Abstract:
Proc. Assoc. Advmt. Anim. Breed Genet. Vol12 TWENTY-FIRST CENTURY CHALLENGES FOR GENETIC IMPROVEMENT IN THE LIVESTOCK INDUSTRIES J. F. Taylor, J. 0. Sanders, and J. L. Rocha Department of Animal Science, Texas A&M University, College Station 77843, USA SUMMARY The 2 1st century challenges for genetic improvement are as they have always been and as they will always be for any century: l- keep it simple; 2- harness the theory and the practice of selection into the shaping of an ideal that is economically meaningful within the context of the specific production and marketing environments; 3- creatively and effectively combine the available stocks in the shaping of that ideal (i.e., efficient crossbreeding systems); 4- the wise use of available technologies that could foster the accomplishment of that ideal. In the 20th century, the dairy, swine and poultry industries evolved into extremely powerful and efficient breeding machines and production systems. Some costs accompanied the success, and to contain these while maintaining the pace of progress will be one of their main challenges in the next century. In beef cattle breeding, remarkable accomplishments were made throughout the 20th century in the development of adapted types that can survive, reproduce regularly and grow in a multitude of production environments. For the 21st century, the genetic challenges will be to continue to focus on the overall biological and economic efficiency of the total production system, but including in that effort the consideration of those characteristics that determine consumer acceptability of the final product. For this to happen, the development of an economic alignment between the different segments of the industry is one of the most important challenges to be met. The 20th century was notable for a genetic concern about means, while in the 2 1st century, genetic improvement must accommodate concerns regarding both means and variances. The U.S. sheep industry is in a period of crisis, and their first genetic challenge for the 21st century will have to be the definition of a clear and realistic vision for the role that the industry is to play in the broader context of agricultural and marketing systems. The essence of genetic improvement will remain the same, but change will be a constant, and to be prepared to anticipate and to cope with change will be one of the key challenges for the livestock industries in the 2 1st century. Keywords: 2 1st century, genetic improvement, livestock breeding, beef cattle, future. INTRODUCTION In 1983, the American Society of Animal Science published its Diamond Jubilee issue, commemorating seventy-five years of progress, and Gordon Dickerson and Dick Willham wrote: 'In pausing to evaluate progress in quantitative genetics and breeding (..), and especially in attempting to forecast future developments, we become acutely conscious of the very real limitations of personal perspective and of the enormous breadth and depth of this one rather specialized discipline' (Dickerson and Willham 1983). As we struggled to seriously address the topic, the truth of their statement became evident. Livestock production constitutes a rather 1 Proc. Assoc. Advmt. Anim. Breed Genet. Vol12 complex system of many interacting components. If the system of reference is carefully bounded, then it may be quite simple to define what genetic improvement means in terms of the profitability of a given operation within a defmed planning horizon. But, as we proceed to expand the system of reference, and if we consider the many sources of variability that are non-genetic, then the definition of just what constitutes genetic improvement is probably beyond consensus. However, if we fail to reach consensus, it is probably meaningless to speak of challenges. Hence, the first and key challenge for genetic improvement, is to defme what the term means. In 1979, Tom Cartwright commented that 'perhaps even Lush did not perceive the complexity of defining and assessing merit' (Cartwright 1979). Cartwright (1979) continued: 'this area of defining and assessing merit is the weakest link in the current application of animal breeding theory to real lijt: at least for some classes of livestock ' Beef cattle breeding, which will be the focus of this paper, certainly suffers from this limitation and, this fast challenge must be faced by all of us, if consensus is to be possible. Just as in every animal breeding text book, we shall conveniently ignore this issue and shall assume that we all understand and agree on the meaning of genetic improvement. But we alert you to the fact that this is not true and that this is the &V challenge. The other great difficulty inherent to the treatment of these types of topics, and which is also often ignored, is who is to benefit from genetic improvement? Whose perspective should we adopt in order to address the topic of challenges ? James (1982) was correct in noting that 'Moav (1973) a'rewattention to a rather d@kxlt problem in evaluating breeding programs. `I The perspective of national interest, that of the established individual breeder, and that of the new investor, are often at odds with each other (Moav 1973). On the brink of the 21st century, we could perhaps add one more perspective, that of the human species. Which of these perspectives should we select in order to address the proposed topic? In other words, whose are these challenges that we have been asked to define? We chose to address the topic from the perspective of those who really make the genetic improvement. Those who own the stock. The individual beef cattle breeder who produces seedstock. The 21st century challenges for genetic improvement are really theirs and not anyone else's. Further, we believe that the future is the past not yet understood. Therefore, in trying to understand the challenges for the 21st century, our fust question was to ask ourselves if we understood what those challenges were for the 20th century. We tried to place ourselves in the year of 1900, possessing the knowledge available at the time, to look into the future that now is already past, exactly as we are doing now for the 21st century, but with the benefit of hindsight. To do that we chose to focus on a particular family of cattle breeders whose successive generations ran a successful operation throughout the entirety of the 20th century. They were successful in the 20th century, and that must mean that they met their challenges. If we succeed in capturing the essence of what were the 20th century challenges for genetic improvement, then we should be better equipped to anticipate the challenges for the 21st century. Perhaps they will be the same. After all, the essence of breeding will not change in the 21st or in any century as long as we continue to deal with the basic reality of biology within an economic context. 2 Proc. Assoc. Advmt. Anim. Breed Genet. Voll2 THE LOMA BLANCA The thing that hath been, it is that which shall be; and that which is done is that which shall be done; and there is no new thing under the sun. Ecclesiastes 1:9 South of the Nueces River, in South Texas, there is a white hill which people call the Loma Blanca. When it is dry, looking out to the southwest one can see a wide expanse of cracked earth, white from the heavy salt content. The eddies of wind carry sand and salt back and forth across the parched surface, and at night the yelping of the coyotes hidden in the brush breaks the silence (Lasater 1985). At least it was like that in the year of 1900 when Ed C. Lasater rode to its top. He had lost all of his family within a three-year period, and he was still slowly recovering from a debt of $130,000 incurred a few years earlier, when the cattle cycle had once again reached its bottom in 1894 (Lasater 1985). That December night of 1900 he was forty-years-old, a new century lay ahead of him, and he rode to the top of the white hill to envisage the future. He was a rancher and a cattle breeder, his personal and business misfortunes were intertwined, and he had begun to face the challenges he would need to overcome if he were to successfully rebuild his life and make his way in the cattle business of the 20th century. As he looked to the future, if he could, he would have seen a towheaded boy riding ponies and giggling with delight (Lasater 1985). It was to be his son, Tom. Next he would see two herds of excellent purebred Hereford and Durham Shorthorn cattle grazing the range. The Herefords had pigmentation around their eyes to reduce the risk of cancer eye (Lasater 1985). These were the cattle that he owned and bred at the time, but they were not the cattle of the future. The Shorthorns were big, wide-framed and blood red (Lasater 1985). Both were good purebred cattle herds, among the best there were in Texas, but in many years of less than enough rain they performed very poorly. The cows had a hard time rebreeding, while the calves were very slow to put on weight. Further, both breeds were bothered by the intense heat of the South Texas summer, and by the numerous ticks, flies and mosquitoes of the region, which resulted in unacceptable death rates and other losses of productivity. The cattle were good, but they were not what was needed to make the best of that range (Lasater 1985). To make his purebred cattle really productive he needed to considerably improve the range. But he knew that he could not afford to do this and that if he was going to make it, he needed a low-cost operation. He had already noticed that crosses between the two breeds produced a somewhat more productive calf, and he took advantage of this strategy (Lasater 1985), but it was still not enough. The key was on the cow side, not the calf. He needed a cow that could produce a calf every year, maintain enough condition to rebreed, yet produce sufficient milk to support the growth of an acceptable calf. He needed a cow that could fully utilize the range and that would not be bothered by the heat, ticks or flies. Earlier that year, in March, across the Atlantic, the editor of the Reports of the German Botanical Society had received for publication a manuscript from a professor of botany at the University of Amsterdam reporting the rediscovery of the work of Mendel (Dunn 1965). This did not impact the 3 Proc. Assoc. Advmt. Anim. Breed Genet. Vol12 man on top of the Loma Blanca. If he could, he would have been absorbed with the vision of a 'grotesque, humped animal' (Lasater 1985). This was a cow that easily took on flesh on short range, was apparently immune to ticks and fever, was heat tolerant, not bothered by flies, that seldom had to be treated for screwworms, and that rapidly multiplied in numbers around the Loma Blanca (Lasater 1985). He would have seen that in years when Shorthorn and Hereford yearlings were not in a condition to sell, humped steers were, and that packers found them to dress well and were ready to pay good prices for them (Lasater 1985). He quickly figured that an animal with these attributes could raise the value of South Texas rangelands by $2.00 an acre, and by 1908 he had bought the frost set of humped bulls and had initiated a long-range crossbreeding program. He crossed Gir bulls on his Shorthorn cows and bred Nellore and Krishna Valley bulls to a herd of Hereford cows (Lasater 1985). Two years later, T.H. Morgan would publish a scientific review concerning the chromosomal organization of the hereditary material (Dunn 1965), and at about the same time many around the Loma BZanca were commenting negatively on the foolish ideas that would lead an otherwise astute cattleman to ruin `damned good he&' of purebred cattle (Laaater 1985). Our man, however, noticed neither event since he saw that his crossbred humped cows were returning in net five to ten percent more than the best management could yield from the same ranch stocked with Shorthorn cows (Lasater 1985). In 19 14, he purchased an additional 162 Brahman bulls to use on his herd (Lasater 1985). In 1928, Frederick Griffith, a Medical Officer with the British Ministry of Health, was a bacteriologist studying the infection of mice with Diplococcus pneumoniae (Moore 1993). These were the experiments that ultimately led to the discovery of DNA, but our horseback rider would never learn of DNA In 1930 he would hand over the reigns to his operation to Tom, the towheaded boy (Lasater 1985). His 20th century challenges were to understand the production system and the environment of his ranch and to identify the right cow to match those resources in order to shape a low-cost yet highly productive operation. He had resolved the key piece of the breeding puzzle - the identification of the right cow-type, and the outline of the system of breeding to produce that cow, crossing of breeds. Building on his father's accomplishments, Tom's two main challenges were to be to defme exactly the crossbreeding system to be implemented, and to decide the direction in which to shape the cow and its calf, i.e., the selection program. Tom's 20th century challenges were difficult to resolve. He needed a cow that was about half of the humped type, but to fdl the other half he had a choice to make among his Herefords and Shorthorns. Tom studied the performance of the two types of crosses, without resolution. Also, the hybrid cow that he needed did not replace itself and he did not want to keep upgrading toward the zebu. To keep purebred herds was not economically feasible. He could purchase replacements, but besides the fact that no one else was producing this type of cow, except for his neighbors to the east (Lasater 1985) that was really not an option for him. If he could find the right. solution for his challenges he would be selling, breeding stock to ranchers, not buying them. After trying different approaches, he found that the Shorthorn cross bulls performed better than the Hereford cross bulls and he bred them to Hereford cross cows. As Tom would explain, 'as soon as the three-way cross c&es hit the groum.4 a blind man could see they were far superior to either of the straight crosses, so we started producirig more of the three-way Shorthorn/HereforaC/Brahman cross' (Probandt Proc. Assoc. Advmt. Anim. Breed Genet. Vol12 1978). Tom decided to breed enough of these three-way crosses to produce a foundation herd with a little less than one-half Brahman blood and the balance being equally divided between Hereford and Shorthorn (Probandt 1978). For about five years he bred a large three-way herd that would allow him to stay free from problems due to inbreeding, and in 1937 he closed the herd and terminated the crossbreeding programs (Probandt 1978). From this point he focused on the improvement of the foundation herd. He had found the right combination of the breeds and had also resolved the problem of how to produce a replacement for the hybrid cow that he needed in the ranges surrounding the Loma Bluncu. Some thirty-five years before the classic paper of Gordon Dickerson, which would formalize the theoretical approach (Dickerson 1969), Tom had formed a new breed of cattle, a synthetic. Two of the major challenges inherited from his father Tom had now successfully met. The definition of the exact breed composition for the cow could be considered a detail building on his father's contribution, but the solution of the synthetic breed was a breakthrough with all the trademarks of a master-breeder. This would again become evident in the shaping of the selection program for the new breed (Lasater 1972), Tom's last remaining challenge. One year before the publication of 'Animal Breeding Plans' by the Iowa State University Press (Lush 1937), Tom had already bought a new set of cattle scales and had initiated a systematic program of performance testing on the ranch around the Loma Bluncu (Probandt 1978). Tom built his program around six essentials: disposition, fertility, weight, conformation, milk production and hardiness (Lasater 1972), but the emphasis was clearly on functional and reproductive efficiency. Any cow that could not wean a good calf every year, beginning as a two-year-old, was culled (Lasater 1972). Sixtyfive day breeding seasons, males and females bred at 12 to 14 months, an SO-90% replacement rate from each heifer-crop in order to intensify culling on the cow herd, and any cow without a good calf at weaning or that needed assistance to calve was culled (Lasater 1972). In order to select for milk production, herd sires and heifers were culled on weight at weaning and there had been no 'eyeballing' of weight with him since as far back as 1936 (Lasater 1972; Probandt 1978). Noticeably excitable or high-strung animals were systematically eliminated from the herd in order to prevent disposition problems and he also had a 'gentling program' at weaning for his replacement cattle. Calves that refused to submit to handling were culled (Lasater 1972). Besides the selection on weaning weight, a post-weaning gain test was conducted under range conditions for bulls up to one-year of age. Females were not selected on weight except at weaning (Lasater 1972). In 194 1, seven years before C.R. Henderson would complete his graduate work laying the foundations for mixed model evaluation of EPDs, Tom began selling breeding bulls providing performance data to his customers, in order to emphasize to the industry the importance of growth rate (Probandt 1978). Based on Warwick's (1958) account of the status of the beef industry in 1958, this appears to have been a pioneering initiative on the part of the son of the man of the Lomu Bluncu. Tom's selection for conformation was an attempt to improve the cutability of his newly formed breed. He culled individuals that were 'weak' in the hindquarters or that showed tendencies towards wasty fatty deposits in the brisket, the flank and the top-line (Lasater 1972), but the selection criteria were clearly subjective. Tom also paid special attention to bad legs, pendulous 5 Proc. Assoc. Advmt. Anim. Breed Genet. Voll2 sheaths and weak eyes to emphasize functional efficiency. Selection for hardiness meant that any animal requiring any special care was culled and that medication and vaccinations were kept to a minimum to develop a disease-resistant breed (Lasater 1972). Tom also believed in multiple sire mating to maxim& the opportunity for all cows to conceive in their fmt heat. He feared that single sire mating could result in the favoring of individuals with low inherent fertility, with all its negative implications for a program with a drastic emphasis on female fertility (Lasater 1972). He also firmly believed that a cow should never be culled on age alone, 'the cow of advanced age whose calves are still meeting all production stanabds is the gem for which everyone is looking. She is introducing effective longevity into the herd' (Lasater 1972). Tom completely disregarded non-functional traits, such as color and other 'breed characteristics,' he was also not very fond of keeping records (Lasater 1972). In 1944, Avery, MacLeod, and McCarty, who for a decade had been following up on the findings of Frederick Griffith, suggested that DNA was the material responsible for heredity (Moore 1993). Four years later, in Denver, Ernie was the Grand Champion Steer. Ernie weighed 895 lbs and his topline hit the showman's beltline (Ritchie 1991). In 1952, A.D. Hershey and Martha Chase worked with bacteriophages and fmally proved that DNA was the material of heredity (Moore 1993). About the same time, 'snorter' dwarfism took the U.S. purebred beef industry by assault. In 1953, Watson and Crick proposed the double helix structure of DNA and published two very short papers in Nature (Moore 1993). Six pages in Nature, all that it takes for a Nobel Prize. In 1958, the American Society of Animal Science commemorated fifty years of growth and progress (Briggs 1958). In 1961, the relationship between nucleotides, codons and amino acids was resolved (Moore 1993). In 1969, while Neil Armstrong was taking one small step, Don Good, of Kansas State University, was taking a leap in the show-ring. He selected Conoco, a CharolaisAngus crossbred steer, as the International Grand Champion in Chicago (Kitchie 1991). Conoco was one of the first crossbred winners of a major show in modem times. He weighed 1,250 lbs, graded Choice and yield-graded 2 (Ritchie 1991). In 1975, the International closed its doors. By the early 1980's some champion show steers were taller than their exhibitors (Ritchie 1991). However, neither Ed nor Tom paid much attention to any of this. Tom's cattle never set foot in a show ring nor did he care much for such fads. Further, Tom was busy implementing the selection program he had designed for his breed. In 1949, he patented the Beefmaster name, and five years later, in 1954, the U.S. Department of Agriculture formally recognized the Beefmaster as an American Breed (Probandt 1978). The man on the top of the Loma Blanca and his son had accomplished a miracle (Mies 1996). In the harsh ranges of South Texas they had created a cow that could survive, reproduce every year, and deliver a calf that could grow, they had produced a profitable and sustainable production system. They did not swing back and forth like Harlan Kitchie's pendulum (Kester 1992), they did not allow directional change signify progress, they did not get carried away with the power of selection, but instead harnessed it into shaping an ideal born years ago under the mesquite trees of the Loma Blanca. They creatively combined breeds in a systematic and planned fashion using a single piece of genetic technology - a scale. These were their challenges for genetic improvement in the 20th century, and they met them all, successfully and masterfully. 6 Proc. Assoc. Advmt. Anim. Breed. Genet. Voll2 A new challenge has developed, but the breeding torch has passed to the grandsons of the man of the Loma Blanca. The calf that Ed and Tom Lasater bred must now perform to new specifications in the food market. It is not enough that the calf be efficiently produced. It must be tender, grade, yield a high percentage of boneless closely trimmed retail cuts, grow and convert feed efficiently to have the quality and price to satisfy consumers and yet command a profit for those who ranch the harsh ranges of South Texas. This new challenge must be addressed while not losing any ground in all that has already been accomplished However, before we focus on the challenges of the 2 1st century we should not forget the words of the master-breeder: 'Cattle breeding is a relatively simple endeavor. The only d@cult profitable' (Lasater 1972). part is to keep it simple; ' 'Truth is both beautzjid and NEW TERRITORY The beef cattle industry is a complex patchwork quilt composed of many somewhat isolated segments, each trying to profit from each other's mistakes (Bill Mies, as interviewed by Andre 199 1; Ritchie et al. 1996). This segmented structure prevents the flowing of economic signals that could and should promote the impetus for the genetic improvement of many traits that are key to ensure consumer acceptability of the final product, and this has hurt the competitive position of beef in the market place (Mies 1991b; Smith et al. 1992; Ritchie et al. 1996). A value-based marketing overhaul of the system such that economic signals for carcass yield and meat quality flow consistently and can quickly be translated into action by the different industry segments is in progress (Value Based Marketing Task Force 1990; Engler 1991; Mies 1991b) and one of the grandsons of the man from the Loma Blanca is working towards this end (Erramouspe 1995). While this challenge is not genetic per se, it is critical for the definition of the genetic challenge to breeders. Jay L. Lush in 1937, and Sewall Wright in 1939, clearly told us how to proceed: clarity of objectives which are supported by rigorous measurements, and the more things that one wants to do the less that one will accomplish in any one of these. However, while everybody agrees on one point - we need consistency, predictability and uniformity of the fmal meat product and we want it inexpensive while commanding a profit, we have yet to agree on a clear and simple objective. Until this is accomplished, it will be very easy to change things but very difficult to improve anything. Some say that what we need is 'young beef,' animals that grow quickly and reach optimum slaughter weights fairly young to assure tenderness without the need for marbling. Others say that marbling is the key. Yet others say that marbling is the problem. Some also say that the main challenges in this area have little to do with genetics, but everything to do with nutritional management and pre- and post-slaughter procedures and technologies including food processing and marketing strategies. Some view crossbreeding as resolving the problem, while others seem to be encouraging selection for the ideal carcass. We don't seem to know what we want, and this is the key challenge that we must first address in this area. Harlan Ritchie (1991) has clearly shown us that we may not be that good at defining what improvement is, but we sure are good at changing things. If we can agree on what we want and the economic signals are flowing, the rest will probably be fairly easy. So, the challenges in this area are the goal and the value-based marketing system. 7 Proc. Assoc. Advmt. Anim. Breed. Genet. Vol12 The question of consistency, predictability and uniformity of the fmal meat product, which was emphasized by the National Beef Quality Audit (Smith et al. 1992) and considered by Hale (1992) to be 'the biggest challenge facing the beef cattle industry, ' raises the issue of the management of genetic variances. While in the 20th century genetic improvement was primarily concerned with means, genetic improvement in the 2 1st century will have to accommodate concerns regarding both means and variances. Some creative thinking in this area would be useful. Breeding strategies utilizing embryo cloning may contribute, but would require careful evaluation. Selection and mating strategies along the lines of those proposed by Kinghom and Shepherd (1994) could be useful and well designed crossbreeding programs could also make a contribution (Sanders 1990). THE CHALLENGES The key 20th century challenges for the genetic improvement of beef cattle were: l- the understanding of the production system and of the environment; 2- the identification of the right cow-type to match (i.e., to maximize the use of) the resources available in the context of a low-cost operation; 3- the outlining and implementation of efficient breeding plans to produce that cow-type; 4- the shaping of a balanced selection program reflecting a keen awareness of the complex interrelationships among traits and of the relative impact of these on the economics of the production system; 5- the weaving of these components into an operational framework of simplicity and efficiency; 6- the understanding of the difference between change and improvement. These are also the key challenges for the genetic improvement of beef cattle in the 21st century. And in their essence, the key challenges for the genetic improvement of livestock in general. Some production systems may, of course, encompass the utilization of special&d sire breeds. Selection programs need, of course, to be shaped in ways that reflect the different roles that different breeds may play in production systems. Reproductive efftciency is the area with the greatest impact on the overall efficiency of beef production (Melton et al. 1979; Green 1996) and its improvement was in focus throughout the 20th century and will continue to be among the greatest challenges to beef cattle breeding in the next century. But a greater emphasis on carcass and meat quality traits needs to be part of the genetic improvement schemes of the 21st century. The relative economic value of these traits is presently unclear, and will have to evolve from a marketing system designed to capture signals of consumer preferences and to transmit these signals quickly throughout the production chain and back to the seedstock segments. The development of alliances among the different industry segments (Neumann and Lusby 1986; Eller 1989; Mies 1991a; Erramouspe 1995; Ritchie et al. 1996) and the economic aligmnent of these under a value based marketing system are specific challenges for the 21 st century which, if successfully met, will benefit the industry in general. Measures of the biological and economic efficiency of the total production systems (Moav and Moav 1966; Joandet and Cartwright 1969; Cartwright 1970; Dickerson 1970; Harris 1970; Gregory 1972; Robinson and Grskov 1975; Morris and Wilton 1976; Cartwright 1979; Wilton 1979; 8 Proc. Assoc. Advmt. Anim. Breed. Genet. Vol12 Tess et al. 1983; Brascamp et al. 1985; Neumann and Lusby 1986; Smith et al. 1986; Amer 1994; De Vries and Kanis 1994) also must be kept in focus throughout the 21st century. These are essential to the definition of the breeding objective within the context of specific production and marketing circumstances, resource inputs and management alternatives. Formal frameworks to address these issues and to try to optimize these complex interrelationships, which may include genotype x environment interactions, are available in the form of computer models of production systems (Sanders and Cartwright 1979; Blackburn and Cartwright 1987; Pittroff 1996; Bourdon 1997). The essence of breeding and genetic improvement will remain the same. But change will also be a constant. Will grain prices escalate to the point that it will significantly affect the structure of many of the livestock industries? Will we be confronted with a future without an abundance of cheap energy? Will there be dramatic technological advances in areas that we cannot even dream of today? Will there be major social and political transformations that will impact our lives and economic activities? We cannot predict these aspects of the future, nor did we view our role as being to make dire predictions. Livestock breeders need to be prepared to anticipate and to cope with change and this is another challenge for the 21st century. Throughout periods of dramatic qualitative change, those who retain flexibility will be among the survivors (Cartwright 1982). Now that we have addressed the essence of the challenges for genetic improvement in the next century, we will discuss in further detail a number of more specific issues that will be relevant to genetic improvement in the 2 1st century. TECHNOLOGIES The key message concerning breeding technologies for the 2 1st century is simple - if you do not have a clear idea of the goals that you are pursuing in your breeding program and why, you had better stay away from them. In the 20th century, with little technology, we rapidly moved from Ernie in 1948, a Grand Champion Steer whose topline hit the showman's beltline, to champion show steers in the early 1980's that were taller than their exhibitors (Ritchie 1991). If we indiscriminately employ the powerful array of technologies that will become available in the 21st century, we will be in trouble. On the other hand, those who know what they are doing, who can sense and seize an opportunity and move quickly, will have the potential to carve competitive advantages in short periods of time. It is the fast lane, however, and mistakes in the fast lane usually have very serious consequences. A more detailed analysis of the breeding