Research and development in 2000: directions and priorities for the world's poultry science community

WORLD’S POULTRY SCIENCE ASSOCIATION INVITED LECTURE Research and Development in 2000: Directions and Priorities for the World’s Poultry Science Community B. L. Sheldon 1A Hampden Road, Pennant Hills, NSW 2120 Australia advances in genetics, nutrition, health, housing, and husbandry still awaiting application in industry; 3) future applications from current and future research in molecular biotechnology, nutrition, health, and reproduction; and 4) the development of efficient, small-scale, extensive poultry production systems especially in countries where over 25% of the world population will still not be able to afford the products of a modern, intensive poultry industry, even in 50 yr. These challenges, targets, and predictions simply cannot be met unless the world’s poultry science community increases its own efficiency, its professional initiatives to deal with the real challenges, and its social initiatives to influence socio-economic decisions on national and world stages.

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gazing into the crystal ball harboring the events of the next century. Progress in science occurs most typically by small, incremental additions to knowledge, much less frequently by major discoveries, and is often made possible by technical innovations such as polymerase chain reaction (PCR) or computers, or rocket technology, and very occasionally by major conceptual changes, recently called paradigm shifts. Most technological applications depend on previous advances in knowledge in the basic sciences. Normally, there is a considerable lag period between the advent of such new knowledge and its application in industry or in other social contexts. For example, in the fields of atomic physics and atomic energy, it was over 40 yr. In the field of poultry genetics, and animal genetics generally, it was similarly over 40 yr from the rediscovery of Mendel’s paper in 1901 to the application of quantitative genetics to commercial animal breeding led by Lush, Lerner, and others in the 1940s and 1950s. It also took about 40 yr from the discovery in 1944 that DNA was probably the genetic material to the first successful industrial or medical applications of recombinant DNA technology in microorganisms in the 1980s. Other examples in the fields of poultry genetics, molecular biology, and biotechnology were given in my previous review papers

INTRODUCTION The American Poultry Science Association (1911) and the World’s Poultry Science Association (1912) have been in existence for most of the 20th century. Their objectives have been similar, i.e., to promote the advancement of knowledge in poultry science and its application in the poultry industry, both locally and worldwide. The time frame of their existence has been contemporary with the century-old growth and development of the “new” sciences of biochemistry, genetics, immunology, microbiology, physiology, and, latterly, of molecular biology and their specific development in poultry and other avian species. I have been closely associated with most of the second half of this century of progress in poultry science and technology. My research and development activities have been primarily in the area of poultry genetics and breeding as well as in the quantitative and developmental genetics of Drosophila. In the second half of my research career, I also became involved in interdisciplinary research in reproductive physiology, cytogenetics, sex determination, immunogenetics, and molecular genetics of poultry. I welcome this opportunity to share my experiences and insights as we try to make some sense out of

Abbreviation Key: MAS = marker-assisted selection; MHC = major histocompatibility complex; QTL = quantitative trait loci.

Received for publication September 20, 1999. Accepted for publication September 20, 1999.

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ABSTRACT The challenges and targets facing the world’s poultry science community in the immediate future are reviewed in the context of meeting the dietary needs for animal protein of the world population. The prior need to provide for the increasing demand for cereals, oil seeds, and grain legumes for human consumption is assessed at having a reasonable chance of success. If this need is met, the requirement for extra feed resources for increased poultry production targets is also assessed as having a reasonable chance of success. A major component of this equation is the prediction of improved efficiency of poultry production of a similar order to that of the last 50 yr arising from 1) extension of the 20th century revolution in poultry technology to over 50% of the world population compared with the present 20 to 25%; 2) recent

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GLOBAL CHALLENGES AND TARGETS Poultry science, technology, and industry obviously do not operate in isolation. In a review paper last year (Sheldon, 1998) I summarized the main socio-economic problems that must be solved if the world’s minimum population in 2060 (8,000 million) is to be fed adequately. The primary problem is that two-thirds of the countries in the world still have a gross domestic product per head that is less than 4% of that of the richest countries. They have extremely low incomes and virtually no purchasing power. Action to reduce very significantly this unconscionable gap as rapidly as possible will require massive

improvements in all components of living standards, especially in those 100 countries (i.e., education, housing, provision of energy sources, productive and sustainable agricultural technologies, health care, communications technology, trade and business practices, liberalization of politics, and growth and diversity of industry). It is well worth repeating that this improvement will happen only if we poultry scientists as world citizens, together with all concerned world citizens, make it happen through our individual social and political processes. As poultry scientists, however, our main contribution to the problems of the 21st century will be in improving the efficiency of poultry (avian) production in all environments. Only then will sufficient poultry and poultry products become available at minimum cost to the whole population of the world rather than to less than half of it as at present. How big is this challenge? In my 1998 review (Sheldon, 1998) of this subject I divided the countries of the world into four groups: 1. About 20 countries where the revolution in application of poultry science and technology is fully mature, more or less complete. These countries represent approximately 15% of the world population. 2. About 30 countries in which the revolution is well advanced but poultry meat consumption currently averages only about half that in the Group 1 countries. These 30 countries also represent about 15% of the world population. 3 China and India, about one-third of the world population. 4 The remaining 40% of the world population spread across some 100 countries. Group 2 countries were predicted to complete the poultry industry revolution and to double their production and consumption of poultry meat without any significant increase in requirements for poultry feeds. The reasons for this prediction were that poultry meats would still largely replace meat consumption from other traditional livestock species, whereas expected smaller increases in egg production would come from more efficient genotypes, thus requiring few extra total feed resources. China was regarded as similar in pattern to Group 2 countries with relatively high levels of egg consumption but poultry meat consumption still around 8 kg per head per year (total meat consumption of all livestock species over 30 kg per head). Increases in egg consumption to levels existing or projected for Groups 1 and 2 is similarly expected to be achieved with superior genotypes, i.e., little extra requirement for feed resources. However, expected increases in poultry meat consumption to say 15 kg per head in the near future were predicted to require about an extra 20 million tonnes of poultry feed per year. India with 13% of world population and the other 100 countries with the remaining 40% of world population are similar in having low to very low levels of poultry egg and meat consumption but showing great variation between countries. With the targets of the Indian Council of Medical Research of 160 eggs and chicken meat consumption at 10 kg per head as a rough guide for all these

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(Sheldon 1978, 1990). Examples in the other sciences of biochemistry, immunology, microbiology, and physiology show similar time lags between discovery and successful application in human or animal nutrition and health and in animal management. Such background historical information is a relevant starting point here because it helps to inform attempts to predict future progress and to delineate the directions and priorities likely to maximize that progress. And maximize it we must if the world population now and in the near future is to be fed adequately. Currently, one of the major differences between science and technology in the early 20th century and the beginning of the 21st century is the relatively new focus on specific applied goals. As the 1900s began, scientific research was driven largely by academic and professional interest—the pursuit of knowledge for its own sake, the centuries-old ideal of the universities. From the 1920s, even earlier in US agriculture, government funding of basic and strategic research in the sciences, relevant to national problems, began and increased in most developed countries, especially in the 1950s and 1960s. Even then, the directions and trends in scientific research, apart from mammoth defense and space projects, were still largely decided by the leading research scientists. In the past 25 to 30 yr, public funding support for uncommitted basic research per se has been steadily decreasing, whereas government and industry funding has favored shorterterm projects directed at more specific applied outcomes. These general trends, no doubt, reflect the competition for finite funds for other worthy activities, the increasingly competitive international environment for applied scientific research, and the pressures to maximize commercial returns from research for the country that funded it. Along with this trend has been an incredible increase in the secrecy and confidentiality surrounding scientific research in public institutions. If all these trends continue, there is a real danger that insufficient basic research will continue to be done to replenish the store of new scientific knowledge in which all applied science and technology ultimately depend. In addition, if the narrow focus on national objectives or those of multinational companies persists at the expense of necessary contributions to solving the world socio-economic and food problems the result in the coming century will be catastrophic.

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the past 50 yr indicate at least that the goals are not impossible.

ROLE OF WORLD POULTRY SCIENCE COMMUNITY The directions that our community research and development must take to try to reach the production targets referred to above are almost self-evident. I shall summarize them, with indications of likelihood of success. To allocate priorities, especially in terms of manpower and funding required, is much more difficult. Indeed, it may be an empty exercise, because of inevitable limitations on resources and the need to pursue all areas of research and development likely to have a significant impact on production targets. I shall deal first with areas of poultry science that will normally find their first application in the modern advanced industry. Then I shall outline briefly what must be done for those peoples where development of an advanced industry is not yet appropriate.

Extension of 20th Century Revolution in Poultry Technology (Advanced Industry) The fully mature and complete development of the poultry technology revolution of the past 50 yr has so far extended to only 15 to 20% of the world population. There are no major inhibitory factors preventing its full extension to the rest of the Group 2 countries in the short term and its partial extension to China (fully for egg consumption, half for meat), to India (75% for egg consumption, 40% for meat), and to the remaining 40% of the world population in 100 countries (averages similar to India). Thus, it can be predicted confidently that these levels of extension of modern poultry industry technology will reach over half the world population in the next 20 to 30 yr. It will need the full involvement of national and international poultry science communities but entails virtually no new research. This extension requires only local development of existing knowledge and technology in poultry breeding, nutrition, health, housing, and husbandry, as has occurred already in many countries around the world. However, it is worth adding a cautionary note that there are significant disadvantages to the past and projected extension of the poultry technology revolution that need to be considered and countered if the full benefits of the technology are to be achieved globally for the future. The first is the structure of the integrated poultry breeding and production industries developed over the past 40 yr, which currently leaves most of the world market for breeding stock and associated multiplier and production components in the control of only a handful of international breeding companies. The market consequences of this situation are a less than optimal level of overall competition between suppliers and, probably, an associated reduction in the potential for innovative research and development in the highest levels of the industry. The second and more insidious disadvantage that flows from

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countries, I predicted that Indian consumption at this level would require an extra 70 to 90 million tonnes of poultry feed per yr, whereas the other 100 countries would require an extra 210 million tonnes per yr. The total increase in poultry feed resources required to meet these targets is thus 300 to 320 million tonnes per yr. The increases in total production of eggs and chicken meat to reach these targets in the next 15 to 30 yr will be on the order of 25 and 100% of current production, respectively, in China, 300 and 900% in India, and 300 to 1000% and 100 to 900% in the remaining 100 countries. Before considering how poultry science and technology can help meet these production targets, it is necessary to summarize whether and how the target for extra feed resources can be met, because to a large extent it is beyond the scope of the activities of poultry scientists. The sheer magnitude of the problem is most daunting. The total increase in feed resources just for projected increases in poultry production represents at least a doubling of current usage for poultry. At the same time, however, production of cereals, oil seeds, and grain legumes for direct human consumption must be increased by more than 50% to provide not only for the increase in population but to raise nutritional standards of much of the present population to adequate levels. My prediction is in broad agreement with those presented recently at a US National Academy of Science colloquium “Plants and Populations: Is there time?” (e.g., Dyson, 1998; Fedoroff and Cohen, 1998). This increase for direct human consumption is two to three times the increase required to meet poultry production targets. The big question is, can both be achieved? In my 1998 review, I listed seven essential areas of action, the contributions from all of which have to be integrated and maximized if there is to be any chance of success. Three of them are in the hands of agriculture practitioners and plant breeders (i.e., increased land area devoted to these crops, maximum use of higher-yielding plant varieties currently available, and future breeding and production of even more efficient plant varieties). Two are in the hands of poultry scientists (i.e., continued research and development for more efficient strains of poultry and greatly increased research into use of alternative ingredients for poultry feed). These two areas will be dealt with further in the next section. The remaining two, and probably the most important, are in the realm of socio-economics and politics. They demand a radically broadened international and global approach to these problems. The first of these two is urgent liberalization of world trading conditions, especially the removal of barriers to maximum world production of human and animal feeds. The second is for urgent, orders-of-magnitude increases in technical aid projects for developing countries aimed at efficient development of both a modern organized poultry industry where appropriate and extensive small-scale (rural) forms of poultry farming. The latter will also be dealth with in a later section. It is difficult to be optimistic about the chances of sufficient success in all of these areas in the next 50 yr, but we have to try. Progress in the same or similar areas in

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Recent Advances Still Awaiting Application As inferred above, the revolution in poultry technology was made possible by a combination of improvements in poultry breeding, nutrition, health, housing, and husbandry developed on the base of advances in genetics, biochemistry, immunology, physiology, and microbiology. Genetic improvement of production per bird was the main component of the total increase in productivity and will continue to be so in the foreseeable future. Genetics. Sheldon and Yoo (1993) argued that further responses to conventional selection for high egg production were still possible but at a much reduced rate per generation. It might take a further 20 to 40 generations (years) to increase from the then (1993) current average of 300 eggs in the pullet year to 320 to 325. However, Sheldon and Yoo (1992, 1993) had shown that selection for short interval between eggs in continuous light, as a way of circumventing the so-called 24-h barrier to further progress, could double this rate of response to conventional selection. Such flocks were thus likely to reach 340 to 350 eggs per pullet in 20 to 30 generations. In addition, this approach offered the possibility of a further response to selection to 380 to 400 eggs per pullet over the ensuing 20 to 30 generations. Although the promising results of this approach had been well publicized for at least 10 to 15 yr (Sheldon and Podger, 1974a, Sheldon et al., 1979, Sheldon et al., 1984, Yoo et al., 1986), there was virtually no evidence in 1993 that the poultry breeding industry was applying the new approach. There is still no such evidence, nor is there any evidence that it does not work.

We look forward to its successful application in the next 10 to 50 yr. A further example in the area of genetics of egg production that has also apparently been ignored concerns the demonstration that useful genetic variation exists for controlling the shape of the curve of egg weight to age of pullet (Sheldon and Podger, 1974b; Podger and Sheldon, 1978; Yoo et al., 1983). In most egg-producing strains, there is uneconomic production of over-sized eggs late in the pullet year. Selection for reduced variability of pullet-year egg size has indicated that it could solve this problem and yield a correlated response in higher egg production. A third neglected example in this area is the potential use of the dwarf gene to expose “new” variation for high rate of lay in selection lines approaching the so-called 24h “limit” (Yoo et al., 1984). I make no apology for quoting examples from my research group because, conceptually, they stem from the seminal work of Waddington in the 1940s to 1950s and some of his successors J. M. Rendel, A. S. Fraser, and myself on the genetics of canalized characters in Drosophila and mice. All aspects reinforce my earlier comments on the time lag between discoveries in basic science and eventual application. I am certain that many other senior poultry scientists could give similar examples from their own fields of science. In the area of genetics of chicken meat production there are probably no similar specific examples of useful discoveries that have not been applied in industry. Pym (1993) and Leenstra (1993) emphasized the problems that arose from previous selection mainly on juvenile growth rate. They predict continuing medium-term gains in efficiency of production through additional selection for feed efficiency, reproductive performance, and overall biological efficiency and against skeletal defects, body fat, and juvenile mortality. Unlike the situation in the egg industry, the chicken meat industry seems to be applying the research discoveries of the previous 20 yr with much less delay. Therefore, we can predict greater proportional productivity gains in this industry in the immediate 20 yr than in the egg production breeding industry, unless the latter chooses to abandon its conservative stance. Nutrition. In a similar review 6 yr ago (Sheldon, 1993), my assessment was that basic research in nutritional biochemistry and physiology of growth and reproduction was being neglected in favor of empirical, applied research, which still seems to be true. Therefore, there are no obvious major areas of new basic knowledge awaiting application in the industry, but the large literature of applied nutrition research results continues unabated. For example, the Proceedings of the 11th European Symposium on Poultry Nutrition in 1997 contains 115 papers or posters. Such research tends to have relatively short lag periods before industry application. Thus, continuing but smaller gains in efficiency of production are assured for the indefinite future. Apart from the traditional areas of nutrition research summarized in my 1993 review paper, further significant progress has been made recently in fine tuning the development of least-cost or most profit-

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the first is the continuation of the irretrievable loss of hundreds of useful poultry strains (improved and unimproved) throughout the world in the past 50 yr. Many attempts in many countries have been made in that time to half this short-sighted process but without success. The latest example that I am familiar with occurred in the past few years in my own country, where a similar process has been occurring for some 40 yr previously during the development of an Australian poultry breeding industry, under the indirect protection of national quarantine regulations. During the past few years, breeding stock of the main international breeding companies were allowed entry to Australia with the inevitable result that a further 20 or more internationally competitive Australian egg or meat strains have been lost. The lack of genetic conservation procedures for very valuable poultry genotypes is not confined to loss of improved commercial strains. In the past 20 yr, public funding for poultry genetics research has decreased largely in response to the overall control by the few international poultry breeding companies. As a result, a high proportion of unique poultry genotypes, developed at universities and research institutes, which are essential to future research needs, have either been lost or are under extreme threat of extinction. This unjustifiable waste of such valuable poultry genetic resources in any of these circumstances must be somehow halted.

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health, and fewer mortalities. Electronic lighting controls have also enabled the application of best lighting patterns for type and age of flock, indicated by physiological and endocrinological studies of the past 20 to 30 yr, including the possibility of ahemeral light treatments (e.g., see Lewis and Morris, 1998 for review of some aspects). Costs of production have also been able to be reduced significantly by modern labor-saving devices allowing automated and intermittent feeding, automated egg collection or even broiler pick-up, and better mechanized or automated manure disposal. The time lags between discovery or innovation and industry application in these areas might be expected to be quite short. However, two factors inhibit this simplistic expectation. The first is that the capital cost of many of these improvements is relatively high. The second is the capital investment in and expected lifetime of existing facilities. In addition, in my experience the rate of acceptance and implementation of innovations in these areas, especially those involving high-tech procedures, is relatively low. Therefore, there is still a very large reservoir of productivity gains to be made from these sources in the next few decades. With respect to animal welfare considerations, which currently loom so large in European thinking and action on poultry husbandry, they are unlikely to make a great impact on efficiency of poultry production in a global context. The vast majority of the world population will most likely continue to assert their right to a desirable level of animal protein in their diets, provided that the production systems are not demonstrably cruel or unduly stressful to the animals. The relatively low level of research on these issues in poultry in the past few decades does not yet allow unequivocal answers to many of these questions. Therefore animal welfare will remain as a priority area for research in the foreseeable future.

Future Applications from Current and Future Research Molecular Biotechnology. It is simply not possible to exaggerate the profound impact that the very recent and continuing explosion of knowledge in molecular biology will have on applications in all the life sciences throughout the next century. So far I have referred only briefly to successful innovations in diagnostic techniques and vaccine production for poultry diseases. The full extent of its potential utility in poultry technology can be assessed to some degree from the incredible advances already made in human genetics, in plant breeding, and in the genetics of the model organisms used in such research: mouse, Drosophila vinegar fly, nematode Caenorhabditis, zebra fish, plant Arabidopsis, and several microorganisms. For example, the mammoth international project for mapping and sequencing the human genome has been in progress for only 10 yr but is planned to be completed by 2003 with a rough draft available by the year 2000 (Marshall, 1999). By 1990 there were some 3,000 molecular markers on the emerging linkage map (Sheldon, 1990).

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able feed formulations and optimum utilization of amino acids, in phase-feeding, in the use of enzymes to deal with digestion problems of nonstarch polysaccharides in some cereals, (Choct, 1998, 1999), in the use of probiotics especially to replace antibiotics in feed (Grashorn, 1998), in use of choice feeding (Gous and Swatson, 1998), and in the development and use of computer simulation models in intensive poultry production (Fisher and Gous, 1998). In 1993, I described two neglected areas urgently needing a great deal more research to meet the needs of the 21st century. In one of them, the need to find, evaluate, and use alternative and cheaper feed ingredients for poultry feed, some progress has been made in the past decade (Sheldon, 1998). The resources being devoted to this area, which is so intimately related to the global challenges and targets discussed above, still need to be increased many fold. In the second area, the need to define specific nutrient requirements for specific commercial strains of layer and meat chickens and other avian species has been addressed only occasionally in the literature (Leclercq, 1999), despite a wide awareness of the problem (Gous, 1993). These two areas clearly must receive much higher priority in the next two decades. Health. Because of the dramatic nature of many disease problems, especially those new or emerging, the lag time from recognition of the problem to research study to application of a solution (vaccine, management, and selection for resistance) is normally quite short, as with applied nutrition. This short time line has been the pattern through most of the 20th century, although the more complicated situation of resolving so-called leukosis complex problems into Marek’s Disease virus and Lymphoid Leukosis virus and then producing Marek’s disease vaccines in the late 1960s and early 1970s may have taken a little longer. In my 1993 review paper, I indicated that such traditional approaches would have continued to provide efficient diagnostic and control measures for the future. However, it had already become apparent that the new molecular biology and biotechnology techniques were starting to be applied effectively in poultry for improved disease diagnostic kits and vaccines (Gavora, 1992; Sheldon, 1990, 1993). As expected, these far more efficient techniques are becoming standard in poultry health research and industry application (Cavanagh et al., 1998, Lutticken, 1998), thus assuring additional gains in productivity for the indefinite future. Housing and Husbandry. The importance of improvements in these areas to overall improved productivity in the modern intensive industry is sometimes overlooked. Significant improvements in design and construction of poultry housing have been made possible by better building materials, including insulating materials, more efficient heating and cooling systems, and automated controls made possible by developments in computers and information technology. The latter developments have also made possible more efficient farm and business management methods. The consequent ability to control the bird environment against extremes of heat and cold has allowed a higher efficiency of feed utilization, better

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Other examples of typical studies attempting to identify by the new biotechnology QTL or other genes suitable for manipulation are reported in Atzmon et al. (1998), Daval et al. (1998), Lagarrigue et al. (1998), Einat et al. (1998), and Barrow and Bumstead (1996). Such studies will also provide the basis for poultry breeding in the coming decades. Clearly the new era in terms of industry application has barely begun. The identification, location, and cloning of candidate genes for manipulation, either by MAS or transgenic approaches, is also assisted very significantly by the amazing genetic homology between genera separated by over 400 million yr of evolutionary time. This knowledge has been reported in the voluminous literature on molecular studies of the developmental genetics of microorganisms, Drosophila, Caenorhabditis, zebra fish, mice, and humans over the past 20 yr. Scarcely a month goes by without a report that another of the main developmental genes of Drosophila has a counterpart gene with a high degree of homology and similar functions in human, mouse, nematode, and even chicken. One example will suffice to demonstrate the potential for application in poultry. The first two circadian rhythm genes were discovered in Drosophila and the fungus Neurospora nearly 30 yr ago (Konopka and Benzer, 1971; Feldman and Hoyle, 1973). Although these genes were useful in studies on the biology of circadian rhythms in the next 20 yr, the period was not noted for further major discoveries. Recent years, however, have witnessed a veritable explosion of knowledge on new circadian rhythm genes in Neurospora, Drosophila, mouse, and plants and on the molecular basis of their function (reviewed by Dunlap, 1998). Several of these genes occur across genera as widely separated as Drosophila, mammals, and other vertebrates including chicken. Indeed a recent series of papers indicates that cytochrome, a light-absorbing protein, plays a similar role in circadian systems in plants, Drosophila, and mouse (Barinaga, 1998). The point of this example is that the work referred to in a previous section on selection for short interval between eggs in continuous light (Sheldon and Yoo, 1992, 1993; Yoo et al., 1986) indicated strongly that the endogenous circadian rhythm of ovulation had been altered in the selection lines. The opportunity therefore exists to identify and clone a circadian rhythm gene responsible for this (e.g., Noakes et al., 1998) and to use it for transgenic manipulation of strains of chickens or other avian species that do not have it. The biggest uncertainty in this situation is whether the selection line genotypes will still be available when needed for this work or will have already been lost due to the forces acting against their survival, as discussed in a previous section. Identification, location, and cloning of useful candidate genes is a prerequisite for their manipulation by the new recombinant DNA technology to produce transgenic chickens. Research on the techniques needed to produce transgenic chickens has been in progress longer than modern poultry genome mapping (Shuman and Shoffner, 1982; Sheldon, 1990). In those early days, it was even optimistically thought that the search for techniques

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Now it is many times that number. By 1990, molecular diagnostic kits were available for only a few human disease genes. Now there are dozens, and in many cases the genes have been located on a chromosome, cloned, and characterized. The completed project embracing some 70,000 genes will provide the knowledge base for human medical research and treatments, including gene therapy, for the unlimited future. However, the success of the project has required the collaborative contributions of many major laboratories, many more smaller ones, hundreds of research scientists, and hundreds of millions of dollars per year. We in the livestock sciences can only gaze in awe and envy at the availability of this level of resources. A second example demonstrating the potential of the new molecular technology when sufficient resources are applied is in the area of transgenic plants. Abelson (1998) refers to the billions of dollars now being spent annually by major commercial companies and to the many successful genetically altered crops, with resistance to herbicides or insect pests, already on the market. He noted that we are still at the very beginning of this new technological revolution and likened its eventual impacts to those of the Industrial Revolution and the recent computer-based revolution that is now well advanced. In contrast to the above areas, the resources available for molecular biology research in livestock species, including poultry, have so far been miniscule. In each main species only a few main laboratories have been involved, starting mostly from the late 1980s or early 1990s. Nevertheless, in poultry, significant progress has been made in several areas as the previous “black box” of quantitative genetics has begun to yield its secrets. The total number of molecular marker loci on the three main poultry genome linkage maps (Compton, East Lansing, and Wageningen) is now over 2,000 (e.g., Groenen et al., 1998). Good progress has been made at integrating the three maps, representing some 1,400 loci so far (M.A.M. Groenen, personal communication). In addition, a few other laboratories have individual maps with fewer loci not yet integrated into a single map. The average spacing between markers on the combined linkage maps is thus approaching 2 centiMorgans (cM), which is adequate for initial location of known functional genes or potential quantitative trait loci (QTL). Good progress has also been made in alignment of linkage groups with the macrochromosomes and in the labeling and genetic mapping of microchromosomes (A. Vignal, personal communication). Such a minimal genome map is normally a prerequisite for locating either useful QTL for subsequent markerassisted selection (MAS) (e.g., Tixier-Boichard et al., 1998; Mariani et al., 1998; Weissmann et al., 1998; Yunis et al., 1998) or known functional genes for subsequent manipulation. Much research effort is being expended on integrating MAS optimally with the conventional quantitative genetics approach to animal breeding (Walton and Holm, 1998; Kinghorn and Van Der Werf, 1998; Andersson, 1998). The results will provide an essential bridge between the old and new approaches for the near future.

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ond, the great need for alternative and cheaper ingredients for poultry feeds is now most urgent. Much of the increased research needed in this area has to be done locally in the developing countries where the need is greatest. Included in this general area of more efficient feed ingredients should be the new potential to produce transgenic plants with higher nutritive value for poultry (e.g., higher levels of S-amino acids from a sunflower gene in lupin, Spencer et al., 1997). Third, definition of specific nutrient requirements for specific strains of birds has to become a regular feature of applied nutrition research. During all the research and development of new poultry genotypes over the past 50 yr, it has been neglected. The rate of change of poultry genotypes over the next 50 yr will not be any less, so efficiency of production will be less than optimal unless these questions are addressed. Included under this heading of specific nutrient requirements should be the potnetial transgenic strains of poultry carrying foreign genes for more efficient feed conversion, e.g., for digestion of fiber or for synthesis of S-amino acids. These will become a reality in the first half of the next century. Health. As referred to above, application of molecular biotechnology to production of improved diagnostic kits and vaccines is now well established. It will continue to grow as a major component of these traditional aspects of disease control in the years ahead. However, the main future contributions to disease control at a more basic biology level will come from further understanding of the structure and function of the major histocompatibility complex (MHC) in relation to components of the immune system and to other genes for resistance or susceptibility to disease. It is almost 50 yr since the B blood group system was discovered and almost 40 yr since an association between it (part of the MHC) and the immune system was found. The elucidation of the genetics and immunology of these systems has taken a long time. However, the advent of molecular biology techniques has recently led to an acceleration of progress in these areas (e.g., Edwards et al., 1999; Gavora, 1998; Hala et al., 1998; Kaufman et al., 1999; Sarker et al., 1998; Van Der Poel et al., 1998; Thoraval et al., 1998). There is no reason why this progress should not continue, allowing many new applications of this knowledge to breeding or otherwise producing disease resistant strains in the next 20 to 30 yr. In addition to the above, significant progress has been made in recent years on many other basic aspects of the immune system of chickens (e.g., Boyd and Siatskas, 1997; Muir, 1999). As with the MHC-related basic studies, the continuation of the present level of basic research on various aspects of the avian immune system will ensure practical industrial applications in the near future. Reproduction. In contrast to the past applied and empirical emphasis in nutrition research, avian reproductive physiology and endocrinology have been characterized by some 30 yr of productive basic research but with few obvious significant applications so far in the poultry industry. The gradual revelation of the complexities of neural, endocrine, and environmental determinants of

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would be successful before suitable candidate genes were available for manipulation, but this has not happened. Despite concentrated efforts by a few laboratories over a 15-yr period and the production of relatively small numbers of germ-line transgenic chickens, the success rate is still short of that required for routine, efficient use in poultry breeding (Naito, 1996; Etches, 1998; Sang et al., 1998). Nevertheless excellent progress has been made in the background techniques required specifically for chicken such as embryo culture; the culture, storage, and use of blastoderm cells or primordial germ cells; and the variety of technical options available for transferring foreign genes. It is simply to be hoped that the lag period from the first dramatic transgenic mice in 1982 to efficient procedures in chicken will still be considerably less than 40 yr. When it does occur, as it inevitably will, dramatic productivity gains will be possible in egg and meat production, in disease resistance, and in the ability to produce foreign proteins of value in the hen egg. The time scale of progress in these areas of molecular biotechnology is, as in most fields of science, largely proportional to the resources made available for the necessary research and development. For poultry biotechnology, so far, these resources have been minimal, barely sufficient to establish a presence in the field. If this revolutionary technology is to make its essential contribution to meeting the world needs for animal protein, through the poultry production targets discussed previously, the research and development resources applied to it in poultry need to be at least trebled or quadrupled. My emphasis on the critical importance of the new molecular biotechnology to the challenge of feeding the world population does not imply a lack of awareness of the current social controversy on the acceptability of genetically modified foods. However, there is neither the time nor space to explore it in detail here. Poultry scientists would share the consensus of most biologists that the perceived problems must be dealt with as objectively as possible by the scientists involved. At the same time, communication with the public must be increased significantly so that an informed public can also make decisions on as objective a basis as possible (for a brief discussion see Bulfield, 1998). Many of the other areas of poultry science and technology that will also assuredly have significant future industrial applications will also depend to a greater or lesser extent on the new molecular biotechnology. However, this is a future fact of life for all the life sciences that must now integrate their accumulated knowledge from biochemistry, genetics, microbiology, and physiology with the new molecular biology. A few of these areas are dealt with separately below, partly for continuity with the past, and partly for convenience. Nutrition. The main comments under this heading in the previous section simply need re-emphasizing. First, there needs to be a large increase in basic research in nutritional biochemistry and physiology (e.g., Watkins, 1999; Wiseman, 1997), so that future nutritional technologies can be more science-based and less empirical. Sec-

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partly reversed as early as hatching by more than one Z chromosome in 3A.ZZW birds or in chimeric birds (e.g., 2AZW/3AZZZ). Sinclair et al. (1997) reported studies searching for novel genes expressed in the chicken embryonic genital ridge, which led to the identification of a gene (ASW) on the W chromosome (O’Neill et al., 2000). Gene ASW was expressed only in female genital ridges and was also shown to be W-linked in 17 bird species from nine families of Aves but not in rattites (emu and ostrich), which do not have Z and W chromosomes. However, O’Neill et al. (1999) also showed that ASW cDNA hybridizes to Southern blots of both male and female bird DNA, indicating a similar gene on the Z chromosome or an autosome. Therefore, they are unable to distinguish at present between a model of a dominant female-determining gene on the W chromosome or a Z dosage model of sex determination. Whichever proves to be correct ultimately, clearly the way has been opened to manipulation of the sex ratio by transgenic, chromosomal, or biochemical treatments. In this field of reproduction, as in most of the others discussed above, unpredictable discoveries and applications will continue to occur just as they always have. More and more they will be multi-disciplinary in nature. However, I am not concerned to try to probe the absolute darkness when so many possibilities exist based on present knowledge. One poultry example will suffice to indicate what could be possible among the more esoteric areas of research. Modern poultry cytogenetics became possible only in the 1960s and early 1970s, after which progress was reasonably rapid, considering the small number of laboratories involved in the work. Although tetraploid (4n) and hexaploid (6n) plants are commonplace in evolution and in experimental science, such phenomena are very rare in vertebrate animals, apart from fish. Nevertheless, Shoffner and his co-workers, using the established chemical techiques for arresting meiotic division in plants, were successful in the early 1980s in producing diploid (2n) sperm in poultry. As far as I remember, diploid ova were not produced by this technique, although it has to be acknowledged that the work was on a pilot scale only. It has also been known for some years that triploid (3A.ZZW) intersex chickens occur at a low frequency (< 1%) in many layer strains of poultry. Thorne and Sheldon (1993) selected a triploidy layer line, which produces 15 to 20% diploid ova, as reflected in 15 to 20% triploid embryos and 8 to 14% live triploid chickens. It also produces occasional live, fertile chimeric chickens, e.g., 1A.Z/2A.ZW, 1A.Z/2A.ZZ. This line does not appear to produce diploid sperm, i.e., the gene(s) responsible for meiotic nondisjunction affects only females. Nevertheless, the opportunity now exists to produce tetraploid chicks, using the diploid sperm approach and females from the triploidy line, provided of course that the triploidy line survives the pressures referred to earlier. This opportunity has not been able to be pursued in the past 15 yr because of lack of funding. As with most fields of science, there is no way of predicting practical applications stemming from this approach. The important thing

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growth, sexual development, and reproduction in male or female adults can be traced in the four yearly, International Symposia on Avian Endocrinology since 1976. Knowledge of the key elements in a system, e.g., egg production, could allow selective breeding based on those criteria or even manipulative treatment of the birds to achieve a desired result. This approach has not yet been possible because the knowledge base is still not complete enough. Probably the most significant residual problem area under this heading is the poor reproductive (mainly egg production) performance of broiler breeder females. Measures to deal with the problem in industry over the past 40 yr have been largely confined to empirically-based restrictive feeding and lighting treatments. Even the best of these has not been able to raise the number of hatchable eggs per broiler breeder female to much more than half the level of layer strain females. Therefore, significant advances in solving this problem will depend on a deeper understanding of the basic neuro-endocrine mechanisms involved. Although good progress is being made (e.g., Goddard et al., 1992; Hertelendy, 1992; Johnson and Wang, 1992; Onagbesan et al., 1992; Peddie, 1992; Johnson, 1992; Morley et al., 1997; Saito and Shimada, 1997; Soboloff et al., 1997), very few basic studies have focused specifically on the recalcitrant broiler breeder problem (Hocking and McCormack, 1992). At this rate, we face probably another 20 yr before solutions to the problem emerge from such studies. However, if the commercial breeders grasp the nettle, selective breeding for higher egg production in their broiler female lines could conceivably provide a solution in a similar time frame. A further area of research likely to yield practical applications on the same time scale is that of the genetics of sex determination and the possibility of manipulating the sex ratio, i.e., to maximize the proportion of male chicks in commercial broiler strains or of female chicks in commercial layer strains. These new possibilities emerged barely 10 yr ago with the discovery and cloning of the testis-determining gene (SRY) on the Y chromosome in human (Sinclair et al., 1990) and mouse (Gubbay et al., 1990). In the intervening period, the complexity of the function of SRY and its interaction with other genes involved in the determination of sex in mammals has begun to be known in detail (Goodfellow et al., 1993; Kent et al., 1996; da Silva et al., 1996; Capel, 1998). The SRY gene has not been identified in birds, which is not surprising as birds have ZZ male, ZW female chromosomal sex, the opposite of XX female, XY male in mammals. However, some of the other interacting mammalian genes have been identified cloned and studied in birds (e.g., SOX9, Kent et al., 1996; anti-Mullerian hormone, Carre-Eusebe et al., 1997; and aromatase, Ono et al., 1988; Mizuno et al., 1997; Nakabayashi et al., 1997). In addition, Thorne and Sheldon (1993) and Sheldon and Thorne (1996), in a series of studies of triploid intersex chickens (3A.ZZW), have shown the primacy of the W chromosome in female sex determination. However, even if there is a female sex-determining gene on the W chromosome, its effect can be inhibited or

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is that it is possible in poultry, whereas virtually all such ploidy events in mammals appear to be embryo lethal.

Special Needs of Extensive Small-Scale Poultry Production

3. Low-cost feed supplements based on local ingredients not needed for human nutrition. 4. Improving the socio-economic factors in rural life that will promote successful development of small-scale poultry businesses. This improvement is at least as important as the above three scientific-technical components. It is well worth repeating that it must include adequate education and training at all levels, including agricultural extension, full involvement of women at all stages of the development, provision of low-cost credit facilities, and development of suitable marketing systems, including cooperatives. Improvements in these directions are in their infancy, but the seeds for an explosive growth of research and development in this field have been sown. The only limitation now is adequate resources and funding (see references of Sheldon, 1998). In helping to meet these special needs of extensive small-scale poultry production, so essential to perhaps 50% of the world population, the world poultry science community faces its greatest challenge of the next half centruy. That is not to say that individual poultry scientists and their institutions have not already made significant contributions to these needs. We thank them for blazing the trail that the rest of us must attempt to follow if we are to be worthy of our profession and its communal objectives, exemplified by the American Poultry Science Association and the World’s Poultry Science Association.

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This is the shortest section of the present paper but its subject is of the highest priority for the world’s poultry science community in the years ahead. This was emphasized in the two review papers already referred to (Sheldon, 1993, 1998), so this presentation is largely an updated summary of those evaluations and conclusions. Let us briefly recapitulate the current and future realities. The advances in poultry science and their future application to industry discussed in this paper will be adopted primarily through an extension of the revolution in poultry technology. This discussion will apply fully only to the countries in Groups 1 and 2, comprising 30% of the world population. However, the realistic targets for poultry egg and meat consumption set by China, India, and, by implication, the other 100 countires are much less than the actual or predicted consumption in the Group 1 and Group 2 countries. This finding reflects the reality that the products of a high-cost, modern industry will remain for a very long time beyond the affordable reach of a large majority of the populations in the Group 3 and Group 4 countries. This condition will still be the situation under any realistic view of how fast the gross domestic product per head and the disposable incomes of people in the poorest economies can be increased. Therefore, in the middle of the coming century, at least 25% and probably much more of the world population will still not be able to capture the consumer benefits of a modern, intensive poultry industry. The only feasible way to deal with this problem is to develop on a grand scale more efficient poultry (avian) production systems based on the traditional small-scale units of the farming communities and villages of most of the world. Thus far, the resources available for research, agricultural extension, and education in this area of greater need have been very modest compared with those supporting research and development for the expansion of the advanced poultry industries. To achieve the grand scale of resources needed to correct this imbalance will require many times the current inputs from all the existing and potential supporters of such initiatives, including the world poultry science community. The following priority objectives that have to be addressed urgently are well recognized: 1. Effective disease control of poultry flocks, primarily by developing efficient, thermostable, low-cost vaccines (e.g., Spradbrow, 1993, 1996). 2. Widest possible criteria for choice of the best poultry genotypes for use in specific environments. This choice could range from local indigenous breeds to crossbreds of various types, not excluding components of improved strains from the advanced industries.

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