Distribution, phenotype and factors influencing the production potential of Nguni sheep.

Abstract

The Nguni sheep of South Africa is an indigenous breed that is adapted to its environment. Migrating from Central Africa down the sweltering east coast of Africa down to Southern Africa, the sheep were exposed to different diseases. Survival of the fittest was synonymous with the breed, resulting in a breed harmonized with its environment. Nguni sheep that formed a part of this migration ended up as a remnant of the original sheep in KwaZulu-Natal. The sheep have been in South Africa for hundreds of years and the breed is primarily recognized by its geographical environment and by the people keeping the sheep than by breed herd books and breed societies. Conservation of the breed is important, but the sheep has to perform competitively with other breeds of sheep, and empirical research is needed to identify its superior characteristics. A survey was done in KwaZulu-Natal to locate Nguni sheep owners and to complete a questionnaire regarding their management and challenges. During the survey process, 52 farmers were found in four prominent agro-ecological zones in KZN, with a total of 1184 sheep. The largest flocks were found in the Ingwavuma zone with 347 animals among 11 owners. One of the primary management problems identified was the frequent death of lambs. Previous work with this breed suggests that this is often caused by gastro-intestinal nematode infection in young lambs. Reasons furnished for keeping the sheep was mostly for extra income and home consumption. The perception exists that the Nguni sheep does not compete with industrial sheep breeds such as the Dorper in terms of mutton production and therefore crossbreeding with Dorper and Merino is being practiced to improve the carcass quality of offspring. As a result, the original breed is now endangered and decisive efforts will have to be made to protect the pure Nguni sheep genome. Little is documented about the characteristics of the sheep, but many anecdotal concepts exist, defining what the phenotypic characteristics of the Nguni sheep should be. These characteristics were assessed by measuring traits such as heart girth, shoulder height, pelvis width, ear length and tail width. The measurements and observations were taken using the Nguni sheep flocks from the Dundee and Makhathini Research Stations. The Research Stations are situated in widely different bioclimatic regions, and the management of the two flocks differs also (intensive versus extensive). However, the original flocks are related because the Dundee flock was obtained from Makhathini in 2009. In the intervening nine years, measurable differences between the two flocks have developed. To investigate their performance when exposed to good and poor feed quality, the performance of Nguni sheep was examined under good (grazing maize) and poor (winter veld) nutritional circumstances. Merinos were used as a comparative breed. The Merino sheep were roughly double the size of the Nguni sheep. In this trial there was no significant difference (P>0.05) regarding lactating ewe performance within the nutritional treatments. There were also no significant differences (P>0.05) in the lamb growth within treatments between the breeds. Regarding ewe efficiency, the Nguni sheep ewes were more efficient over treatments than the Merino ewes. This data lead to the conclusion that the Nguni sheep has production comparable to that of the Merino. Under conditions of nutritional stress Nguni sheep tend to outperform Merino sheep. The final trial was to determine the relative levels of resistance or susceptibility of Nguni and Merino weaner lambs to gastrointestinal nematode (GIN) infection. This trial was done using lambs that were weaned from the winter trial mentioned above. They were placed on either Kikuyu or veld pasture for the summer. Faecal egg count (FEC) was to measure the level of GIN infection on the two different forages (as it is postulated that the inoculum level of GINs will be higher on the dense, humid environment in the Kikuyu). FEC indicated a significant difference (P<0.05), between the breeds, but there was no significant difference (P>0.05) between the two forage treatments. However, the Nguni weaner lambs in poor body condition could withstand GIN infection better than the Merino weaner lambs. An overall observation from the feeding trials was that if nutritional stress was removed, the Nguni sheep performed as well as an industrial sheep breed such as the Merino, although the mean Nguni live mass was approximately half that of the Merino weaners. The challenge for the future of the Nguni breed is to make the breed commercially attractive, i.e., with larger forequarters and hindquarters, without diluting the genome and losing the positive traits of the pure Nguni sheep. A cross with the Dorper breed, followed by back-crossing back to the Nguni parentage for seven generations, could be used to achieve this, with less than a 1% dilution of the genome. A detailed DNA fingerprint of the pure Nguni genome could be used to confirm the process.