Pasture Grazing Management During Dry Summers
WARREN J. PARKER AND
LAWRENCE D. MULLER
Penn Slate University
UNIVERSITY PARK (Centre
Co.) A slump in pasture growth
during the summer is normal in
Pennsylvania. The dry weather
during May and June in Central
Pennsylvania and other parts of
the state have caused the
decreased pasture growth earlier
than normal this year. Although
early spring pasture growth and
first cutting forage yields and
quality were excellent, the dry
weather and low levels of soil
moisture have made the manage
ment of a pasture system more
challenging than ever. In fact,
many dairymen may be question
ing their decision to implement a
grazing system this year compared
to the less risky practice of provid
ing feedstuffs under a dry lot sys
tem. Even in a good pasture grow
ing season, maintaining a supply
of high quality pastures by grazing
can be more challenging and
requires more management than
“traditional’’ stored feeding
systems.
Dairymen who have adopted or
are thinking about implementing
intensive grazing must remember
that a pasture system is an impor
tant part of the total (12 month)
forage program. During excellent
growing seasons such as 1990,
proper management of pastures
including harvesting of pasture
surplus to the cows requirements
in the spring can provide forage
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for a major portion of the year
when pastures are not productive.
Most dairymen using grazing
should already have the 1991
spring surplus in storage but the
decisions that now need to be
made are more difficult than those
faced in 1990, because of the dry
conditions. Learning how to man
age grazing of pastures during dry
periods as well as in good years is
important.
Cows have been grazing for
about 7-8 weeks until mid June,
but the dry weather has necessi
tated the need to reduce grazing
and begin more supplementation.
While the dry conditions impact
on the feed supplies for all dairy
men, the shortage of pasture has a
more immediate and obvious
impact where grazing systems
have been adopted. Following are
some points that may help
improve grazing during dry
conditions.
1, Regularly measure the
amount of pasture available. Use a
visual assessment or a measuring
aid such as a capacitance meter or
sward stick. This information,
together with the tonnages of
stored forage, provides a feed
inventory for the farm. Knowing
the amount of pasture available in
each paddock enables the number
of grazing days to be calculated
and can indicate the need to adjust
the supplementary feeding prog
ram. The decreased rate of pasture
production during the past couple
of weeks should be compensated
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for by increased feeding of stored
forage in the ration. The nutrient
composition of the grain rations
may need to be adjusted for any
change in the type and quality of
the forage fed.
2. Make adjustments to grazing
management. Avoid over-grazing,
but utilize the pasture that is avail
able while the quality is still rea
sonable. To avoid over-grazing,
reduce the grazing period and (or)
increase the level of supplemen
tary feeding. With the anticipation
of low forage supplies during the
dry year, it is tempting to let ani
mals graze. However, cool season
pastures will be more productive
later in the year if overgrazing is
avoided. Temporarily stopping
grazing due to dry conditions
should not be viewed as a failure.
Our experience on items (1) and
(2) with the Penn State Dairy Pas
ture Systems Research project
may be helpful. At the time we
started grazing in the spring, we
did some forward planning based
on the expected intake of Holstein
cows and the land area available.
Nearly 60% of our land area was
not grazed in the spring but was
“set aside” for harvesting in late
May. This stored silage is normal
ly the “bank account” reserve for
summer (if needed) or winter
feeding. We harvested nearly 2
tons of high quality grass silage
dry matter per acre in early May.
When the dry weather continued
into early June, our measures indi
cated inadequate pasture availa
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bility for the forage dry mattei
needs of our cows. With no rain
the land area from which we
harvested silage had little
regrowlh and was not ready to be
introduced into the grazing rota
tion. Initially, the cows remained
in the bam during the hot days and
were fed stored grass silage from
our “bank account”. The amount
fed was based on the difference
between the amount of forage dry
matter required in relation to the
measured amount of pasture dry
matter available. For example, the
cows required approximately 30
lb. forage dry matter DM per day.
The pastures could only provide
15 to 18 lb. (DM) each day ((pre
graze pasture per acre post
graze pasture per acre) - number
of cows). The 12 to 15 lb. (DM)
difference was made up with sil
age fed in the bam. After the most
recent grazing cycle, the lack of
rain and low levels of available
pasture have necessitated keeping
the cows in the bam and feeding
all the forage from the stored
“bank account”. The amount of
grain fed has not been altered. The
quality of grass silage harvested in
mid-May is high and of compar
able quality to that of the early
spring pastures. Thus, the nutrient
composition of the grain has not
been altered.
3. Make important decisions to
maintain productivity and profit.
The tendency in a dry year is to
put off decisions with the hope
that it will rain. Collect all the
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Lancaster Farming, Saturday, June 22, 1991-A37
relevant information on your feed
position (inventory of supply and
needs), list alternative courses of
action, and make a decision. Some
alternatives and potential deci
sions during this time include:
• Cull low producing, non
profitable cows. The lack of for
age supply, low milk prices, and
high cull cow prices make this a
high priority decision to improve
profit.
• Allocate the highest quality
pasture and forage to the early lac
tation cows.
• With the marginal available
pastures and high temperatures,
adopt night time grazing if ade
quate pasture is available and keep
cows in the bam during the day.
• Make sure an adequate supply
of cool water is available.
• Consider a summer brassica
crop to provide late summer and
autumn forage. This will only be
worthwhile if there is sufficient
rainfall in July and to establish the
crop.
• Consider purchasing some
forage now in case the dry year
persists.
When the dry period is broken
initially adopt a slow rotation and
maintain a high level of forage
supplementation to allow feed
reserves to rebuild. An application
of nitrogen should be considered
as soon as the dry period breaks
because the increased amount of
dead plant material may cause a
short term deficit of nitrogen.