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Animals
Special
Oktober 2016
24
Conservation agriculture:
Ultra-high stock density grazing systems
T
his article highlights the methods of utilising crop species
that play an imperative role in conservation agriculture
(CA)-based crop-pasture rotations. Besides improving the
physical, chemical, hydrological and biological properties
of the soil, such species, including annual or perennial cover crops,
can successfully be used as animal feed.
Livestock production systems are in many ways dependent on the
utilisation of forage species, or pasture ley and cover crops (used
interchangeably in this article), and can therefore become an integral
component of CA-based crop-pasture rotations.
To qualify as a pasture ley crop, a plant species must fulfil the re-
quirements of a dual purpose crop, i.e. it must be functional for
livestock fodder and for soil restoration.
This article focuses on the components and value of multi-camp or
ultra-high stock density grazing (or so-called ‘mob’ grazing) as a pre-
ferred grazing strategy on pasture ley crops in an integrated crop
and pasture-based livestock production system. The term ‘pasture
ley’ can include a variety of annual or perennial species, legumes,
grasses or root forage crops used in short- or long-term rotations.
It is therefore important to distinguish between a short-term and
long-term ley cropping system.
Ultra-high stock density grazing systems
This grazing management practice is generally characterised by
high stock density (i.e. number of animals/unit area) in a small
camp of mature forage and short grazing periods and most impor-
tantly long forage recovery (regrowth) periods.
These grazing systems have a few key benefits and include:
Improved soil quality.
Improved forage quality.
Reduced selective grazing.
Increased pasture productivity.
Reduced weed problems.
Minimised equipment costs.
Increased diversity of plant species.
More uniform manure/urine deposition.
Increased harvest efficiency.
Increased livestock production per unit area.
Reduced hay and feed costs.
So how does it work? One has to approach this grazing strategy
with a large animal herd migration, such as those of the Serengeti
wildebeest, in mind. The system is mimicking how huge herds of
these animals used to move through an area, trampling and grazing
all around them before they departed – literally – for new pastures,
leaving the grasses to grow, mature and produce once more.
These animals freely grazed and never stayed in one area for too
long and then moved once the area is soiled with manure and
urine. These animals often did not return for months or even years,
which allowed the lands to rest and recover. When these pastures
are given time to rest after defoliation, new growth is stimulated
and pasture quality improves.
Grass plants have evolved over millions of years under such grazing
regimes and it is only during the past few hundred years that we
have started using enclosures (camps) and fields, exposing the
grasses to completely different grazing pressures, involving con-
stant grazing and re-grazing of the immature plants. Grasses and
other forage plants are poorly adapted to such treatments and con-
sequently productivity is much reduced.
So when one applies this strategy, the objective of such a system
will be to create smaller camps to be utilised by ultra-high stock
rates for short periods and then allow each camp to rest for longer
periods of time before returning animals to these camps.
Allowing plants to grow to maturity means that bulk grazers can
eat bulky forage material with a good combination of fibre, protein
and energy for the animals, resulting in much healthier animals.
Firm dung produced by the right nutritional forage quality can be
used by the producers as an indicator of good nutrition. Using this
mob grazing system to incorporate animals into an arable system
offer real environmental and financial benefits.
Management approach
To achieve success with such an ultra-high stock density grazing
system, it is advised to determine an optimal stock density
(animal kilograms per hectare). It is important to remember that
the higher the density of animals, the shorter the grazing period
and the more uniform the urine/manure distribution will be. This
method of organic fertilisation has a major advantage compared
to having to fertilise with inorganic fertiliser. The key is to utilise
smaller areas of pasture and ideally have multiple daily moves to get
the most out of your forage.
There are a few important holistic principles of successful ultra-
high stock density grazing management one should keep in mind,
which essentially aim to combine scientific principles and local
knowledge to adaptively manage animals so that the animals can
influence important ecosystem processes.
These principles are:
Efficient conversion of solar energy by plants.
Interception and retention of precipitation in the soil.
Optimal cycling of nutrients and promotion of high ecosystem
biodiversity with more complex mixtures and combinations of
desirable plant species (Teague
et al
., 2013).
There are, however, limitations when using ultra-high stock density
grazing practices. Firstly, the intensity of management increases
as the number of camps per herd increases.
WAYNE TRUTER,
University of Pretoria,
LINDEQUE DU TOIT,
Grass SA,
HENDRIK SMITH,
Grain SA,
GERRIE TRYTSMAN,
ARC-Animal Production Institute and
ANDRÉ LUND,
producer