SECTION of DOCUMENT:
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SESSION I: IMPACT OF GENETIC ENGINEERING ON AGRICULTURE
POSSIBLE IMPACT OF GENETIC ENGINEERING ON ZIMBABWE AGRICULTURE
S.S. Mlambo 1 and S.B. McCarter2
The prehistoric era in human civilization was characterized by hunting for food, and was succeeded in time by domestication of crops for food, fibre and fuel. At the beginning of the modern calendar in 0 A.D, the global population was around 300 million. There was plenty of fertile land to satisfy the needs of human population on this planet.
Figure 1. A Profile of Population Growth
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However, as population growth accelerated, the need for food also grew and we have now reached a situation where the production of food is struggling to keep pace with the demand of the growing population. In 1994 human population on earth was 5.7 billion and by 2025 it is expected that it will touch 8.5 billion (figure 1). It is abundantly clear with such rapidly increasing populations that agricultural productivity must also be accelerated.
IMPROVEMENT IN FOOD PRODUCTION
In the early days of civilization the improvement in food production was based on domestication and natural selection of a relatively limited range of crops . This procedure was succeeded by deliberate selection or plant breeding. In the last century the accumulation of desirable genes in crops of economic importance has resulted in a tremendous increase in yields. The green revolution of Asia, particularly with reference to wheat and rice, is an example of this success story. However, the phenomenal increase in crop productivity in Asia to a certain extent needed additional inputs in the form of chemical fertilizers, pesticides and irrigation. It appears that in spite of this available technology and products, Africa as a whole has continued to show declining per capita agriculture productivity (figure 2). Hence the problems of food insecurity, malnutrition and poverty gained the upper hand on human endeavors, a trend which must be reversed as productivity per unit of land will need to double over the next twenty years in order to meet the demands of increasing numbers of people
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Increasing shortages of food, particularly in Africa has been caused by:
The combination of these factors has resulted in low food productivity per unit area, critical availability of dietary intake, poverty and malnutrition (Andandajayasekeram and Rukuni, 1999).
RECOURSE TO BIOTECHNOLOGY AND GENETIC ENGINEERING
Conventional breeding through transfer of pollen and semen in plants and animals respectively is a time consuming process. For example it takes approximately 10 years to develop an improved more productive maize variety. This process is relatively slow due to the number of generations required to cross, select and evaluate new progenies. The process is as efficient as the breeders experience with the crop and their ability to measure productivity gains in the target farmers fields. In the United States maize yields in the pre-biotechnology era were increasing at a rate of 1% per year with approximately 50% of this gain from plant breeding and 50% from improved management practices.
In 1997/98 the United States planted 32.6 million hectares of maize with an average yield of 8.06 tones /hectare. Total production was estimated at 263 million tonnes of which some 20% was exported (Soyabean Digest, 1998). The whole of sub-Saharan Africa plants approximately 22 million hectares of maize with an average yield of 1.20 tonnes/hectare. Total annual production is estimated at 26 million tonnes which frequently results in a food deficit. In order to bridge this gap African farmers need to improve management practices and have access to the best available technology - including biotechnology where it can be demonstrated to be safe, cost effective and contribute to increasing crop yields.
In order to reduce the breeding development period the use of biotechnology or genetic engineering has rapidly been adopted in some countries. Genetic engineering or biotechnology can be defined as integration of alien genes into an organism (plant, animal, microorganism) using other microorganisms, cells, DNA enzymes or a chemical entity to modify the character(s) of target living object. As a matter of fact biotechnology is not a new procedure and process. It has been with us for centuries but its complexity and related costs had rapidly increased in recent years (figure 3).
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Figure 3. Gradient of Biotechnologies
Biotechnology is a costly process of biology/biochemistry/molecular biology and their combinations and requires considerable human resource and infrastructural (laboratories, glass houses, equipment, chemicals, etc) development. It is reported that Monsanto spent US$500 million on the development of the glyphosate tolerance gene (Feder, 1996).
GROWTH IN TESTING OF TRANSGENIC CROPS
Table 1 indicates that up to 1995 56 crops in 34 countries on 6 trait groups had been evaluated at some 15 000 sites. So rapid has been the increase in frequency in testing that the two year period 1996 to 1997 saw 60 crops in 45 countries on 10 trait groups being tested at 10 000 sites. While it is clear that the USA and Canada continue to dominate the number of field tests it is significant that over 7 000 field trials have been conducted in other countries during this period.
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The global area planted to Transgenic crops in 1995 was small but this rapidly increased to 2,8 million hectares in 1996, 12.8 million hectares in 1997 and 27.8 million hectares (excluding China) in 1998 (Table 2). By the year 2000 more than 50% of the maize (16.0 million hectares), 50% of the soyabens (13.3 million hectares) and 60% of the cotton (3.4 million hectares) in the United States are expected to be planted to transgenic varieties. This exponential growth in the adoption of this new technology is unparalleled in agriculture and must be reflective of farmer satisfaction particularly in the USA, Argentina and Canada. Note that Spain , France and South Africa all commercialized significant areas for the first time during 1998.
Table 3 reflects that same data but related crops where soyabeans , maize, cotton and Canola dominate current transgenic utilization by farmers
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Adapted from James 1998
THE NEED FOR BIOSAFETY ASSESSMENTS
The field evaluation and approval for commercial use of the transgenics referred to above have been subject to Biosafety requirements in the countries mentioned. In the United States the US department of Agriculture, Federal Drug Administration and Environmental Protection Agency have all been involved in the approval process. Risk assessments, environmental concerns, public information and opinion are key issues that will need independent experimentation, verification and acceptance in the Zimbabwean context.
"Biosafety is one term that is used to describe the policies and procedures adopted to ensure the environmentally safe application of modern biotechnology" (Persley, 1993). A number of key points need consideration:
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COST BENEFIT ANALYSIS
The cost benefit analysis of the new technology has to relate the significant additional costs related to the seed as an input (seed plus technology costs) to the additional benefit in the hands of the farmer.
In countries where transgenic varieties have been adopted the benefits have been identified as:
While the technology costs are significant it would appear that a 3:1 philosophy may be influencing price policy at present. In other words, for every dollar charged for the new transgenic the farmer could expect an additional net return of three dollars. If the technology developers require too high a technology fee the process will self regulate as farmers will not realize sufficient additional benefits to support the related costs. However, in all likelihood, like all new technologies, when it becomes more freely available, from more competitive sources, the lower the price. It goes without saying that farmers are only going to purchase this technology if they are going themselves to generate higher revenues. This principle would apply equally in Zimbabwe, except that the capacity of small farmers to pay significantly more upfront for their seed is limited.
A few examples will be given as illustrative of the current cost structure in the USA and to indicate possible benefits in the Zimbabwe context. Note that the Zimbabwe dollar values quoted are at an exchange rate of 38 Z$ to 1 US$ applicable in August 1999.
ROUNDUP READY (GLYPHOSATE) SOYABEANS
One hundred and ninety dollars ($190) per bag of 20 kilograms (approximately $950/hactare) has been charged as a licensing fee in addition to the seed price. In the Zimbabwe context this would equate to approximately 40% premium on the seed price. It might be noted that the overall cost of weed control in the USA is considerably reduced with this technology. A recent survey indicated that 95% of farmers were satisfied with the "package" and would plant the Roundup Ready varieties again.
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LIBERTY LINK (GLUFOSINATE) RESISTANT MAIZE
This technology has been made available by AgrEvo to many seed companies. The additional price of seed is minimal and the herbicide costs approximately $950 per hectare at recommended rates. AgrEvo clearly wishes to compete with Roundup Ready maize and is aiming to recover development costs from the herbicide sales. It is estimated that 2.4 million hectares of Liberty resistant maize were planted in 1998.
Weeds cause significant yield losses in smallholder maize crops and the cost of a herbicide spray could be recovered by increasing yields by approximately 300 kg/ha.
In 1996 this seed sold at a premium of approximately $950 per hectare. By 1998 this figure had declined from some seed companies to $475 per hectare. Yield gains of 10 percent (worth $4 180 per hectare) if the insect is present have commonly been reported and a single control spray would cost $1900 per hectare. American farmers are so convinced of the technology that seed companies cannot keep up with the demand.
In the African context stalk borer is a major pest of maize causing economic losses in most of sub-Saharan Africa. Since significant work has not yet been conducted in Zimbabwe at present it may only be speculated that 10% more harvestable yield may result from the application of BT on smallholder farms. At a grain price of $4200 per tonne and a seed premium of $415 per hectare is applied then the following returns many be expected:
Clearly significant benefits may result to smallholder farmers, even at relatively low yields. The impact of the technology cost on the selling price of seed is still, however, an issue that will need careful analysis.
BOLLGARD (BT) COTTON:
Bollgard cotton seed carried approximately a $2 850 per hectare licensing fee (Monitor, 1996) in addition to the cost of seed, which contains the Bt gene. However, $5 320 to $10 640 per hectare could be saved in chemical applications and average yield increases of 7% have been reported.
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Trials in South Africa conducted during 1997/98 on Bollgard indicated an average advantage of $4 940 to $7 220 per hectare. The relative gain was higher on smallholder farms where 1885 kg per hectare were reaped compared to 1487 kg per hectare for non-Bt cotton.
CONDITIONS OF LICENSING FARMERS IN THE USA
Licensing agreements, like pricing structures, are still in the process of evolution. The following examples may serve to illustrate the directions being taken in the USA:
Roundup Ready Soyabeans
The licensing agreement requires farmers not to sell or dispose of any grain as seed or to retain any for planting the following season. In addition only Monsanto glyphosate may be used and the farmer must permit Monsanto to inspect crops.
The following Licence Contract Summary is extracted from the Delta & Pineland, 1995 Annual report:
The grower will agree to:
Monsanto will agree to
These two examples clearly reflect the rights granted to the holder of patents on transgenic varieties to enforce the principles of both the 1991 UPOV convention and patent law (Protection of Intellectual Property and the Right to derive income from its commercialization).
ADVANTAGES AND DISADVANTAGES OF GENETIC ENGINEERING
Like any other science or technology, biotechnology has its strengths and weaknesses. Some of the advantages and disadvantages of genetic engineering as related to agriculture are tabulated in Table 5.
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Analysis of Table 5 shows that both conventional and genetic engineering have advantages and disadvantages, which need to be considered as and when policies and decisions are made based on the traits in question. It may be necessary to take cognisance of national, regional and international opinions on a trait by trait basis.
The development of Biotechnology has increased discussion on issues related to plant breeders rights, UPOV, farmers rights , convention on Bio-diversity, costs to farmers , benefit sharing, risk assessments and ethical issues.
The "terminator technology" is a concept where a gene inserted into a crop variety ensures that farmer retained seed does not germinate. Hence the developer/seller of such seed has perfected intellectual property protection but the farmers right to retain the seed of such varieties to plant their next crop has been removed. In Zimbabwe most sorghum, millet and groundnut seed is farmer retained so such technology should not be permitted to be marketed in Zimbabwe on ethical grounds.
CONCLUSIONS AND WAY FORWARD
There are differing opinions on the use of genetic engineering around the world especially its use in agriculture. There are heated debates on the subject particularly in North America and Europe where recent report on the development and use of transgenics have created negative attitudes among consumers and some policy makers in developed countries. In the Zimbabwe context each case needs to be considered on its own merit. It may be necessary to introduce the concept of Genetic Engineering Impact Assessment (GEIA) in much the same way, as we are required to do Environmental Impact Assessment (EIA) in most developmental projects.
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The Government of Zimbabwe has already produced "Biosafety Regulations and Guidelines " which will govern the preparation and implementation of genetic engineering projects and programmes.
Areas where biotechnology may make an impact on Zimbabwe agriculture include:
In brief genetic engineering needs to be used for the benefit of mankind, and not for the benefit of individuals or corporate bodies. In the Zimbabwean context genetic engineering in agriculture should be treated like any other new technology which has to be rigorously tested, in a contained/controlled environment, until sufficient data has accumulated to show effectiveness and safety to flora and fauna before it can be recommended for adoption and use. The applications currently being received at the Biosafety Board from various organizations should be handled within the framework of the requirements stipulated in the Biosafety, Phytosanitary Regulations, the Seed Act, Plant Breeders Rights Act and other relevant national legislation.
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Anandajayasekeram, P and M. Rukuni (1999). Agriculture Research and Poverty
Delta and Pineland, (1995). Annual Report, p 8
Feder, B.J. (1996). Out of the Laboratory. A revolution on the Farm. The New York Times, Sunday, March (1996).
Food and Agriculture Organization (FAO) FAO Production Year Book. Various Issue.
James, C. (1997). Global Status for Transgenic Crops in 1997. ISAA Briefs. No5-1998, p3
James, C. (1998). Global Review of Commercialized Transgenic Crops: 1998, p 4-7.
McCarter, S.B. (1998). Case studies on the Impact of biotechnology on the seed industry in the United States and its implications for African Farmers. CIMMYT in publication.
Paraly, P, J. Roseboom and J. Anderson (eds). (1991). Agriculture Research Policy. International Quantitative Perspectives. Cambridge University Press. Cambridge U.K.
Perssely, G.L., Gidding and C. Juma. (1993). Biosafety: The safe Application of Biotechnology in Agriculture and the Environment Research Report: the Hague: International Service for National Agricultural Research 1992. P v
United Nations Population fund. (1994). The state of World Population 1993-1994. United National NY. USA
Soyabean Digest, Intertec Publishing Corporation, Minneapolis. January 1998, p 110.
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GENETICALLY MODIFIED ORGANISMS AND VACCINES IN LIVESTOCK PRODUCTION
Animal species embraced as livestock are generally those of utility for human living. Most of them including cattle, sheep, goats, poultry, rabbits and fish are major components in the food and nutrition equation. Others are wildlife from which some are tamed for farm production. Some of these today include ostrich, impala and crocodile also providing food, nutrition and high value exportable goods. Some cattle, donkeys, mules and horses are important as work animals.
It is doubtless that most important purpose of farm livestock is in providing food both directly and indirectly, and fibre. The commercialization of production necessitates that production levels are economic for farming to remain viable. In doing so, it also becomes an industry increasing the provision of marketable food of high quality protein, for both local consumption and export. Incomes are generated in the process and downline industries are sustained. Production increases will also lead to greater availability of affordable protein. Farmers and researchers are therefore constantly looking for better ways to increase production and productivity and to attain greater efficiency and quality in production by maximizing available inputs while minimizing losses. Farm production efficiency forms the basis of economics of agriculture. The major aims of livestock production improvement at national level are therefore to gain food and nutritional self -sufficiency; improve economics performance. At farm level, it is to maintain business viability of the farm enterprise, or for the smallholder to allow entry into economic production and improve income levels. In Zimbabwe, the lessons learnt in times of drought indicate that agriculture can proact by intensifying production in good years while linking up with strategies for long term preservation, so that deficits in bad years are offset.
Phenotypic selection and production improvement
Over time, production maximization has been achieved through phenotypic animal selection and selective breeding for given traits, environments and production enterprises, application of improved animal management practices with respect to housing, feeding, disease, programming of breeding , product handling and management of the animals' environment. While largely useful, these approaches suffered from lack of precision as they were manipulations of the whole animal and the broad environment both of which are constituted of a large variety of functional components. It is known however that ultimately, performance increases such as those sought in production are encoded genetically, above all.
The advent of precision technologies afforded by genetic modification has introduced an infinite set of possibilities for manipulation at a much finer level in the organism or
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animal. This way, such that the separate components of a biological system can be tackled individually, but the effect on full final production can then be assessed at the whole organism level. For example genes specific for milk of high cream content could theoretically be transferred to a cow producing high volume but low cream milk, instead of depending on two cows for the traits, one would offer both advantages. Some of these technologies are already being applied to biological systems of the animal and its environment.
2. Opportunities for genetic interventions
In the animal production system, he biological systems in which biotechnologies have a potential are the following:
Some of these which have been tackled over time include diagnostics, vaccines, drugs, in-vitro embryos, growth hormone production and administration, insulin production, processing of feeds microbiologically, biogas production and most recently, cloning of animals (sheep and pigs).
Of these, those in which genetic modification has been applied are diagnostics, where large quantities of test antigens are produced in a vector systems after gene transplantation for instance in bacteria. This has been applied locally in anaplasmosis and cowdriosis to produce test antigens. Recombinant genes have been applied as probes in diagnosis of Cowdria rumination in the tick vector in locally conducted research. In attempts to improve vaccines against heartwater naked genes have been used in test trials in sheep and mice under laboratory conditions. In North America and elsewhere, growth hormone transgenetic fish such as Atlantic salmon, carp and tilapia encoded with genes for growth hormone have been created. The ability for the trait to be transmitted to offspring was however, not fully successful. Genetically engineered growth hormone (rBST) has already been in use in cattle in the USA for several years. On the continent, genetic modification at animal level has not yet been attempted. Traits for disease resistance, feed conversion efficiency, meat and milk production are some genetic determinants that will obviously be sought. They are the reasons for studying the bovine genome at international centres like ILRI. Suggestions have also been tabled to produce foods of animal origin which are fortified for certain nutrients which are of therapeutic value, such as milk with clotting factors for haemophiliacs.
Genetic modification is simply speeding up several hundred times a process which is a normal evolutionary process in practice encouraged by cross-breeding as opposed to in-breeding. If applied, the main reason would be to keep pace with food and nutritional demands of fast growing populations and the need to reduce commodity prices to affordable levels. It could however, be argued that the process is also speeding up the rate at which "genetic accidents" including malformations and environmental spoilage
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could have occurred, thereby potentially leading to environmental catastrophes. Extreme caution needs to be exercised particularly at micro-organisms level. Safeguards have been drafted in the form of biosafety regulations especially with containment. The question is therefore the effectiveness of an audit system for checks and balances. In the event that complete reversal is called for, sufficient gene banks have to be available in stand by for the re-establishment of the state of nature as we know it. There is however, no policy in place yet about the application of genetic techniques in agriculture or health management. Another area of concern is the possibility of genetic piracy should there be traits unique to the country or region.
Development of vaccines for animal diseases is strongly a factor of the complexity of the structure of the organisms. Generally the simpler , i.e. if the structure is nucleic acids such as either DNA or RNA, the easier it is to make effective vaccines. Thus even before the genetic revolution of the 1980's and 1990's, vaccines against viral diseases were largely available and could easily be produced against variable strains. Up the ladder , bacteria being the smallest free living nucleated organism have been relatively easy to produce vaccines against. This has been possible because the bacterial cell typically has only a single circular chromosome with no nuclear membrane (procaryotic).
Challenges have however been faced with more complex microorganisms such as protozoa, helminths and ticks, among which are many species and genera responsible for diseases in animals. Improved vaccines are still required for diseases like Trypanosomiasis, Babesioses and theileriosis among some examples. It is in these groups that large research programmes in national, regional and international centres have been based in some cases for decades, searching for accurate diagnostic products and simple effective low cost vaccines. Larger organisms, visible with the naked eye appear to be even more challenging. It would appear that being multicellular, multi-organ and being associated with a battery of basic protein, make the feasibly of a single effective vaccine difficult. It is in such complex organisms that selection of genes encoded for specific protective proteins is mandatory. When identified such genes can then be re-combined and introduced into a suitable vector system where they can be expressed in the form of their protein products. Present thinking is around the possible production of single vaccine effective against a number of different diseases based on a genetic re-combination and artificial production of such products would be custom made to fit the requirements of given situations. The vaccines would be more specific, have long shelf lives and be easier to store and administer, advantages lacking in the present live vaccines against diseases like Babesioses and theileriosis.
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ARTIFICIAL INSEMINATION (AI) AND EMBRYO TRANSFER (ET) -
S. Moyoa and P. Moyob
a) Department of Research and Specialist Services, Matopos Research Station, P B K 5137, Bulawayo, Zimbabwe
Agriculture dominates the country's economy and provides income to almost seventy five percent of the population. Over seventy percent of the land is best suited for animal production with cattle dominating. Small ruminants (sheep and goats), pigs and poultry are also fast expanding. Despite this contribution of animals to food production, intake of animal protein remains very low in Zimbabwe, and as a result nutritional standards and health are equally low. For example, currently the country produces 180 million liters of milk a year which translates to
15 l per person per year
The population requires double this amount. The situation is worse on the consumption of meat products.
The greatest challenge facing animal breeders is to rapidly increase productivity of the animals in order to meet the consumers demand for animal products (milk and meat) while sustaining the natural resource base. One of the most limiting factors to increased productivity is low reproductive rates (numbers born) of the animals. Biotechnology is regarded as a tool which can be used to help increase reproductive rates.
The purpose of this paper is to discuss the role of artificial insemination (AI) and embryo transfer (ET) in improving livestock production in Zimbabwe. In addition the aspect of impact of this biotechnology to agriculture and the society in general will be discussed.
1. Artificial Insemination (AI)
Artificial insemination is one of the most widely available technologies in the world. This technology involves semen collection, dilution and storage and insemination.
In Zimbabwe artificial insemination is being used widely in the commercial sector and has generally remained unexploited for potential use in the small holder sector. Artificial
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insemination services in the country are privately managed by Animal Breeders Company (ABC).
Most dairy farmers use AI only or in conjunction with natural services. Pedigree beef breeders import a substantial amount of semen to upgrade their stud herds. Limitation of use in the commercial beef herds has mainly been due to the difficulty in detecting heat in large beef herds kept under ranch conditions. In sheep and goats there is scope for improvement of the technology, while in pigs it is hampered by the inability to successfully store boar semen.
The country collects 36 000 straws per year and imports 5 000 straws. The dairy farmers use 30 000 straws while the beef industry uses 11 000.
Reasons for use of Artificial Insemination
Factors that limit a wider adoption of AI (especially in the small holder sector)
Potential use of AI in a wider scale.
Some countries have implemented AI to the smallholder sector with some degrees of success. These experiences can be applied to the Zimbabwean situation as well. There is need for capacity within government departments and local communities. AI could be incorporated into breeding strategies aimed at disseminating germplasm to the small holder sector (e.g. Restocking exercise after the drought or to promote a wide use of a specific breed).
2. Embryo transfer (ET)
Embryo transfer technology has been the biggest advance in cattle breeding this century since the introduction of AI. Like AI, ET in Zimbabwe has remained a commercial venture managed by a private company (ABC). ET involves the collection of fertilized eggs (embryos) from a cow (donor) for transfer into foster dams which carry the calves to term. This allows valuable cows to produce more than one calf a year and if treated with hormones to induce multiple ovulation (super-ovulation), they can produce up to 20 calves a year. The producer has the option of retaining these animals or selling the surplus stock, or embryos.
Embryo transfer consists of a series of steps (about 22), all of which should be done well or failure will result. Some of these include: Selection of fertile donors, purchase of high fertility semen, superovulation of the donor, recovery of most embryos from each donor, transfer of embryos to the recipient, and good and proper management of the animals, and etc.
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Objectives of embryo transfer (ET)
Disadvantages of embryo transfer (ET)
Legislation and Safety of Products
Any new bio-technique should be accompanied by the correct legislation, government policy, regulatory institutions, monitoring mechanisms and adequate biosafety rules.
At the present moment there is a legislation covering the setting up of AI station and import of semen into Zimbabwe. The main aim is to ensure that there is no introduction of diseases into the country. Bulls used for semen collection should be free of diseases. Only qualified people are allowed to do AI.
Currently there is no specific regulation governing the application of ET. However, import conditions are set on a specific import by the Veterinary Department. These
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conditions depend on the country of origin. For example if embryos are imported from the UK, the herd should be free from mad cow disease, and the embryos should be washed several times.
All imported semen and embryos should have a Veterinary import permit.
We would like to note that animals from AI and ET are as normal as animals from natural service. This poses no threat to consumers of animal products.
AI and ET could have a great impact on the genetic improvement and rebuilding of the national herd. AI utilizes the superiority of the males, while ET takes advantage of both male and female traits.
AI and ET greatly reduce generation intervals, this helps in speedy selection of superior animals for breeding
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.THE ROLE OF GMOs IN PRODUCTION OF PHARMACEUTICALS AND INDUSTRIAL PRODUCTS
This paper will first highlight two approaches to the manufacture of industrial and pharmaceutical products:
It will then highlight the unique biological diversity that plant secondary metabolism endows upon a plant. It will then touch on specific examples of both industrial and pharmaceutical products that have been produced through genetic engineering. Finally the paper will also hint at new opportunities that have been developed, such as those in the areas of nutraceuticals and bioinformatics.
By and large the demand for new products and improved commercial products will be met through bioprocessing, a type of advanced manufacturing that involves chemical, physical and biological processes employed by living organisms or their cellular components. Bioprocessing enables the translation of research discoveries into commercial products with unique and highly desirable characteristics and offers new production opportunities for a wide range of items, including:
Bioprocessing has its advantages, it offers a level of specificity, predictability and productivity that would normally not be found in the ordinary manufacture of these products. It makes use of the complex structures, that raw materials already contain to synthesize products that can not be made by any other means. These capabilities provide for new process designs that are cost effective, energy efficient, product specific in an environmentally friendly manner.
Metabolic Engineering (ME) is the use of recombinant DNA technology to enhance the activities of a cell by manipulating its metabolic pathways. The goal of metabolic engineering in plants is to produce transgenic crops in which the range, scope or nature of a plants existing natural products is modified to provide a commercial, agronomic and/or post-harvest- processing benefits. The genetic manipulation of plant biochemical
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pathways can create new products for food and nonfood uses that will expand markets and increase the value of agricultural commodities (Taylor, 1998).
Specific examples include plants that may accumulate unusual edible or industrial oils, lignins with different subunit compositions that interfere less extensively with the paper production, starches with different milling qualities, and so on. The use of starch as a co-polymer in biodegradable plastic is being explored. To exploit this approach, scientists must develop an improved understanding of cell metabolism. Even at that one can not always predict what the outcome of such manipulations would be. Some modifications result in the slow growth of the cell and increased levels of stress proteins which ultimately compromise yield. Others compromise plant growth and development even in cases where appropriate targeting, sorting and compartmentalization have been clearly worked out. For instance the occurrence of environmental perturbations on well- characterized transgenic plants has been reported.
It has become apparent that knowing more about the biochemical pathway to be manipulated has a tremendous effect on the likelihood of success of the ME. However having a detailed understanding of a particular pathway is not always enough. Regulation of the various enzymes in question at either the gene expression level or at the level of the feedback/forward inhibition is also critical.
This is where transcription factors (TFs) are fast becoming a useful tool for ME. The anthocyanin biosynthetic pathway is one such pathway where metabolic engineering could be applied. A lot of information gathered on the pathway in the last 20 years suggest that different TFs that operate on a single pathway regulate a subset of genes downstream. These subsets of genes encode enzymes that participate in individual branches of complex pathways. It is therefore possible to manipulate the expression of a single TF and end-up affecting the expression of several coordinately regulated biosynthetic enzymes downstream. Furthermore, it has been shown that TFs can operate in heterologous systems. Despite the fact that plant secondary products are dispensable, they still play a vital role in plant biology.
Novel Products from Plants
Higher plants synthesize a wide spectrum of chemical compounds. Many of these compounds have known value such as drugs (e.g taxol), biomaterials (e.g rubber), solvents, flavourings, fragrances, or colouring agents. By adding or deleting a gene through transgenic technology one can enhance the purity of these chemicals. Plants can now be engineered to produce hydroxylated fatty acids which can be used from applications ranging from hydraulic fluids to nylons.
Plants can accumulate biodegradable thermoplastics (Bongman and Poirier, 1999). This type of plastic can decompose in compost within a period of less than a year. While certain classes of secondary compounds such as flavonoids, cyanogenic glycosides and alkaloids have been extensively studied, other classes such as terpenoids have not. These compounds are important for plant growth and as essential oils, resins acids and
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pigments. There is a myriad of applications that both native and improved plants secondary metabolites can be used for.
The Second Plant Revolution
In the United States of America (USA) a large acreage grown has been grown to GM crops. In 1999, there were 29 million hectares cultivated to soybean, half of which were herbicide-resistant soybean seeds. The advantages of which range from minimum tillage, relative ease of controlling weeds to minimization of soil erosion. Worldwide slightly less acreage (28 million hectares) was planted with the area predicted to triple in the next five years (Plant Biotechnology: Food and Feed Review).
New opportunities are coming up in area of improved quality traits. There is increasing evidence transgenic produce healthier foods, especially in the over expression of micro- and macronutrients. Increasingly plants are being used as chemical factories, with the multinationals taking the lead as usual. Plants are now being engineered with traits that benefit the consumer directly, and not just the farmer as was previously the case. Now the consumer can purchase soybean improved in oleic acid composition for instance. Dupont have been able to channel plants into producing industrial feeds-tocks, pharmaceutical and nutraceutical products. They have produced transgenic soybeans with 85% oleic acid (up from 25%) and others that produce vernolic and ricinoleic acid all of which are derivatives of oleic acid that are used as hardeners in plastics and paints.
Macronutrient & micronutrient deficiencies
Macronutrients consist of carbohydrates, proteins and fats, whereas the essential micronutrients are made up of 17 minerals and 15 vitamins. In developing countries some of these components are derived from plants, although they may not necessarily be in a bioavailable form to be directly utilized by the body (see below). Also many phytochemicals such glucosinolates and phytoestrogens have an effect on human health (see table1). Nearly half a million children per year in developing countries suffer from irreversible blindness due to vitamin A deficiency. In developed nations where the caloric intake is adequate and in some cases even excessive, micro-nutrient deficiencies are common due to poor eating habits. For instance a burger, French fries and a diet coke easily pass for dinner.
The consumption of genetically engineered foods has met up with a huge backlash especially in Europe. For a while it looked like the Americans were more accepting of GM-foods, however this is may not be the full story (Gaskell et al., 1999). This paper will not talk about this controversial issue, except to say that the story is rather different when it comes to one's health. Pharmaceuticals that have been produce through genetic engineering are widely accepted and in full use in industrialized countries (Table 2). So
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what is going on here? Is what we ingest for general sustenance so, so different from what we ingest in the form of a pill, or what we take by intramuscular or intravenous routes?? Biopharming is largest growing sector in Biotechnology product development. Pharming is the production of human pharmaceuticals in transgenic animals. The technology dates back to 1982 when the first transgenic mouse was made. Then tissue plasminogen activator (tPA) was produced in 1987. The use of recombinant products such as recombinant bovine growth hormone (also known as bovine somatotropin [bST]) sparked controversy with dairy farmers in the Mid-Western States of the USA. Nevertheless the technology spells huge profits for the multinational companies, with an average transgenic pig expressing human protein C valued at $1million! The list of diseases given in table 1 are all disease conditions that can be treated with this new arsenal of drugs.
Source: Reference, Dean DellaPenna 1999
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Some Recombinant Proteins That Have Been Approved for Human Use by The US Food & Drug Administration.
Source reference Glick and Pasternak, (1998).
New tools and bioinformatics will accelerate the acquisition of knowledge about the function of a whole organism's genes. Those organisms whose genomes have not been mapped might be inferred through synteny (e.g rice vs maize, sorghum and millet) (Somerville and Somerville, 1999)
Drugs are being designed from the three-dimensional structure of a protein. Cybermolecules are viewed on the screen to select the best fit. Edible vaccines are being made against diarrhoeral diseases in bananas. Nucleic acid therapeutic agents using antisense technology are being developed. The use of Brassica species and improved microbes in industrial and clean-ups and soil pillages are fast become routine applications for these species. Instead of hyper-accumulating just toxic chemicals, such plants are
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now being made to accumulate useful compounds that can be taken as dietary supplements e.g calcium and selenium. This comes in the wake of non-bioavailability of some of these compounds. For instance while a whole glass of milk contains an equivalent amount of calcium as that found in green beans per unit weight, one would have to consume kilogram quantities to absorb a comparable amount of calcium from the vegetable source. Transgenic technology can change all that so that one only has to take a concentrate in capsule form.
On the home front
Some biotechnology products are already on the market in Zimbabwe. The hepatitis B virus vaccine, Engerex is in widespread use in Zimbabwe. I suppose the question is whether the Zimbabwean consumer knew they were using a recombinant vaccine or not. A DNA vaccine against Cowdria ruminatium is being developed under the leadership of Dr. Suman Mahan at the Central Veterinary Laboratories, here in Harare.
Thus as biotechnology continues to offer more and more tools, it is predicted that the technology will continue to offer new ways to exploit these biological resources. On would hope that new products can be utilized to the maximum benefit of society.
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Bongman, V. and Poirier, Y. (1999). International News on Fats, Oils and Related Materials (Inform) 10 (8) 768-774.
DellaPenna, D. (1999). Nutritional Genomics: Manipulating Micronutrients to improve Human Health. Science 285: 375-379.
Glick, B.R and Pasternak,J. J.(1998). Molecular Biotechnology: Principles and Applications of recombinant DNA.2nd edition. ASM Press, Washington D. C.
Plant Biotechnology: Food and feed Review. (1999). Science 265370-389.
Taylor, C. B. (1998). Editorial The Plant Cell.
Somerville, C. R. and Somerville, S. (1999). Plant Functional Genomics. Science 285: 380-387.
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THE IMPACT OF GENETIC ENGINEERING ON AGRICULTURE
RAPPORTEUR'S REPORT: ANDREW E. MATIBIRI
© Friedrich Ebert Stiftung | technical support | net edition fes-library | August 2001