Dorper Sheep Research Articles

Productive performance of hair and wool type Dorper sheep under extensive conditions

The reproductive performance, growth, slaughter traits, and several conformation characteristics in Dorper sheep (hair and wool types) were evaluated under extensive conditions in the north-western Karoo region of South Africa. From 1993 to 2000, lambs of hair ( n=1070) and wool ( n=1044) type Dorper sheep, and corresponding reproductive records from 872 and 874, respectively, were analysed. There was no significant differences between hair and wool type lambs for body weight from 42 days till 12 months of age, and for pre- or post-weaning growth rate. The analysis of conformation tend to suggest that the hair type lambs were blockier with shorter legs, compared to the leggier appearance of the wool type lambs. This is also evident from the longer carcass length (108.5 vs. 107.2 cm) and hind leg length of wool type lambs compared to hair type lambs. With regard to other carcass traits, wool type lambs had heavier carcasses (19.6 vs. 19.2 kg) and higher dressing percentage (49.9 vs. 49.0%), though, fat measurements and carcass grades were similar. The ewes of the hair type were heavier at mating than wool type (57.4 vs. 56.4 kg). No differences were, however, observed for percentage of ewes lambed, lambs born, lambs weaned, survival rate of lambs or kg lamb produced per ewe per year. It was concluded that the economically important reproduction and growth traits were similar between the hair and wool types of Dorper sheep. Differences that do occur in some conformation and carcass traits will not effect the economic realisation from the different types.

The growth of sheep scab lesions in relation to sheep breed and time of the year.

Numerically equal groups of between five and ten young Merino and Dorper sheep were artificially infested with sheep scab mites, Psoroptes ovis. Separate groups of sheep were infested during the early winter of two successive years as well as during the early summer of the second year. Lesion growth was measured at two-weekly intervals for a period of six weeks during the first winter and for eight weeks during the second winter and in the summer. The rate of lesion growth and mean lesion size on Merino sheep was significantly greater than that on Dorper sheep at each two-weekly recording during the winter of both years. The rate of growth of the lesions did not differ significantly between the two sheep breeds during summer, although, with the exception of eight weeks post-infestation, the mean lesion size on Merino sheep was significantly larger than that on Dorper sheep at each assessment.

Growth and mortality in sheep and goats under high tsetse challenge in Kenya.

Trypanosomosis is a major impediment to livestock production and economic development in those areas of Africa where it is endemic. Although small ruminants appear to perform better than cattle in various agro-ecological zones, the importance of trypanosomosis has not been extensively investigated in these livestock. This study was designed to investigate the prevalence of trypanosomosis in sheep and goats in an endemic area and to evaluate the performance of different breeds under high tsetse challenge and the potential role of chemoprophylaxis in the control of the disease. The results showed that tsetse flies feed readily on small ruminants, and that these animals are susceptible to trypanosomosis. The Small East African goats acquired fewer infections than the Black Head Persian and Dorper sheep used in the study. In both sheep and goats, chemoprophylaxis with isometamidium chloride (Samorin, Rhone Merieux, Annecy, France) was protective, resulting in fewer infections and higher body weight gain. Trypanosomosis caused anaemia in both sheep and goats, and animals whose PCV fell below 15% rarely recovered, even with trypanocidal drug treatment. The peak transmission period was between 1 and 3 months after the peak tsetse fly density, which raises the possibility of effective strategic prophylaxis.

Grazing behaviour and diet selection by Dorper sheep

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 scientific information on other behaviour aspects of this unique breed.

Status of Dorper sheep as hosts of ectoparasites

Seventeen ixodid tick species or subspecies have been collected from Dorper sheep in South Africa. The diseases transmitted or the conditions caused by these ticks in sheep are discussed. Although Dorper sheep may be infested with the scab mite, Psoroptes ovis, this does not seem to cause production losses. These sheep may, however, serve as a source of mite infestation for woolled sheep. The majority of Dorper sheep are infested with the larvae of the nasal bot fly, Oestrus ovis, they may also be subject to myiasis caused by the larvae of two calliphorid flies. In certain regions of the country Dorper sheep are prone to serious fly worry by female Simulium chutteri. Although Dorper sheep may be infested by various louse species these do not seem to reach large numbers or cause production losses.

Productive performance of Dorper sheep

The Dorper is a hardy South African composite breed, derived from a cross between the Black-headed Persian and the Dorset Horn. Dorpers are regarded as early-maturing, and ewes lambed at an age of 1 year in one study. Age at first lambing was higher in other literature sources cited. The fertility of Dorper ewes was approximately 0.90 ewes that lambed per ewe mated, with a litter size ranging from 1.45 to 1.60. The gestation length of Dorper ewes was approximately 147 days, while they were reported to start cycling as soon as 52 days after parturition. The pre-weaning survival of Dorper lambs was cited at approximately 0.90. Overall reproduction rate of Dorpers ranged from 0.99 to 1.40 lambs weaned per ewe mated, while it exceeded 1.40 lambs weaned per ewe mated per annum under accelerated mating conditions. Dorper lambs gained from 0.24 to 0.28 kg per day under vastly different environmental conditions. When weaned early at 2–3 months of age, post-weaning gains in excess of 0.18–0.20 kg per day were recorded. At slaughter, Dorper lambs had dressing percentages of approximately 50%. Two divergent genotypes in the breed (with a hairy or a woolly fleece cover) were evaluated under natural pasture conditions. No conclusive advantage in favour of either genotype could be demonstrated as far as productive traits were concerned. It was concluded that the breed adapts well to a wide variety of environmental conditions. In view of the scarcity of estimates of genetic parameters for the breed, the maintenance and expansion of datasets suitable for this purpose should receive high priority.

The development of the Dorper, its nutrition and a perspective of the grazing ruminant on veld

The development of the non-woolled Dorper sheep breed is briefly reviewed. Despite the large number of Dorpers in South Africa, precious little research results have been published on its nutrition under harsh, arid grazing conditions, especially since this has been an objective for creating and developing the breed. Results from the limited number of trials with free ranging Dorpers on natural pasture (veld) regarding diet selection, voluntary feed intake and rumen variables are used in conjunction with production data to create a nutritional perspective of the free ranging ruminant.

A comparative assessment of Dorper sheep in different production environments and systems

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 ( E L/ E J) 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 ( L B/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 prolific 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 efficiency of Dorper and Dorper crosses were higher than Merino, Afrino, Döhne 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.

The history of the Dorper sheep

This short history of the Dorper sheep traces its background and the steps taken to develop that breed in South Africa. The most important traits considered for the developing of the Dorper are listed and the breeding system outlined. The development of the White Dorper is also detailed and the breed improvement programs are indicated.

Voluntary intake of maize stover supplemented by urea lick in dorper and local Malawi sheep.

Ten Dorper (16.0 to 37.0 kg) and Local (12.0 to 28.5kg) rams were used to determine the voluntary intake, digestibility, nitrogen retention of maize stover and live weight change. Dietary treatments were maize stover offered to meet the requirement for maintenance with urea lick, 1.5 or 2 times maintenance with urea lick. Stover stems had higher fibre content (78.5 % NDF) and lower content of nitrogen (0.34 %) and metabolizable energy than leaves. The sheep consumed leaves and rejected all stems. Intake of maize stover increased (P < 0.001) with increasing level of feed offered above maintenance. Sheep offered stover at 1.5 times maintenance had highest intake of stover (24.7 g/kg body weight) and nitrogen (1.5 % feed intake). There were no differences in intake between levels higher than maintenance. Digestibility was highest (P < 0.01) for sheep offered stover at 1.5 times maintenance. Higher nitrogen intake of stover diet increased digestibility and intake of dry matter owing to the stimulation of microbial activity. Liveweight gain was higher (P < 0.05) for sheep offered stover at 1.5 times maintenance (52 g/day) reflecting high intake, while sheep offered stover at maintenance lost weight (-105 g/day). Metabolizable energy intake increased with increasing total dry matter intake. Nitrogen balance was positive for diets with nitrogen intake of more than 1 % of feed intake. Nitrogen retention increased with high nitrogen intake. Breeds did not differ in voluntary intake. Dorper sheep had higher digestibility, higher nitrogen retention and gained more weight than local sheep (P < 0.001). It was concluded that for sheep fed low quality maize stover, voluntary intake, digestibility, nitrogen retention and liveweight gain increased by offering greater amounts of stover with high nitrogen intake (1 % feed intake). Differences in digestibility suggest that the Dorper breed could be a valuable resource for sheep production even in areas where low quality maize stover limit the use of European breeds.UNISWA Jnl of Agric Vol 8 1999: pp 44-49

Genetic resistance to endoparasites in sheep and goats. A review of genetic resistance to gastrointestinal nematode parasites in sheep and goats in the tropics and evidence for resistance in some sheep and goat breeds in sub-humid coastal Kenya

SummaryThe evidence for both between- and within- breed genetic variation for resistance to gastrointestinal (GI) nematode parasites is reviewed. It is concluded that much of the published research on breed characterisation for resistance suffers from poor experimental design. Prior to the initiation of a 6-year study that has just been completed in coastal Kenya there were no estimates of within-breed genetic variation (i.e. heritabilities) of resistance in sheep or goats in the tropics. This study has confirmed that Red Maasai sheep and Small East African (SEA) goats are more resistant to GI parasites (predominantly Haemonchus contortus) than Dorper sheep and Galla goats. Heritability estimates for logarithm transformed faecal egg counts (an indicator of resistance) in 8-month-old lambs was 0.18±0.08 for all lambs, but higher in the susceptible Dorper-sired lambs (0.35±0.16) than in the resistant Red Maasai-sired lambs (0.06±0.07). This difference in heritability suggests that many centuries of natural selection have fixed most of the genes for resistance in the Red Maasai sheep. The resistant Red Maasai sheep and SEA goats were two to three times more productive than the susceptible Dorper sheep and Galla goats in the sub-humid coastal Kenya environment.

Interbreed differences in the efficacy of 1% deltamethrin pour-on to protect small livestock against infestation with Ixodes rubicundus (Acari: Ixodidae)

Synthetic pyrethroid pour-on compounds have been developed for use on cattle but many are now also registered for the control of ectoparasites on small ruminants. The breed of small livestock has been known to influence the efficacy of various pour-ons and we hypothesized that differences in the duration of protection afforded by a synthetic pyrethroid pour-on against ticks on small livestock, would be greatest between hairy and woolly breeds. Angora goats with mohair, Dorper sheep with hairy wool, and Merino sheep with wool were treated with 1% m/v deltamethrin pour-on with an oil base at a dosage rate of 1 ml 5kg −1 body mass. The duration of effective protection against Ixodes rubicundus, the Karoo paralysis tick, was determined under field conditions. Angora goats proved to be the highest risk group, but were afforded the least protection. Efficacy never reached 100% in this group and within 3 weeks the goats were already at risk of paralysis. Dorper sheep were afforded above 90% protection for 3 weeks and 85% after 4 weeks. In the case of the Merino sheep efficacy of protection remained above 90% up to 7 weeks post-treatment and was still 87% during Week 8. Differences in the amount of sebum and suint in the epidermis of the different breeds may be responsible for differences in the rate of spread and the rate of dilution of the active compound in the epidermis.

Diet selection by sheep and goats in the Noorsveld

Abstract The diet selection of Angora and Boer goats, and Dorper and Merino sheep was studied in the Noorsveld to ascertain differences in their food preferences. This information will facilitate the identification of possible goat and sheep combinations to improve the utilization of this veld type. Dorper and Merino sheep and Angora goats selected very similar diets while the diet selected by Boer goats differed by approximately 30% from those of the other animals. We therefore hypothesise that a combination of Boer goats and either Merino or Dorper sheep in the appropriate ratio could lead to the improved utilization of Noorsveld. This needs further investigation as intake of preferred plants may additionally play an important role in establishing better stock ratios.

Diet selection by sheep and goats in the Arid Karoo

Abstract The diet selected by Afrino, Dorper and Merino sheep, and Angora goats was studied in the Arid Karoo at Carnarvon. The diets selected by these small stock species and breeds was established through breed by breed comparisons, with a view to raising the stocking rate by combining different breeds. It was established by means of the d‐index, that the diets differed by only 4% to 5% during the growing season. This margin is too small to recommend combining small stock breeds in an effort to ensure greater utilization efficiency through multiple use of the vegetation. During the dormant seasons the diets differed by 14% to 21%. Although this represents a large margin, stocking rate adjustments are made on the basis of the growing season's results.

Comparative assessment of biological efficiency of crossbred lambs from two Composite lines and Dorper sheep

Reproduction, growth and biological efficiency of two Composite dam lines, developed from Finnsheep and indigenous breeds, were investigated and compared to Dorpers. Composite and Dorper ewes were mated to Dorper rams. Ewes were exposed to three 30-d joining periods in 2 years. Litter size was 1.35, 1.48 and 1.08 lambs born to Composites 1, 2 and Dorpers, respectively. Lambs born per lambing opportunity (fecundity) were 0.88, 0.93 and 0.75 for the three groups, respectively. Birth weights (BW) of lambs of Dorper ewes were higher than those of Composite ewes ( P ⩽ 0.05), but not weaning weight (WW) (at approx. 63 d) or 100 d weight (100 W). Cumulative DDM intake (DDMI) was 49% greater in Dorper ewes than in Composites. Total carcass weight (CW) and carcass energy content produced (E) per ewe was higher in Dorper, while CW/ 100 kg DDMI and E/kg DDMI were higher in Composites. In terms of these efficiency parameters, Composites were 84 and 79% more efficient than Dorpers in the 2-yr period. Ewes producing twins were 43% more efficient than those producing singles. Optimum efficiency was calculated at approx. one twin slaughtered every 8 months. Results demonstrated that owing to the outstanding performance and small size of these Composites, efficiency can be improved considerably by using them in crossbreeding systems.

Identification de &lt;em&gt;Cowdria ruminantium&lt;/em&gt; dans la tique &lt;em&gt;Amblyomma gemma&lt;/em&gt; par une sonde ADN, pCS 20

Amblyomma gemma ticks were collected from wild animals on a 20,000 acre game ranch in a heartwater endemic area in Kenya, close to Nairobi. A. variegatum is the main vector of heartwater in Kenya. E.A. LEWIS, 1947, in a one sentence report has implicated A. gemma to be a vector of heartwater without giving any details. Adult A. gemma were collected from giraffe Giraffa camelopardalis, hartebeest Alcephalus busephalus, Eland Taurotragus oryx and ostrich Struthio camelus during cropping exercises. The unengorged ticks were fed on 3 susceptible Dorper sheep which were monitored daily for the clinical symptoms of heartwater. All the ticks, including those that were fed on sheep were dissected and the guts probed for the presence of Cowdria ruminantium using a cloned DNA probe, the pCS20. None of the sheep on which the ticks were fed showed heartwater symptoms up to 60 days from the attachment of the ticks. The DNA probe identified Cowdria ruminantium in the ticks collected from eland and giraffe.

Body mass loss and body fluid shifts during dehydration in Dorper sheep

SUMMARYDorper sheep are raised in extreme desert areas. Body mass loss and body fluid shifts were measured in Dorper rams denied water for 4 days and offered only wheat straw. The rams lost 16·3% body mass, 22·0% total body water volume, 35·1 % extracellular fluid volume and 41·7% plasma volume. On first drinking following dehydration, Dorpers were able to consume 19·7% of their dehydrated body mass and 100·3 % of their body mass loss. It was concluded that Dorpers can survive in harsh deserts through their ability to withstand dehydration and quickly replenish body mass losses when water becomes available.

Performance of Dorper sheep under an accelerated lambing system

Lambing records from 1984 to 1989 comprising 699 ewe lambing years were used. Ewes were exposed to three fixed 30-d joining periods/yr to lamb during February/March (first season), June/July (second season) and October/November (third season). Number of ewes lambed/ewes joined/yr was 0.85, and the number of lambs born/ewe joined/yr was 1.21. Average litter size was 1.41 with a repeatability estimate of 0.32. Average survival rate from birth to 100 d was 0.83. Most reproductive parameters were influenced by year, season, dam age, sex and type of birth. Pre-joining BW (average 61.3 kg) was an unimportant predictor, except in the case of rate of lambing (interval between date of ram introduction and date of lambing). Average age at first lambing was 19.6 months and was influenced by season of birth only. Conception rates were 0.51, 0.56 and 0.68 for the three seasons, respectively, indicating higher oestrous activity during the third season, which was confirmed in the faster rate of lambing during this season. Average birth, weaning (at approx. 52.8 d of age) and 100-d weights were 4.2, 18.2 and 27.9 kg, respectively. Growth performance was suppressed in lambs born in the third season. Average pre-weaning daily gain was 264 g/d. Post-weaning daily gain up to 100 d of age was 205 g/d. Influence of year, season of birth, age of ewe, ewe pre-mating BW, sex of lamb, birth type, and first-order interactions were investigated. Weight at 100 d was significantly ( P < 0.001) influenced by all variables tested. Birth weight was significantly ( P < 0.05) affected by all variables except for year of birth, and weaning weight ( P < 0.01) by all variables except for pre-mating BW. Productivity, expressed as lamb output was 18.7 and 31.4 kg at weaning and 100 d, respectively, and was significantly ( P < 0.01) affected by year and age of ewe, but not their interaction or ewe pre-mating BW. Seasonal limitations on both reproduction and growth were indicated. Management practices to improve productivity are proposed.

Phenotypic and genetic parameters of weaning traits in Dorper sheep in Zimbabwe

Data on weight and conformation score of 2466 Dorper lambs at weaning obtained over three lambing seasons in each of five years were analysed by least-squares procedures. Year-season of birth, rearing class, weaning age, age of dam and sex of lamb were significant sources of variation in weaning weight, and, with the exception of sex of lamb, in conformation score as well. Heritability estimates for weaning weight and conformation score were 0.19 and 0.09, and repeatability estimates 0.27 and 0.10, respectively. The heritability estimate for weaning weight was larger in twin lambs, than in singles. The genetic correlation between weaning weight and conformation score was 0.47.

Evaluation of shrub species for sheep grazing in the Strandveld of the Cape West Coast of South Africa

The production of three exotic shrub species, Atriplex nummularia (old man saltbush), A. canescens (four‐winged salt‐bush) and Medicago arborea (tree lucerne) and one indigenous evergreen shrub, Chrysanthemoides monilifera subsp. pisifera (west coast bitou), was evaluated in the Strandveld of the Cape West Coast in terms of grazing capacity (ssu ha−1) and average daily gain (ADG) (g ssu−1 day−1) using mature Dorper sheep. Medicago arborea died out during the first season. The other three shrubs, however, survived and over a seven‐year period mean grazing capacities of 1.7, 1.6 and 1.0 ssu ha−1 were obtained, respectively, for C. monilifera, A. nummularia and A. canescens, which is in excess of the area norm of 5 ha ssu−1 for natural veld. Positive ADGs of 80 and 30 g ssu−1 day−1 were obtained on A. nummularia and A. canescens, respectively, but not on C. monilifera (‐180 g ssu−1 day−1).