Directory UMM :Data Elmu:jurnal:S:Small Ruminant Research:Vol36.Issue2.May2000:
Small Ruminant Research 36 (2000) 147±158
Grazing behaviour and diet selection by Dorper sheep
T.S. Brand*
Elsenburg Agricultural Research Centre, Private Bag X1, Elsenburg 7607, South Africa
Abstract
The grazing behaviour and diet selection by Dorper sheep, as well as other related aspects (pasture intake, walking habits
and trampling) is reviewed. It was clear that Dorper sheep are less-selective grazers, compared to Merino-type breeds. Dorpers
utilised shrubs and bushes to a greater extent, but grass to a lesser extent in relation to Merino sheep. The Dorper also utilised a
larger number of different plant species than Merinos. Dorpers walked less to select food, or a suitable spot to graze, which
consequently led to a shorter grazing time and less separate grazing periods. Dorpers consumed less herbage per metabolic
size compared to Merino-type sheep. No uniform pattern in the walking distance of Dorpers was observed when compared to
other sheep breeds. The relative trampling factor for Dorper sheep was less than that of evaluated Merino-type sheep. The
review revealed a lack on information on the grazing behaviour and diet selection of Dorper sheep under more intensive
grazing conditions. There is also a total lack of scienti®c information on other behaviour aspects of this unique breed. # 2000
Elsevier Science B.V. All rights reserved.
Keywords: Dorper sheep; Diet selection; Grazing behaviour; Walking habits; Pasture intake
1. Introduction
Large parts of South Africa are described as desert
or semi-desert, and are suitable for sheep farming
only. There was, therefore, a need to create a tough,
non-woolled mutton breed with excellent meat and
milk production characteristics, combined with hardiness, to adapt to the prevailing conditions in the
extensive parts of the country (Bonsma, 1944).
Cross-breeding experiments to achieve this goal were
started in 1930 by the Department of Agriculture and
led to the decision to use the Dorset HornBlack
Headed Persian cross for the new breed in 1942 (Nel,
*
Tel.: 21-8844620; fax: 21-8844226.
E-mail address: [email protected] (T.S. Brand)
1993). The history of this new breed, the Dorper, was
integrated with sheep farming in the barren and semibarren North Western Cape area of South Africa (Nel,
1958). Erasmus (1961) reported that the most important characteristic of the breed was its hardiness and
adaptation to dry and extensive veld conditions.
Although the Dorper was initially selected only for
areas in the country with a rainfall of less than
250 mm/year (Meyer, 1951), its adaptability and
excellent characteristics led to the distribution of
the breed throughout South Africa and the rest of
the world. This review describes the behaviour of this
unique breed with special reference to grazing behaviour and diet selection. Localities throughout South
Africa where grazing experiments with Dorper sheep
were executed are illustrated in Fig. 1. Veld types were
described according to Acocks (1988).
0921-4488/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 9 2 1 - 4 4 8 8 ( 9 9 ) 0 0 1 5 8 - 3
148
T.S. Brand / Small Ruminant Research 36 (2000) 147±158
Fig. 1. Localities throughout South Africa where grazing experiments with Dorper sheep were done.
2. Diet selection
The Dorper is described as a hardy sheep breed,
which can thrive under poor veld conditions. It is also
believed that the breed is a strong and non-selective
grazer (South African Stud Book and Livestock
Improvement Association, 1998). A lot of studies
have been done to verify this point and to compare
the diet selection of Dorpers with other sheep breeds
or other small stock and animal species.
2.1. Physical composition
Aucamp (1979) studied the diet preference of Dorper sheep and Boer goats in die Valley Bushveld near
Stutterheim in the Eastern Cape. The main plant
component of Valley Bushveld is semi-succulent
thorny bushes and grasses. The two animal species
grazed the veld at two stocking rates (6 Dorper ewes
plus 8 lambs on 21 ha and 40 Dorper ewes plus 42
lambs on 20 ha versus 6 Boer goat does plus 6 lambs
on 20 ha and 42 Boer goat does plus 59 lambs on
21 ha). His results (Fig. 2) clearly indicated that
Dorper sheep preferred grass (70.2%), while the goats
preferred shrubs (80.6%). Stocking rate did not alter
these preferences.
Botha (1981) studied the diet selection of different
animal species on Mixed Karoo near Middelburg in
the Eastern Cape. The contribution of the different
components of Mixed Karoo veld to the diets of
different animal species (Dorper sheep, Merino
sheep, Boer goats and Afrikaner cattle) are presented
in Fig. 3. He concluded from this study that Afrikaner
cattle selected more grass (average of 56%) than
the small ruminants (average of 14.8, 22.9 and
11.5% for the Dorpers, Merinos and Boer goats,
T.S. Brand / Small Ruminant Research 36 (2000) 147±158
149
Fig. 2. Diet preferences and selection by Dorper sheep and Boer goats when grazing Valley Bushveld (Adapted from Aucamp, 1979).
respectively). The small ruminants concentrated to a
greater extent than the cattle on seasonal annuals,
when available. It was also clear that small ruminants
utilised more shrubs (average 56.8, 53.4 and 63.4% for
the Dorpers, Merinos and Boer goats, respectively)
than cattle (average of 33.7%). Botha (1981) accentrated the fact that the small ruminants utilised a large
value of shrubs that are regarded as unpalatable for
sheep.
It was evident from a study by Botha et al. (1983)
that a large variety of plant species were commonly
selected by Dorper sheep as well as Merinos
(82.42.3%), Boer goats (75.54.1%) and cattle
(55.811.6%). The extent whereto the diets overlapped was larger in genetically related small ruminants. However, when the extent of overlap in the diets
was expressed on a quantitative basis (i.e. the percentage contribution of each plant specie was also con-
Fig. 3. Diet preferences and selection by different animal species when grazing Mixed Karoo (Adapted from Botha, 1981).
150
T.S. Brand / Small Ruminant Research 36 (2000) 147±158
Fig. 4. Diet selection by Dorpers and Merinos on both low and high occupation areas on Mixed Karoo (Adapted from Roux, 1992).
sidered) less overlap were observed in diet selection
between animal breeds and species. The diets selected
by Dorper sheep overlapped with 61.05.3% (Merino
sheep), 56.915.4% (Boer goats) and 31.76.6%
(Afrikaner cattle), respectively, when expressed on
a quantitative basis (Botha et al., 1983).
Roux (1992) determined the diet selection of Dorpers and Merinos on both low and high time occupation areas on Mixed Karoo at Grootfontein in the
Eastern Cape. He observed that although there was
a difference in botanical composition, both breeds
tended to select the same types of diets on these areas
(Fig. 4). His study clearly indicated that Dorper sheep
selected more shrubs (35.7% versus 13.9%) while
Merino sheep selected more grass compared to Dorpers (86.1% versus 63.7%).
Du Toit (1998) studied the selective grazing behaviour of Dorper and Merino sheep on three different
veld types, that is Arid Karoo (Carnarvon), Mixed
Karoo (Grootfontein) and Noorsveld (Jansenville) in
the Eastern Cape area of South Africa. Oesophageal
®stula extrusa samples were collected during winter,
spring, summer and autumn for 3 years, and microscopically examined and grouped into functional plant
groups. In the Arid Karoo, Dorpers, selected more
(11±18%) karoo bushes than Merino sheep, while
Merino sheep during all seasons on the other hand,
selected more (12±16%) grasses than Dorper sheep.
Similarly, in Noorsveld (except autumn), Dorpers
selected more karoo bushes (8±11%) and Merinos
selected more (8±15%) grasses. In Mixed Karoo,
Merinos selected more grass (7±12%) while Dorpers
selected more (6±13%) karoo bushes than Merinos
over all seasons, except during summer. Merinos
selected more karoo bushes and the Dorpers consumed
a large quantity of annuals during this season. Combined data for all seasons, as adapted from Du Toit
(1998), are presented in Fig. 5. It was evident that
Dorper sheep concentrated their grazing more on the
woody plant component, that is karoo bushes in the
Arid and Mixed Karoo and the tree and shrub component in the Noorsveld, while Merino sheep concentrated their grazing on grass. Du Toit (1998) concluded
from his study that Dorper sheep was the less selective
grazer of the two breeds, while the Merino was more
selective.
Du Toit et al. (1995) compared diet selection of
Afrino sheep (a 25% fat tailed Afrikaner, 25% Merino
and 50% South African Mutton Merino cross breed),
Dorper sheep, Merino sheep and Angora goats on Arid
Karoo. He found that the diet selected by Dorper sheep
differed 7±10, 6±9 and 6±45% from the diets selected
by, Afrino sheep, Merino sheep and Angora goats
(Table 1), respectively. Du Toit and Blom (1995)
compared the diet selection of Dorper and Merino
sheep and Angora and Boer goats on Noorsveld to
151
T.S. Brand / Small Ruminant Research 36 (2000) 147±158
Fig. 5. Diet preferences and selection by Dorper and Merino sheep when grazing three different veld types (Adapted from Du Toit, 1998).
ascertain differences in their food preferences. The
diet selected by Dorper sheep differed only between
2±13% from that of Merino sheep over the four
seasons. Differences in diet selection between Dorper
sheep and Angora (7±33%) and Boer goats (26±55%)
were much larger (Table 1). The mean overlap in diet
Table 1
The mean overlapa in the selected diets of Dorpers and other small stock breeds and species on three different veld types (adapted from Du
Toit et al., 1995; Du Toit and Blom, 1995; Du Toit, 1998)
Veld type and season
Overlap between Dorper and other breeds and species
Afrino sheep
Merino sheep
Angora goats
Boer goats
Du Toit et al., 1995
Arid Karoo
Winter
Spring
Summer
Autumn
0.91
0.93
0.90
0.93
0.91
0.94
0.92
0.94
0.55
0.94
0.91
0.70
±
±
±
±
Du Toit and Blom, 1995
Noorsveld
Winter
Spring
Summer
Autumn
±
±
±
±
0.87
0.98
0.97
0.97
0.83
0.93
0.80
0.67
0.74
0.57
0.51
0.45
Du Toit, 1998
Mixed Karoo
Winter
Spring
Summer
Autumn
±
±
±
±
0.97
0.89
0.75
0.75
±
±
±
±
±
±
±
±
a
An index value of one indicate that the two animal groups being compared utilised very similar components. As the index value
approached zero, the animal groups compared consumed widely divergent diets.
152
T.S. Brand / Small Ruminant Research 36 (2000) 147±158
selection of Dorper and Merino sheep on Mixed Karoo
varied between 3 and 25% for the four seasons
(Table 1) (Du Toit, 1998).
2.2. Chemical composition
Engels et al. (1974) studied the selective grazing
behaviour of Dorper and Merino sheep when grazing a
mixed type of natural veld (consisting of 60% Themeda triandra, 6% shrubs and the remainder a mixture
of annual grasses) near Glen in the Free State area of
South Africa. Samples were collected by oesophageally ®stulated (OF)-wethers over a 6-month period.
The authors found that the differences between breeds
with regard to chemical composition and in vitro
digestibility were not signi®cant (Table 2). They
concluded that the selective grazing behaviour of
the Dorper and the Merino appeared to be similar
on this veld type. De Waal et al. (1980) made similar
observations in the same area (Themeda triandra,
Eragrostis chloromelas and Cymbopogon plurinodis
were the prominent grasses, accounting for 61.8% of
the basal plant cover), when compared the monthly
OF-collected herbage samples of Dorper and Memo
wethers over a 12-month period.
Aucamp (1979) studied the effect of animal
specie (Dorper sheep or Boer goats) and stocking rate
on the chemical composition of diets selected by OFanimals in the Valley Bushveld near Stutterheim. The
author concluded from his results (Table 2) that Dorper sheep and Boer goats selected material of different
quality within the same veld type. Stocking rate
depressed the quality of the material selected by both
animal species.
In a study performed by Brand and Franck (1998),
the quality of wheat stubble grazing were determined
monthly over a 5-month period by OF Dorper and SA
Mutton Merino wethers. The study was performed at
the Langgewens Experimental Farm near Moorreesburg in the Western Cape Province of South Africa.
The grazing existed out of straw, weeds and residual
ears and straw. The sheep grazed the stubble at two
stocking densities (one or two ewe units/ha) for 154
days. Sixteen samples per breed were selected
monthly for 5 months. Signi®cant breedstocking
rate interactions occurred. No signi®cant differences
in the quality of diets selected at the low stocking rate
were found between breeds (Table 2). Dorpers, however, selected diets with a lower CP and higher NDF
content when grazing at the high stocking rate. It was
Table 2
The chemical composition and digestibility of pasture samples selected by different sheep breeds
Breed
Composition of selected sample (g/kg)
Ash
CP
DOM
CF
ADF
NDF
Engels et al., 1974
Dorper
Merino
168
162
116
113
568
563
300
292
±
±
±
±
Aucamp, 1979b
Dorper: lowc
Dorper: highc
Boer goat: low
Boer goat: high
±
±
±
±
122
103
142
126
±
±
±
±
±
±
±
±
±
±
±
±
±
±
±
±
Brand and Franck, 1998a
Dorper: low
Dorper: high
SA Mutton Merino: low
SA Mutton Merino: high
16026
14115
1692,36
17938
14434
8813
13936
10526
591NS11
571NS12
565NS13
593NS12
35819
480211
358112
468214
509110
65939
524117
615214
a
a
Chemical composition on an ash free basis.
Chemical composition on an DM basis.
c
Indicate low and high stocking rates.
1,2,3
Denote signi®cant (p0.05) differences in columns.
b
T.S. Brand / Small Ruminant Research 36 (2000) 147±158
argued that, under the higher stocking density, Dorpers
were willing to select samples of lower quality than
SA Mutton Merinos.
3. Plant selection
The number of different plant species selected by an
animal is an indication of the degree of selective
grazing by the animal. In the study of Botha
(1986), it was evident that Boer goats selected the
highest number of plant species (i.e. 44 from a possible 95). This was followed by Merinos and Dorpers
(37±38 species), while Afrikaner cattle selected only
24 species. In a comparative study between Dorper
and Merino sheep in Arid Karoo, Du Toit (1998),
however, found that Dorper sheep selected a diet
containing about 90% of the karoo bush species group,
while the Merino sheep selected only between 60 and
65% of the karoo bush species group.
4. Grazing habits
Data on grazing habits of sheep is scarce in South
Africa. Roux (1992) did the only experiment on the
grazing habits of Dorper sheep at Middelburg in the
Eastern Cape. Four camps of 0.5 ha on two different
localities were used. The grazing habits of Dorper and
153
Memo sheep were recorded during January (®rst
observation period) and March (second observation
period). Observation of the daily movement of the
sheep started half-an-hour before sunrise and ended
half-an-hour after sunset. The time subdivision of
physical activities of the two breeds is presented in
Fig. 6. Data is presented as a percentage of time from
4:50±19:35 hours during the ®rst observation period
and from 6:30±18:30 hours during the second observation period. The average time that Dorpers spent
grazing per day during the two observation periods
was 465 and 525 min, respectively. This consisted of
two, approximately equal grazing period each. Merinos grazed an average of 555 and 570 min/day,
respectively. These grazing hours consisted of four
or more separate grazing periods of different intensities during the day.
Dorpers avoided grazing in 50 and 36%, respectively, of their camps, while Merinos avoided grazing
in 30 and 45% of their camps. Roux (1992) found
that there were more periods of high intensity grazing
on certain areas with Merinos than for Dorpers.
The longest time Dorpers grazed on a particular
area was 13±18 min, compared to 25±30 min for
Merinos. Roux (1992) also observed that Merinos
walked larger distances (2.75±3.50 km/day) to
select food, or a suitable spot to graze. Dorpers walked
shorter distances (1.80±2.23 km/day) to ®nd food and
their next preferred grazing area was never far off.
Fig. 6. The time budget of physical activities of Dorper and Merino sheep while grazing Mixed Karoo (Roux, 1992).
154
T.S. Brand / Small Ruminant Research 36 (2000) 147±158
Roux (1992) concluded that Memos were more
inclinated to area selection grazing and in general
grazed more selectively, compared to the Dorper
which consequently utilised a greater spectrum of
plant species.
Roux (1992) noted that the Dorpers did not visit the
watering point for drinking during the daytime, while
the Merinos did in fact drink water once a day in the
afternoon. In contrast, Louw et al. (1948), however,
concluded from his studies with different sheep breeds
(Black Headed Persians, Black Headed PersianDorset Horn, Karakoel and Merino) that all
breeds went to drink water once a day and that the
time varied between 9 a.m. and 6 p.m.
A characteristic that is found in both the Black
Headed Persian and the Dorper is the habit to creep
through fences from one paddock to another (Nel,
1993). Although the thickness of their skins probably
prevent them to get hurt while creeping through the
fences, it is probably also related to their grazing
habits, since this phenomenon occurred to a larger
extent when grazing become scarce.
5. Pasture intake
Engels et al. (1974) determined the monthly voluntary feed intake of Dorper, Merino and South African
Mutton Merino wethers under free grazing conditions
on mixed natural pasture (Glen) over a 12-month
period. Their results indicated that the organic matter
intake of the Merinos and SA Mutton Merinos was,
with exception of 1 month, consistently higher than
that of the Dorper. The average organic matter intake
of the three breeds is presented in Table 3. It must,
however, be stressed that the adult Dorper is heavier
than the adult Merino which will consequently cancel
this difference when expressed on an intake per sheep
basis (Engels et al., 1974).
De Waal et al. (1981) also determined the monthly
voluntary feed intake of young Dorper and Merino
wethers at Glen on mixed natural pasture. Similar to
the results of Engels et al. (1974), they found signi®cantly higher DOM and CP intakes with Merinos
compared to Dorpers (Table 3) when calculated on a
metabolic weight basis.
Table 3
The voluntary feed intake of different sheep breeds under free grazing conditions
Breed
Average daily intake
OM
DOM
CP
Engels et al., 1974
Dorper
SA Mutton Merino
Merino
57.2 g kg W0.75
66.1 g kg W0.75
67.2 g kg W0.75
±
±
±
±
±
±
De Waal et al., 1981
Dorper
Merino
±
±
43.1 g kg W0.75
47.4 g kg W0.75
8.02 g kg W0.75
8.85 g kg W0.75
±
±
39.7 g kg W0.75/1782 g/day
46.5 g kg W073/805 g/day
112 g/day
115 g/day
±
±
32.7 g kg W0.75/568 g/day
36.8 g kg W075/595 g/day
67 g/day
70 g/day
±
±
40.4 g kg W075/742 g/day
47.4 g kg W075/749/g/day
113 g/day
115 g/day
±
53.9 g kg W075/881 g/day
173 g/day
±
88.8 g kg W0.75/1563 g/day
467 g/day
De Waal and Biel, 1989
Early lactation, 1981
Dorper
Merino
Late lactation, 1981
Dorper
Merino
Early lactation, 1982
Dorper
Merino
Early lactation, 1983
Dorper
Early lactation, 1984
Dorper
155
T.S. Brand / Small Ruminant Research 36 (2000) 147±158
In a subsequent study by De Waal and Biel (1989),
the feed intake of lactating Dorper and/or Merino ewes
were determined on grassveld in the Free State area of
South Africa during ®ve seasons (1981±84). Differences in herbage intake between breeds (1981±82)
were relatively small (Table 3). Dorper ewes were
heavier than Merino ewes, and thus, consumed less
herbage per metabolic size than Merino ewes. De
Waal and Biel (1989) ascribed the higher intake values
during 1983 and 1984 to higher pasture availability as
well as a possible substitution effect because of supplementary energy during 1981 and 1982.
6. Walking habits
Bonsma (1944) reported that the Dorset HornBlack Headed Persian cross was active and hardy
sheep, well adapted to the more extensive and arid
regions of South Africa. Louw et al. (1948) argued that
an animal, which is able to cover vast distances in a
minimum time, would be able to go out in search of
food in more arid regions of the country. He therefore
conducted a study at Middelburg Cape in a 125 ha
camp to compare the walking habits of different sheep
breeds. In the ®rst study (during winter), four different
breeds were compared (Table 4) to each other in either
a single ¯ock or separate ¯ocks. In the second study
(during summer), three separate tests were done and
only selected combinations were compared to each
other (Table 4). Louw et al. (1948) concluded from
their studies that the Black Headed Persian and the
Black Headed PersianDorset Horn walked the same
distances each day, while the Merino and Karakoel
breeds walked considerably less. All breeds walked
considerably less during the winter compared to the
summer, probably due to a shorter day-length.
In an experiment by Roux and Schlebusch (1987),
different types of small stock and sheep breeds range
together with a ¯ock of the same breed on Mixed
Karoo vegetation on an area of 31 ha, while daily
walking distances were monitored. Appreciable differences in the walking distances of breeds and types
of small stock were indicated (Table 4).
Roux (1992) monitored the walking distances of
Dorper and Merino wethers while grazing 5 ha paddocks in separate ¯ocks of 10 each. He repeated his
study in two paddocks per breed. In both cases, the
Table 4
Distances covered by Dorper and other sheep breeds during
ranging (km/day)
Sheep breed or animal specie
Flock type
Single
flock
Separate
flock
3.94
3.77
3.18
3.14
4.94
5.10
3.47
3.60
±
±
7.72
8.13
±
±
7.12
5.22
±
±
5.19
5.37
Roux and Schlebusch, 1987
Dorper ewe
Merino ewe
Boer goat doe
Angora doe
Merino wether
Angora kapater
4.90
4.96
4.70
2.57
9.18
4.94
±
±
±
±
±
±
Roux (1992)
Dorper
Merino
Dorper
Merino
±
±
±
±
1.80
2.75
2.23
3.50
Louw et al., 1948
Black Headed Persian
Black Headed PersianDorset Horna
Karakoel
Merino
Louw et al., 1948
Test 1
Black Headed Persian
Black Headed PersianDorset Horna
Test 2
Black Headed Persian
Karakoel
Test 3
Merino
Karakoel
a
To become the Dorper.
distance walked per day by the Merino wethers
exceeded that of the Dorper wethers (Table 4). He
argued that the Merinos walked more than the Dorpers
to select food, or a suitable spot where they could
graze. The Dorpers walked less to ®nd food and it
appeared from his study that their next preferred
grazing area was never far off.
7. Trampling
The damaging effects of trampling on veld, especially in low rainfall areas, is well-known. Roux
(1979) introduced the relative trampling (RT) factor,
which includes elements like bodyweight, stride
156
T.S. Brand / Small Ruminant Research 36 (2000) 147±158
Table 5
Relative trampling factor (RT) and RTD-indices for some small
stock breeds on Mixed Karoo veld (Roux and Schlebusch, 1987)
Parameter
Angora doe
Boer goat doe
Dorper ewe
Merino ewe
Angora kapater
Merino wether
RT-factor
RTD-index
1.13
0.75a
0.84
1.07
1.20a
0.93
0.40
0.43
0.54
0.64
0.71
0.85
a
Estimated values.
length and hoofprint area to measure the effect
of trampling on the veld. The higher the RT-factor,
the greater the potential ability to disturb surfaces
by trampling. Roux and Schlebusch (1987) argued
that the relative capacity of breeds or types of
breeds to trample (RTD-index) can be re¯ected by
RT-factordistance walked per day (D). Comparative
RTD-indexes for some local small stock breeds are
presented in Table 5.
Clear differences in RTD-indices between breeds
and types of breeds existed, which accentuated the
differences between breeds to trample during the
process of ranging. The RTD-index of the Dorper
ewes was approximately 6.5% less than that of Merino
ewes.
8. The effect of grazing on the veld
Barnard (1987) compared the effect of different
animal species on the change in veld composition
in the Sandveld area at the Nortier Experimental farm
near Lambertsbaai in the Western Cape area of South
Africa. The animals grazed the area for 7±13 years and
plant surveys were done once a year. The change in the
palatable and unpalatable plants as well as the grass
component of the veld are presented in Table 6.
Barnard (1987) ascribed the increase in total plants
in the paddocks grazed by cattle for 13 years and Boer
goats for 7 years to the increase in the grass component, although the palatable shrubs also increased by
17.0 and 8.7%, respectively. When this ®gures were
compared to the paddocks grazed by Dorpers, it
seemed that the unpalatable shrubs and grass components increased, while the palatable shrub component
decreased. Barnard (1987) ascribed the decrease in
the total plant component in the camps grazed by
Merinos to the selective grazing behaviour of the
breed. Barnard (1987) noted that Boer goats did more
damage to the shrubs than expressed by the ®gures in
Table 6.
9. Synopsis and conclusions
Clear differences in the diet selection of Dorpers
and other sheep breeds occurred. Dorpers utilised
shrubs and karoo bushes to a greater extent than
Merino sheep. Merino sheep, under the same grazing
conditions, concentrated more on grass as part of their
diet. The Dorper also utilised a larger number of
different plant species than the Merino.
The chemical composition of diets selected by
Dorpers or Merino-type sheep did not differ when
suf®cient grazing is available. When nutrients,
however, became limited, the Dorper was willing to
select samples of lower quality than Merino-type
sheep.
Table 6
The effect of grazing by different types of farm animals on veld composition (Adapted from Barnard, 1987)
Treatment
Cattle
Cattle plus Dorper sheep
Dorper sheep
Cattle
Merino sheep
Boar goats
Sheep units/ha
4.3
4.3
4.3
3.4
4.8
5.3
Period years
13
13
13
7
7
7
Change in veld composition
Palatable
plant
Less palatable
plants
Grass
Total
plants
17.0
ÿ3.2
3.2
ÿ1.5
ÿ7.7
8.7
3.8
7.6
6.5
ÿ0.5
1.7
ÿ1.8
14.7
5.9
5.1
ÿ2.0
ÿ1.7
10.2
16.7
5.9
7.8
0.4
ÿ3.4
8.6
T.S. Brand / Small Ruminant Research 36 (2000) 147±158
De®nite differences exist in the grazing habits of
Dorper and Merino sheep. Dorpers walked less to
select food or a suitable spot to graze, which led to
fewer separate grazing periods during the day. The
total grazing time of Dorpers were also less than that
of Merinos.
Merino-type sheep consumed more herbage per
metabolic size than Dorpers. The Dorper is, however,
heavier than Merino sheep, which consequently cancel the differences when expressed on an intake per
sheep basis.
No uniform pattern in the walking distances of
Dorpers, when compared to other sheep breeds was
observed. Generally, Dorpers walked less during grazing than Merinos, when ef®cient grazing is available.
Under more extensive conditions, however, earlier
data revealed that Dorper sheep covered larger distances during ranging than Merino sheep.
The relative trampling factor for Dorper sheep was
calculated to be less than that of evaluated Merinotype sheep. This, due to the shorter distances covered
during grazing, lead to a smaller trampling index for
Dorpers compared to Merino-type sheep.
In an experiment to determine the effect of grazing
by different types of farm animals on veld composition, veld condition improved after utilisation by
Dorpers for a relatively long period.
In conclusion, its evident that Dorpers were indeed
less-selective grazer compared to Merino-type sheep.
It also utilised a larger range of different plant species.
Most of the available studies were, however, performed under extensive conditions. The unique grazing behaviour and diet selection of Dorper sheep will,
however, also be of bene®t under more intensive
grazing conditions. Future research on this subject
will be worthwhile, especially in view of the fact that
the breed is expanding to the rest of the world. Apart
from grazing behaviour, a lack of scienti®c justi®ed
information on other aspects of behaviour of Dorpers
exists, which must be addressed in the future.
References
Acocks, J.P.H., 1988. Veld types of South Africa. Memoirs of the
Botanical Survey of South Africa 57, 1±146.
Aucamp, A.J., 1979. The product: on potential of valley Bushveld
as pasture for Boer and Angora goats (in Afrikaans). M.Sc.
thesis, University of Pretoria, Pretoria, South Africa.
157
Barnard, S.A., 1987. The effect of grazing by small stock and
cattle on the covering and composition of the Strandveld
area of the West coast (in Afrikaans). Nortier Information day,
Lambertsbay, South Africa, 12 August 1987, 14pp.
Bonsma, F.N., 1944. Milk production studies with sheep. Farming
in South Africa, May 1944, pp. 311±328.
Botha, P., 1981. The effect of selection by sheep, goats and cattle
on the composition of Mixed Karoo veld (in Afrikaans). D.Sc.
Agric. thesis, Potchefstroom University, South Africa.
Botha, P., 1986. Diet selection by different animal species on
Mixed Karoo veld and the effect on the veld (in Afrikaans).
Karoo Agric. 3(8), 24±26 (in Afrikaans).
Botha, P., Blom, C.D., Sykes, E., Barnhoorn, A.S.J., 1983. A
comparison between the diet of small and large stock on Mixed
Karoo veld. Proc. Grassld Soc. S. Afr. 18, 101±105.
Brand, T.S., Franck, F., 1998. Diet selection by SA Mutton Merino
and Dorper sheep on wheat stubble grazing. Progress Report,
Elsenburg Research Centre, Private Bag XI, Elsenburg 7607,
South Africa (in Afrikaans).
De Waal, H.O., Biel, L.C., 1989. Supplementation of lactating
Dorper and Merino ewes on Themeda cymbopogon veld. 2.
Diet quality and feed intake. S. Afr. J. Anim. Sci. 19, 148±
155.
De Waal, H.O., Engels, E.A.N., Van der Merwe, F.J., 1980.
Supplementation of sheep with protein and phosphorus on
native pasture of the Central Orange Free State. 1. Diet
composition, digestibility and rumen ammonia concentration.
S. Afr. J. Anim. Sci. 10, 203±208.
De Waal, H.O., Engels, E.A.N., Van der Merwe, F.J., Biel, L.C.,
1981. Supplementation of sheep with protein and phosphorus
on native pasture of the Central Orange Free State. 2. Feed
intake, mass change and wool production. S. J. Afr. Anim.
Sci.11, 217±227.
Du Toit, P.C.V., 1998. A comparison of the diets selected by
Merino and Dorper sheep on three range types of the Karoo. S.
Afr. Arch. Zootec. 47, 21±32.
Du Toit, P.C.V., Blom, C.D., 1995. Diet selection by sheep and
goats in Noorsveld. Afr. J. Range For. Sci. 12, 27±37.
Du Toit, P.C.V., Blom, C.D., Immelman, W.F., 1995. Diet selection
by sheep and goats in Arid Karoo. Afr. J. Range For. Sci. 12,
16±26.
Engels, E.A.N., Malan, A., Baard, M.A., 1974. The voluntary feed
intake of three breeds of sheep on natural pasture. S. Afr. J.
Anim. Sci. 4, 27±29.
Erasmus, L.S., 1961. Be carefull to give Dorper sheep special
treatment. Farming in South Africa. December 1961, pp. 27±28
(in Afrikaans).
Louw, D.J., Havenga, C.M., Hamersma, J., 1948. The walking
habits of sheep. Farming in South Africa, November 1948, pp.
753±755.
Meyer, W.D., 1951. The Dorper: its characteristics and value.
Farming in South Africa, September 1951, pp. 289±290.
Nel, J.W., 1958. The Dorper: most important of the non-woolled
types. Farming in South Africa, March 1958, pp. 14±15.
Nel, J.A., 1993. History of the Dorper. The Dorper Breeder's
Association of South Africa. PO Box 26, Middelburg CP 5900,
South Africa (in Afrikaans).
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Roux, F.A., 1992. The in¯uence of the composition of Mixed
Karoo vegetation on the grazing habits of Merino and Dorper
wethers. M.Sc. Agric.-thesis, Rhodes University, Gramstown,
South Africa.
Roux, P.W., Schlebusch, P.A., 1987. Trampling by small stock.
Karoo Agric. 3 (9), 8±10.
Roux, P.W., 1979. Elements of the trampling factor in stock. Karoo
Agric. 1 (2), 9±12.
South African Stud Book and Livestock Improvement Association,
1998. Sheep breed: Dorper. South African Stud Book and
Livestock Improvement Association, P.O. Box 270, Bloemfontein, 9300, South Africa, pp. 156±157.
Grazing behaviour and diet selection by Dorper sheep
T.S. Brand*
Elsenburg Agricultural Research Centre, Private Bag X1, Elsenburg 7607, South Africa
Abstract
The grazing behaviour and diet selection by Dorper sheep, as well as other related aspects (pasture intake, walking habits
and trampling) is reviewed. It was clear that Dorper sheep are less-selective grazers, compared to Merino-type breeds. Dorpers
utilised shrubs and bushes to a greater extent, but grass to a lesser extent in relation to Merino sheep. The Dorper also utilised a
larger number of different plant species than Merinos. Dorpers walked less to select food, or a suitable spot to graze, which
consequently led to a shorter grazing time and less separate grazing periods. Dorpers consumed less herbage per metabolic
size compared to Merino-type sheep. No uniform pattern in the walking distance of Dorpers was observed when compared to
other sheep breeds. The relative trampling factor for Dorper sheep was less than that of evaluated Merino-type sheep. The
review revealed a lack on information on the grazing behaviour and diet selection of Dorper sheep under more intensive
grazing conditions. There is also a total lack of scienti®c information on other behaviour aspects of this unique breed. # 2000
Elsevier Science B.V. All rights reserved.
Keywords: Dorper sheep; Diet selection; Grazing behaviour; Walking habits; Pasture intake
1. Introduction
Large parts of South Africa are described as desert
or semi-desert, and are suitable for sheep farming
only. There was, therefore, a need to create a tough,
non-woolled mutton breed with excellent meat and
milk production characteristics, combined with hardiness, to adapt to the prevailing conditions in the
extensive parts of the country (Bonsma, 1944).
Cross-breeding experiments to achieve this goal were
started in 1930 by the Department of Agriculture and
led to the decision to use the Dorset HornBlack
Headed Persian cross for the new breed in 1942 (Nel,
*
Tel.: 21-8844620; fax: 21-8844226.
E-mail address: [email protected] (T.S. Brand)
1993). The history of this new breed, the Dorper, was
integrated with sheep farming in the barren and semibarren North Western Cape area of South Africa (Nel,
1958). Erasmus (1961) reported that the most important characteristic of the breed was its hardiness and
adaptation to dry and extensive veld conditions.
Although the Dorper was initially selected only for
areas in the country with a rainfall of less than
250 mm/year (Meyer, 1951), its adaptability and
excellent characteristics led to the distribution of
the breed throughout South Africa and the rest of
the world. This review describes the behaviour of this
unique breed with special reference to grazing behaviour and diet selection. Localities throughout South
Africa where grazing experiments with Dorper sheep
were executed are illustrated in Fig. 1. Veld types were
described according to Acocks (1988).
0921-4488/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 9 2 1 - 4 4 8 8 ( 9 9 ) 0 0 1 5 8 - 3
148
T.S. Brand / Small Ruminant Research 36 (2000) 147±158
Fig. 1. Localities throughout South Africa where grazing experiments with Dorper sheep were done.
2. Diet selection
The Dorper is described as a hardy sheep breed,
which can thrive under poor veld conditions. It is also
believed that the breed is a strong and non-selective
grazer (South African Stud Book and Livestock
Improvement Association, 1998). A lot of studies
have been done to verify this point and to compare
the diet selection of Dorpers with other sheep breeds
or other small stock and animal species.
2.1. Physical composition
Aucamp (1979) studied the diet preference of Dorper sheep and Boer goats in die Valley Bushveld near
Stutterheim in the Eastern Cape. The main plant
component of Valley Bushveld is semi-succulent
thorny bushes and grasses. The two animal species
grazed the veld at two stocking rates (6 Dorper ewes
plus 8 lambs on 21 ha and 40 Dorper ewes plus 42
lambs on 20 ha versus 6 Boer goat does plus 6 lambs
on 20 ha and 42 Boer goat does plus 59 lambs on
21 ha). His results (Fig. 2) clearly indicated that
Dorper sheep preferred grass (70.2%), while the goats
preferred shrubs (80.6%). Stocking rate did not alter
these preferences.
Botha (1981) studied the diet selection of different
animal species on Mixed Karoo near Middelburg in
the Eastern Cape. The contribution of the different
components of Mixed Karoo veld to the diets of
different animal species (Dorper sheep, Merino
sheep, Boer goats and Afrikaner cattle) are presented
in Fig. 3. He concluded from this study that Afrikaner
cattle selected more grass (average of 56%) than
the small ruminants (average of 14.8, 22.9 and
11.5% for the Dorpers, Merinos and Boer goats,
T.S. Brand / Small Ruminant Research 36 (2000) 147±158
149
Fig. 2. Diet preferences and selection by Dorper sheep and Boer goats when grazing Valley Bushveld (Adapted from Aucamp, 1979).
respectively). The small ruminants concentrated to a
greater extent than the cattle on seasonal annuals,
when available. It was also clear that small ruminants
utilised more shrubs (average 56.8, 53.4 and 63.4% for
the Dorpers, Merinos and Boer goats, respectively)
than cattle (average of 33.7%). Botha (1981) accentrated the fact that the small ruminants utilised a large
value of shrubs that are regarded as unpalatable for
sheep.
It was evident from a study by Botha et al. (1983)
that a large variety of plant species were commonly
selected by Dorper sheep as well as Merinos
(82.42.3%), Boer goats (75.54.1%) and cattle
(55.811.6%). The extent whereto the diets overlapped was larger in genetically related small ruminants. However, when the extent of overlap in the diets
was expressed on a quantitative basis (i.e. the percentage contribution of each plant specie was also con-
Fig. 3. Diet preferences and selection by different animal species when grazing Mixed Karoo (Adapted from Botha, 1981).
150
T.S. Brand / Small Ruminant Research 36 (2000) 147±158
Fig. 4. Diet selection by Dorpers and Merinos on both low and high occupation areas on Mixed Karoo (Adapted from Roux, 1992).
sidered) less overlap were observed in diet selection
between animal breeds and species. The diets selected
by Dorper sheep overlapped with 61.05.3% (Merino
sheep), 56.915.4% (Boer goats) and 31.76.6%
(Afrikaner cattle), respectively, when expressed on
a quantitative basis (Botha et al., 1983).
Roux (1992) determined the diet selection of Dorpers and Merinos on both low and high time occupation areas on Mixed Karoo at Grootfontein in the
Eastern Cape. He observed that although there was
a difference in botanical composition, both breeds
tended to select the same types of diets on these areas
(Fig. 4). His study clearly indicated that Dorper sheep
selected more shrubs (35.7% versus 13.9%) while
Merino sheep selected more grass compared to Dorpers (86.1% versus 63.7%).
Du Toit (1998) studied the selective grazing behaviour of Dorper and Merino sheep on three different
veld types, that is Arid Karoo (Carnarvon), Mixed
Karoo (Grootfontein) and Noorsveld (Jansenville) in
the Eastern Cape area of South Africa. Oesophageal
®stula extrusa samples were collected during winter,
spring, summer and autumn for 3 years, and microscopically examined and grouped into functional plant
groups. In the Arid Karoo, Dorpers, selected more
(11±18%) karoo bushes than Merino sheep, while
Merino sheep during all seasons on the other hand,
selected more (12±16%) grasses than Dorper sheep.
Similarly, in Noorsveld (except autumn), Dorpers
selected more karoo bushes (8±11%) and Merinos
selected more (8±15%) grasses. In Mixed Karoo,
Merinos selected more grass (7±12%) while Dorpers
selected more (6±13%) karoo bushes than Merinos
over all seasons, except during summer. Merinos
selected more karoo bushes and the Dorpers consumed
a large quantity of annuals during this season. Combined data for all seasons, as adapted from Du Toit
(1998), are presented in Fig. 5. It was evident that
Dorper sheep concentrated their grazing more on the
woody plant component, that is karoo bushes in the
Arid and Mixed Karoo and the tree and shrub component in the Noorsveld, while Merino sheep concentrated their grazing on grass. Du Toit (1998) concluded
from his study that Dorper sheep was the less selective
grazer of the two breeds, while the Merino was more
selective.
Du Toit et al. (1995) compared diet selection of
Afrino sheep (a 25% fat tailed Afrikaner, 25% Merino
and 50% South African Mutton Merino cross breed),
Dorper sheep, Merino sheep and Angora goats on Arid
Karoo. He found that the diet selected by Dorper sheep
differed 7±10, 6±9 and 6±45% from the diets selected
by, Afrino sheep, Merino sheep and Angora goats
(Table 1), respectively. Du Toit and Blom (1995)
compared the diet selection of Dorper and Merino
sheep and Angora and Boer goats on Noorsveld to
151
T.S. Brand / Small Ruminant Research 36 (2000) 147±158
Fig. 5. Diet preferences and selection by Dorper and Merino sheep when grazing three different veld types (Adapted from Du Toit, 1998).
ascertain differences in their food preferences. The
diet selected by Dorper sheep differed only between
2±13% from that of Merino sheep over the four
seasons. Differences in diet selection between Dorper
sheep and Angora (7±33%) and Boer goats (26±55%)
were much larger (Table 1). The mean overlap in diet
Table 1
The mean overlapa in the selected diets of Dorpers and other small stock breeds and species on three different veld types (adapted from Du
Toit et al., 1995; Du Toit and Blom, 1995; Du Toit, 1998)
Veld type and season
Overlap between Dorper and other breeds and species
Afrino sheep
Merino sheep
Angora goats
Boer goats
Du Toit et al., 1995
Arid Karoo
Winter
Spring
Summer
Autumn
0.91
0.93
0.90
0.93
0.91
0.94
0.92
0.94
0.55
0.94
0.91
0.70
±
±
±
±
Du Toit and Blom, 1995
Noorsveld
Winter
Spring
Summer
Autumn
±
±
±
±
0.87
0.98
0.97
0.97
0.83
0.93
0.80
0.67
0.74
0.57
0.51
0.45
Du Toit, 1998
Mixed Karoo
Winter
Spring
Summer
Autumn
±
±
±
±
0.97
0.89
0.75
0.75
±
±
±
±
±
±
±
±
a
An index value of one indicate that the two animal groups being compared utilised very similar components. As the index value
approached zero, the animal groups compared consumed widely divergent diets.
152
T.S. Brand / Small Ruminant Research 36 (2000) 147±158
selection of Dorper and Merino sheep on Mixed Karoo
varied between 3 and 25% for the four seasons
(Table 1) (Du Toit, 1998).
2.2. Chemical composition
Engels et al. (1974) studied the selective grazing
behaviour of Dorper and Merino sheep when grazing a
mixed type of natural veld (consisting of 60% Themeda triandra, 6% shrubs and the remainder a mixture
of annual grasses) near Glen in the Free State area of
South Africa. Samples were collected by oesophageally ®stulated (OF)-wethers over a 6-month period.
The authors found that the differences between breeds
with regard to chemical composition and in vitro
digestibility were not signi®cant (Table 2). They
concluded that the selective grazing behaviour of
the Dorper and the Merino appeared to be similar
on this veld type. De Waal et al. (1980) made similar
observations in the same area (Themeda triandra,
Eragrostis chloromelas and Cymbopogon plurinodis
were the prominent grasses, accounting for 61.8% of
the basal plant cover), when compared the monthly
OF-collected herbage samples of Dorper and Memo
wethers over a 12-month period.
Aucamp (1979) studied the effect of animal
specie (Dorper sheep or Boer goats) and stocking rate
on the chemical composition of diets selected by OFanimals in the Valley Bushveld near Stutterheim. The
author concluded from his results (Table 2) that Dorper sheep and Boer goats selected material of different
quality within the same veld type. Stocking rate
depressed the quality of the material selected by both
animal species.
In a study performed by Brand and Franck (1998),
the quality of wheat stubble grazing were determined
monthly over a 5-month period by OF Dorper and SA
Mutton Merino wethers. The study was performed at
the Langgewens Experimental Farm near Moorreesburg in the Western Cape Province of South Africa.
The grazing existed out of straw, weeds and residual
ears and straw. The sheep grazed the stubble at two
stocking densities (one or two ewe units/ha) for 154
days. Sixteen samples per breed were selected
monthly for 5 months. Signi®cant breedstocking
rate interactions occurred. No signi®cant differences
in the quality of diets selected at the low stocking rate
were found between breeds (Table 2). Dorpers, however, selected diets with a lower CP and higher NDF
content when grazing at the high stocking rate. It was
Table 2
The chemical composition and digestibility of pasture samples selected by different sheep breeds
Breed
Composition of selected sample (g/kg)
Ash
CP
DOM
CF
ADF
NDF
Engels et al., 1974
Dorper
Merino
168
162
116
113
568
563
300
292
±
±
±
±
Aucamp, 1979b
Dorper: lowc
Dorper: highc
Boer goat: low
Boer goat: high
±
±
±
±
122
103
142
126
±
±
±
±
±
±
±
±
±
±
±
±
±
±
±
±
Brand and Franck, 1998a
Dorper: low
Dorper: high
SA Mutton Merino: low
SA Mutton Merino: high
16026
14115
1692,36
17938
14434
8813
13936
10526
591NS11
571NS12
565NS13
593NS12
35819
480211
358112
468214
509110
65939
524117
615214
a
a
Chemical composition on an ash free basis.
Chemical composition on an DM basis.
c
Indicate low and high stocking rates.
1,2,3
Denote signi®cant (p0.05) differences in columns.
b
T.S. Brand / Small Ruminant Research 36 (2000) 147±158
argued that, under the higher stocking density, Dorpers
were willing to select samples of lower quality than
SA Mutton Merinos.
3. Plant selection
The number of different plant species selected by an
animal is an indication of the degree of selective
grazing by the animal. In the study of Botha
(1986), it was evident that Boer goats selected the
highest number of plant species (i.e. 44 from a possible 95). This was followed by Merinos and Dorpers
(37±38 species), while Afrikaner cattle selected only
24 species. In a comparative study between Dorper
and Merino sheep in Arid Karoo, Du Toit (1998),
however, found that Dorper sheep selected a diet
containing about 90% of the karoo bush species group,
while the Merino sheep selected only between 60 and
65% of the karoo bush species group.
4. Grazing habits
Data on grazing habits of sheep is scarce in South
Africa. Roux (1992) did the only experiment on the
grazing habits of Dorper sheep at Middelburg in the
Eastern Cape. Four camps of 0.5 ha on two different
localities were used. The grazing habits of Dorper and
153
Memo sheep were recorded during January (®rst
observation period) and March (second observation
period). Observation of the daily movement of the
sheep started half-an-hour before sunrise and ended
half-an-hour after sunset. The time subdivision of
physical activities of the two breeds is presented in
Fig. 6. Data is presented as a percentage of time from
4:50±19:35 hours during the ®rst observation period
and from 6:30±18:30 hours during the second observation period. The average time that Dorpers spent
grazing per day during the two observation periods
was 465 and 525 min, respectively. This consisted of
two, approximately equal grazing period each. Merinos grazed an average of 555 and 570 min/day,
respectively. These grazing hours consisted of four
or more separate grazing periods of different intensities during the day.
Dorpers avoided grazing in 50 and 36%, respectively, of their camps, while Merinos avoided grazing
in 30 and 45% of their camps. Roux (1992) found
that there were more periods of high intensity grazing
on certain areas with Merinos than for Dorpers.
The longest time Dorpers grazed on a particular
area was 13±18 min, compared to 25±30 min for
Merinos. Roux (1992) also observed that Merinos
walked larger distances (2.75±3.50 km/day) to
select food, or a suitable spot to graze. Dorpers walked
shorter distances (1.80±2.23 km/day) to ®nd food and
their next preferred grazing area was never far off.
Fig. 6. The time budget of physical activities of Dorper and Merino sheep while grazing Mixed Karoo (Roux, 1992).
154
T.S. Brand / Small Ruminant Research 36 (2000) 147±158
Roux (1992) concluded that Memos were more
inclinated to area selection grazing and in general
grazed more selectively, compared to the Dorper
which consequently utilised a greater spectrum of
plant species.
Roux (1992) noted that the Dorpers did not visit the
watering point for drinking during the daytime, while
the Merinos did in fact drink water once a day in the
afternoon. In contrast, Louw et al. (1948), however,
concluded from his studies with different sheep breeds
(Black Headed Persians, Black Headed PersianDorset Horn, Karakoel and Merino) that all
breeds went to drink water once a day and that the
time varied between 9 a.m. and 6 p.m.
A characteristic that is found in both the Black
Headed Persian and the Dorper is the habit to creep
through fences from one paddock to another (Nel,
1993). Although the thickness of their skins probably
prevent them to get hurt while creeping through the
fences, it is probably also related to their grazing
habits, since this phenomenon occurred to a larger
extent when grazing become scarce.
5. Pasture intake
Engels et al. (1974) determined the monthly voluntary feed intake of Dorper, Merino and South African
Mutton Merino wethers under free grazing conditions
on mixed natural pasture (Glen) over a 12-month
period. Their results indicated that the organic matter
intake of the Merinos and SA Mutton Merinos was,
with exception of 1 month, consistently higher than
that of the Dorper. The average organic matter intake
of the three breeds is presented in Table 3. It must,
however, be stressed that the adult Dorper is heavier
than the adult Merino which will consequently cancel
this difference when expressed on an intake per sheep
basis (Engels et al., 1974).
De Waal et al. (1981) also determined the monthly
voluntary feed intake of young Dorper and Merino
wethers at Glen on mixed natural pasture. Similar to
the results of Engels et al. (1974), they found signi®cantly higher DOM and CP intakes with Merinos
compared to Dorpers (Table 3) when calculated on a
metabolic weight basis.
Table 3
The voluntary feed intake of different sheep breeds under free grazing conditions
Breed
Average daily intake
OM
DOM
CP
Engels et al., 1974
Dorper
SA Mutton Merino
Merino
57.2 g kg W0.75
66.1 g kg W0.75
67.2 g kg W0.75
±
±
±
±
±
±
De Waal et al., 1981
Dorper
Merino
±
±
43.1 g kg W0.75
47.4 g kg W0.75
8.02 g kg W0.75
8.85 g kg W0.75
±
±
39.7 g kg W0.75/1782 g/day
46.5 g kg W073/805 g/day
112 g/day
115 g/day
±
±
32.7 g kg W0.75/568 g/day
36.8 g kg W075/595 g/day
67 g/day
70 g/day
±
±
40.4 g kg W075/742 g/day
47.4 g kg W075/749/g/day
113 g/day
115 g/day
±
53.9 g kg W075/881 g/day
173 g/day
±
88.8 g kg W0.75/1563 g/day
467 g/day
De Waal and Biel, 1989
Early lactation, 1981
Dorper
Merino
Late lactation, 1981
Dorper
Merino
Early lactation, 1982
Dorper
Merino
Early lactation, 1983
Dorper
Early lactation, 1984
Dorper
155
T.S. Brand / Small Ruminant Research 36 (2000) 147±158
In a subsequent study by De Waal and Biel (1989),
the feed intake of lactating Dorper and/or Merino ewes
were determined on grassveld in the Free State area of
South Africa during ®ve seasons (1981±84). Differences in herbage intake between breeds (1981±82)
were relatively small (Table 3). Dorper ewes were
heavier than Merino ewes, and thus, consumed less
herbage per metabolic size than Merino ewes. De
Waal and Biel (1989) ascribed the higher intake values
during 1983 and 1984 to higher pasture availability as
well as a possible substitution effect because of supplementary energy during 1981 and 1982.
6. Walking habits
Bonsma (1944) reported that the Dorset HornBlack Headed Persian cross was active and hardy
sheep, well adapted to the more extensive and arid
regions of South Africa. Louw et al. (1948) argued that
an animal, which is able to cover vast distances in a
minimum time, would be able to go out in search of
food in more arid regions of the country. He therefore
conducted a study at Middelburg Cape in a 125 ha
camp to compare the walking habits of different sheep
breeds. In the ®rst study (during winter), four different
breeds were compared (Table 4) to each other in either
a single ¯ock or separate ¯ocks. In the second study
(during summer), three separate tests were done and
only selected combinations were compared to each
other (Table 4). Louw et al. (1948) concluded from
their studies that the Black Headed Persian and the
Black Headed PersianDorset Horn walked the same
distances each day, while the Merino and Karakoel
breeds walked considerably less. All breeds walked
considerably less during the winter compared to the
summer, probably due to a shorter day-length.
In an experiment by Roux and Schlebusch (1987),
different types of small stock and sheep breeds range
together with a ¯ock of the same breed on Mixed
Karoo vegetation on an area of 31 ha, while daily
walking distances were monitored. Appreciable differences in the walking distances of breeds and types
of small stock were indicated (Table 4).
Roux (1992) monitored the walking distances of
Dorper and Merino wethers while grazing 5 ha paddocks in separate ¯ocks of 10 each. He repeated his
study in two paddocks per breed. In both cases, the
Table 4
Distances covered by Dorper and other sheep breeds during
ranging (km/day)
Sheep breed or animal specie
Flock type
Single
flock
Separate
flock
3.94
3.77
3.18
3.14
4.94
5.10
3.47
3.60
±
±
7.72
8.13
±
±
7.12
5.22
±
±
5.19
5.37
Roux and Schlebusch, 1987
Dorper ewe
Merino ewe
Boer goat doe
Angora doe
Merino wether
Angora kapater
4.90
4.96
4.70
2.57
9.18
4.94
±
±
±
±
±
±
Roux (1992)
Dorper
Merino
Dorper
Merino
±
±
±
±
1.80
2.75
2.23
3.50
Louw et al., 1948
Black Headed Persian
Black Headed PersianDorset Horna
Karakoel
Merino
Louw et al., 1948
Test 1
Black Headed Persian
Black Headed PersianDorset Horna
Test 2
Black Headed Persian
Karakoel
Test 3
Merino
Karakoel
a
To become the Dorper.
distance walked per day by the Merino wethers
exceeded that of the Dorper wethers (Table 4). He
argued that the Merinos walked more than the Dorpers
to select food, or a suitable spot where they could
graze. The Dorpers walked less to ®nd food and it
appeared from his study that their next preferred
grazing area was never far off.
7. Trampling
The damaging effects of trampling on veld, especially in low rainfall areas, is well-known. Roux
(1979) introduced the relative trampling (RT) factor,
which includes elements like bodyweight, stride
156
T.S. Brand / Small Ruminant Research 36 (2000) 147±158
Table 5
Relative trampling factor (RT) and RTD-indices for some small
stock breeds on Mixed Karoo veld (Roux and Schlebusch, 1987)
Parameter
Angora doe
Boer goat doe
Dorper ewe
Merino ewe
Angora kapater
Merino wether
RT-factor
RTD-index
1.13
0.75a
0.84
1.07
1.20a
0.93
0.40
0.43
0.54
0.64
0.71
0.85
a
Estimated values.
length and hoofprint area to measure the effect
of trampling on the veld. The higher the RT-factor,
the greater the potential ability to disturb surfaces
by trampling. Roux and Schlebusch (1987) argued
that the relative capacity of breeds or types of
breeds to trample (RTD-index) can be re¯ected by
RT-factordistance walked per day (D). Comparative
RTD-indexes for some local small stock breeds are
presented in Table 5.
Clear differences in RTD-indices between breeds
and types of breeds existed, which accentuated the
differences between breeds to trample during the
process of ranging. The RTD-index of the Dorper
ewes was approximately 6.5% less than that of Merino
ewes.
8. The effect of grazing on the veld
Barnard (1987) compared the effect of different
animal species on the change in veld composition
in the Sandveld area at the Nortier Experimental farm
near Lambertsbaai in the Western Cape area of South
Africa. The animals grazed the area for 7±13 years and
plant surveys were done once a year. The change in the
palatable and unpalatable plants as well as the grass
component of the veld are presented in Table 6.
Barnard (1987) ascribed the increase in total plants
in the paddocks grazed by cattle for 13 years and Boer
goats for 7 years to the increase in the grass component, although the palatable shrubs also increased by
17.0 and 8.7%, respectively. When this ®gures were
compared to the paddocks grazed by Dorpers, it
seemed that the unpalatable shrubs and grass components increased, while the palatable shrub component
decreased. Barnard (1987) ascribed the decrease in
the total plant component in the camps grazed by
Merinos to the selective grazing behaviour of the
breed. Barnard (1987) noted that Boer goats did more
damage to the shrubs than expressed by the ®gures in
Table 6.
9. Synopsis and conclusions
Clear differences in the diet selection of Dorpers
and other sheep breeds occurred. Dorpers utilised
shrubs and karoo bushes to a greater extent than
Merino sheep. Merino sheep, under the same grazing
conditions, concentrated more on grass as part of their
diet. The Dorper also utilised a larger number of
different plant species than the Merino.
The chemical composition of diets selected by
Dorpers or Merino-type sheep did not differ when
suf®cient grazing is available. When nutrients,
however, became limited, the Dorper was willing to
select samples of lower quality than Merino-type
sheep.
Table 6
The effect of grazing by different types of farm animals on veld composition (Adapted from Barnard, 1987)
Treatment
Cattle
Cattle plus Dorper sheep
Dorper sheep
Cattle
Merino sheep
Boar goats
Sheep units/ha
4.3
4.3
4.3
3.4
4.8
5.3
Period years
13
13
13
7
7
7
Change in veld composition
Palatable
plant
Less palatable
plants
Grass
Total
plants
17.0
ÿ3.2
3.2
ÿ1.5
ÿ7.7
8.7
3.8
7.6
6.5
ÿ0.5
1.7
ÿ1.8
14.7
5.9
5.1
ÿ2.0
ÿ1.7
10.2
16.7
5.9
7.8
0.4
ÿ3.4
8.6
T.S. Brand / Small Ruminant Research 36 (2000) 147±158
De®nite differences exist in the grazing habits of
Dorper and Merino sheep. Dorpers walked less to
select food or a suitable spot to graze, which led to
fewer separate grazing periods during the day. The
total grazing time of Dorpers were also less than that
of Merinos.
Merino-type sheep consumed more herbage per
metabolic size than Dorpers. The Dorper is, however,
heavier than Merino sheep, which consequently cancel the differences when expressed on an intake per
sheep basis.
No uniform pattern in the walking distances of
Dorpers, when compared to other sheep breeds was
observed. Generally, Dorpers walked less during grazing than Merinos, when ef®cient grazing is available.
Under more extensive conditions, however, earlier
data revealed that Dorper sheep covered larger distances during ranging than Merino sheep.
The relative trampling factor for Dorper sheep was
calculated to be less than that of evaluated Merinotype sheep. This, due to the shorter distances covered
during grazing, lead to a smaller trampling index for
Dorpers compared to Merino-type sheep.
In an experiment to determine the effect of grazing
by different types of farm animals on veld composition, veld condition improved after utilisation by
Dorpers for a relatively long period.
In conclusion, its evident that Dorpers were indeed
less-selective grazer compared to Merino-type sheep.
It also utilised a larger range of different plant species.
Most of the available studies were, however, performed under extensive conditions. The unique grazing behaviour and diet selection of Dorper sheep will,
however, also be of bene®t under more intensive
grazing conditions. Future research on this subject
will be worthwhile, especially in view of the fact that
the breed is expanding to the rest of the world. Apart
from grazing behaviour, a lack of scienti®c justi®ed
information on other aspects of behaviour of Dorpers
exists, which must be addressed in the future.
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