This mini review aimed to discuss and compare the findings of a genotypic study done by Gor-nas et al., 2011 and some environmental and social factors discussed previously in Sudan. The main conclusion was the agreement of the genotypic analysis with the previous observations done on the phenotypic part. The important recommendation was to support the nomadic system so as to preserve the biodiversity of livestock in Sudan.
Sheep are highly adaptable and versatile domestic species, which has made them a critically important resource in human societies around the world. The beginning of livestock domestication, some 10000 - 11000 years ago in the fertile crescent, was a crucial event in human history. The earliest zoo-archaeological evidence for domestic sheep comes from sites in present day Iran, Turkey, and Cyprus [1-4].
Following Mesolithic man’s domestication of sheep approximately 8000 - 9000 years ago [
Molecular genetics has proven to be highly informative for investigating the relationships between animal populations as well as for documenting the levels of genetic variation resident within breeds. Variation within autosomal microsatellites has been used successfully to make inferences about population history [
Managing genetic diversity is one of the primary goals in a conservation program. In recent years there has been a growing interest not only in the implementation of methods for optimizing the election of the breeding individuals and the mating system but also in developing techniques for the analysis of genealogies and to monitor the changes in genetic diversity that has occurred in a conservation program [
The use of different statistical methods for analysis offered much information on relationships of genetic back ground of the breeds investigated. One of these valuable statistical tools is FIS (inbreeding coefficient).
FIS is one of three interrelated parameters to describe the genetic structure of diploid populations. These parameters are FIT, the correlation between gametes within an individual relative to the entire population; FIS the correlation between gametes within an individual relative to the sub-population to which that individual belongs; and FST the correlation between gametes chosen randomly from within the same subpopulation relative to the entire population [
In this review we aim to look for the effect of environment and human action on the phenotypic and genetic structure of some local Sudanese sheep breeds.
Sudan desert sheep are reared strictly within the semidesert belt of Sudan, in association with camels. They are owned exclusively by nomadic tribes of Arab origin or others closely related to them in the region. Because of their nomadic existence their origin is difficult to trace.
However, it is well established that nomadic Arab tribes entered Sudan through the West and north-western borders via northern Chad or southern Libya, reaching their ultimate destination at the river Nile [
Desert sheep homeland is roughly bound in the south by latitude 12˚N. The western border is marked by the range of rocky hills from Jebel Marra in the south to Zaghwa plateau in the north. To the east, the area extends to the Red sea hills. To the north it fades away with the undulating border in the Nubian desert [
This area is the main habitat of the most of Desert sheep breeds under nomadic system including Ashgar and Dubasi in Gezira scheme and Kabashi and Hamry in Kurdufan area. It also includes the Arid upland and West African breeds in Darfur area.
Sudan desert sheep, like other range sheep, do not tolerate prolonged confinement. Frequent shiftings of the camp and night bedding ground are always practiced for the animal’s well-being. The herder carries a few articles on his donkey, such as bag of grain flour, a water-skin, cooking and eating utensils and a netting bag. He keeps one or more dogs to protect the sheep from predatory animals at night [
The time of grazing varies between seasons. In dry seasons most of the grazing is done at night. The herders are aware of the benefit of night grazing in lessening water requirements and avoiding the stress of solar heat. In the rainy season the availability of drinking water and succulent grazing enables sheep to ingest their daily requirements in a few hours. Because of the mild temperature and frequent cloud, the sheep will continue to graze and lie down in the open air until late in the afternoon. Rainy season grazing is restricted to the period from 09:00 hours to about 16:00 hours when the plants are without dew. Diseases such as foot-rot and nematode infestation are known to result from grazing at night or early morning while the grasses are cold and damp [
The only desert member which is raised under semiresidential system is Dongla sheep, which is reared in the north by farmers in households. Dongla sheep was the only desert population found to have a high value of inbreeding coefficient (0.107) and also deviated from Hardy-Weinberg equation in the ILSTS011 locus [
Under tropical environmental conditions, sheep are raised primarily for meat, although milk is also of importance. The value of the breeding ewe is determined by the quantity and the quality of lamb or mutton produced and the length of its productive life.
Field collected data on the lambing rate of Sudan Desert sheep indicate wide range of difference between localities presumably attributable to climatic, nutritional and management factors [
Wide difference in lambing rates exist among individual flocks under semi-residential system maintained in irrigated areas [
The report of (SSMO, 2007) [
In an investigation done by Gornas et al., 2011 [
The locality and tribal origin of Desert sheep are identified in local market by their colours. In the central and south-eastern part of irrigated Gezira and Rahad, the sheep population is dominated by the Dubasi (Muslami) variety. They carry a black patch on the back (saddle), the muzzle and legs. The rest of the coat is white with coarse hairy fibres. Gornas et al. 2011, [
Vast areas of traditional grazing land of Dubasi and Ashgar have been converted into crop farms, where many nomadic families have settled. Their sheep spend dry season within or around the cropping areas and sustain themselves on crop residues. Encroachment on farms and damage to crops has caused a series of clashes between farmers and herdsmen and security forces have been frequently called to drive livestock away from the vicinity of farms [
The Hamary population in south-western Kordofan and south-eastern Darfur are predominately brown and dark brown. Whereas, the Kababesh of Northern Kordofan and Northern Darfur are multicoloured. The sheep in these areas have shorter legs and a heavy body, for here range grazing and drinking water are abundant, grazing distance is small and the seasonal migration is relatively small [
The lowest value of inbreeding coefficient was recorded in ND/Baggara (–0.009). This population is a crossbred between Nilotics and Desert breeds and owned by Baggara tribe nomads who move along Kurdufan area from south to north in specific time every year. This nomadic system give bigger chance for livestock to cross bred with other breeds and opportunity to look for better places of pasture which resulted in keeping the biodiversity of this population [
In the lake Chad basin and further north, live the northern Fulani tribes, the Balami, whose sheep are uniformly white, and the Auda, whose sheep are white with a brown or black neck and front body. Both breeds have a large frame, long legs and long thin tails. [
It is worth mentioning that Sudan Desert sheep and West African sheep undergo similar methods of management and exist in a similar ecological habitat. Many of their body features, such as the shape of the head and face, length of the body and texture of coat, are similar. Sudan Desert sheep, however, possess a thicker tail and fuller rump. These valuable characteristics might have been attributed to partial inheritance from their Asian ancestors [
Going South, the Nilotics population kept also the phenotypic structure of their relatives in west Africa , the Yankassa breed which was studied by Aebambo et al. (2003) [
As a conclusion of this mini-review, the genetic analysis of Sudanese sheep breeds stated in (Gornas et al., 2011) [
This work was supported by Central Laboratory, Ministry of Science and Technology, Khartoum, Sudan. The authors wish to thank the D.G, Animal Resources Research Corporation, Khartoum, Sudan for permission to publish this work.