temperatures.
Prior over grazing or adverse weather conditions
may reduce desirable plant vigor. Indicators of
good plant vigor are abundant new tillers or rhizomes,
rapid re-growth, and an appropriate amount of plant
material remaining unused at the end of the season.
When vigor is low, reduced stocking rate can encourage
renewal of plant health.
Uniform grazing should be encouraged throughout
the grazing area. When this is not possible, stocking
rates should be reduced proportionately to the
areas avoided or inaccessible to the livestock.
Forage intake changes very little for a group
of livestock during a grazing season (except when
large weight changes occur) so stocking rate adjustments
are not needed. However, environmental stress,
forage quality, and previous nutrition of the animal
may influence level of forage consumption by livestock.
Insects, rodents, game animals, and other herbivores
also consume forage and may alter the amount available
to livestock at certain times of the season.
Overstocking and overgrazing leads to a reduction
in palatable plant species and an increase in less
desirable plants. Overuse also means that livestock
must forage for longer periods of time to meet
Increasing grazing time by two hours per day will
lead to significant reductions in cattle gain.
Therefore plan and monitor your pasture routinely.