Browsing by Author "Dzama, Kennedy"
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- ItemAre we making genetic progress in growth performance and carcass characteristics in the South African Pig Industry>(2010) Dube B; Mulugeta SD; Van der Westhuizen RR; Dzama, Kennedy
- ItemDomestic free-range pig genetic resources in Southern Africa : progress and prospects(MDPI, 2020) Halimani, Tinyiko Edward; Mapiye, Obvious; Marandure, Tawanda; Januarie, Diedre; Imbayarwo-Chikosi, Venancio Edward; Dzama, KennedyPig genetic resources in Africa originate from different regions and were introduced through several migration pathways. Genetic analysis has shown a strong phylogeographic pattern, with pigs on the eastern parts showing a high frequency of alleles from the Far East while the ones on the western parts show a strong European influence. This highlights the influence of trade routes on the genetic legacy of African pigs. They have, however, since adapted to the local environments to produce unique populations with unique attributes. Most of the pigs are now reared in resource-constrained smallholdings under free-range conditions. They are largely owned by women who spread ownership of the resource through kinship networks. Very little work has been done to characterize, conserve, and sustainably utilize pig genetic resources in Southern Africa. The risk status of the breeds together with population numbers, distribution, and other attributes are largely unknown. This paper proposes several strategies for the sustainable utilization of the pig genetic resources: A market-driven in situ conservation program and two complementary ex situ strategies. In addition, the possibility of community-based breed improvement programs is discussed. It was concluded that genetic characterization of domestic free-range pig populations should be a supreme priority.
- ItemGenetic traits of relevance to sustainability of smallholder sheep farming systems in South Africa(MDPI, 2017) Molotsi, Annelin; Dube, Bekezela; Oosting, Simon; Marandure, Tawanda; Mapiye, Cletos; Cloete, Schalk; Dzama, KennedySustainable livestock production is important to ensure continuous availability of resources for future generations. Most smallholder livestock farming systems in developing countries have been perceived to be environmentally, socially and economically unsustainable. Farming with livestock that is robust and adaptable to harsh environments is important in developing countries especially in semi-arid and arid environments. This review discusses the different sheep farming systems employed by smallholder farmers and associated sustainability problems facing them. The review also gives an overview of sustainability indicators and limitations to the sustainability for the different smallholder sheep production systems in South Africa. It is argued that genetic diversity is important for sustainability and needs to be maintained in sheep for sustainable production and reproduction performance. The application of traditional breeding and genomics to ensure sustainable production is explored. Animal breeding approaches, specifically genomics can be applied to improve areas of environmental sustainability of smallholder sheep farming systems but must be targeted to the specific production environments, challenges, and opportunities of smallholder production. The genetic traits important for sustainability, the role of genomics in improving these traits and linking these genetic traits to different farming systems in South Africa are discussed.
- ItemGenetic variation in and relationships among faecal worm eggs recorded in different seasons of the year at the Tygerhoek farm in South Africa(AOSIS Publishing, 2017-07-07) Mpetile, Ziyanda; Dzama, Kennedy; Cloete, Schalk W. P.ENGLISH ABSTRACT: Gastrointestinal nematodes result in severe economic and production losses to the sheep industry. An increase in resistance of the nematodes to chemicals used for control, as well as a demand of consumers for meat products free from chemicals, has fostered research on alternative control strategies. Breeding for resistance to nematodes offers an alternative to control parasitism but its effectiveness depends on genetic variation in faecal worm egg count (FWEC), an indirect measure of parasite resistance. A historic dataset of FWEC from four Merino lines subjected to natural parasite challenge was used to estimate genetic parameters for FWEC in three seasons (autumn, winter and spring) using a repeated records animal model, followed by a three-trait animal model analysis treating FWEC in different seasons as separate traits. The effects of selection line, birth year, sex, the sex x birth year interaction, season and the season x year interaction were significant when using 4994 records recorded from 1997 to 2000 (p < 0.001). The heritability of log-transformed FWEC amounted to 0.09 ± 0.02, with no contribution from the animal permanent environmental variance to the between animal variation across seasons. Three-trait heritability estimates for log-transformed FWEC amounted to 0.07 ± 0.05 in autumn, 0.13 ± 0.05 in winter and 0.19 ± 0.05 in spring. These results suggest sufficient genetic variation in FWEC to support selection for lower log-transformed FWEC. However, the best time to record data for selection is after the break of the season in winter and in spring, when sheep are stimulated by a greater intake of infective larvae from the pasture after the first rains. Genetic correlations among FWEC in the respective seasons were moderate to high, ranging from 0.55 to 0.89. Phenotypic correlations, on the other hand, were significant but lower in magnitude, ranging from 0.09 to 0.16. These results provide useful information for developing strategies for the genetic improvement of ovine resistance to gastrointestinal nematodes under Mediterranean conditions in South Africa by using FWEC as an indicator trait.
- ItemGenomic population structure and prevalence of copy number variations in South African Nguni cattle(BioMed Central, 2015-11) Wang, Magretha Diane; Dzama, Kennedy; Hefer, Charles A.; Muchadeyi, Farai C.Background: Copy number variations (CNVs) are modifications in DNA structure comprising of deletions, duplications, insertions and complex multi-site variants. Although CNVs are proven to be involved in a variety of phenotypic discrepancies, the full extent and consequence of CNVs is yet to be understood. To date, no such genomic characterization has been performed in indigenous South African Nguni cattle. Nguni cattle are recognized for their ability to sustain harsh environmental conditions while exhibiting enhanced resistance to disease and parasites and are thought to comprise of up to nine different ecotypes. Methods: Illumina BovineSNP50 Beadchip data was utilized to investigate genomic population structure and the prevalence of CNVs in 492 South African Nguni cattle. PLINK, ADMIXTURE, R, gPLINK and Haploview software was utilized for quality control, population structure and haplotype block determination. PennCNV hidden Markov model identified CNVs and genes contained within and 10 Mb downstream from reported CNVs. PANTHER and Ensembl databases were subsequently utilized for gene annotation analyses. Results: Population structure analyses on Nguni cattle revealed 5 sub-populations with a possible sub-structure evident at K equal to 8. Four hundred and thirty three CNVs that formed 334 CNVRs ranging from 30 kb to 1 Mb in size are reported. Only 231 of the 492 animals demonstrated CNVRs. Two hundred and eighty nine genes were observed within CNVRs identified. Of these 149, 28, 44, 2 and 14 genes were unique to sub-populations A, B, C, D and E respectively. Gene ontology analyses demonstrated a number of pathways to be represented by respective genes, including immune response, response to abiotic stress and biological regulation processess. Conclusions: CNVs may explain part of the phenotypic diversity and the enhanced adaptation evident in Nguni cattle. Genes involved in a number of cellular components, biological processes and molecular functions are reported within CNVRs identified. The significance of such CNVRs and the possible effect thereof needs to be ascertained and may hold interesting insight into the functional and adaptive consequence of CNVs in cattle.
- ItemA gross margin analysis for Nguni cattle farmers in Limpopo Province, South Africa(Public Library of Science, 2021-06-24) Nkadimeng, Mapule Valencia; Makombe, Godswill; Mapiye, Obvious; Mapiye, Cletos; Oluwatay, Isaac; Dzama, Kennedy; Mojapelo, Cedric; Mollel, Naftali; Ngambi, Jones; Mautjana, Madimetja Human; Vasa, LaszloFactors such as increases in population, urbanization, growth in per capita income and changes in consumer taste and preferences are causing gradual increases in livestock product consumption and demand. South Africa is addressing this predicted increase in livestock products demand by commercializing smallholder livestock producers. The Limpopo Industrial Development Corporation (IDC) Nguni Cattle Development Project is an example of such effort. The economic performance of these efforts needs to be evaluated. We use gross margin analysis to evaluate the performance of the Limpopo IDC Nguni Cattle Development Project. Additionally, we use regression analysis to identify factors influencing gross margins. Our results indicate that although smallholders show potential to commercialize, they lack commercial farming experience and require that a strong extension support system be used as one of the strategies to improve profitability. We also noted that individual farmers were more profitable than group farmers. Multiple regression analysis shows that three variables could be used to stimulate gross margin among the Limpopo IDC Nguni Cattle Development Project farmers. These are herd size, distance to market and farm size. Since farm size is a given, policy should focus on assisting farmers to build their herds and to have better access to markets.
- ItemLivelihood, food and nutrition security in Southern Africa : what role do indigenous cattle genetic resources play?(MDPI, 2020) Mapiye, Obvious; Chikwanha, Obert C.; Makombe, Godswill; Dzama, Kennedy; Mapiye, CletosOf the 345 million people in the Southern African Development Community (SADC), 30.6% are severely food insecure, 8% malnourished and 50% live with less than US $1 per day, respectively. Livelihood, food and nutrition security have, therefore, become key priorities for the SADC region in response to these complex challenges. Given that 70% of the SADC population directly rely on agriculture for food, nutrition and income, sustained agricultural productivity may play an important role in achieving livelihood, food and nutrition security in the region. Being an important part of the agri-food system of marginalised communities in the region, cattle have great potential to contribute to the goal of reducing food and nutrition insecurity. The region has a population size of about 64 million cattle of which 75% of the population is kept under the smallholder farming systems, and primarily composed of indigenous tropical breeds. Most indigenous cattle breeds are, however, either undergoing rapid genetic dilution or at risk of extinction. At the same time, their environments, production and marketing systems are experiencing high rates of change in time and space. More importantly, indigenous cattle breeds in the region are undervalued. This makes it uncertain that future systems will have the adapted cattle breeds required for optimal livelihoods, food and nutrition security. To this end, the promotion of sustainable use of indigenous cattle for livelihood, food and nutrition security in the SADC region is strongly recommended.
- ItemStrategies for sustainable use of indigenous cattle genetic resources in southern Africa(MDPI, 2019-11-12) Mapiye, Cletos; Chikwanha, Obert C.; Chimonyo, Michael; Dzama, KennedyIndigenous cattle breeds are the most important livestock species in the Southern African Development Community (SADC) region owing to their role in human food, nutrition, income, and social security. Despite the role of these breeds in the household and national economies, they are currently underutilised, their productivity remains low, and populations are faced with extinction. In addition, there are insufficient measures taken to secure their present and future value. The current review highlights strategies for sustainable use of indigenous cattle genetic resources in the region, including the use of novel production and marketing practices, women and youth empowerment, and development of the appropriate capacity building, legislative, and policy structures. At present, the lack of coordination among the different stakeholders still poses a challenge to the implementation of these strategies. To this end, partnerships, collaboration, and stakeholders’ participation are recommended to effectively implement strategies for sustainable use of indigenous cattle breeds.
- ItemTowards a new phenotype for tick resistance in beef and dairy cattle : a review(CSIRO Publishing, 2019-07-04) Burrow, Heather M.; Mans, Ben J.; Cardoso, Fernando F.; Birkett, Michael A.; Kotze, Andrew C.; Hayes, Ben J.; Mapholi, Ntanganedzeni; Dzama, Kennedy; Marufu, Munyaradzi C.; Githaka, Naftaly W.; Djikeng, AppolinaireAbout 80% of the world’s cattle are affected by ticks and tick-borne diseases, both of which cause significant production losses. Cattle host resistance to ticks is the most important factor affecting the economics of tick control, but it is largely neglected in tick-control programs due to technical difficulties and costs associated with identifying individualanimal variation in resistance. The present paper reviews the scientific literature to identify factors affecting resistance of cattle to ticks and the biological mechanisms of host tick resistance, to develop alternative phenotype(s) for tick resistance. If new cost-effective phenotype(s) can be developed and validated, then tick resistance of cattle could be genetically improved using genomic selection, and incorporated into breeding objectives to simultaneously improve cattle productive attributes and tick resistance. The phenotype(s) could also be used to improve tick control by using cattle management.Onthe basis of the present review, it is recommended that three possible phenotypes (haemolytic analysis; measures of skin hypersensitivity reactions; simplified artificial tick infestations) be further developed to determine their practical feasibility for consistently, cost-effectively and reliably measuring cattle tick resistance in thousands of individual animals in commercial and smallholder farmer herds in tropical and subtropical areas globally. During evaluation of these potential new phenotypes, additional measurements should be included to determine the possibility of developing a volatile-based resistance phenotype, to simultaneously improve cattle resistance to both ticks and biting flies. Because the current measurements of volatile chemistry do not satisfy the requirements of a simple, cost-effective phenotype for use in commercial cattle herds, consideration should also be given to inclusion of potentially simpler measures to enable indirect genetic selection for volatile-based resistance to ticks.