Directory UMM :Data Elmu:jurnal:S:Small Ruminant Research:Vol36.Issue2.May2000:
Small Ruminant Research 36 (2000) 137±146
A comparative assessment of Dorper sheep in different
production environments and systems
S.J. Schoeman*
Department of Animal Sciences, Faculty of Agriculture, University of Stellenbosch, Stellenbosch, South Africa
Abstract
Performance of Dorper sheep was compared to other breeds in pure and cross-breeding evaluations under different
production systems. The number of ewes lambed per ewe joint (EL/EJ) varied for the Dorper from 0.68 to 0.91 (average 0.81)
and for other breeds and crosses from 0.65 to 0.91 (average 0.82). Average litter size (LB/lambing) varied from 1.02 to 1.52
(average 1.28) and from 1.02 to 1.70 (average 1.30) for the two groups, respectively. In general, the Afrino and Finnish
composite lines were more proli®c than the Dorper. Post-weaning mortality rates in Kenya were high (49%) among Dorper
lambs compared to the local Red Maaisai breed, owing to a high susceptibility to gastrointestinal parasites. Average weaning
weights (WW) (100 days) were 12.4% heavier in the Dorper than in the breeds it was compared to, but 31.7% heavier than the
woolled breeds. Total WW and ef®ciency of Dorper and Dorper crosses were higher than Merino, Afrino, DoÈhne merino,
South African Mutton Merino, but lower than in Finnish Landrace composite lines. Both Dorper and Dorper cross-breeds
reached target slaughter weight of approx. 40 kg earlier than Merino, Afrino, Suffolk and Ile de France crosses. Average daily
gain to slaughter was 44% higher in the Dorper than the average of the groups it was compared to. It is concluded that the
Dorper was superior in reproductive and growth traits to woolled and other indigenous breeds. However, there is a lack of
information on the performance of the Dorper in cross-breeding systems. # 2000 Elsevier Science B.V. All rights reserved.
Keywords: Dorper sheep; Cross-breeding; Reproduction; Growth; Review
1. Introduction
Southern Africa has a rapid growing human population. This increase has resulted in a corresponding
increase in demand for meat and mutton. The per
capita consumption of mutton and lamb in South
Africa is 4 kg, which is high compared to many other
countries, while annual production is 107103 t and
annual demand 160103 t (Abst. Agric. Stat., 1997).
*
Fax: 27-21-808-4750.
E-mail address: [email protected] (S.J. Schoeman)
The total number of sheep in South Africa has
dropped from 36.5 million in 1965 to 25.4 million
in 1995, while the largest decline was in Merino
sheep numbers. For several decades sheep production
was primarily aimed towards wool production. However, this has changed during the past three decades
owing to inter alia the high demand for mutton and
lamb, the meat vs. wool price structure and input
costs. The numbers of mutton and dual-purpose-types
has consequently increased accordingly. Approximately 70% of all sheep are still woolled sheep
and mainly Merino or merino lines (e.g. the DoÈhne
Merino).
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 7 - 1
138
S.J. Schoeman / Small Ruminant Research 36 (2000) 137±146
The need of a breed suitable for lamb production in
the arid, extensive areas of southern Africa, resulted in
the formation of the Dorper. It became a popular
breed, not only in the extensive areas, but also in
other parts of southern Africa and consequently
became numerically the second most important sheep
breed in South Africa.
1.1. The state of cross-breeding in sheep
Combining appropriate breeds in cross-breeding
systems offers the opportunity to increase productive
ef®ciency through both additive and non-additive
genetic effects. Breed characterization programmes
have revealed large differences among breeds for a
variety of economic important traits. This is especially
evident in the beef cattle industry across the world
(Gregory et al., 1991). Cross-breeding among sheep
breeds is mostly practiced in countries of the Northern
Hemisphere, while in countries of the Southern Hemisphere wool production plays an important part in the
sheep industries.
Despite the decline in woolled sheep numbers, the
wool industry is still considered of great importance.
Cross-breeding woolled sheep with other breeds, and
especially those having hair, kempy or black ®bres in
their ¯eeces is highly opposed owing to the possibility
of contamination of wool ¯eeces. The wool industry,
supported by The South African National Wool
Growers' Association has launched a campaign
against the use of hairy breeds in cross-breeding with
woolled sheep. The Dorper is one of those also being
mentioned due to a high frequency of spotted and even
black lambs produced in woolled sheep. Dorper rams
are nevertheless being used by many farmers in crossbreeding with Merino ewes. However, owing to the
above-mentioned disapproval, little information is
available on the use of the Dorper in cross-breeding
systems.
White Dorper rams were used in the initial crossbreeding phase during the development of the
Afrino breed. Some of these results were reported
by Olivier et al. (1984). In a later study Du Toit (1996)
compared several sire breeds, including the White
Dorper, in cross-breeding with Merino ewes in extensive farming conditions. In this study, 50 Merino ewes
in each group were mated to ®ve fertility tested
rams of each breed. Performance characteristics and
relative gross income per 100 ewes were recorded in
this study.
The performance of composite lines, developed
from indigenous sheep breeds and the Finnish Landrace and subsequently crossed with Dorper rams, was
reported by Schoeman et al. (1993, 1995) and Schoeman and Van der Merwe (1994).
Dorper sheep were also exported to Zimbabwe,
Zambia, Kenya, Israel and Saudi Arabia. In Zambia
they are mainly owned by commercial farmers on
mixed farms in the central and southern provinces
(Stafford and Hansson, 1991). In various parts of
Africa attempts were made to assess the potential
of indigenous sheep breeds when crossed with Dorper
sheep. Stafford and Hansson (1991) mentioned that
indigenous sheep in Zambia, known as Rhodesian
sheep, were crossed with Dorper to improve productivity, while Red Maaisai sheep (RM) were crossed
and evaluated against the Dorper in Kenya (Inyangala
et al., 1991, 1992; Baker et al., 1994, 1998).
The objective of this paper is to review comparisons
in literature between Dorper and other breeds in pure
and cross-breeding systems.
2. Reproductive performance
The reproductive performance of Dorper sheep
and other breeds, as well as some of their crosses,
were compared under a variety of environmental
conditions. A summary of these results is shown in
Table 1.
2.1. Age at ®rst lambing
Differences in age at ®rst lambing were only
reported in one study (Schoeman, 1990), where the
Dorper was compared to two woolled-mutton breeds,
viz. the DoÈhne Merino (DM) and the South African
Mutton Merino (MM) in an accelerated lambing
system. Mean ®rst lambing age was 3 and 4 months
earlier in the Dorper compared to the other two breeds,
respectively. This is probably partly related to earlier
sexual maturity in the Dorper due to the contribution
of the early maturing Blackhead Persian (Visser,
1991), but also due to a longer natural breeding season
in the Dorper (Boshoff et al., 1975). In a comparison
between the Dorper and ewes of the composite lines,
139
S.J. Schoeman / Small Ruminant Research 36 (2000) 137±146
Table 1
Comparative reproductive performance of Dorper ewes in pure and cross-breeding evaluations
Parameter
Means for breeds/crossesa
D
b
EL/EJ (Fertility)
LB/lambing
(litter size)
0.91
0.83
0.88c
0.81
0.74d
0.68d
1.18
1.39c
1.52
1.50
1.08d
LB/EJ/year
1.02
1.57
1.46c
1.80
1/2 D
1/2 M
0.91
M
Sources
MM
0.85
0.65
DM
Finn
Comp
A
RM
SA
0.86
0.87c
0.80d
0.73
0.91c
0.77c
1.03
1.02
1.32d
1.32d
1.54
1.31
1.70
1.44c
1.02
1.18
1.42c
1.21
1.25d
1.26
1.76
Basson et al. (1969)
Olivier et al. (1984)
Schoeman (1990)
Eltawil and Narendran (1969)
Schoeman and Van der
Merwe (1994)
Baker et al. (1998)
Olivier et al. (1984)
Schoeman (1990)
Eltawil and Narendran (1969)
Snyman (unpubl.)
Schoeman and Van der
Merwe (1994)
Baker et al. (1998)
Basson et al. (1969)
Schoeman (1990)
Snyman (unpubl.)
a
D ± Dorper; M ± Merino; MM ± South African Mutton Merino; DM ± DoÈhne merino; Finn Comp. ± Finnish Landrace composite;
A ± Afrino; RM ± Red Maaisai; SA ± Saudi Arabian indigenous breeds (Najdi, Awassi and Harri).
b
EL ± number of ewes lambed; EJ ± number of ewes joint; LB ± number of lambs born.
c,d
p0.05.
developed from crosses between indigenous sheep
breeds in South Africa and the Finnish Landrace,
no difference was obtained in age at puberty (Schoeman et al., 1993). An earlier onset of puberty was also
reported by Greeff et al. (1993) in Romanov and
RomanovDorper cross-bred ewes as compared to
Dorper ewes.
2.2. Ewe fertility
The number of ewes lambing per ewe joint (EL/EJ)
varied in the Dorper from 0.68 (Baker et al., 1998) to
0.91 (Basson et al., 1969) (Table 1). The highest
fertility of 0.91 was recorded in the Dorper (Basson
et al., 1969), the (1/2)D (1/2)M cross-bred ewes
(Olivier et al., 1984) and the Finn composites (Schoeman and Van der Merwe, 1994), while the lowest value
of 0.65 was that reported by Olivier et al. (1984) in the
Merino. The study carried out by Olivier et al. (1984)
was under harsh dry Karoo-veld conditions, while in
the case of Basson et al. (1969) and Schoeman and Van
der Merwe (1994) comparisons were made where the
ewes were maintained in individual pens from mating
until weaning of their lambs. Baker et al. (1998) also
compared the Dorper to the local Red Maaisai sheep
breed (RM) in the sub-humid coastal region in Kenya
and reported an approx. 12% higher performance in
the RM. Generally, it appears that the Dorper has an
acceptable fertility rate which tends to be higher than
those of the woolled sheep breeds.
2.3. Litter size
Litter size (LB/lambing) in the Dorper varied from
1.02 (Baker et al., 1998) under extremely unfavourable conditions to 1.52 (Eltawil and Narendran, 1969)
in Saudi Arabia (Table 1). Average litter size in the
Dorper was 1.28 as compared to the 1.30 recorded in
the breeds it was compared to. It was higher than those
of the woolled breeds (Olivier et al., 1984; Schoeman,
1990; Snyman, unpubl.), approx. the same as in the
RM (Baker et al., 1998) but lower than in the Afrino
140
S.J. Schoeman / Small Ruminant Research 36 (2000) 137±146
(Snyman, unpubl.) and Finn composites (Schoeman
and Van der Merwe, 1994), respectively. In the latter
case (Schoeman and Van der Merwe, 1994), litter size
in the proli®c composite was 33% larger than in the
Dorper. In two other reports average litter sizes in
Dorper sheep of 1.59 (Cloete and De Villiers, 1987)
and 1.21 (Schoeman and Burger, 1992) were obtained,
respectively.
In a comparative study among maiden ewes of
Romanov, Dorper and RomanovDorper crosses,
ovulation rates of 1.9, 1.0 and 1.4, respectively, were
reported by Greeff et al. (1993). Age at ®rst oestrus
was also signi®cantly (p0.05) lower in the Romanov
and the crosses than in the Dorper. In both this study as
well as that of Schoeman and Van der Merwe (1994)
with the Finnish Landrace composite line, it was
indicated that a substantial increase in lambs born
could be obtained by the infusion of genes from
proli®c populations to the Dorper via the application
of appropriate cross-breeding programmes.
In an accelerated lambing system, where the ewes
were joint at 8-month intervals, lambing performance
per year (LB/EJ/y) was signi®cantly (p0.05) higher in
the Dorper (1.46) compared to the DM (1.25) (Schoeman, 1990). In an earlier study Basson et al. (1969)
reported corresponding values of 1.57, 1.21 and 1.18
for the Dorper, DM and Merino, respectively. In
another study (Schoeman and Van der Merwe,
1994) LB/LO (every 8 months) was 54% more
(p0.05) in the proli®c Finn composites than in the
Dorper (1.28 vs. 0.83). The Dorper could therefore
not be designated as a high proli®c breed, although
it compares favourably with most other breeds in
a variety of environmental and management conditions.
2.4. Survival rate
Survival rates of Dorper and Dorper crosses
were only compared by Olivier et al. (1984); Schoeman (1990); Baker et al. (1994); Snyman (unpubl.)
(Table 2). Higher neonatal mortalities among lambs
were reported by Olivier et al. (1984) when Merino
ewes were crossed with either Dorper or Dorset Horn
rams (6.1 and 7.1%, respectively) compared to the
Dorper (4.8%) and the Merino (3.5%), respectively. It
is well-known that the use of fast growing terminal sire
breeds tends to increase mortality at birth in both ewes
and lambs in the Merino.
Survival rates from birth to weaning were higher
(p0.05) in the Dorper than in the DM and Merino,
respectively (Schoeman, 1990; Snyman, unpubl.)
under fairly favourable conditions, but lower than in
the RM and RMDorper crosses between birth and
weaning (90 days) (Baker et al., 1994). However, from
weaning to 9 months of age mortality rates amongst
Dorper lambs were much higher than in the RM and
RMDorper crosses. Mortality rates declined as the
contribution of the RM in the crosses increased (see
Fig. 1).
In a later report by the same authors (Baker et al.,
1998), pre-weaning mortality rates of 10.3% for the
RM and 30.0% for the Dorper were obtained, while
corresponding post-weaning mortalities were 18.4 and
39.2%, respectively. These high mortality rates were
mainly caused by low resistance of Dorper lambs to
endoparasites (see Section 5). It was suggested by
these authors that although differences in pregnancy
rates and litter sizes were small, the number of lambs
weaned per ewes joint in the RM was almost double
that of the Dorper (0.61 vs. 0.34). It clearly shows that
Table 2
Comparative survival rates of Dorper lambs in pure and crossbreeding evaluations
Period
Birth ± 90 days
Birth ± 100 days
Birth ± 120 days
90 days to 9 months
a
Means for breeds/crossesa
D
M/DM
MM
0.81
0.84b
0.89
0.51
0.81c
0.78
0.83b
For abbreviations, see Table 1.
p0.05.
b,c
Sources
A
RM
RMX
0.88
0.89
0.90
0.78
0.88
Baker et al. (1994)
Schoeman (1990)
Snyman (unpubl.)
Baker et al. (1994)
141
S.J. Schoeman / Small Ruminant Research 36 (2000) 137±146
the Dorper, developed for the arid South African
conditions, is not suitably adapted to the humid tropical parts of Africa.
3. Body weights and growth performances
Body weight and growth performance are important
traits in all lamb-producing sheep breeds. This applies
to both the pre-weaning and post-weaning phases.
3.1. Birth weight
Fig. 1. The in¯uence of genetic composition in Dorper, Red
Maaisai and crosses on postweaning mortality rate (Source: Baker
et al., 1994).
Birth weight (BW) of Dorper lambs and those
they are compared to are in Table 3. BW of Dorper
Table 3
Comparative birth and weaning weights of Dorper lambs in pure and crossbreeding evaluations
Parameter
Means for breeds/crossesa
D
Birth weight
(kg)
4.2
1/2 D
1/2 M
M/DM
4.5
3.8
4.3c
3.8
4.0b
Sources
MM
26.8
22.1
85 days
90 days
100 days
4.6d
4.1
d
13.8
15.5
20.0
10.6
28.6
For abbreviations, see Table 1.
p0.05.
22.7
25.0c
25.8c
26.5c
23.7
Schoeman (1990)
Eltawil and Narendran
(1969)
Inyangala et al. (1991)
Inyangala et al. (1992)
Schoeman and Van der
Merwe (1994)
Snyman (unpubl.)
Schoeman (1990)
21.4
33.4
b,c,d
4.4
c
16.8b
120 days
a
SA
3.4c
16.3
16.0
19.4
11.8
32.0
28.6b
26.7c
RMX
3.7
4.2
b
75 days
RM
3.9
4.3
17.3c
A
Olivier et al. (1984)
3.7
4.1
5.0b
Weaning
weight (kg)
50 days
1/2 D 1/2
Finn Comp
32.2
16.1
19.8
11.3
Schoeman and Van der
Merwe (1994)
Basson et al. (1969)
Eltawil and Narendran
(1969)
Inyangala et al. (1991)
Inyangala et al. (1992)
Baker et al. (1994)
Olivier et al. (1984)
Schoeman (1990)
Schoeman and Van der
Merwe (1994)
Snyman (unpubl.)
142
S.J. Schoeman / Small Ruminant Research 36 (2000) 137±146
Table 4
Comparative birth, 42- and 100-day body weights of lambs of
different breedsa
Breed
Weights (kg) at
Birth
42-day
100-day
Dorper
Afrino
Corriedale
Damara
Dormer
Hampshire
Ile de France
Merino Landsheep
SA Mutton merino
Suffolk
4.4
3.5
4.0
3.6
3.5
3.4
4.2
3.6
3.5
3.4
16.4
19.0
16.5
13.0
20.5
19.5
17.9
18.9
18.5
20.0
29.2
24.9
31.5
23.7
35.9
36.8
33.4
36.4
33.4
35.0
a
Source: ARC ± Animal Improvement Institute (National
Sheep Performance Testing Scheme).
lambs were in most cases heavier than in the woolled
breeds, except for the MM which is also known to
have high BW and a high incidence of dystocia.
Average BW, 42-day weights and 100-day weights
of more than 117 000 records obtained from the
South African Sheep Performance Testing Scheme
for various breeds are in Table 4. There is no
obvious explanation for the high BW of the Dorper
in these data. These results could, however, be biased
since it does not take into account the effect of
differences in production environments and management levels. Dorper, Afrino and Damara sheep are
mostly found in the extensive grazing areas, whereas
some other breeds, e.g. the Ile de France and Hampshire are mostly farmed within intensive high input
systems.
In the comparison of the Dorper with the Finn
composites (Schoeman and Van der Merwe, 1994),
where both ewe groups were mated to the same Dorper
rams, BW of the Dorper exceeded that of the DorperFinn composite lambs by 47%, probably indicating a negative maternal effect restricting BW in the
composite lines. In this case an exceptionally high BW
of 5.0 kg compared to the other reports was recorded
in the Dorper, probably due to the very favourable
conditions in nutrition and management. In the Kenya
studies (Inyangala et al., 1991, 1992) BW of Dorper
lambs were almost identical to those of the DorperRM crosses.
3.2. Weaning weights
Weaning weights (WW) were recorded at various
ages, depending on whether an accelerated lambing
system or a traditional once-a-year lambing system
was applied. WW of Dorper lambs (Table 3) varied
considerably from 11.8 kg at 90 days (Baker et al.,
1994) to 33.4 (Snyman, unpubl.). The results obtained
in the Kenya study (Baker et al., 1994) are an indication of the impediment of the severely stressful environment prevailing in the sub-humid coastal region of
Kenya on WW. It also applied, although to a lesser
degree, to the results obtained by Inyangala et al.
(1991) at the Ol'Magogo Research Station in Kenya.
WW reported in all other investigations were almost
double those which were obtained in the Kenya studies. WW of Dorper lambs were also signi®cantly
(p0.05) higher than those of the DM, M and MM,
respectively (Basson et al., 1969; Schoeman, 1990),
but not signi®cantly different from the DorperFinn
composite lambs, although BW and dam weights
differed by 47 and 42%, respectively (Schoeman
et al., 1993). In the data of the National Sheep
Performance Testing Scheme (Table 4), WW of the
Dorper was lower than that of the MM, while only
lambs of the Afrino and Damara were smaller than
those of the Dorper.
Early weaning weights in accelerated lambing systems were reported by Basson et al. (1969), Schoeman
(1990) and Schoeman and Van der Merwe (1994) only
(Table 3). 50 dW was higher in the Dorper than in both
the DM and MM. These differences may be due to
variation in milk production, although it has as yet not
been investigated. Contrary to that, average pre-weaning weight (42 days) of Dorper lambs (Table 4) was
lower than those of all other breeds with the exception
of the Damara, which may be an indication of either
poor milk production or composition or inferior conditions under which the Dorper was maintained.
Despite the large differences in BW between the
Dorper and the DorperFinn cross-bred lambs and
mature weights of their dams, 50 dW were not signi®cantly different (Table 3), which might be the result
of a difference in milk composition as was suggested
by Schoeman et al. (1993). Carstens (1969) compared
the milk production of the Dorper with that of the
Dormer and obtained a signi®cantly (p0.05) higher
butterfat content in the milk of the Dormer, while yield
143
S.J. Schoeman / Small Ruminant Research 36 (2000) 137±146
Table 5
Comparative weights from 6 months to mature ewe weight of Dorper and cross-bred sheep
Parameter
Means for breeds/crossesa
D
Body weight (kg) at:
6-months
1/2 D
1/2 M
M
Sources
DM
MM
1/2 D 1/2
Finn. Comp
RM
RMX
21.1
24.5
22.0
25.5
Inyangala et al. (1991)
Inyangala et al. (1992)
9 months
26.8
29.8
27.4
30.6
Inyangala et al. (1991)
Inyangala et al. (1992)
12 months
49.8
33.7
36.5
19.7
44.7
34.8
37.7
18.4
Olivier et al. (1984)
Inyangala et al. (1991)
Inyangala et al. (1992)
Baker et al. (1998)
57.3
51.9
18 months
Mature ewe weight (kg)
b
61.0
74.0b
30.1
35.4
39.9
Olivier et al. (1984)
b
55.3
b
61.8
52.0b
26.2
Schoeman (1990)
Schoeman et al. (1993))
Baker et al. (1998)
a
For abbreviations, see Table 1.
b
p0.05.
was not signi®cantly (p>0.05) different between the
two breeds. Dormer lambs grew 10% faster than the
Dorpers, while total feed intake was not signi®cantly
(p>0.05) different. Growth rate between 50 and 100
days was 20% faster in the Dorper than in the MM
although mature weight was not signi®cantly p>0.05)
different between the two breeds (Schoeman, 1990).
Since these lambs were weaned early, the faster
growth rate could be the result of a higher growth
potential only.
3.3. Weights at later ages
Body weights from 6 months to mature ewe weight
are in Table 5. Dorper lambs and ewes were in most
cases heavier than those they were compared to,
except for the DorperRM crosses reported by Inyangala et al. (1991), where the opposite prevails. Body
weights at 12 and 18 months between Dorper, Merino
and their crosses were investigated by Olivier et al.
(1984) who found the Dorper to be approx. 40±45%
heavier than the Merino and approx. 10% heavier than
their crosses. DorperMerino crossbred lambs were
approx. 5±7% heavier than the mid-parent value,
indicating the contribution of heterosis. In the Kenya
studies (Inyangala et al., 1991, 1992; Baker et al.,
1998) DorperRM crosses were in most cases slightly
heavier than their Dorper counterparts and concluded
that the conditions under which the comparisons
were carried out seem to favour the DorperRM
crosses. Body weights reported by Inyangala et al.
(1992) were at all ages slightly higher than those
previously reported by the same authors (Inyangala
et al., 1991).
Mature body weights of Dorper ewes varied from
30.1 kg (Baker et al., 1998) to 74.0 kg (Schoeman
et al., 1993), a difference of 146%, resulting from the
large environmental constraints in the Kenya studies.
A mating weight of 72.3 kg was also reported for
Dorper ewes by Cloete and De Villiers (1987). Schoeman (1990) compared mature ewe weights of Dorper
with MM and DM (Table 5). Weights of the Dorper
and MM were not signi®cantly (p>0.05) different,
while the Dorper was on average 10% heavier than
the DM. Mature weight of the Dorper was also 42%
heavier than the Finn composites (Schoeman et al.,
1993), but only 15% heavier than the RM (Baker et al.,
1998).
Several authors (Carstens, 1969; Du Toit, 1996;
Snyman, unpubl.) compared growth performance of
the Dorper with other breeds from birth to slaughter.
Some of these results are summarized in Table 6.
144
S.J. Schoeman / Small Ruminant Research 36 (2000) 137±146
Table 6
Comparative growth performance and carcass grade from birth to slaughter in Dorper sheep in pure and cross-breeding evaluations
Means for breeds/crossesa
Parameter
D
Slaughter weight (kg)
41.4
Slaughter age (days)
ADG (birth to slaughter
(g/day))
191
297c
215
Highest grade (%)
a
M
39.2
43.6
363
379
A
Sources
1/2 IdF
1/2 M
1/2 A
1/2 M
1/2 S
1/2M
1/2MM
1/2M
1/2 D
1/2 M
40.9
39.9
38.8
40.0
39.5
DO
41.7
303
307
312
325
287
207
327b
102
15
196
22
9
33
23
46
Du Toit (1996)
Snyman (unpubl.)
Du Toit (1996)
Snyman (unpubl.)
Carstens (1969)
Snyman (unpubl.)
Du Toit (1996)
D ± Dorper; M ± Merino; A ± Afrino; IdF ± Ile de France; S ± Suffolk; MM ± South African Mutton Merino; Do ± Dormer.
p0.05.
b,c
In the study by Carstens (1969) Dorper and Dormer
lambs were pen-fed and slaughtered at a constant age
of 14 weeks, while in the studies of Du Toit (1996) and
Snyman (unpubl.) they grazed on natural veld until
slaughter at a constant live weight of approx. 40 kg.
Snyman (unpubl.) obtained a 10.8% faster growth rate
in the Dorper compared to their Afrino counterparts
and they reached target weight more than 20 days
earlier than the Afrino. Carstens (1969) reported a
10% faster growth rate in the Dormer. In the study
carried out by Du Toit (1996) the 1/2 Dorper 1/2
Merino lambs reached slaughter weight 76 days earlier than the Merino and 16 days earlier than the
second fastest growing, viz. the 1/2 Ile de France 1/
2 Merino lambs. Growth rate (ADG) was, however,
not reported by Du Toit (1996) since he failed to
record BW of lambs. The best carcass grades of the
eight groups were awarded to the 1/2 Dorper 1/2
Merino cross-bred lambs.
4. Productivity and ef®ciency
Little has as yet been done on the productivity and
productive ef®ciency of Dorper sheep compared to
other breeds or crosses. Some results are presented in
Table 7. The Dorper maintained a higher output and
were more ef®cient than either the DM, M or MM
(Basson et al., 1969; Schoeman, 1990). Expressed on a
per dam weight basis, productivity for the Dorper, DM
and MM were 57.5, 47.0 and 48.1 kg of lamb at 100
days per 100 kg of dam weight, respectively. In the
comparison between the Dorper, Afrino and Merino,
Snyman (unpubl.) reported total weaning weights (at
120 days) produced per ewe per year of 48.0, 43.2 and
22.3 kg, respectively. Basson et al. (1969) reported an
annual lamb production of 2.4, 1.8 and 1.8 for the
Dorper, DM and M, respectively with annual WW per
ewe of 64.3, 42.3 and 34.7 kg for the three breeds,
respectively. However, Finn composites produced
Table 7
Comparative productivity and ef®ciency parameters of Dorper sheep in pure and cross-breeding evaluationsa
Breed/cross
Dorper
Finn Comp.
Mutton Merino
DoÈhne Merino
a
b
Parameters
Totalb W/ewe/y (kg)
CW/100 kg bDDMI/ewelamb
Output at 100-day/ewe/y (kg)
Output/bW0.75
24.0
34.3
1.22
2.24
35.1
1.76
29.7
26.0
1.45
1.39
Sources: Schoeman (1990); Schoeman and Van der Merwe (1994); Schoeman et al. (1995).
CW ± cold carcass weight; DDMI ± digestable dry matter intake of lamb(s) and ewe; W ± mating weight of dam.
S.J. Schoeman / Small Ruminant Research 36 (2000) 137±146
74% more lambs than the Dorper and the total CW per
ewe was also 43 % higher in the Composites than in
the Dorper. Per 100 kg of dam weight the Dorper
produced 36.0 kg of lamb at 100 days, while the Finn
composite produced 51.0 kg (Schoeman and Van der
Merwe, 1994; Schoeman et al., 1995). The Composites were furthermore 84% more ef®cient in CW/
100 kg DDMI/ewe and lamb(s) than the Dorper. This
large difference in ef®ciency was obviously the result
of the combined effects of a higher reproductive rate,
smaller size of the dam and resulting lower maintenance requirements and the relatively higher growth
rate of the DorperComposite cross-bred lambs, compared to the Dorper.
In the investigation carried out by Du Toit (1996)
only gross income per 100 ewes available for mating
was reported. In this case the 1/2 Dorper 1/2 Merino
was 8% superior to the Merino from a lamb output
point of view. However, ¯eeces of Merino ewes were
contaminated with kempy ®bres to such an extent that
the use of Dorper rams on Merino ewes was not
recommended. This supports the earlier ®nding of
Olivier et al. (1984) who also obtained unacceptable
levels of kempy ®bres in the ¯eeces of White DorperMerino crosses.
145
Fig. 2. The in¯uence of genetic composition in Dorper, Red
Maaisai and crosses on packed blood cell volume (-^-) and faecal
egg counts (-&-). (Source: Baker et al., 1994).
Dorper sheep grazing on the same Karoo veld in South
Africa. Peak abundance of these ticks was reached
earlier in the Dorper as compared to the Merino. It also
reached signi®cantly (p0.05) higher levels in the
Dorper (mean17.9) than in the Merino (mean7.3).
These authors suggested that differences may be
related to differences in grazing patterns between
the two breeds.
6. Conclusions
5. Disease and parasite resistance
Resistance of Dorper ewes and lambs compared to
other and mostly indigenous sheep breeds to natural
and arti®cial infestation with Haemonchus contortus,
a gastrointestinal parasite endemic to Africa, was
studied in Kenya by Baker et al. (1994, 1998),
Mugambi et al. (1996, 1997) and Wanyangu et al.
(1997). In all these studies the RM indigenous breed
was more resistant, measured on faeceal egg counts
(FEC) and packed blood cell volume (PCV), than the
Dorper, Blackheaded Somali and Romney Marsh
breeds. PCV, a measure of anaemia, and FEC, a
measure of endoparasite infestation obtained from
faecal samples at 90 days in Dorper, RM and their
crosses are in Fig. 2. The higher the genetic contribution of the Dorper, the lower the PCV values and the
higher the FEC values, indicating that the Dorper is
not suitably adapted to these regions.
Fourie and Kok (1996) investigated tick resistance
(Ixodes rubicundus) to infestation in Merino and
Dorper sheep play an important role mainly in the
extensive grazing areas of South Africa, but also in
other parts of Africa. Owing to several socio-economical factors, Dorper sheep become more numerous at
the cost of woolled sheep numbers. Dorper sires are
also being used by commercial farmers in crossbreeding with woolled sheep breeds to the detriment
of the wool ¯eece quality. A lack of well-planned
cross-breeding studies is evident. Reports thus far
published were mostly based on small numbers in
ad hoc comparisons.
In comparative reproductive and growth studies the
Dorper was generally superior to woolled and other
indigenous breeds. It also compares favourably with
the specialized mutton breeds. Although generally
considered as being `well-adapted', the Dorper, however, proved to be unsuitable for commercial use in the
African tropics.
It is apparent that literature on comparative research
on Dorper sheep in both straight and cross-breeding is
146
S.J. Schoeman / Small Ruminant Research 36 (2000) 137±146
limited. Therein lies a challenge for researchers to
obtain more objective results in a variety of breeding
systems.
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in some indigenous breeds of sheep and goats in East Africa.
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1969. The productive and reproductive potential of three sheep
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conditions. Proc. S. Afr. Soc. Anim. Prod. 8, 149±154.
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ewes on three nutritional levels (in Afrikaans). MSc. (Agric.)
thesis, University of Stellenbosch.
Cloete, S.W.P., De Villiers, T.T., 1987. Production parameters for a
commercial Dorper ¯ock on extensive pasture. S. Afr. J. Anim.
Sci. 17, 121±127.
Du Toit, J.E.J., 1996. The performance of Merino crosses under
harsh conditions. Proc. All Africa Conference on Animal
Agriculture, 1±4 April 1996, Pretoria, pp. 3.2.15±16.
Eltawil, E.A., Narendran, R., 1969. Ewe productivity in four breeds
of sheep in Saudi Arabia. Wld. Rev. Anim. Prod. 25 (1), 93±
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paralysis tick (Ixodes rubicundus): A comparative study of
Merino and Dorper sheep. Onderstepoort J. Vet. Res. 63, 273±
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Greeff, J.C., Langenhoven, J., Wyma, G.A., 1993. Puberty and
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Gregory, K.E., Cundiff, L.V., Kock, R.M., 1991. Breed effects and
heterosis in advanced generations of composite populations for
growth traits in both sexes of beef cattle. J. Anim. Sci. 69,
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Inyangala, B.A.O., Itulya, S., Rege, J.E.O., 1991. Factors affecting
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productivity from indigenous sheep on small scale farms in
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Mugambi, J.M., Wanyangu, S.W., Bain, R.K., Owango, M.O.,
Duncan, J.L., Stear, M.J., 1996. Response of Dorper and Red
Maaisai lambs to trickle Haemonchus contortus infections. Res.
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Mugambi, J.M., Bain, R.K., Wanyangu, S.W., Ihiga, M.A., Duncan,
J.L., Murray, M., Stear, M.J., 1997. Resistance of four sheep
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Olivier, J.J., Marais, P.G., Cloete, J.A.N., 1984. Evaluering van
verskillende raskruisings in die ontwikkeling van 'n witwolvleisras: Die Afrino (Afrikaans). S. Afr. J. Anim. Sci. 14, 105±
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4th Wld. Cong. Genetics Appl. Livest. Prod., Vol 15,
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in crossbreeding with FinnsheepSubtropical ewe composites.
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Livest. Prod. Vol 18, Guelph, Canada, pp. 91±94.
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Assessment of the reproductive and growth performance of two
sheep composites, developed from the Finnish Landrace,
compared to the Dorper. S. Afr. J. Anim. Sci. 23, 207±210.
Schoeman, S.J., De Wet, R., Botha, M.A., Van der Merwe, C.A.,
1995. Comparative assessment of biological ef®ciency of
crossbred lambs from two composite lines and Dorper sheep.
Small Rumin. Res. 16, 61±67.
Snyman, M.A., unpubl. Genotype, environment and interaction
effects in three South African sheep breeds evaluated in two
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Stafford, K.J., Hansson, L., 1991. Sheep production in Zambia.
Bull. Anim. Hlth. Prod. Afr. 39, 61±68.
Visser, J.A., 1991. An evaluation of basic production characteristics
of three South African sheep genotypes under an intensive
production system, M.Sc. Agric. thesis, University of Pretoria.
Wanyangu, S.W., Mugambi, J.M., Bain, R.K., Duncan, J.L.,
Murray, M., Stear, M.J., 1997. Response to arti®cial and
subsequent natural infection with Haemonchus contortus in
Red Maasai and Dorper ewes. Vet. Parasitol. 69, 275±282.
A comparative assessment of Dorper sheep in different
production environments and systems
S.J. Schoeman*
Department of Animal Sciences, Faculty of Agriculture, University of Stellenbosch, Stellenbosch, South Africa
Abstract
Performance of Dorper sheep was compared to other breeds in pure and cross-breeding evaluations under different
production systems. The number of ewes lambed per ewe joint (EL/EJ) varied for the Dorper from 0.68 to 0.91 (average 0.81)
and for other breeds and crosses from 0.65 to 0.91 (average 0.82). Average litter size (LB/lambing) varied from 1.02 to 1.52
(average 1.28) and from 1.02 to 1.70 (average 1.30) for the two groups, respectively. In general, the Afrino and Finnish
composite lines were more proli®c than the Dorper. Post-weaning mortality rates in Kenya were high (49%) among Dorper
lambs compared to the local Red Maaisai breed, owing to a high susceptibility to gastrointestinal parasites. Average weaning
weights (WW) (100 days) were 12.4% heavier in the Dorper than in the breeds it was compared to, but 31.7% heavier than the
woolled breeds. Total WW and ef®ciency of Dorper and Dorper crosses were higher than Merino, Afrino, DoÈhne merino,
South African Mutton Merino, but lower than in Finnish Landrace composite lines. Both Dorper and Dorper cross-breeds
reached target slaughter weight of approx. 40 kg earlier than Merino, Afrino, Suffolk and Ile de France crosses. Average daily
gain to slaughter was 44% higher in the Dorper than the average of the groups it was compared to. It is concluded that the
Dorper was superior in reproductive and growth traits to woolled and other indigenous breeds. However, there is a lack of
information on the performance of the Dorper in cross-breeding systems. # 2000 Elsevier Science B.V. All rights reserved.
Keywords: Dorper sheep; Cross-breeding; Reproduction; Growth; Review
1. Introduction
Southern Africa has a rapid growing human population. This increase has resulted in a corresponding
increase in demand for meat and mutton. The per
capita consumption of mutton and lamb in South
Africa is 4 kg, which is high compared to many other
countries, while annual production is 107103 t and
annual demand 160103 t (Abst. Agric. Stat., 1997).
*
Fax: 27-21-808-4750.
E-mail address: [email protected] (S.J. Schoeman)
The total number of sheep in South Africa has
dropped from 36.5 million in 1965 to 25.4 million
in 1995, while the largest decline was in Merino
sheep numbers. For several decades sheep production
was primarily aimed towards wool production. However, this has changed during the past three decades
owing to inter alia the high demand for mutton and
lamb, the meat vs. wool price structure and input
costs. The numbers of mutton and dual-purpose-types
has consequently increased accordingly. Approximately 70% of all sheep are still woolled sheep
and mainly Merino or merino lines (e.g. the DoÈhne
Merino).
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 7 - 1
138
S.J. Schoeman / Small Ruminant Research 36 (2000) 137±146
The need of a breed suitable for lamb production in
the arid, extensive areas of southern Africa, resulted in
the formation of the Dorper. It became a popular
breed, not only in the extensive areas, but also in
other parts of southern Africa and consequently
became numerically the second most important sheep
breed in South Africa.
1.1. The state of cross-breeding in sheep
Combining appropriate breeds in cross-breeding
systems offers the opportunity to increase productive
ef®ciency through both additive and non-additive
genetic effects. Breed characterization programmes
have revealed large differences among breeds for a
variety of economic important traits. This is especially
evident in the beef cattle industry across the world
(Gregory et al., 1991). Cross-breeding among sheep
breeds is mostly practiced in countries of the Northern
Hemisphere, while in countries of the Southern Hemisphere wool production plays an important part in the
sheep industries.
Despite the decline in woolled sheep numbers, the
wool industry is still considered of great importance.
Cross-breeding woolled sheep with other breeds, and
especially those having hair, kempy or black ®bres in
their ¯eeces is highly opposed owing to the possibility
of contamination of wool ¯eeces. The wool industry,
supported by The South African National Wool
Growers' Association has launched a campaign
against the use of hairy breeds in cross-breeding with
woolled sheep. The Dorper is one of those also being
mentioned due to a high frequency of spotted and even
black lambs produced in woolled sheep. Dorper rams
are nevertheless being used by many farmers in crossbreeding with Merino ewes. However, owing to the
above-mentioned disapproval, little information is
available on the use of the Dorper in cross-breeding
systems.
White Dorper rams were used in the initial crossbreeding phase during the development of the
Afrino breed. Some of these results were reported
by Olivier et al. (1984). In a later study Du Toit (1996)
compared several sire breeds, including the White
Dorper, in cross-breeding with Merino ewes in extensive farming conditions. In this study, 50 Merino ewes
in each group were mated to ®ve fertility tested
rams of each breed. Performance characteristics and
relative gross income per 100 ewes were recorded in
this study.
The performance of composite lines, developed
from indigenous sheep breeds and the Finnish Landrace and subsequently crossed with Dorper rams, was
reported by Schoeman et al. (1993, 1995) and Schoeman and Van der Merwe (1994).
Dorper sheep were also exported to Zimbabwe,
Zambia, Kenya, Israel and Saudi Arabia. In Zambia
they are mainly owned by commercial farmers on
mixed farms in the central and southern provinces
(Stafford and Hansson, 1991). In various parts of
Africa attempts were made to assess the potential
of indigenous sheep breeds when crossed with Dorper
sheep. Stafford and Hansson (1991) mentioned that
indigenous sheep in Zambia, known as Rhodesian
sheep, were crossed with Dorper to improve productivity, while Red Maaisai sheep (RM) were crossed
and evaluated against the Dorper in Kenya (Inyangala
et al., 1991, 1992; Baker et al., 1994, 1998).
The objective of this paper is to review comparisons
in literature between Dorper and other breeds in pure
and cross-breeding systems.
2. Reproductive performance
The reproductive performance of Dorper sheep
and other breeds, as well as some of their crosses,
were compared under a variety of environmental
conditions. A summary of these results is shown in
Table 1.
2.1. Age at ®rst lambing
Differences in age at ®rst lambing were only
reported in one study (Schoeman, 1990), where the
Dorper was compared to two woolled-mutton breeds,
viz. the DoÈhne Merino (DM) and the South African
Mutton Merino (MM) in an accelerated lambing
system. Mean ®rst lambing age was 3 and 4 months
earlier in the Dorper compared to the other two breeds,
respectively. This is probably partly related to earlier
sexual maturity in the Dorper due to the contribution
of the early maturing Blackhead Persian (Visser,
1991), but also due to a longer natural breeding season
in the Dorper (Boshoff et al., 1975). In a comparison
between the Dorper and ewes of the composite lines,
139
S.J. Schoeman / Small Ruminant Research 36 (2000) 137±146
Table 1
Comparative reproductive performance of Dorper ewes in pure and cross-breeding evaluations
Parameter
Means for breeds/crossesa
D
b
EL/EJ (Fertility)
LB/lambing
(litter size)
0.91
0.83
0.88c
0.81
0.74d
0.68d
1.18
1.39c
1.52
1.50
1.08d
LB/EJ/year
1.02
1.57
1.46c
1.80
1/2 D
1/2 M
0.91
M
Sources
MM
0.85
0.65
DM
Finn
Comp
A
RM
SA
0.86
0.87c
0.80d
0.73
0.91c
0.77c
1.03
1.02
1.32d
1.32d
1.54
1.31
1.70
1.44c
1.02
1.18
1.42c
1.21
1.25d
1.26
1.76
Basson et al. (1969)
Olivier et al. (1984)
Schoeman (1990)
Eltawil and Narendran (1969)
Schoeman and Van der
Merwe (1994)
Baker et al. (1998)
Olivier et al. (1984)
Schoeman (1990)
Eltawil and Narendran (1969)
Snyman (unpubl.)
Schoeman and Van der
Merwe (1994)
Baker et al. (1998)
Basson et al. (1969)
Schoeman (1990)
Snyman (unpubl.)
a
D ± Dorper; M ± Merino; MM ± South African Mutton Merino; DM ± DoÈhne merino; Finn Comp. ± Finnish Landrace composite;
A ± Afrino; RM ± Red Maaisai; SA ± Saudi Arabian indigenous breeds (Najdi, Awassi and Harri).
b
EL ± number of ewes lambed; EJ ± number of ewes joint; LB ± number of lambs born.
c,d
p0.05.
developed from crosses between indigenous sheep
breeds in South Africa and the Finnish Landrace,
no difference was obtained in age at puberty (Schoeman et al., 1993). An earlier onset of puberty was also
reported by Greeff et al. (1993) in Romanov and
RomanovDorper cross-bred ewes as compared to
Dorper ewes.
2.2. Ewe fertility
The number of ewes lambing per ewe joint (EL/EJ)
varied in the Dorper from 0.68 (Baker et al., 1998) to
0.91 (Basson et al., 1969) (Table 1). The highest
fertility of 0.91 was recorded in the Dorper (Basson
et al., 1969), the (1/2)D (1/2)M cross-bred ewes
(Olivier et al., 1984) and the Finn composites (Schoeman and Van der Merwe, 1994), while the lowest value
of 0.65 was that reported by Olivier et al. (1984) in the
Merino. The study carried out by Olivier et al. (1984)
was under harsh dry Karoo-veld conditions, while in
the case of Basson et al. (1969) and Schoeman and Van
der Merwe (1994) comparisons were made where the
ewes were maintained in individual pens from mating
until weaning of their lambs. Baker et al. (1998) also
compared the Dorper to the local Red Maaisai sheep
breed (RM) in the sub-humid coastal region in Kenya
and reported an approx. 12% higher performance in
the RM. Generally, it appears that the Dorper has an
acceptable fertility rate which tends to be higher than
those of the woolled sheep breeds.
2.3. Litter size
Litter size (LB/lambing) in the Dorper varied from
1.02 (Baker et al., 1998) under extremely unfavourable conditions to 1.52 (Eltawil and Narendran, 1969)
in Saudi Arabia (Table 1). Average litter size in the
Dorper was 1.28 as compared to the 1.30 recorded in
the breeds it was compared to. It was higher than those
of the woolled breeds (Olivier et al., 1984; Schoeman,
1990; Snyman, unpubl.), approx. the same as in the
RM (Baker et al., 1998) but lower than in the Afrino
140
S.J. Schoeman / Small Ruminant Research 36 (2000) 137±146
(Snyman, unpubl.) and Finn composites (Schoeman
and Van der Merwe, 1994), respectively. In the latter
case (Schoeman and Van der Merwe, 1994), litter size
in the proli®c composite was 33% larger than in the
Dorper. In two other reports average litter sizes in
Dorper sheep of 1.59 (Cloete and De Villiers, 1987)
and 1.21 (Schoeman and Burger, 1992) were obtained,
respectively.
In a comparative study among maiden ewes of
Romanov, Dorper and RomanovDorper crosses,
ovulation rates of 1.9, 1.0 and 1.4, respectively, were
reported by Greeff et al. (1993). Age at ®rst oestrus
was also signi®cantly (p0.05) lower in the Romanov
and the crosses than in the Dorper. In both this study as
well as that of Schoeman and Van der Merwe (1994)
with the Finnish Landrace composite line, it was
indicated that a substantial increase in lambs born
could be obtained by the infusion of genes from
proli®c populations to the Dorper via the application
of appropriate cross-breeding programmes.
In an accelerated lambing system, where the ewes
were joint at 8-month intervals, lambing performance
per year (LB/EJ/y) was signi®cantly (p0.05) higher in
the Dorper (1.46) compared to the DM (1.25) (Schoeman, 1990). In an earlier study Basson et al. (1969)
reported corresponding values of 1.57, 1.21 and 1.18
for the Dorper, DM and Merino, respectively. In
another study (Schoeman and Van der Merwe,
1994) LB/LO (every 8 months) was 54% more
(p0.05) in the proli®c Finn composites than in the
Dorper (1.28 vs. 0.83). The Dorper could therefore
not be designated as a high proli®c breed, although
it compares favourably with most other breeds in
a variety of environmental and management conditions.
2.4. Survival rate
Survival rates of Dorper and Dorper crosses
were only compared by Olivier et al. (1984); Schoeman (1990); Baker et al. (1994); Snyman (unpubl.)
(Table 2). Higher neonatal mortalities among lambs
were reported by Olivier et al. (1984) when Merino
ewes were crossed with either Dorper or Dorset Horn
rams (6.1 and 7.1%, respectively) compared to the
Dorper (4.8%) and the Merino (3.5%), respectively. It
is well-known that the use of fast growing terminal sire
breeds tends to increase mortality at birth in both ewes
and lambs in the Merino.
Survival rates from birth to weaning were higher
(p0.05) in the Dorper than in the DM and Merino,
respectively (Schoeman, 1990; Snyman, unpubl.)
under fairly favourable conditions, but lower than in
the RM and RMDorper crosses between birth and
weaning (90 days) (Baker et al., 1994). However, from
weaning to 9 months of age mortality rates amongst
Dorper lambs were much higher than in the RM and
RMDorper crosses. Mortality rates declined as the
contribution of the RM in the crosses increased (see
Fig. 1).
In a later report by the same authors (Baker et al.,
1998), pre-weaning mortality rates of 10.3% for the
RM and 30.0% for the Dorper were obtained, while
corresponding post-weaning mortalities were 18.4 and
39.2%, respectively. These high mortality rates were
mainly caused by low resistance of Dorper lambs to
endoparasites (see Section 5). It was suggested by
these authors that although differences in pregnancy
rates and litter sizes were small, the number of lambs
weaned per ewes joint in the RM was almost double
that of the Dorper (0.61 vs. 0.34). It clearly shows that
Table 2
Comparative survival rates of Dorper lambs in pure and crossbreeding evaluations
Period
Birth ± 90 days
Birth ± 100 days
Birth ± 120 days
90 days to 9 months
a
Means for breeds/crossesa
D
M/DM
MM
0.81
0.84b
0.89
0.51
0.81c
0.78
0.83b
For abbreviations, see Table 1.
p0.05.
b,c
Sources
A
RM
RMX
0.88
0.89
0.90
0.78
0.88
Baker et al. (1994)
Schoeman (1990)
Snyman (unpubl.)
Baker et al. (1994)
141
S.J. Schoeman / Small Ruminant Research 36 (2000) 137±146
the Dorper, developed for the arid South African
conditions, is not suitably adapted to the humid tropical parts of Africa.
3. Body weights and growth performances
Body weight and growth performance are important
traits in all lamb-producing sheep breeds. This applies
to both the pre-weaning and post-weaning phases.
3.1. Birth weight
Fig. 1. The in¯uence of genetic composition in Dorper, Red
Maaisai and crosses on postweaning mortality rate (Source: Baker
et al., 1994).
Birth weight (BW) of Dorper lambs and those
they are compared to are in Table 3. BW of Dorper
Table 3
Comparative birth and weaning weights of Dorper lambs in pure and crossbreeding evaluations
Parameter
Means for breeds/crossesa
D
Birth weight
(kg)
4.2
1/2 D
1/2 M
M/DM
4.5
3.8
4.3c
3.8
4.0b
Sources
MM
26.8
22.1
85 days
90 days
100 days
4.6d
4.1
d
13.8
15.5
20.0
10.6
28.6
For abbreviations, see Table 1.
p0.05.
22.7
25.0c
25.8c
26.5c
23.7
Schoeman (1990)
Eltawil and Narendran
(1969)
Inyangala et al. (1991)
Inyangala et al. (1992)
Schoeman and Van der
Merwe (1994)
Snyman (unpubl.)
Schoeman (1990)
21.4
33.4
b,c,d
4.4
c
16.8b
120 days
a
SA
3.4c
16.3
16.0
19.4
11.8
32.0
28.6b
26.7c
RMX
3.7
4.2
b
75 days
RM
3.9
4.3
17.3c
A
Olivier et al. (1984)
3.7
4.1
5.0b
Weaning
weight (kg)
50 days
1/2 D 1/2
Finn Comp
32.2
16.1
19.8
11.3
Schoeman and Van der
Merwe (1994)
Basson et al. (1969)
Eltawil and Narendran
(1969)
Inyangala et al. (1991)
Inyangala et al. (1992)
Baker et al. (1994)
Olivier et al. (1984)
Schoeman (1990)
Schoeman and Van der
Merwe (1994)
Snyman (unpubl.)
142
S.J. Schoeman / Small Ruminant Research 36 (2000) 137±146
Table 4
Comparative birth, 42- and 100-day body weights of lambs of
different breedsa
Breed
Weights (kg) at
Birth
42-day
100-day
Dorper
Afrino
Corriedale
Damara
Dormer
Hampshire
Ile de France
Merino Landsheep
SA Mutton merino
Suffolk
4.4
3.5
4.0
3.6
3.5
3.4
4.2
3.6
3.5
3.4
16.4
19.0
16.5
13.0
20.5
19.5
17.9
18.9
18.5
20.0
29.2
24.9
31.5
23.7
35.9
36.8
33.4
36.4
33.4
35.0
a
Source: ARC ± Animal Improvement Institute (National
Sheep Performance Testing Scheme).
lambs were in most cases heavier than in the woolled
breeds, except for the MM which is also known to
have high BW and a high incidence of dystocia.
Average BW, 42-day weights and 100-day weights
of more than 117 000 records obtained from the
South African Sheep Performance Testing Scheme
for various breeds are in Table 4. There is no
obvious explanation for the high BW of the Dorper
in these data. These results could, however, be biased
since it does not take into account the effect of
differences in production environments and management levels. Dorper, Afrino and Damara sheep are
mostly found in the extensive grazing areas, whereas
some other breeds, e.g. the Ile de France and Hampshire are mostly farmed within intensive high input
systems.
In the comparison of the Dorper with the Finn
composites (Schoeman and Van der Merwe, 1994),
where both ewe groups were mated to the same Dorper
rams, BW of the Dorper exceeded that of the DorperFinn composite lambs by 47%, probably indicating a negative maternal effect restricting BW in the
composite lines. In this case an exceptionally high BW
of 5.0 kg compared to the other reports was recorded
in the Dorper, probably due to the very favourable
conditions in nutrition and management. In the Kenya
studies (Inyangala et al., 1991, 1992) BW of Dorper
lambs were almost identical to those of the DorperRM crosses.
3.2. Weaning weights
Weaning weights (WW) were recorded at various
ages, depending on whether an accelerated lambing
system or a traditional once-a-year lambing system
was applied. WW of Dorper lambs (Table 3) varied
considerably from 11.8 kg at 90 days (Baker et al.,
1994) to 33.4 (Snyman, unpubl.). The results obtained
in the Kenya study (Baker et al., 1994) are an indication of the impediment of the severely stressful environment prevailing in the sub-humid coastal region of
Kenya on WW. It also applied, although to a lesser
degree, to the results obtained by Inyangala et al.
(1991) at the Ol'Magogo Research Station in Kenya.
WW reported in all other investigations were almost
double those which were obtained in the Kenya studies. WW of Dorper lambs were also signi®cantly
(p0.05) higher than those of the DM, M and MM,
respectively (Basson et al., 1969; Schoeman, 1990),
but not signi®cantly different from the DorperFinn
composite lambs, although BW and dam weights
differed by 47 and 42%, respectively (Schoeman
et al., 1993). In the data of the National Sheep
Performance Testing Scheme (Table 4), WW of the
Dorper was lower than that of the MM, while only
lambs of the Afrino and Damara were smaller than
those of the Dorper.
Early weaning weights in accelerated lambing systems were reported by Basson et al. (1969), Schoeman
(1990) and Schoeman and Van der Merwe (1994) only
(Table 3). 50 dW was higher in the Dorper than in both
the DM and MM. These differences may be due to
variation in milk production, although it has as yet not
been investigated. Contrary to that, average pre-weaning weight (42 days) of Dorper lambs (Table 4) was
lower than those of all other breeds with the exception
of the Damara, which may be an indication of either
poor milk production or composition or inferior conditions under which the Dorper was maintained.
Despite the large differences in BW between the
Dorper and the DorperFinn cross-bred lambs and
mature weights of their dams, 50 dW were not signi®cantly different (Table 3), which might be the result
of a difference in milk composition as was suggested
by Schoeman et al. (1993). Carstens (1969) compared
the milk production of the Dorper with that of the
Dormer and obtained a signi®cantly (p0.05) higher
butterfat content in the milk of the Dormer, while yield
143
S.J. Schoeman / Small Ruminant Research 36 (2000) 137±146
Table 5
Comparative weights from 6 months to mature ewe weight of Dorper and cross-bred sheep
Parameter
Means for breeds/crossesa
D
Body weight (kg) at:
6-months
1/2 D
1/2 M
M
Sources
DM
MM
1/2 D 1/2
Finn. Comp
RM
RMX
21.1
24.5
22.0
25.5
Inyangala et al. (1991)
Inyangala et al. (1992)
9 months
26.8
29.8
27.4
30.6
Inyangala et al. (1991)
Inyangala et al. (1992)
12 months
49.8
33.7
36.5
19.7
44.7
34.8
37.7
18.4
Olivier et al. (1984)
Inyangala et al. (1991)
Inyangala et al. (1992)
Baker et al. (1998)
57.3
51.9
18 months
Mature ewe weight (kg)
b
61.0
74.0b
30.1
35.4
39.9
Olivier et al. (1984)
b
55.3
b
61.8
52.0b
26.2
Schoeman (1990)
Schoeman et al. (1993))
Baker et al. (1998)
a
For abbreviations, see Table 1.
b
p0.05.
was not signi®cantly (p>0.05) different between the
two breeds. Dormer lambs grew 10% faster than the
Dorpers, while total feed intake was not signi®cantly
(p>0.05) different. Growth rate between 50 and 100
days was 20% faster in the Dorper than in the MM
although mature weight was not signi®cantly p>0.05)
different between the two breeds (Schoeman, 1990).
Since these lambs were weaned early, the faster
growth rate could be the result of a higher growth
potential only.
3.3. Weights at later ages
Body weights from 6 months to mature ewe weight
are in Table 5. Dorper lambs and ewes were in most
cases heavier than those they were compared to,
except for the DorperRM crosses reported by Inyangala et al. (1991), where the opposite prevails. Body
weights at 12 and 18 months between Dorper, Merino
and their crosses were investigated by Olivier et al.
(1984) who found the Dorper to be approx. 40±45%
heavier than the Merino and approx. 10% heavier than
their crosses. DorperMerino crossbred lambs were
approx. 5±7% heavier than the mid-parent value,
indicating the contribution of heterosis. In the Kenya
studies (Inyangala et al., 1991, 1992; Baker et al.,
1998) DorperRM crosses were in most cases slightly
heavier than their Dorper counterparts and concluded
that the conditions under which the comparisons
were carried out seem to favour the DorperRM
crosses. Body weights reported by Inyangala et al.
(1992) were at all ages slightly higher than those
previously reported by the same authors (Inyangala
et al., 1991).
Mature body weights of Dorper ewes varied from
30.1 kg (Baker et al., 1998) to 74.0 kg (Schoeman
et al., 1993), a difference of 146%, resulting from the
large environmental constraints in the Kenya studies.
A mating weight of 72.3 kg was also reported for
Dorper ewes by Cloete and De Villiers (1987). Schoeman (1990) compared mature ewe weights of Dorper
with MM and DM (Table 5). Weights of the Dorper
and MM were not signi®cantly (p>0.05) different,
while the Dorper was on average 10% heavier than
the DM. Mature weight of the Dorper was also 42%
heavier than the Finn composites (Schoeman et al.,
1993), but only 15% heavier than the RM (Baker et al.,
1998).
Several authors (Carstens, 1969; Du Toit, 1996;
Snyman, unpubl.) compared growth performance of
the Dorper with other breeds from birth to slaughter.
Some of these results are summarized in Table 6.
144
S.J. Schoeman / Small Ruminant Research 36 (2000) 137±146
Table 6
Comparative growth performance and carcass grade from birth to slaughter in Dorper sheep in pure and cross-breeding evaluations
Means for breeds/crossesa
Parameter
D
Slaughter weight (kg)
41.4
Slaughter age (days)
ADG (birth to slaughter
(g/day))
191
297c
215
Highest grade (%)
a
M
39.2
43.6
363
379
A
Sources
1/2 IdF
1/2 M
1/2 A
1/2 M
1/2 S
1/2M
1/2MM
1/2M
1/2 D
1/2 M
40.9
39.9
38.8
40.0
39.5
DO
41.7
303
307
312
325
287
207
327b
102
15
196
22
9
33
23
46
Du Toit (1996)
Snyman (unpubl.)
Du Toit (1996)
Snyman (unpubl.)
Carstens (1969)
Snyman (unpubl.)
Du Toit (1996)
D ± Dorper; M ± Merino; A ± Afrino; IdF ± Ile de France; S ± Suffolk; MM ± South African Mutton Merino; Do ± Dormer.
p0.05.
b,c
In the study by Carstens (1969) Dorper and Dormer
lambs were pen-fed and slaughtered at a constant age
of 14 weeks, while in the studies of Du Toit (1996) and
Snyman (unpubl.) they grazed on natural veld until
slaughter at a constant live weight of approx. 40 kg.
Snyman (unpubl.) obtained a 10.8% faster growth rate
in the Dorper compared to their Afrino counterparts
and they reached target weight more than 20 days
earlier than the Afrino. Carstens (1969) reported a
10% faster growth rate in the Dormer. In the study
carried out by Du Toit (1996) the 1/2 Dorper 1/2
Merino lambs reached slaughter weight 76 days earlier than the Merino and 16 days earlier than the
second fastest growing, viz. the 1/2 Ile de France 1/
2 Merino lambs. Growth rate (ADG) was, however,
not reported by Du Toit (1996) since he failed to
record BW of lambs. The best carcass grades of the
eight groups were awarded to the 1/2 Dorper 1/2
Merino cross-bred lambs.
4. Productivity and ef®ciency
Little has as yet been done on the productivity and
productive ef®ciency of Dorper sheep compared to
other breeds or crosses. Some results are presented in
Table 7. The Dorper maintained a higher output and
were more ef®cient than either the DM, M or MM
(Basson et al., 1969; Schoeman, 1990). Expressed on a
per dam weight basis, productivity for the Dorper, DM
and MM were 57.5, 47.0 and 48.1 kg of lamb at 100
days per 100 kg of dam weight, respectively. In the
comparison between the Dorper, Afrino and Merino,
Snyman (unpubl.) reported total weaning weights (at
120 days) produced per ewe per year of 48.0, 43.2 and
22.3 kg, respectively. Basson et al. (1969) reported an
annual lamb production of 2.4, 1.8 and 1.8 for the
Dorper, DM and M, respectively with annual WW per
ewe of 64.3, 42.3 and 34.7 kg for the three breeds,
respectively. However, Finn composites produced
Table 7
Comparative productivity and ef®ciency parameters of Dorper sheep in pure and cross-breeding evaluationsa
Breed/cross
Dorper
Finn Comp.
Mutton Merino
DoÈhne Merino
a
b
Parameters
Totalb W/ewe/y (kg)
CW/100 kg bDDMI/ewelamb
Output at 100-day/ewe/y (kg)
Output/bW0.75
24.0
34.3
1.22
2.24
35.1
1.76
29.7
26.0
1.45
1.39
Sources: Schoeman (1990); Schoeman and Van der Merwe (1994); Schoeman et al. (1995).
CW ± cold carcass weight; DDMI ± digestable dry matter intake of lamb(s) and ewe; W ± mating weight of dam.
S.J. Schoeman / Small Ruminant Research 36 (2000) 137±146
74% more lambs than the Dorper and the total CW per
ewe was also 43 % higher in the Composites than in
the Dorper. Per 100 kg of dam weight the Dorper
produced 36.0 kg of lamb at 100 days, while the Finn
composite produced 51.0 kg (Schoeman and Van der
Merwe, 1994; Schoeman et al., 1995). The Composites were furthermore 84% more ef®cient in CW/
100 kg DDMI/ewe and lamb(s) than the Dorper. This
large difference in ef®ciency was obviously the result
of the combined effects of a higher reproductive rate,
smaller size of the dam and resulting lower maintenance requirements and the relatively higher growth
rate of the DorperComposite cross-bred lambs, compared to the Dorper.
In the investigation carried out by Du Toit (1996)
only gross income per 100 ewes available for mating
was reported. In this case the 1/2 Dorper 1/2 Merino
was 8% superior to the Merino from a lamb output
point of view. However, ¯eeces of Merino ewes were
contaminated with kempy ®bres to such an extent that
the use of Dorper rams on Merino ewes was not
recommended. This supports the earlier ®nding of
Olivier et al. (1984) who also obtained unacceptable
levels of kempy ®bres in the ¯eeces of White DorperMerino crosses.
145
Fig. 2. The in¯uence of genetic composition in Dorper, Red
Maaisai and crosses on packed blood cell volume (-^-) and faecal
egg counts (-&-). (Source: Baker et al., 1994).
Dorper sheep grazing on the same Karoo veld in South
Africa. Peak abundance of these ticks was reached
earlier in the Dorper as compared to the Merino. It also
reached signi®cantly (p0.05) higher levels in the
Dorper (mean17.9) than in the Merino (mean7.3).
These authors suggested that differences may be
related to differences in grazing patterns between
the two breeds.
6. Conclusions
5. Disease and parasite resistance
Resistance of Dorper ewes and lambs compared to
other and mostly indigenous sheep breeds to natural
and arti®cial infestation with Haemonchus contortus,
a gastrointestinal parasite endemic to Africa, was
studied in Kenya by Baker et al. (1994, 1998),
Mugambi et al. (1996, 1997) and Wanyangu et al.
(1997). In all these studies the RM indigenous breed
was more resistant, measured on faeceal egg counts
(FEC) and packed blood cell volume (PCV), than the
Dorper, Blackheaded Somali and Romney Marsh
breeds. PCV, a measure of anaemia, and FEC, a
measure of endoparasite infestation obtained from
faecal samples at 90 days in Dorper, RM and their
crosses are in Fig. 2. The higher the genetic contribution of the Dorper, the lower the PCV values and the
higher the FEC values, indicating that the Dorper is
not suitably adapted to these regions.
Fourie and Kok (1996) investigated tick resistance
(Ixodes rubicundus) to infestation in Merino and
Dorper sheep play an important role mainly in the
extensive grazing areas of South Africa, but also in
other parts of Africa. Owing to several socio-economical factors, Dorper sheep become more numerous at
the cost of woolled sheep numbers. Dorper sires are
also being used by commercial farmers in crossbreeding with woolled sheep breeds to the detriment
of the wool ¯eece quality. A lack of well-planned
cross-breeding studies is evident. Reports thus far
published were mostly based on small numbers in
ad hoc comparisons.
In comparative reproductive and growth studies the
Dorper was generally superior to woolled and other
indigenous breeds. It also compares favourably with
the specialized mutton breeds. Although generally
considered as being `well-adapted', the Dorper, however, proved to be unsuitable for commercial use in the
African tropics.
It is apparent that literature on comparative research
on Dorper sheep in both straight and cross-breeding is
146
S.J. Schoeman / Small Ruminant Research 36 (2000) 137±146
limited. Therein lies a challenge for researchers to
obtain more objective results in a variety of breeding
systems.
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