Download AgriProbe - Department of Agriculture: Western Cape

For the extensive small grain cropping industry in the
Western and Southern Cape to become viable, the
natural vegetation (including all the trees and the
shrubs) had to be removed. The trees occurring naturally
in the Western Cape are all slow growers. This resulted
in foreign trees (like Eucalyptus) being planted to provide
shade in the few places it was desired. However, plantings
were limited, because of the shade the tall Eucalypts
casted on adjacent crops, and also because of a “dead
zone” in the root area of these plants. Trees and other
structures for the provision of shade to extensive livestock
is therefore largely absent in the cropping areas of the
Western and Southern Cape.
Against this background we provide results of a study
on the provision of shade to sheep in the Swartland cropping
area.
The study was conducted at the Langgewens Research
Station of the Western Cape Department of
Agriculture between Malmesbury and Moorreesburg. The
climate at the experimental site is Mediterranean, and
78% of the total long-term annual precipitation of 395 mm
is recorded during winter (normally lasting from April to
September). The Swartland area is characterised by dry,
hot and windy summers. Long term weather data indicate
that average monthly temperatures exceeding 30°C are
common during the period from December to February.
Merino ewes annually lambed in eight paddocks of
approximately 1ha each from 1996 to 1998. Data of 497
ewes and their offspring were recorded. The ewes were
adapted to the paddocks for two weeks prior to the com-
Provide shade
for reproducing
ewes
7
mencement of lambing usually by about 20 February each
year. They remained in the paddocks throughout lambing,
and for an extra 14-21 days prior to lambmarking, usually
towards the end of April. Shade structures were erected
in four of the paddocks, while the other four paddocks
served as controls. Shade structures consisted of corrugated
iron roofs, mounted on the top of six wooden posts.
The roof area of the structures was 3x4 m, and the roofs
were elevated to 1.8 meter above ground level. Water meters
were installed in the water supply line to all paddocks.
This allowed the measurement of water consumption on a
per paddock basis. Concentrate and roughage consumption
were recorded similarly. This allowed the calculation
of water and feed intake on a per ewe basis. Birth weight,
survival to weaning and weaning weight were recorded for
individual lambs.
Average feed intake on a paddock basis was not affected
by shading treatment (1.505kg/ewe/day in control
paddocks vs. 1.504kg/ewe/day in paddocks with shade
structures). The lack of response in feed intake between
the shaded and control groups could possibly be ascribed
to cooler environmental conditions at night when animals
were able to maintain a normal feed intake. Ewes kept in
control paddocks without shade drank 26% more water
during the experimental period than sheep in paddocks
with shade (3.878 vs. 3.076l/ewe/day respectively).
Casual observations of the behaviour of sheep with and
without access to shade indicated that most ewes stayed
in the shade with their lambs from about 10:00 until late afternoon.
They moved out of the shade for varying intervals
AgriPROBE Photo: September Schalk 2007 Cloete