Agriculture

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Browsing Agriculture by Author "Bezuidenhout, C.C."

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    Genetic variation between and within six selected South African sheep breeds using random amplified polymorphic DNA and protein markers
    (2011) Hlophe, Sambulo Revelation; Kunene, N.W.; Bezuidenhout, C.C.; Opoku, A.R.
    Six South Africa sheep breeds comprised of indigenous, imported and locally developed sheep were sampled. These breeds include Nguni sheep (Zulu, Swazi and Pedi), South African Merino, Damara and Dorper. Nguni goats were used as an out group. The first objective of this study was to determine the intra and inter-population genetic relationships among six South African (SA) sheep breeds using random amplified polymorphic DNA (RAPD) and protein markers. The second objective was to compare the efficiency between RAPD and protein markers in assessing the genetic variation. The Nei‟s genetic distance produced by the RAPD analysis ranged from 0.0430 – 0.1193 for the six selected sheep breeds. The results indicated that Zulu and Swazi breeds were the most genetically identical with a genetic distance of 0.0430. The second closest sheep breeds were the SA Merino and Damara with a genetic distance of 0.0595. The Pedi was related to the Dorper sheep breed with a genetic distance of 0.0814. The greatest genetic distance was between the Pedi and the SA Merino (0.1193) indicating that these two breeds are relatively distant from one another. Genetic identity was the largest (0.9579) between Swazi and Zulu breeds, followed by 0.9423 between SA Merino and Damara breeds. On the UPGMA dendogram the Zulu sheep formed a cluster with the Swazi sheep and the Damara clustered with the SA Merino. The Nguni goats did not cluster with the sheep breeds. The degree of genetic similarity within the sheep breeds ranged from 66.48 - 88.48 percent. The relationship within the Zulu sheep breed was 72.77%, Pedi 70.76%, Dorper 75.38% and Damara 83.24%. The Swazi sheep breed demonstrated the lowest percentage (66.48%) of genetic similarities between the individuals. On the other hand, the SA Merino breed with 88.48% showed the highest percentage of genetic similarity. When using the iso-enzymes of transferrin, the Damara and SA Merino formed a cluster with a genetic similarity of 97.13%. Just as in the RAPD results, the Pedi did not form a cluster with other Nguni sheep. The transferrin profile was able to characterise the Nguni goats as an out group species. The dendogram constructed using the data of the protein profile could not differentiate clearly between the sheep breeds and the Nguni goats. It can be concluded that although genetic relationships exist, the genetic distances vary among the six sheep breeds. The RAPD analysis demonstrated that these breeds can be treated differently. The genetic variation gave an indication that some breeds such as South African Merino are more uniform. The study showed that the RAPD markers can be used as a tool to estimate the genetic diversity and phylogenetic relationships among breeds of sheep. However, the protein markers must be used with caution. It is recommended that more research should be done to determine the genetic origin of the three Nguni sheep breeds (Zulu, Swazi and Pedi).
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    Phenotypic characterization of Zulu sheep: implications for conservation and improvement
    (University of Zululand, 2012) Mavule, Bafowethu Sibanda; Kunene, N.W.; Bezuidenhout, C.C.
    Understanding the characteristics of the Zulu sheep breed in its home tract is an essential step towards the development of a sustainable conservation and improvement programme. A survey was conducted in 11 rural areas of KwaZulu-Natal in the quest to (i) describe traditional Zulu sheep production systems, (ii) describe the morphological structure of the breed, and (iii) to quantify morphological variation among sheep populations. Most farmers began sheep production with an initial stock size of less than four, either bought from other farmers or inherited. Sheep were mainly used as a source of food and income. Flock sizes were 39.8±7.5 on average, with each flock constituting of 3.12±0.31 rams, 21.8±5.61 ewes, 5.0±0.87 yearlings and 9.9±2.05 lambs. About 28.0% of the flocks occurred in isolation while 43.7% interacted with two or fewer neighbouring flocks. There was about 7.4% decrease in sheep numbers in the past 5 years. Drought and diseases were the major causes of sheep loss. Principal component analysis of morphometric traits extracted two components with a total variance of 66.9% in young sheep and four components in adult sheep with a total variance of 62.1%. The first factor (PC1) in each case had high loadings for variables relating to body size, while PC2 had high association with traits reflecting body shape. PC3 had high factor loadings for head length and head width, representing head size. The use of principal components was more appropriate than the use of original correlated variables in predicting body weight of Zulu sheep. Dark brown was the most prevalent coat colour. It occurred as either solid or mixed with white. Sheep from Nqutu measured highest in most morphometric variables whilst sheep from Empangeni measured lowest. Discriminant analysis identified rump width (RW), head width vi (HW), heart girth (HG), thorax depth (TD) and tail length (TL) as the most discriminative variables in differentiating Zulu sheep populations. Two major groups were identified by cluster analysis, one formed by Empangeni, Mtubatuba and Nongoma and the other by Jozini Msinga and Eshowe populations. Estcourt and Nqutu joined these major groups as individual entities at distance with the latter being furthest. Discriminant function analysis was able to correctly classify 62.2% of individual sheep into their original populations. The high morphological variation among Zulu sheep populations, infer considerable genetic variability. Maintaining this genetic variation is important if the goal is to continue and improve the productive performance of the animals and respond to change in climate, disease or consumer preference while improving the livelihoods and food security of livestock keepers.