AGRICULTURE DEPENDS ON GENETIC DIVERSITY for its stability, yet in 2007 the United Nations Food and Agriculture Organization estimated that at least one livestock breed per month had become extinct since the turn of the twenty-first century. The fundamental difference between agricultural and other biological systems is the widespread human selection involved in agriculture. Habitats within agriculture are essentially the result of human activity, and the diversity of those habitats must be protected to ensure the long-term survival of genetic diversity in domestic animals and plants.
For over 10,000 years, domesticated animals have been essential to human society, filling a wide array of human needs, including food, fiber, draft power, land management, protection, and transportation. Domestic livestock are also deeply engrained in human culture, and are often the first animals we learn about as the subject of nursery rhymes and children’s stories. Livestock have always been integral to farming systems, and today they are essential to current efforts to diversify agriculture.
The uses of livestock can be roughly divided into two categories: animal products and animal services. The most widely recognized animal product is food—meat, eggs, and dairy products. As a complement to cultivated food crops, livestock can be raised in regions poorly suited to row crops, and they can transform forage nutrients unavailable to humans into high-quality foods for human consumption. Rather than competing with plant production for human foods, foraging livestock can supplement food crop production, as long as they are appropriately managed.
Other animal products include high-quality natural fibers such as wool, cashmere, mohair, and feathers. These natural fibers remain in high demand since they have qualities unequaled by synthetic fiber. Leather is an important animal product for clothing, furniture, and other uses. Manure is the most widely used fertilizer in the world and provides essential soil nutrients not found in synthetic fertilizers. And because animals are mobile, they can be moved around a farm to deposit the manure where it is needed.
Animal services such as grazing, brush clearing, power, and pest control are less well known to the current agricultural generation, even less so to the general public, and therefore merit additional consideration. These services are often the only practical complement or alternative to the use of chemicals, fossil fuels, and machinery. Further, well-managed livestock production systems have a positive environmental impact by reducing erosion, increasing plant diversity, and protecting grasslands from invasion by woody scrub growth.
Grasses and other types of forages are part of a biological system that developed under the pressure of grazing. Grazing must be continued to sustain and to maintain the plant diversity of natural grasslands, although it has recently come under intense scrutiny as the effects of a century of overgrazing in the American West are being recognized. Overgrazing rapidly degrades natural resources, while well-managed grazing can enhance grassland environments. Managed forage production is an excellent method for healing and recovering abused and damaged land. Much of the marginal farmland now in use could be taken out of row crop production and put into permanent or semipermanent forage crops. This decrease in row crops would reduce water runoff and soil erosion and allow the reestablishment of organic material and carbon sequestration within the soil. Research has shown, and the growing market has underscored, the increased value of the enhanced nutrition and flavor of grass-produced animal products.
Goats, sheep, and some breeds of cattle are good browsers, consuming saplings, shrubs, and other woody plants, as well as rapidly growing pest plants such as leafy spurge, blackberry, kudzu, poison ivy, and other tenacious invaders. Goats are being used to reduce the risk of fire by consuming brush and decreasing fuel load buildup. Hogs can be used as self-motivated bulldozers to clear land for cultivation, to glean fields after harvest, or to turn over compost or manure pack in readiness for use.
Draft power and transportation are other important services provided by cattle, horses, donkeys, and mules. Globally, oxen are the most widely used draft animals, though horses are far more common in America. More people are coming to appreciate the versatility, usefulness, and economy of animal power, particularly given the rising cost of fossil fuel. Draft animals are used in selective logging because of the minimal environmental damage they impart to the soil and the remaining trees.
Interest is growing in the use of livestock as part of integrated pest management systems. Swine and poultry work well to control pests in gardens and orchards. Before the introduction of heavy pesticide use in fruit production, sheep were often pastured in orchards; with organic production they can again be used for grass and weed control. St. Croix sheep are now being grazed in organic macadamia nut plantations in Hawaii, and Southdown sheep are grazed in Christmas tree plantations in Vermont and in California vineyards. Using animal services is doubly beneficial—the services are in themselves positive, and they replace expensive or potentially detrimental inputs such as chemical pesticides or fossil fuels—while the animals are also producing marketable food and fiber products.
When the value of animal service is understood, the complicated and rewarding interconnections between humans and livestock become more obvious. Agricultural systems that utilize the complex interrelationships of people, livestock, and specific environments to the fullest extent are also the ones that benefit most from the availability of traditional breeds of livestock and poultry.
Genetic diversity within a species is the presence of a large number of genetic variants for each of its characteristics. This variability allows the species to adapt to changes by selection for the most successful variant. A variant for long hair, for example, would better adapt to a cold climate than a variant for short hair. A population that is genetically uniform may be exquisitely suited to a particular environment, but specialization frequently results in an inability to meet the challenges imposed by any change in the environment or in selection goals. A truly uniform population has no reserve of options for change.
The global importance of genetic diversity is widely recognized as it relates to wildness—rainforests, wetlands, tidal marshes, and prairies. Diversity of habitats, species, and genes allows evolution to continue apace and makes possible the constant adaptations to slight or marked changes in the environment that are necessary for interacting life forms to continue living and functioning together. Similarly, agriculture depends on genetic diversity for its stability. The fundamental difference between agricultural and other biological systems is the widespread human selection involved. Habitats within agriculture are essentially the result of human activity, and the diversity of such habitats must be protected to ensure the long-term survival of genetic diversity in domestic animals and plants.
The accomplishments of modern agriculture have been made possible through the selection and use of genetic diversity in animals and plants from around the world, coupled with various modern technologies. Future selection of different characteristics and development of new breeds are completely dependent on the presence of genetic variation within existing populations. While livestock breeders in North America have historically imported the genetic diversity they needed, much of that diversity has now been extinguished. We can no longer assume that someone else will have the genetic resources we need for the future. Stewardship of existing genetic resources must become a priority.
Genetic variation in domestic animals is manifested in different ways than in wild animals, owing largely to the impact of human selection. Most of the ancestral wild relatives are extinct, and domesticated animals are the only living representatives of some historic lineages. Domesticated animals are thus a critical component of the total biodiversity of life on Earth.
The primary taxonomic unit of variation in domestic animals is the breed, a classification that roughly coincides with the subspecies in wild animals. A breed is a group of animals that may be readily distinguished from other members of the species and when bred to one another reproduce this distinguishing type (i.e., like begets like). Breeds are created by geographic or political isolation coupled with selection by humans and the environment to concentrate characteristics of the population. It is important to realize that more than external physical qualities define a breed. Breeds are also defined by specific complex behaviors and other heritable traits. All of these characteristics, collectively known as the “phenotype,” are not easily attributed to specific identifiable genes. Rather they are the result of unique gene configurations and combinations developed through generations of reproductive selection and isolation.
Beginning in the 1700s, the formal organization of breeds through the use of flock, herd, or stud books codified the genetic isolation of breeds. Since livestock breeds were developed to be different from one another and have been maintained in isolation from one another, they are identifiable packages of distinct genetic content and configuration. The number of breeds and the numbers of animals within the breeds are good indicators of the status of genetic diversity within each livestock species.
The status of genetic diversity can best be understood through an appreciation of breed population dynamics. Breeds are the units of most significant genetic variation in domestic animals and are also the units about which information is most readily available. When a breed declines in numbers, specific genes as well as specific gene combinations within the breed become less common, and certain genes and gene combinations will cease to exist within the breed. If the breed becomes extinct, then both the specific genes as well as gene combinations in that breed are lost to the species as a whole.
Genetic erosion by breed reduction or extinction can be counteracted by timely action, but effective conservation efforts can only be implemented if breed status is understood. A complete evaluation of livestock breeds includes an inventory of the number of breeds per species and the number of animals per breed. Equally important is the genetic breadth of the breed, the number of parents for each successive generation.
The number of breeds within a species is a useful indicator of the diversity available to the species. The domination of a livestock species by a single breed or a few breeds is a recent phenomenon. For example, the Holstein breed exceeds all other cattle breeds in the quantity of milk produced per cow and is now the dominant dairy breed around the world. The popularity and prevalence of this breed has come at the expense of most other dairy breeds, several of which are threatened with extinction. Yet the Holstein is a specialized animal dependent on high-quality feed and intensive management. Its advantages decline under lower-input systems, where other breeds may be more efficient.
Swine provide another example of reduced diversity as a result of the loss of entire breeds and the selection of all breeds for the same characteristics—thus deleting some unique characteristics of the species. While the most significant and obvious genetic loss is total extinction, genetic dilution through the combination of breeds may also remove unique genetic combinations and decreases the integrity of the original genetic package available to the species. The introduction of Australian Illawarra and Red and White Holstein genetics into the American Milking Shorthorn breed to increase milk production has threatened the loss of unique genetic combinations within the breed, and the pre-Illawarra strain of Milking Shorthorn is now extremely rare. Fortunately, the value of the grazing characteristics of the breed for grass-based production and the identification of valuable and unique milk characteristics have focused attention on these original or “native” animals.
Rapid genetic erosion is occurring in all the livestock species of North America. Over 150 breeds are in decline or in danger of extinction. C. M. A. Baker and C. Manwell assert: “It is often assumed that the spread or decline of a breed is solely or mainly because of its relative merit. In fact, a complicated web of interacting socio-economic reasons is involved, and merit or lack thereof may make a relatively small contribution.”1 The web of factors is readily observed in American agriculture today: uniform industrial selection, substitution of nonrenewable resources for animals’ natural abilities, devaluation of the purebred, consolidation of the livestock resources, and attitudes favoring standardization. These factors apply generally to all livestock species and directly or indirectly have led to loss of genetic diversity.
Traditionally, many breeds were utilized, and they all served more than one purpose. Current selection has generally been concentrated on a single breed or type for each animal product. As a result, a single breed or a very few breeds have become dominant. These highly selected populations are known as industrial breeds. The high production levels of industrial stocks are not to be disparaged, however. Industrial livestock provide most of the animal products in our diet. At the same time, these incredibly successful animals are functioning in a very recently developed, expensive, and specialized environment, one that is unique in agricultural history.
New technologies eliminate geographical limits to the reproduction of animals. Artificial insemination, embryo transfer, and cloning have the potential to reproduce the most productive individuals many times over their natural capacity. As fewer and fewer animals are used for breeding, the genetic base of the breed is narrowed with every generation. The drive toward uniformity has become a problem at the species level. Not only are individuals in a breed increasingly uniform, but all commercial breeds within a species are being selected toward the highest-producing types.
Industrial selection largely ignores the innate abilities of livestock now made redundant through substitution of capital, energy, and other inputs. The breeds that are climate adapted, show strong maternal instincts, and thrive under extensive husbandry are not relevant to current intensive industrial production systems and have generally been cast aside. Modern agriculture has used a variety of inputs to support and expand production levels. Animal feed now consists of high-energy grain and protein supplements. These feeds are frequently coupled with additives and growth enhancers. Single-purpose, high-tech housing for industrial production has removed the need for climate adaptation. Intensive husbandry creates an increased need for veterinary support and monitoring of health status owing to the concentration of large numbers of animals. Increased management is also required for successful reproduction and includes fertility enhancement, birthing assistance, and the hand rearing of young.
“Hybrid vigor” is the performance boost attained through crossing distantly related parents. Also called heterosis, hybrid vigor is the foundation of modern commercial livestock production. It is now assumed that the crossbred will outperform the purebred. In the rush to utilize crossbreeding, however, the necessity to maintain genetically distinct parent breeds has been widely ignored. If all breeds become uniform, through selection or through crossbreeding, the potential benefits of hybrid vigor will be greatly diminished. Decreasing emphasis on purebred stock has also resulted in a diminished appreciation of the art of livestock breeding and the host of associated skills that are also in danger of being lost.
Since World War II, all agricultural resources, including livestock, have become consolidated into fewer units of larger size. Genetic resources have also been concentrated, and many nonindustrial stocks have been lost. While we have enjoyed an abundance of cheap and varied foods as a benefit of modern production and distribution systems, there have also been significant unanticipated consequences. The increasing size and specialization of agricultural operations have meant the separation of livestock production from food crop and forage production. Livestock are now considered an end product only, rather than an integral part of a diversified agricultural system.
Much of our food is produced by a few international conglomerates. The consolidation of breeding, production, and processing has encouraged a move toward the selection of animals that are uniform, interchangeable units. The impact on breeds has been tremendous. Those breeds that perform best under industrial conditions have been further modified to excel when given additional resource inputs. The vast majority of our food-producing animals are selected only for industrial conditions. Consolidation has meant a reduction in the number of decision makers in agriculture. In contrast, the history of agriculture is the result of the genius of millions of creative and skilled individuals.
Inseparable from these trends are the attitudes that support them, attitudes that favor increased uniformity of animals and management systems. In its acceptance of uniform, high-input livestock production systems, livestock agriculture may inadvertently destroy the very base of its own success—genetic diversity.
The single system favored by industrial producers is the use of intensive management for maximized output. Concentrated and intensive animal farming has been assumed to be the only modern way to produce livestock and the single system believed to be appropriate for all climates and geographies for the entire future of society. Research has been narrowly focused, and the answers generated are likewise narrow. With fewer decision makers, the results tend to be more widely implemented and fostered than the original questions and assumptions would warrant. As a result, agricultural systems become more similar, and choices of acceptable genetic resources also become increasingly narrow.
During the last fifty years, for example, there has been virtually no research on the production of livestock on low-input, forage-based systems. This lower-cost production system is a potential option for many farmers, but the research to support its implementation remains to be done. If the assumptions that undergird modern agriculture—such as the continued availability of cheap energy—were to change, it is reasonable to expect that the animals necessary in future agriculture would be different from those functioning well today. It is for this reason that the rare breeds need to be kept intact as functional and viable genetic units that can be used in the future.
Livestock genetic diversity, as represented by a wide variety of genetically distinct breeds, must be conserved to meet six societal needs: food security, economic opportunity, environmental stewardship, scientific knowledge, cultural and historical preservation, and ethical responsibility.
The very fabric of American society depends on a secure food supply, which assumes a continuation of domestic agriculture. At risk is the genetic breadth required to produce an array of foods, in a variety of climates, and utilizing a variety of systems. Genetic diversity is also the basis for responding to future environmental challenges such as global warming, evolving pests and diseases, and availability of energy. Along with market demand and human needs, these challenges are profoundly unpredictable. The necessity of genetic diversity in food crops is well illustrated by the Irish potato famine of the 1840s, caused by a blight to which the genetically uniform Irish potato crop was not resistant. The blight destroyed potatoes for five years with staggering social consequences—the dislocation or death of millions of people. Luckily there were potato varieties in the Americas that were resistant to the blight.
Examples of such disasters for livestock are also compelling. Parasite control in sheep has been a universal management problem. Modern parasiticides have eliminated the need to select for parasite resistance, but suddenly the literature is documenting sheep parasites with complete resistance to current drugs. Gulf Coast sheep and Caribbean Hair sheep show remarkable genetic parasite resistance—an adaptation to the heat, humidity, and parasite loads of their native habitats. Epidemics of foot and mouth disease and avian influenza are recent disease scares that could challenge the genetic uniformity of our industrial stocks. An old adage warns against putting all your eggs in one basket. A genetically uniform livestock and/or crop base does just this. Diversity is essential for long-term food security.
The value of breed conservation and genetic diversity lies in long-term economic potential. Many breeds yield high-value products such as naturally colored wool, free-range poultry products, grass-fed meat, and unusual cheeses. Rare breeds may also be a foundation for development of domestic industries to serve markets that now rely on imports. For example, we now import almost all the sheep’s milk cheeses, such as feta and Roquefort, and over 10 percent of the lamb consumed in the United States.
Unique genetic combinations in endangered breeds—particularly those that are distantly related to commercial stocks—must be conserved if these opportunities are to be protected. Breeds that are rare today may carry traits that will be of commercial importance tomorrow. Not long ago St. Croix, Barbados Blackbelly, and other hair sheep were considered oddities, but with the decline in the wool support system, these breeds become sought after as meat producers without the necessity of shearing and marketing wool. Genetic conservation makes possible the development of new breeds such as Senepol cattle (a blend of N’dama and Red Poll) and Katahdin sheep (developed from a foundation of genetics contributed by Wiltshire Horn, Gulf Coast, and Caribbean Hair sheep).
Agriculture is the chief human interaction with the environment. Maintaining genetic resources allows for the adaptation of agriculture to environmental changes; improves the environmental sustainability of agricultural production; and substitutes livestock services and products for the environmentally and economically costly use of chemicals, energy, and other inputs. Increasingly these alternatives make economic as well as environmental sense.
In addition, properly managed grazing of livestock can be used to recover diversity in damaged habitats, such as restored strip mines, wetlands, woodlands, and prairies, as well as in the recovery of abused and eroded crop and range lands. Grazing is essential to the long-term health of grasslands, which cover more global land surface that any other ecosystems. Grasslands are an important collector of solar energy and are essential in global recycling systems for energy, water, minerals, and oxygen. Given the extinction of many wild herbivores, their domestic counterparts are of great ecological importance.
A full understanding of the animal kingdom requires the protection of maximum genetic diversity. Many rare breeds are biologically unusual and provide opportunities to study adaptation, disease and parasite resistance, reproduction differences, and feed utilization under a variety of forage systems. The Ossabaw Island hog is a research model for non-insulin-dependent diabetes and cardiovascular diseases. Myotonic goats are a similar model for human myotonia congenita.
Historic breeds of livestock are the result of human creativity and culture, worthy of being protected along with complex artifacts such as language, works of art, and technological innovations. Solutions to contemporary problems are often found in records of the past. Many traditional livestock husbandry techniques retain their usefulness today, but the common wisdom of the past is no longer valued or taught in institutions of higher education. Our responsibility to future generations requires us to pass on as complete an agricultural record as possible, giving farmers the opportunity to learn from past generations the uses of heritage breeds, which have been the basis for American agriculture.
Stewardship of the Earth includes not only the myriad species of wild creatures, plants, and habitats but also the domestic animals and plants that are part of the biological web of life. Those who appreciate the role of livestock in conserving the environment and in providing services, companionship, food, and other products believe that domestic animals have a right to continued existence, as do wild species. Human beings have a particular obligation to protect the domestic species that have been our partners for millennia of coevolution and interdependence.