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MADE POSSIBLE BY
BAYER
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The influence of cover crops on the
flow of
FODDER, STOCK
and
CASH
C
OVER CROPS AND GRAZING THEM ARE BECOM-
ING INCREASINGLY POPULAR. INITIALLY THE
COVER CROPS WERE ONLY PLANTED, BUT THESE
DAYS THEY ARE ALSO USED AS A SOURCE OF
FODDER FOR THE STOCK. ALTHOUGH THIS SYS-
TEM ALWAYS APPEARS NICE, IT ALSO HAS PITFALLS AND
PROBLEMS.
The aim of the system is mainly to improve soil
health, retain cover on the soil and increase bio-
diversity. It is important to realise that this is a
production system with which producers have to
become comfortable. Profits have to be ploughed
back in order to expand the system, but there
should also be a shift in assets.
Producers have to understand how the system
works, what the most important aspects are, and
how these aspects can complement or penalise one
another. The cover crops produce a certain amount
of material that can be utilised by the stock, and it
is the task of the producer to ensure that there is
enough fodder for the stock for every stage of the
year. The first two ‘flows’ that should therefore
receive a lot of attention from a producer are feed
flow and stock flow.
THE IMPORTANCE OF FEED FLOW
Every fodder crop that is planted has its own pro-
duction curve. Some crops start quickly, grow fast
and decline rapidly. Other crops start out slowly,
but continue growing for longer, with a peak in pro-
duction that realises only considerably later. Given the crops that are
planted together, a certain quantity of fodder will be produced.
It is important for the producer to know how much fodder will
be available when. If possible, you should also determine how the
crop will perform when the fodder is grazed. Decide whether there
will be enough regrowth to leave the required cover and whether
the stock should be managed to leave sufficient material to ensure a
good cover. It is important that there should be sufficient cover after
the grazing and that enough living roots remain behind in the soil.
The nutritional value of the fodder will determine how the animals
grow. It is important to know what the energy values of the different
sources of roughage are. These values of the different crops are ex-
pressed in metabolisable energy (ME) and as MJ/kg. The total digest-
ible nutrients (TDN) of fodder is also important information – it is a
further indication of the energy value of the fodder.
Energy absorption (in terms of TDN or ME intake) sets the pace
for production. The higher the animal’s energy intake, the higher the
production is – provided the other essential nutrients are consumed
in the correct proportion and quantity. If the animal has a high energy
intake but the protein intake is too low, the animal’s system will start
breaking down the muscles to supplement the protein deficiency. For
optimal utilisation of the nutrients consumed the energy and protein
intake should therefore always be in a specific ratio. For each produc-
tion function or stage the animal requires a certain amount of energy
to ensure optimum performance. The producer must ensure that the
ratios between the elements are always right.
To ruminants, dry material is the basis in terms of which their
fodder consumption is expressed, whether it comes from veld or
from cultivated pastures. All fodder must be converted to dry mate-
rial to be able to compare them. The rule of thumb is usually that
every animal will consume approximately 3% of his body mass as
dry material. A weaner weighing 200 kg and growing 500 g per day
will therefore require approximately 6 kg of dry material, together
with 518 g protein and 3,4 kg energy. There are various tables that
indicate animals’ nutrient requirements. The
Nutrient requirements
of domestic animals
of the National Research Council (NRC) is a very
good source that is used widely in the industry.
The production of fodder must also be converted to dry material. The
fodder could sometimes be ensiled. If maize is used as example, it would
be easy to produce 31 tons of material per hectare. A large part of this
(approximately 65%) is moisture, however. This means that only 11 tons
of dry material are produced per hectare. The yield of feed sorghum, a
crop that is often planted, can vary between 4 tons and 20 tons of dry
material per hectare, depending on the rainfall.
It is important to establish the production of every crop that is
planted. It must then be converted to dry material in order to establish
how many animals can be maintained. If the crop that was planted is
Pietman Botha, Pula Imvula
contributor. Send an email to
pietmanbotha@gmail.com