Swine Production System Management: Open Dirt or Pasture Lots
Prepared by:
James C. Barker, Professor and Extension Specialist
Biological and
Agricultural Engineering
North Carolina State University, Raleigh, NC
Published by: North Carolina Cooperative Extension
Service
Publication Number: EBAE 179-93
Last Electronic Revision: March 1996 (JWM)
Solid concrete floors and slotted floor swine feeding units have noticeably
increased due to greater inherent production efficiencies and higher net farm
incomes resulting from cycles of higher market hog prices. However, open
dirt lots or pastures are still used to finish approximately 20-30% of the
market hogs and maintain about 30-40% of the breeding stock. The producer
who feeds out hogs on dirt is substituting labor and land for capital
investment. Where labor is plentiful relative to capital, a producer may be
able to feed out two or three times as many hogs in an open lot system as he
could afford in confined housing. Open dirt or pasture production units have
the lowest density of hogs but are considered confinement operations since
animals are fed within fenced areas.
Pasture Stocking Density
Animal densities are sometimes low enough to
maintain pasture areas where wastes are utilized naturally by the soil-vegetation receiver. The Midwest Plan Service recommends 10 gestating sows
per acre or 7 sows and litters per acre and 50-100 growing-finishing hogs per
acre depending on rainfall and soil fertility. Dobson, NCSU Crop Science
Dept., recommends no more than 30 market hogs per acre on permanent pasture
such as bermuda grass or fescue and ladino clover. Beyond this density, bare
areas will begin to appear. For pasture to survive, animals must be removed
during the dormant or non-growing season or lots rested by a rotation scheme.
Pastured situations do not represent feedlot conditions and should not be
subject to effluent limitations. However, the proportion of animals finished
on pasture is insignificant compared to those finished on dirt lots.
Dirt Lot Stocking Density
Lots with 100 or more hogs per acre will not
support vegetative cover. The most widely practiced stocking density ranges
from 50 to 200 animals per acre, but densities up to 500 per acre are
employed in some cases. It is estimated that less than 10% of hogs produced
on open dirt are in lots stocked below 50 animals per acre and less than 15%
in lots stocked above 200 per acre. Actual lot location as well as stocking
densities are determined by such factors as annual rainfall, temperature,
shade cover, soil type, vegetation, topography, drainage and proximity to
surface waters.
Drylot Management
Soil types generally determine how heavily a lot can
be stocked and how much runoff will occur. Higher stocking densities can be
maintained on sandy soils which are well-drained and have high infiltration
capacities. Manure buildup and compaction are minimal since the animal
activity tends to keep the waste well mixed with the sandy surface. Drylots
are rotated after two groups of animals or one year's production to control
disease and parasites and to allow rejuvenation of the soil surface. These
lots are then seeded to grasses or allowed to remain fallow for at least two
years before being put back into production.
Lower stocking densities are usually necessary on heavier clay soils or
highly organic soils. In low-rainfall areas, surface compaction occurs
resulting in a manure pack characteristic of high density beef feedlots.
Infiltration is drastically decreased, causing more rainfall runoff. When
these lots are taken out of rotation, any manure build-up will usually be
disked into the soil or scraped up and spread on crop land. In addition
the lot may be deep plowed with subsoilers to break up the surface compacted
layer and increase infiltration. In high-rainfall areas, animal activity in
dirt lots tend to cause the heavy soils to become very muddy. This
condition decreases the animal feed utilization efficiency and increases the
potential for odor generation, mosquito production and diseases. Animal
mortality rates are higher compared to confined housing. When these lots are
taken out of rotation, the soil surfaces may be chemically treated for
disease and parasite control.
Feeder Location
Hogs raised on dirt lots are usually fed by self-feeding
feeder troughs. These feeders are located just inside the fenceline at the
highest elevation within the lot to obtain maximum drainage away from the
feeders. An approximate 10-foot concrete or wooden pad usually surrounds the
feeders to prevent the area from becoming a hog wallow; however, since hogs
tend to congregate here, muddy and compacted soil conditions usually prevail.
It is in this vicinity that most of the defecated waste is deposited.
Shade Cover
Lots are developed when possible to take advantage of
existing wooded areas for shade cover. Trees are rapidly killed, however, in
densely populated swine lots due to soil compaction and stripping of the bark
by the hogs. Animals which have access to wetlands should be moved to higher
ground. These practices necessitate the need for development of new lots and
the construction of sun shades in existing lots. Shades should be built at
least 8 feet high with their long axis oriented east-west. Pole-supported
shade covers can be constructed with fence and straw roofs, nylon mesh shade
cloth, or metal painted brightly on the upper side and black on the
underside. Some producers use a row of fogging or spray nozzles for cooling
the animals during extended periods of high temperatures.
Runoff Buffer
Many swine drylots are located on topography sloping toward a
drainageway or stream but are separated from the stream by a wooded or
vegetated buffer strip. In addition, large swine production units
characteristic of the Coastal Plain usually drain toward a low-lying swampy
area through which an ill-defined stream traverses. These conditions
constitute a living, biological filter and tend to improve the quality of
drylot runoff before it reaches a stream.
Distributed in furtherance of the Acts of Congress of May 8 and June 30,
1914. Employment and program opportunities are offered to all people
regardless of race, color, national origin, sex, age, or disability. North
Carolina State University, North Carolina A&T State University, U.S.
Department of Agriculture, and local governments cooperating.
EBAE 179-93
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