The horse contributes to human culture not only with meat and milk production, but also, and perhaps primarily, by its draught power in agriculture, transport and with other activities such as racing and leisure sports. The horse is closer to man than the other domestic animals because it has been a participant in the history of mankind throughout war and peace. It would not be right to limit this recognition only to the horse species and to forget the wild ancestors, the wild and feral relatives and the smaller “brothers and sisters”, the donkeys. In fact the latter with their hybrids, mules and hinnies, are in some places and circumstances even more important in everyday human life than the horse. (see table 4).
2 Horse and donkey population of the world
Table 1 gives a general survey of the zoological taxa of Equidae. These species of Equidae can all interbreed and produce viable foals which are rarely fertile. The exceptions are the wild ass and domestic donkey, horses and Przewalski horse give fertile progeny despite the different chromosome numbers (Table 2).
Table 1. Equidae (after Walker, 1983 and Clutton-Brock 1987)
|Przewalski||(survived only in zoos)|
|Gmellini||(tarpan, extinct in Poland)|
|(kulan, onager, from Syria to Manchuria in Pakistan and India extinct in Syria)|
|E. kiang||(in Tibet)|
|africanus||(Nubian wild ass, extinct)|
|somaliensis||(Somali wild ass)|
|E. grevyi||(zebra in Ethiopia. Somalia, Kenya)|
|E. zebra||(Angola, Namibia, S.Africa)|
|E. quagga||(extinct in S.W.Africa)|
|E. burchelli||(extinct in S.W.Africa).|
All the wild species of Equidae are in danger of extinction or already extinct; therefore they are listed in the IUCN Red Data Books. Their survival is also in the interest of the breeders of domestic horse. The wild horse should be distinguished from the feral (de-domesticated) horses. These feral stocks are in competition with domestic herds and also with wild fauna and in this way they can sometimes cause problems. However, from a scientific and preservationist point of view they have great value. Feral populations in different parts of the world are shown in Table 3.
1 Department of Animal Breeding, University of Veterinary Science, Budapest, Hungary
Table 2. Chromosome number of Equidae species (Clutton-Brock 1987)
E. caballus 64
E. Przewalski 66
E. hemionus 56
E. asinus 62
E. a. africanus 62
E. zebrae 32–46
Table 3. Feral populations of Equidae (after Rudge, 1986)
The stocks of domestic horses, donkeys and their hybrids are summarized in table 4.
Table 4. Horse stocks of the world (1000 heads) (FAO, 1991)
The overall increases in stock show the important role of horses in the world economy. The greater part of these animals is in the developing countries despite the fact that scientific work and literature, with few exceptions, are focused upon the improvement of horses for performance and leisure (Fielding and Pearson 1991).
Table 5. Countries with more than one million horses (FAO, 1991)
3 The homogenization for horse stocks
A constant danger for the maintenance of genetic diversity in horse species is the homogenization of horses. History shows that horse breeders have always been aware of the importance of genetic improvement to meet current requirements. Therefore horse breeds have changed under the impact of commercial fashion and demands of the era (Bodó 1990). Today this tendency should not be under estimated. In the evolution of warm blood (light) horses the impact of two basic breeds can be observed. These are the Mongolian horse (affecting horses from East Asia to India and to Europe) and the Arabian horse (affecting horse breeds all over the world, including the heavy draught horse and pony breeds). Nowadays the English Thoroughbred is the common factor found in most competition horses (Cook, 1991). This means that all horses for hunting, competition, show jumping and dressage are being improved by the English Thoroughbred breed. The genes of this breed are now used everywhere because demand for animal power has largely been replaced by machines and the demands for leisure horses is best served by the well selected Thoroughbred. This tendency has a detrimental effect on the local breeds like Cleveland Bay, Irish Draught horse and also the Dales and Fell ponies (Allen and Emmerson, 1990).
Crossbred, warm-blood breeds now dominate the sports events especially grand prix, jumping and competitive driving. The creation of these breeds has caused confusion over the concept of the breed (Bixby, 1991). There are some breeds which have been changed during recent decades from an agricultural draught horse to an excellent sport horse breed without changing the name of the breed, for example the Hannoverian and the Holstein. Without any doubt it can be considered an enormous genetic improvement, but not a contribution to conservation since the old types of these breeds are not preserved (Bodó, 1985 and Bodó, 1987). Therefore the older horse breeds should be considered valuable genetic resources with sufficient merit to justify preservation either because they are not too greatly infiltrated with genes of the widely used international breeds or because they have some special and exclusive traits. The most useful characters are found in commercial breeds and generally the comparative characterization of all the horse breeds of the world is not yet established.
In general horse populations, breeds and famous studs are not large compared to the other domestic animal species. The advantage of small populations is the detailed knowledge of individuals and the possibility of a complex matrix control on breeding which means that increases of inbreeding rate are sometimes lower than expected (Pirchner, 1984). Even in the former USSR, animals with no foreign ancestors in the second and third generations are regarded as belonging to the breed, but only those without foreign genes up to the fifth generation are considered as purebreds (Dmitriev and Ernst, 1989). In China exotic breeds are used in addition to the Mongolian horses (such as the Kazah, Orlov and Arabian) (Cheng, 1984). The show rings in developed countries with their uniform fashion are also causes of the loss of genetic material and this is also a reason for maintaining breeds which are not currently popular, so as to cater for changing demand in the future.
Sometimes breeds without commercial attractions need financial support (Allen and Emmerson 1990). The survival of breeds which are well adapted to the harsh environment of their natural habitat is desirable. However hobby breeders sometimes take horses to another environment and then phenotypic changes due to different environments and genetic change caused by other selection pressures may occur. An example is the Caspian pony which has been investigated by Alderson (1990). On the other hand valuable genetic material can be preserved if strong breeders associations, for example in North America (Crawford, 1990, Bixby 1991) are aware of the concept of conservation. According to Crawford (1990), in North America only one horse breed from the seven rare horse breeds is of local origin; and of the six feral populations five are of local origin. The others are imported breeds.
The widespread use of Thoroughbred stallions causes an increase of inbreeding rate. The average degree of inbreeding of Thoroughbred horses based on 20 generations was 12.9 percent (Mahon and Cunningham 1982). The problem of hereditary disease like OCD (osteochondrosis dissecans) or RLN (recurrent laryngeal nervopathy) is increasing even in middle weight horses. Inbreeding increments of about 0.5% per generation appear tolerable when the minimum number of stallions is 2–3 dozen per generation and the import of related breeds can keep down the inbreeding rate. The problem can be solved also by several semi-isolated groups with somewhat different breeding goals (Pirchner 1983). The breeding method known as the nucleus system, which is now being applied to other domestic species, was invented by horse breeders long ago when they used small nuclei (national studs) for the permanent improvement of breeds like the Lipizzan and others in the Danubian countries Bodó 1985). Inbreeding depression was not observed with 0.61–0.75 percent increase in inbreeding rate per generation; in fact when the increased inbreeding was based upon superior animals the performance of the inbred animals was better (Petzold 1983). However Müller and Schleger (1983) found a significant relationship between heterozygosity and fitness (fertility, longevity and performance) using blood group markers in Lipizzan and Trotter horses.
The phenomenon of homogenization can also be observed in pony breeds. Suitability for children's riding and the performance of ponies is increased by using small sized Arabian and English Thoroughbred horses. There is no doubt that everybody is going to improve the applicability and marketability of the small sized horses. The use of modern, high performance sires is counterbalanced only by conservative breeders being in favour of pure breeding. Heavy draught horse breeds lost ground after the Second World War due to the mechanization of farm work and transport. In the case of several famous breeds there is a serious danger of extinction. The role of heavy draught horses changed in those countries, where the human population consumes horse meat (Belgium, France and Italy). In some cases, due to the energy crisis, the newly used draught horses can be seen in use for short distance transport.
4 Main types of horses and donkeys by regions
Within the domesticated horse species three main breed groups are usually distinguished:
The distinction is not always exact as shown by the standard deviation within breeds and because of transition breeds which can not be listed specifically in one group. For example, the Friesian horse in The Netherlands can be considered both a cold blood and a warm blood type. Therefore it seems more reasonable to summarize the different horse types of the world briefly by regions rather than by breed groups.
Moving across Asia from the north-east to the south-west, a transition from Mongolian horses to the Arabian can be observed. Some examples follow. In China, of the 66 registered horse breeds, 29 are local breeds the populations sizes of which are:
|6 breeds||100||-||9,000 head|
|7 "||10,000||-||50,000 "|
|5 "||50,000||-||100,000 "|
|11 "||100,000||plus "|
Despite the relatively large population sizes the danger of genetic loss exists because of crossing and the introduction of exotic breeds as was already reported in 1974 (Epstein, 1974).
In the Asian states of the former Soviet Union there are many different horse breeds. Some of them can be considered as pure and ancient, for example the Ahal Teke; others derive from these indigenous breeds or from the show Arabian horses or other introduced influences (Dmitriev and Ernst, 1989). In Asia there are many local variants within the Mongolian and Arabian type groups providing populations or sub populations of value. In China, near the Vietnamese border, a new breed called the Debao pony has been discovered (Allen and Emmerson, 1990). In addition to the local breeds, the international breeds like the English Thoroughbreds or Standardbred horses can be found, as in all other continents.
Adebambo (1991) listed 22 horse breeds and 27 pony breeds of Africa. The north coastal area is characterized by the Arabian horse type. The western variation of it is called the Barb and it is distinguished also by blood polymorphisms (Ouragh et al., 1991). Most African breeds derived from this Barb type and from Dongola varieties adapted to the north-east and central African environments. The Dongola practically disappeared in its homeland and residual populations can be found only in Sudan and in the western lowland of Eritrea. The Baronali horse (a Barb type) is extinct. The Basuto pony of Lesoto is threatened by crossing and upgrading with other breeds. These populations are good sources of meat and for carrying loads and drawing farm implements. However, despite this value, they are ignored in the search for solutions to transport problems in rural communities (Doutressoule, 1952, Mason and Maule 1960, Adebambo, 1991).
4.3 South America
This continent is characterized by the Criollo horse which has Spanish origin. There are many variations within this type. The Peruvian Paso is a famous breed and the polo-pony of Argentine is the result of crossing with the English Thoroughbred. There are also some small local populations which are well adapted to harsh environmental conditions such as the Pantaneiro (in flooded areas of the river Paraguay). The feral horses of Lavradeiro can also be mentioned (Roraima).
4.4 North America
In this continent nearly all the horse breeds can be found in the hands of hobby breeders and sometimes breeders' associations. Two great international performance breeds have their origin here: the Standard Bred Trotter and the Quarter Horse. Many show horse populations are born in North America for example, those described by coat color (Palomino, Cremello, Painted etc.), or by gait (Tennessee Walking Horse). The feral populations of mustangs should be also mentioned. These are a mixture of different breeds and crosses of which the most valuable is the pure progeny of the colonial Spanish horse which does not include the genes of international breeds (Sponenberg, 1991).
Tendencies which are seen throughout the world are observable in Europe. These include the homogenization of riding horses and ponies and the decline or disappearance of heavy draught horse breeds. These trends are indicated by some examples. In The Netherlands the population sizes of the breeds now threatened by extinction is the following:
|The Dutch Draught Horse||40||males||1200||females|
The Dutch Draught horse is already improved by the use of Belgians horses and Oldenburg stallions are used to avoid the extinction of the Groningen breed (Buis, 1984). In Hungary 6 blood horse populations and one draught horse population are considered as traditional and endangered (Bodó and Pataki, 1984). The Lipizzan nuclei are kept also in neighbouring countries and crossed only after 8 – 10 generations. The Jutland breed in Denmark has an average inbreeding coefficient of 14.7 and the rate of increase is 0.9 per generation. The Suffolk breed from Great Britain is used to avoid further increase in the rate of inbreeding (Johansen, 1984). The small Bosnian ponies are improved by Arabian horses in the Balkan peninsula (Habe and Telelbasic, 1988). In Germany there are many endangered horse breeds in a critical situation such as the Oldenburger, Ostfries, Rottaler, Schwarzwalder Fuchs and the Rhein-Westfalia Cold Blood; activities for their conservation started only in recent years (Bogner 1988, Kretschmar and Schwark 1988). In Scandinavia draught horses have become endangered because of the decreased demand for working horses such as the Norwegian Dole. The Icelandic horse is really a living gene museum because of its 1000 years of isolation and today it is more and more popular also in other countries. In Nordic countries the responsibility for each endangered horse breed is given to the countries concerned (Maijala et al., 1991).
In this continent the Waler halfbred was famous in the war. The common improved horse is called Australian stock horse. There is also a feral population which has the name Brumby.
4.7 Donkey breeds
Within the donkey breeds there are not such a good series of well improved breeds as in horses. Big sized and small sized donkeys can be distinguished. The small donkeys are widely spread all over the world and the donkey populations are scarcely distinguished as breeds, even in the so-called developed countries. In China 18 donkey breeds are registered of which one is really endangered while the population sizes of the others are larger than 10,000 heads (Changjiang, 1991). In the former USSR asses are small with height at wither of 90–110 cm. An exception is the Mary (Merv) breed having 142 cm. This breed is similar to the Iranian Hamadan. They carry in general 40–60 kg of pack weight and even up to 100 kgs, (Dmitriev and Ernst, 1989). In Europe among the many thousands of small animals there were three big ass populations in Sicily, in the Iberian peninsula and in France. The famous French large sized Poitou ass (145 cm) is in critical status and in 1977 only 44 animals existed. To save this valuable population some she asses were imported from Portugal (Audiot and Langlois, 1984).
5 Criteria for choice of breeds or populations of horses for improvement and preservation
The most important issues affecting the choice for conservation or preservation of horse populations are first, adaptability to a harsh environment and second the valuable and sometimes rare or even unique traits which distinguish a breed from others. Examples of the well adapted breeds are the Huzul or the other small mountain breeds which proved their value compared with other breeds during the World War, or the Pantaneiro breed which is well adapted to the flooded area of the river Paraguay. Work or draught power is doubtless the most important trait of horses and donkeys. In agriculture generally there is competition with other species primarily with cattle. Mules and donkeys are used all over the world as pack animals. In some places their replacement by machines is impossible. In modern life in developed countries, saddle horses serve leisure purposes rather than having a contribution to production. The genetic improvement of performance and use of population genetics in the field of race horses and sport horses (eventing, show jumping, dressage and competitive driving) is in an advanced stage. The production of horse meat is also important and competitive even with beef cattle (Bodó et al. 1991).
The milk production of horses is limited to the rearing of foals, but in some countries is used to produce alcoholic or non-alcoholic drinks for human consumption. The composition of horse milk is close to human milk and therefore some hospitals use it in therapy. The serum of the horse plays an important role in pharmacology but nobody wants to use genetic methods to increase this production. Morphological traits can be considered also as valuable parameters for improvement or preservation. Such a trait is, for instance, the body size of the horse which shows a wide range from the giant Shire breeds to the smallest Fallabella or mini-horse. Other traits like curly hair can also be mentioned (Thomas, 1990). The special gaits of horses also have great value because they touch the main use of these animals. Walk, trot, gallop, (jump and swimming) are quite common but there are some pacer breeds and even populations with five gaits. The high step is very elegant (Lipizzan or Spanish horses and Friesians) and therefore can be considered as a valuable trait. The sure step of pack animals in mountainous areas is indispensable. In modern life professional horse men are rare. Therefore the good and quiet temperament of horses is important to avoid problems when animals are handled by outsiders or tourists (Haflinger). The value of individual populations depends on their distinctiveness from the other horse breeds. Therefore the most valuable ones are those which are more or less free of the genes of the large international breeds such as the Thoroughbreds, Arabians and Mongol horses. It is very difficult to find such pure breeds; even the Ahal Teke which is an indigenous breed of Turkish origin has a distant relationship with historical Arabian horses. The biochemical polymorphisms and other results of biological research (RFLP, VNTR, fingerprinting etc.) help in determining the differences between populations. For example, the priority of the American Minor Breeds Conservancy is to preserve breeds which are distinct from the Thoroughbred-Arabian family of breeds (Spanish Mustang) (Christman, 1991). Sometimes such a distinction is difficult due to the lack of pedigrees (Silvestrelli, 1991).
6 Priorities in conservation of horse and donkey breeds
Following what has been said above, it is obvious that it is not easy to give priorities among horse breeds for improvement or preservation. The first priority must be given to the characterization of the breeds and also to save those in a critical state. The identification of some populations and the evaluation of their value should be carried out urgently in certain cases, for example with donkeys and conservation programmes should be based upon the results. Some small populations, well adapted to their natural habitat, can sometimes be found with merits for preservation or improvement. Sometimes such operations do not need much support or money and even moral support can be important. The wild relatives and ancestors of horses, which are under the protection of IUCN are not mentioned here, although it is noted that a programme for the restoration of the Przewalski horse is well advanced (FAO/UNEP,1986).
The collaboration of horse breeders is of course desirable in this field. The old endangered and separate populations, like the Ahal Teke horse breed in Turkmenia, have priority. The Turkmanian horse was famous from the 8th century in both Western and Eastern countries because of its conformation. It has a light and clean cut head, long and muscular neck sometimes with a protruding throat-latch, long and high withers, long and often slightly dipped back, long loin, straight croup and a not very deep, narrow chest. It has sloping shoulders, clean long legs, hard but moderately developed joints, long and often steeply sloping pasterns, large and hard low-heeled hoofs, tight thin skin, thin hair coat, main and tail. The height at withers of stallions is about 158 cm, oblique body length 159.8 cm, chest girth 176.3 cm, cannon bone girth 19.1 cm and body weight 30–500 kg. It is a late maturing horse with excellent speed though lacking range and strength. Its movement is well appreciated in modern sport events. The jump is very soft and elastic. The breed combines average fertility with longevity. The gene pool of pure Ahal Teke is limited. In the 1981 stud book there were only 87 stallions and 300 mares comprising 7 male lines and 5 mare families. Cross breeding with Trakehner, Hannover and Latvian riding horses is going on, (Dmitriev and Ernst, 1989). Ahal Teke can be a priority breed because its traits are well known.
On the other hand priorities must also be given to some endangered working horse breeds in Africa like the Dongola breed. The value of the traits is not completely clear but they are well adapted populations or strains and preservation can start in parallel with the identification and description of these breeds. The same can be said of some less well known breeds in Asia or South America like the Pantaneiro breed. When the programme of improvement and preservation of horse breeds is planned some European breeds should not be neglected such as the heavy draught horses (Clydesdale, Murinsulaner) and warm blooded working horses like old Mecklenburger or the Kladrub breed. The maintenance of pony breeds in their original habitat is also important with the original use included, for example the Caspian pony and the Dartmoor Pony. Concerning asses, the identification and description of the most valuable populations is of great importance. The big sized asses all over the world should be saved from extinction (Iran, Spain, Italy, France etc.).
Horses and donkeys are as important in the economic life of the world as other farm animals. It would be a great mistake to consider them only as hobby animals. They work all over the world as draught, saddle and pack horses or donkeys and even their meat and milk production is not yet exploited enough. It is difficult to give priorities in preservation and improvement of the horse stock of the world for several reasons. First there are many populations which can not be considered as breeds and their evaluation would be necessary. Some breeds with well known characteristics are in danger of extinction first of all in developed countries where economic factors are not in favour of draught horses. In some cases the moral support of FAO could help in addition to money. Priority should be given to in situ conservation and to the development of cryogenic methods. Those populations which serve the everyday life of farmers must be given priority.
In spite of these facts there are some breeds which could be made the focus of preservation activity of the world like the Ahal Teke horse in Turkmenia or the Dongola in Africa or some small horse or ass populations all over the world with valuable traits. In summary, a survey on the horse breeds and small populations is needed in order to create a world programme for Equidae.
Adebambo, O.A. (1991): African breeds of livestock: their genetic status and conservation. Paper at the World Conference on Gene Conservation and Rare Breeds Survival. Budapest. 35.p.
Alderson, L. (1990): The effect of environment and selective breeding programmes on the height of Caspian horses. In : Genetic Conservation of Domestic Livestock CAB Int. Wallingford. 160–164.p.
Allen, W.R. and Emmerson S.A. (1990): Current problems in conservation programmes. Horses. In: Genetic Conservation of Domestic Livestock. CAB Int. Wallingford. 165–167.p.
Audiot, A. and Langlois, B. (1984): Programme of conservation in the “Baudet de Poitou” breed. EAAP. The Hague.H.3b.5.
Bixby, D.E. (1991): The North American livestock census. Paper at the Conference on Gene Conservation and Rare Breeds Survival. Budapest.5.p.
Bodó I. and Pataki B. (1984): Special problems in conservation of traditional horse lines in small herds. EAAP. The Hague. H.3b.3.
Bodó I. (1985): Appreciation and protection of genetic resources in the horse breeding. In: Proc. of The Role of Mezohegyes Horse Breeds in the Eastern European Horse Breeding. 84–94.p.
Bodó I. (1987): Importance of the type in preservation of genetic resources of domestic animals. EAAP. Lisbon. G.1.15.
Bodó I. (1990): The maintenance of Hungarian breeds of farm animals threatened by extinction. In: Genetic Conservation of Farm Animals. CAB Int. Wallingford. 73–84.p.
Bodó I., Szabara l., Hamza l., Pataki B. (1991): The comparison of mare and suckler cow in meat production. EAAP. Berlin. H.6.2.
Bonger, H. (1988): Vorschlage fur eine Zuchtstrategie in dem von Aussterben bedrohten Pferderassen in der Bundesrepublik Deutschland. Proc. of V.Int. Wissentsch. Symposium Leipzig. 539 – 541. p.
Buis, R.C. (1984): Conservation of breeds menaced by extinction. EAAP. The Hague. H. 3b. 2.
Changjiang, Shen (1991): Conservation strategies based on the characteristics of Farm Animal Resources in China. Paper at the Conference on Conservation of Genes and Rare Breeds Survival. Budapest. 13.p.
Cheng, Peilieu (1984): Livestock breeds of China. FAO. An. Prod. Health Paper 46.217.p. Christman, C. (1991): The homogenization of horse breeds. Paper at the Conference on Conservation of Genes and Rare Breeds Survival. Budapest. 2.p.
Clutton-Brock, J. (1987): A natural history of domestic mammals. Cambridge University Press. Vol.2. 208.p.
Cook, W.R. (1991): Some problems relating to the genetic welfare of the middle weight horse breeds in the British Isles. Paper at the Conference on Conservation of Genes and Rare Breeds Survival. Budapest 29. p.
Crawford, R. (1990): The work of the American Minor Breeds Conservancy with special respect to the conservation of poultry breeds. In: Genetic Conservation of Domestic Livestock. CAB Int. Wallingford. 3–17.p.
Dmitriev, N.G., Ernst, L.K. (1989): Animal genetic resources of the USSR. FAO. Rome. An. Prod. Health Paper. 65. 254.p.
Doutressoule, G. (1952): L'elevage au Sudan Francais. 2nd.ed, Alg. (cit.Adebambo)
Epstein, H. (1974): Vanishing livestock breeds in Africa and Asia. Proc. 1st World Cong. on Genetics Appl. to Lives. Prod. Madrid. 2. Round tables. 31–35.p.
FAO (1991): Yearbook. Production 1990.Vol 44. FAO Statistics series. No.99. 283.p.
FAO/UNEP (1986): The Przewalski horse and restoration to its natural habitat in Mongolia.FAO. Rome An. Prod. Health Paper. 61.181 p.
Fielding, D. and Pearson R.A. (1991): ed. Donkeys, mules and horses in tropical agricultural development. Proc. of a Colloquium organized by the Edinburgh School of Agriculture and the Centre for Tropical Veterinary Medicine of the Univ. of Edinburgh.
Habe, F. and Telalbasic, R. (1988): Zuchstrategie in dem vom Aussterben bedrohten Pferderassen Jugoslaviens. Proc. V. Int. Wissensch. Symposium Leipzig. Band II. 533–538. p.
Johansen, E.O. (1984): Inbreeding and relationship within the national Danish draught horse - The Jutland breed. EAAP. The Hague. H. 3b. 4.
Kretschmar, L. and Schwark, H.J. (1988): Merkmalausspragung und Zuchtstrategie beim schweren Warmblut in der DDR. Proc. V. Int. Wissentsch. Symposium Leipzig. Band II. 558–574p.
Mahon, G.A.T. and Cunningham, E.P. (1982): Inbreeding and the inheritance of fertility in the Thoroughbred mare. Livestock Prod. Sci. 9. 743–754. p.
Maijala, K., Adalsteinsson, S., Danell, B., Gjelstad, O., Vangen, O., Neimann-Sorensen (1991): Conservation of genetic resources in Scandinavia. Paper at the World Conference on Conservation of Genes and Rare Breeds Survival. Budapest 12 p.
Mason, I.L. and Maule, J.P. (1960): The indigenous livestock of Eastern and Southern Africa CAB Farnham Royal Bucks. England.
Müller, S. and Schleger, W. (1983): Fitnessvarianz in Pferdepopulationen und Schlussfolgerungen fur die Zuchtung. Proc. IV.Int. Wissentsch. Symposium. Leipzig. 50–54. p.
Ouragh, L., Meriaux, J.C., Braun, J.P., Elkohen, M. (1991): Les marquers genetiques sanguins des chevaux Arabes-barbes au Maroc. EAAP. Berlin H. 5. 8.
Petzold, P. (1983): Inzucht in der Haflinger Zucht der DDR und Schlussfolgerungen fur die Zucht in kleinen Populationen. Proc. IV. Int. Wissentsch. Symposium. Leipzig 42–49. p.
Pirchner, F. (1983): Anwendung der Populationsgenetik in kleinen Populationen und ihre Nutzung in der Pferdezucht. Proc. IV. Int. Wissentsch. Symposium. Leipzig 30–41 p.
Pirchner, F. (1984): Prospects of selection in small populations. EAAP The Hague H.3b. 1. Rudge, M.R. (1986): The role of feral mammals in conserving the genetic diversity of livestock. AGRI 5. 7–23. p.
Silvestrelli, M. Pieramati, C. Martino, G. Daneri, S. (1991): Maremmano horse, autochton and non autochton components. Paper at the World Conference on Conservation of Genes and Rare Breeds Survival. Budapest 8. p.
Sponenberg, D.P. (1991): Colonial Spanish horses in North America. Paper at the World Conference on Conservation of Genes and Rare Breeds Survival. Budapest. 7. p.
Thomas, S. (1990): The curly horse identification project of the C S Fund Conservancy (a case study). in Genetic Conservation of Domestic Livestock. CAB Int. Wallingford. 154–159. p.
Walker, S. (1983): Mammals of the World. Novak, M.L., Paradiso, J.L. John Hopkins. University Press.
The loss of biodiversity within wild faunas and floras that has been steadily increasing since the first spread of agriculture, has now become evident in domesticated species, too. This lack of diversity in domesticated livestock is particularly dangerous for those species whose wild progenitor is already extinct, for once the genetic material of the wild form is lost, it is gone forever. And recourse to captive-bred stocks for genetic material may not be satisfactory since some wild species have been held in captivity for many generations and are based on a very small gene pool which may already be exhibiting signs of inbreeding depression.
Domestication itself -- and one may call captive breeding whether in zoological collections or in more extensive conditions, a form of creeping domestication -- is an irreversible genetic process that removes the animals from the selective pressures of their natural environment.
In the event, genetic material from wild animals, whether for storage in cryopreservation or for the production of hybrids, should wherever possible be taken from a healthy, wild population occupying the environment to which it has become adapted.
1 This paper gives the summary and conclusions from a more extensive paper made available at the Expert Consultation.
2 Washington, D.C., U.S.A.
There is then the question as to whether we should be attempting to domesticate new species of wild animals at all. It seems likely that we may have already exploited to the full the indigenous genes of our domestic stock that adapted most of them to their original temperate environment. It has even been suggested (Short, 1976) that apart from the romantic appeal it may have for conservationists there may be little point in preserving rare domestic breeds for their genetic potential. Their very scarcity may be an indication that they have lost their usefulness and become museum pieces. Maybe what we should be doing now is collecting and evaluating the genes of more tropical and polar species for infusion into existing domestic stock of temperate origin.
Tropical species are not usually seasonal breeders and even when transported to temperate zones their reproduction may continue to be non-seasonal. Examples are the chital or axis deer, Axis axis, of India, the Barbary sheep, Ammotragus lervia, of North Africa and the eland, Taurotragus oryx, of southern Africa, all of which breed throughout the year in their natural habitats and continue to do so even when translocated to northerly latitudes such as Britain (Zuckerman, 1952). The introduction of these tropical genes into a domestic species might therefore be expected to extend its mating season. In contrast to this, animals living in polar regions or at high altitudes in the temperate zone would be expected to have a very restricted breeding season. This would be an undesirable characteristic in a domestic animal. Nevertheless, they would theoretically have a number of highly desirable attributes, such as large body size, evolved to minimize heat loss, and a rapid growth rate and high food conversion ratio, associated with the need to reach maturity in the short summer growing season. Thus the introduction of “polar genes” or “high altitude genes” into a suitable domestic species might be expected to increase body size, accelerate growth rates and improve efficiency of food conversion. The ideal new domestic animal could thus be a man-made blend of desirable genes selected for under environmental extremes and infused into stock of proven domestic temperament (Short, op. cit.)
3 Which wild species ?
The question of what wild species should be given priority for both in situ and ex situ conservation must be addressed.
From the documentation it would seem that those wild cattle which are classified as “vulnerable” or “endangered” should receive priority. The wild cattle of Asia comprise several potentially valuable species: the kouprey, Novibos sauveli, of Thailand, Laos, Vietnam and Cambodia; the gaur, Bos gaurus, of India and the forests of southeast Asia; two species of anoa, Bubalis spp., from Indonesia and the tamaraw, Bubalis mindorensis, on Mindoro in the Philippines. The productive and economic potential of these tropical, forest-dwelling bovids is almost unknown. A little more is known of the banteng, Bos javanicus, of which a domesticated form, known as “Bali cattle” is kept for draught and meat production in Indonesia and for the production of hybrids when crossed with zebu cattle on the island of Madura. Yaks, Bos grunniens, too, are domesticated in the high country of the Himalayas and hybrids with both humped and hump-less cattle (yakows) are also produced in Central Asia. The mithan, Bos frontalis, is believed to be a domesticated form of the gaur, however, some authorities think that it is a progeny of a gaur/cattle cross while others favour a gaur/banteng cross. Whichever is correct, the mithan has valuable attributes of great docility and high milk production. Most of the wild Asian cattle species are threatened with extinction and attention to their conservation is urgent. All inhabit tropical forests and savannas, regions which are subject to environmental extremes to which conventional livestock is poorly adapted and in which more than half the world's human population subsists. While the wild cattle of Asia may be resistant to some of the disease and parasites which occur in their native environment, there is however no doubt that diseases of domestic cattle are a serious threat to their continued existence in some areas.
3.1.1 Other wild relatives of cattle
Some wild species which are truly relatives of domesticated forms (yak, banteng, gaur) are important genetic reservoirs and yet others may have potential for the production of new domesticates (anoa, tamaraw, kouprey).
The African Cape buffalo, Syncerus caffer, is not threatened with extinction and the European and American bison, Bison bison, (now thought to be conspecific) are safely conserved by governments and individuals.
The mouflon-urial are considered to be the ancestors of the domestic sheep. The taxonomic status of the members of genus Ovis is open to dispute (Schaller, 1977). For mouflon and urial some authorities distinguish a single species, Ovis orientalis, while others call the mouflon O. gmelini and the urial O. vignei.
Almost all European, Asiatic and north American wild sheep species will produce fertile hybrids when crossed with domestic sheep and there may be some advantages especially in the production of extended breeding seasons by back-crossing to the ancestral stock (Zuckerman, 1952).
The wild goat species, believed to be the ancestor of the domestic goat is Capra aegagrus. This species is well distributed throughout the Middle East but the populations, often small and isolated, occur mainly outside protected areas. In Turkey alone is the wild goat population not threatened. A hybrid between the Sinai Desert goat, and the wild Nubian ibex, C. ibex nubiana, has been developed in Israel with the object of improving the palatability of the desert goat's meat.
Przewalski's horse, Equus przewalskii, is now extinct in the wild but is safe in captivity. Plans are being made to return this species to its native environment in Mongolia. The wild asses of the world are in a critical state, especially the one surviving African species, the Somali wild ass, Equus africanus somalicus, thought to be the progenitor of the domestic donkey. No representative of the eight sub-species of the Asian wild ass has been domesticated and all are now considered either endangered or vulnerable. The Somali wild ass will interbreed with its Asian cousins but the hybrids are infertile.
The wild ancestor of the majority of the domestic breeds of pig is the Eurasian wild pig, Sus scrofa. The Sulawesi warty pig, Sus celebensis, has also long been domesticated on the island of Sulawesi and elsewhere in Indonesia. The species only occurs in its wild, native form on Sulawesi and some adjacent islands. Pigs are likely to be of increasing importance to mankind as a source of protein and the regional genetic variants of the Eurasian wild pig and those of the Sulawesi warty pig and other Asian wild pigs species are of great interest.
Of the three wild camelids, two occur in Latin America and one in central Asia. The Latin American wild camelids are the vicuna, Vicugna vicugna, and the guanaco, Lama guanicoe. The latter is the ancestor of the domesticated llama and alpaca. The largest population of vicuna is in Peru where political unrest threatens the species. The world population of the vicuna is stable by could rapidly fall if conservation efforts were to be relaxed.
The guanaco is present in considerable numbers in Argentina but everywhere in Latin America it is over-hunted and persecuted by farmers who believe that it competes for grazing with their sheep and presents a disease risk.
The wild two-humped, so-called Bactrian camel, Camelus ferus, is now reduced to about 500 head and confined to two small areas Mongolia and China.
Some deer species are officially considered to be domesticated and others will follow them. Their wild relatives, although often under pressure, are generally not immediately threatened but in a world in which the human population is increasing by one million every four days this can hardly be a matter for complacency. Musk deer, Moschus spp., are over-exploited throughout their range which stretches from Afghanistan through northern India to China, for the musk used by the perfume industry. Pere David's deer, Elaphus davidianus, has been extinct in the wild for 800 years and has recently been returned to its original habitat in China from captive sources in Britain.
Hybridization of deer of temperate zone origin with other species of tropical origin is becoming a common practice, especially in New Zealand deer farms, in an attempt to maximize production by manipulating changes in the time of the mating season and gestation length which are displayed by the hybrids. Wapiti, Cervus canadensis, sika, C. nippon, and Pere David's deer all hybridise with red deer, C. elaphus, and produce fertile offspring. Tuberculosis is proving to be a considerable problem in domesticated deer herds especially in New Zealand, United Kingdom and U.S.A. New Zealand now has over 5,000 deer farms carrying more than a million deer.
There are a number of African and Asian antelopes which may have potential for domestication or semi-domestication. These come from diverse habitats ranging from moist rain forest to arid savanna and semi-desert. They are thus adapted to some environmental conditions which are marginal for the production of conventional livestock because of drought, heat, disease, altitude, humidity and other constraints. Even if not subjected to the long process of domestication their genes may be of value for improving the performance of domestic stock in marginal areas.
3.9 Musk Ox
Among the wild species which have potential for future domestication are the musk ox, Ovibos moschatus.
The rodents particularly are likely to become extremely important as a source of future domesticates. Some Latin American and African rodents have potential for domestication. They are the world's most adaptable and prolific animals. They reproduce well in captivity, grow fast and adapt to a wide variety of local conditions. Many convert coarse vegetation into meat efficiently even though they have only a simple stomach. Much rodent meat is consumed throughout the world, especially in Latin America and west Africa. Peru alone has 20 million domestic guinea-pigs and several other species are undergoing experimental domestication. Some of these are more productive than domestic livestock in marginal or degraded areas and others are adapted to thrive where for one reason or another conventional livestock do not.
Many valuable rodent species are classified by IUCN as “endangered” or “vulnerable” and some have already been hunted to extinction. If the considerable productive potential of these and other members of the Order Rodentia was more widely known in development and agricultural economic circles, it is possible that an important incentive would be provided for the urgent conservation actions needed to ensure that these most valuable food animals do not become extinct. Under semi-domestication few have been selectively bred for docility or productivity, nor have the characteristics of the various races of those species which occupy a variety of different habitats been tested. However, there are several important factors to be considered before recommending the introduction of a newly domesticated rodent (or indeed any other species) into a new country or culture. Largely because of their fecundity many rodents are agricultural pests in their natural range and since some species have a remarkable propensity for escape there is a danger that an alien species could establish itself in an exotic new environment and become a serious problem for local farmers. For this reason, rodents may be appropriate for raising only where they are already indigenous. Such potentially invasive animals should not be introduced into another environment where they could escape and become an agricultural liability. The subject of disease carriage has also been mentioned. Some rodent species are carriers of dangerous human disease, e.g. Chaga's disease, leishmaniasis, trichinellosis, tuberculosis, bubonic plague and tularaemia and this must be borne in mind when the introduction of a new domesticated animal into a new area is considered.
In the case of poultry, the genes of the high arctic breeding species such as the greater snow goose, Anser caerulescens, and the red-breasted goose, Branta ruficollis, will surely be needed for the improvement of the domestic goose, as will those of the bar-headed goose, Branta indicus, and the ne-ne, Branta sandvicensis, (Kear, 1975). The first two of these wild geese are high arctic nesters and have incubation periods of only 23–24 days (the domestic goose incubates for 33–35 days) and have a very rapid growth rate and an excellent efficiency of food conversion. The red-breasted goose, for example, attains 17.7 times its hatching weight by three weeks of age, which is about twice the growth rate of the domestic gosling. The bar-headed goose nests at high altitudes and has an advantage over the high latitude species in that it has a long breeding season. The endangered ne-ne from Hawaii actually lays its eggs on a decreasing day-length in winter.
Large lizards have been important food animals since prehistoric times. Some, such as the monitor lizards, Varanus spp., frequently seen trussed-up in the markets of Indo-China, are carnivorous species and may be difficult to raise economically for meat. However, they may be very valuable to raise for “medicine” for the Chinese pharmacopeia as is done on a small scale in Thailand. Iguana meat is popular in Latin America and everywhere the lizards are hunted relentlessly. As a result they are now becoming scare and their decline is accelerated by habitat destruction as the tropical forests are felled. But iguanas are forest-edge species and will thrive on farms and ranches as long as some patches of woodland are left standing.
Iguanas, Iguana spp., are best semi-domesticated since they normally inhabit the treetops, feeding on leaves, shoots and fruit in the canopy. Few other herbivores are able to convert such forest foliage into food for human consumption. Research indicates that 200– 300 kg of iguana meat can be produced each year from an hectare of forest. The meat tastes like chicken and the eggs are also consumed throughout Latin America. Iguana skin has barely been exploited as yet. It sells on the international reptile leather market as “chameleon lizard” and is used for making ladies' accessories. The main constraint on iguana farming is that the lizards take three years to reach marketable size.
Two civet cats, one African and one Asian are currently exploited for the very valuable musk secreted by their anal glands. The African civet, Civetrictis spp., is kept in some numbers in semi-domestication by small farmers in Ethiopia, solely for its musk production which is exported for the perfume industry.
The Small Indian civet, Viverricula indica, is similarly raised in Thailand. The musk produced by this species is exported to China for the Chinese pharmaceutical industry. The Thai civet farms are run in association with chicken hatcheries and the civets are fed on boiled dead-in-shell chicks. Both these civet cats are common and are widely distributed throughout Africa and Asia respectively.
Genetic material from all the wild relatives of domestic livestock and indeed from those species which are unrelated but exhibit attributes that could be of potential use for improving the productive performance of existing domesticated animals, must be collected and stored whenever the opportunity presents itself, and material from truly wild populations must have priority over captive-bred or zoo specimens.
Kear, J. 1975. How wildfowl could improve our domestic breeds. Waterfowl Ybk. Buyer's Guide. 1975–76: 37–41.
Schaller, G.B. 1977. Mountain Monarchs: Wild Sheep and Goats of the Himalaya. University of Chicago Press, Chicago.
Short, R.V. 1976. The introduction of new species of animals for the purpose of domestication. Symp. Zool. Soc. Lond. 1976, 40: 321–333.
Zuckerman, S. 1952. The breeding seasons of mammals in captivity. Proc. Zool. Soc. Lond. 122: 827–950.
There is a multitude of breeds, local types, strains or geographically separated populations of domestic animals in the tropical and developing countries, and they are presumed to be generally well-adapted to the existing climate-husbandry-economic conditions. However, they have not, in general, been well characterized or evaluated for their productive performance.
The future improvement and development of livestock to meet human needs is dependent on genetic variation - both the variation within breeds and the variation between breeds, strains and populations. Genetic variation is the primary resource, and loss of variation will restrict the options available to meet unpredictable future requirements. While loss of genetic variation within breeds or populations is continually countered by the introduction of new variation through mutation, the genetic variation represented as differences among breeds, strains or populations cannot be readily regenerated. Each breed or strain is the product of separate evolution and adaptation over many centuries, with differing selection pressures imposed by climate, endemic parasites and diseases, available nutrition and criteria imposed by man. Each is thus likely to represent a unique combination of genes.
However, high production of breeds in developed countries relative to that of native strains in less developed countries has lead in the past to unrealistic expectations of the potential for rapid improvement of productivity in the less developed countries through importation. Whether this importation and crossbreeding with native strains be indiscriminate or planned, the net result will be loss of the native genetic resources before their true value is known.
Already a substantial number of local populations or strains in the less developed countries have been seriously diluted by transfer of genetic material from exotic breeds or have disappeared completely. This increasing loss of diversity has been recognized for some years, as has the consequent need for conservation of animal genetic resources.
Since the FAO/UNEP Technical Consultation in 1980 (FAO, 1981), methodologies for a global programme for animal genetic resources have been researched. These have included procedures for description and characterization of breeds and the development of data banks (FAO, 1986a, b, c), and for the establishment of genebanks as repositories for frozen animal genetic material (Hodges 1989, 1990a), and the overall programme has been reviewed by Hodges (1990b).
1 Department of Animal Science, University of New England, Armidale NSW 2351, Australia.
As a result, three key issues for an immediate programme for the conservation of animal genetic resources have been identified, namely:
characterization and enumeration of all breeds of livestock used in animal agriculture,
an action program to identify breeds at risk of extinction, coupled with appropriate preservation measures,
a development programme to enhance the productivity of those indigenous breeds at risk of being replaced in breed substitution or up-grading (continuous crossbreeding) programmes.
Here we deal with the third of these issues - conservation and improvement of priority breeds.
2 Specification of breeds for development
Ideally, the choice of breeds to be given priority in development programmes would be based on objective evaluation of the current status of all breeds and strains of each species - number and distribution, trends in numbers (increasing or decreasing), population structure, productive performance, adaptive characters and existence of specific or unique traits such as resistance to particular diseases/parasites and tolerance of environmental stresses.
Unfortunately, but in reality, we are not in this ideal situation, and this required information will only become available as specific and conscious efforts are made to document and collect it, and record it in the global data bank. That, however, is not an excuse for doing nothing; the need for action is critical, and our best available subjective judgement must be exercised. The breeds that are chosen and recommended for development programmes may turn out later not to include some that should have been given priority. That will be a price of not having sufficient information, but it will be a small price relative to the potential improvement to be made in the chosen breeds, and the knowledge gained and expertise developed in the process of organizing, initiating and maintaining breeding programmes for the first set of priority breeds.
The programme for the specification of priority breeds, therefore, should have two components:
identification of those breeds with highest priority for development - based on whatever information is available, and a considered, but certainly partially subjective judgement,
identification of breeds for future development - specification of procedures for continuous monitoring of data bank information, and initiation of programmes for comparative evaluation of breeds and strains.
3 Identification of priority breeds for immediate development
This identification is one of the briefs for this Expert Consultation. In order to provide a basis for discussion, the authors of each of the six Working Papers for this Session were asked to provide a brief review of the global situation and to indicate those breeds judged to be of highest priority for development. Their recommendations are summarized in Table 1.
Table 1. Breeds suggested as those having highest priority for immediate development
|Poultry||Domestic ducks||Guinea fowl||Indig. Turkeys|
|Muscovy ducks||Chickens||Muscovy ducks|
Clearly the authors of papers on individual species for this Expert Consultation had a very difficult task, given the lack of a comprehensive data base containing breed characterizations in terms of population numbers, productivity, unique characteristics, and so on.
In general, the principles used in the selection of the breeds that they have suggested include:
the breed possesses one or more highly desirable attributes in terms of productivity and/or adaptation,
the breed is threatened, or is not efficiently utilized,
the breed should be one whose improvement could have the potential to influence large populations, either of the same breed in one or more countries, or other very similar breed types.
Further, the breeds were selected to include a range of different types within each species, and where appropriate, to include representatives from each of the three main regions of the developing world. In four cases, for poultry in general, swamp buffalo, alpaca and West African pigs, either no specific breeds are recognized and/or the species exists over a wide geographical area including more than one country, so these present a special problem. While in his paper entitled “A Global Review of the Genetic resources of Poultry” in this volume, Dr. R.D.Crawford emphasizes the lack of documented information on indigenous poultry, all four species are similar in that breeds as such are not defined. Many different local types and strains or geographic populations exist, but the extent of genetic differences among them or particular attributes of any of them are unknown.
If a genetic improvement programme is to be initiated for any of these species, there is then the problem of identifying which particular population should be used. In the absence of any other criteria, a decision could be based on:
the country (or region of a country) where the species is, relative to other countries, more important to the small farmer and to the national economy,
availability of infrastructure, facilities and expertise.
4 Identification of breeds for future development programmes
Breed characterization information will be accumulated in the global data bank, but obviously this information will need to be monitored so that:
threatened breeds are identified as soon as possible,
gaps in the data base are recognized, and specific efforts made to collect the information, or if no information is available, programmes developed to generate it,
comparative evaluation studies are planned, so as to provide a sound basis for optimum utilization of between breed or strain genetic variation.
Comparative evaluation provides the major problem. Comparisons of performance and other data in the data bank, for say two breeds, will not necessarily reflect their true relative genetic merits, as their performance, etc. will likely have been measured in two different environments. Even with extensive and excellent data, subjective judgements will have to be made, and great care will be needed in making them.
Ideally again, and something to be planned for the longer term, evaluation is the prerequisite to optimum utilization - to provide the data on the comparative productivity and adaptability of existing native breeds and strains, and of crosses, backcrosses, etc., both among them and with exotic breeds. Utilization then involves the development of breeding programmes (selection and/or crossbreeding) to increase productivity and efficiency of production.
5 Genetic improvement programmes
For each of the breeds identified for immediate improvement, appropriate breeding programmes are to be developed and implemented. Here “appropriate” is the key word - it is not just a matter of transferring designs and technology from the developed countries.
While specific details of the improvement programme for each of the priority breeds will vary from breed to breed, it is suggested that all should be based on the Genetic Screening/Open Nucleus Breeding System (GS/ONBS).
The concept of an Open Nucleus Breeding System (James 1977) developed from cooperative (or group) breeding schemes in Australia and New Zealand. By concentrating selection in part of the total population (the Nucleus), ONBS offers the potential for higher rates of genetic progress than would be obtained by traditional within-herd selection.
For breeds in the developing countries, herd or flock sizes often are small and the basic infrastructure for recording of performance and pedigree does not exist, so that within-herd selection is not an option. The particular advantage of the open nucleus system in this case is again the concentration of selection in the nucleus - so that smaller numbers of animals need to be performance recorded and more detailed information can be obtained on each animal, yet the genetic gains achieved in the nucleus are transmitted to the whole population. The principles of the system are shown in Figure 1. The nucleus is established by selecting the best animals (males and females) from the base herds. Depending on the efficiency of this initial selection, a substantial immediate gain in merit of the nucleus relative to the base can be obtained. Once the nucleus is established, all males selected to be used as sires in the nucleus are bred in the nucleus, as are most of the females selected as dams for the nucleus. However, some proportion of the females needed for breeding in the nucleus are selected from the base herds. Selected males and females in the nucleus that are surplus to requirements for breeding in the nucleus are transferred to the base herds. Thus the genetic improvement made in the nucleus is continuously transmitted to the base population.
Fig. 1: OPEN NUCLEUS BREEDING SCHEME (ONBS)
6 Open nucleus breeding systems - operational considerations
While the theory of the system as outlined is quite straightforward, there are many issues which must be addressed in designing a system for any particular breed. These include:
breeding objectives and selection criteria, including measurement techniques and recording procedures,
size of nucleus - number of males and females to be used for breeding, and selection intensity,
initial sampling of population (base herds) to set-up the nucleus,
environment and management practices of the nucleus,
ownership of the scheme and the nucleus animals, and access to the genetic material, i.e. availability of animals, semen or embryos to other populations, organizations, etc.,
storage of germplasm as insurance against disease losses, changes in future direction of breeding programme, etc.,
The overall design that follows from consideration of these issues will likely differ from species to species, breed to breed, or country to country, depending on the biology of the species (reproductive rates, etc.) and constraints specific to each case. Therefore, no single general system can be defined, but the factors to be considered in developing a particular system can be outlined.
6.1 Breeding objectives and selection criteria
Clearly the first step in any breeding programme is to define the objectives - what characteristics of the animals are to be improved, and the criteria for which animals will be evaluated and selected, in order to produce genetic improvement in the objectives. While apparently obvious, the importance of this step is often overlooked. The breeding objective and the selection criterion may sometimes be the same, but not necessarily so. For example, an objective might be increased resistance to a particular disease, with the selection criterion an immunological response test.
However, specification of the breeding objectives and the overall economic goal implies knowledge of the relevant genetic parameters - heritabilities of and genetic correlations among the traits of interest in the breeding objective. The need for this information is emphasized by Dr.R.W. Ponzoni in his paper in this volume entitled “A Global Review of the Genetic Resources of Sheep and Goats”, who suggests therefore a period of intense research activity before implementation of a genetic improvement programme.
Obviously, all available information on genetic parameters for the species in question should be reviewed from the literature, and used in defining breeding objectives and the economic goal. Nevertheless, this available information may be inadequate. In this case, but given the critical need to implement improvement programmes, it would seem better to start the programme as soon as possible, but using a limited breeding objective - perhaps even a single trait. Where possible, research to estimate genetic parameters for all traits of importance could be done using the animals and facilities of the nucleus, as well as any other institution herds or flocks that may be available.
Clearly it may take some years to obtain these estimates, but the breeding objectives can be refined as information becomes available. Any concern that the breeding programme may in some way be directed towards objectives that later prove not to be optimal should be lessened by recognizing that genetic progress in the early years will be slow, and that adequate stored semen samples will provide a backup.
The breeding objectives must be those that are relevant and of most significance to the potential users of nucleus stock. Preconceived notions of which traits should be improved may lead to failure because the “improved” animals are not acceptable to the users. Thus the potential users (i.e. primarily the owners of animals in the base herds) must be involved in development of the system. It is essential that they understand the programme and that all known (or likely) consequences of selection for the defined objectives are discussed with them. This will ensure not only that the objectives are right, but that they feel part of the programme, that it is their programme and that they will benefit.
6.2 Size of nucleus
The optimum size of the nucleus, i.e. the size that will maximize the rate of genetic improvement, varies with the selection intensity to be imposed in both males and females in the nucleus, but generally will be about 10–20% of the total female population (James 1977). While the optimum size can be defined, practical constraints may limit the size that can be used. On the one hand, the numbers in the nucleus should not be so small that selection is inefficient and inbreeding accumulates rapidly. On the other, it should not be so large that standard management and conditions for all animals cannot be maintained.
One advantage of the open nucleus system, as compared with a closed population of the same size, is the increase in effective size and thus reduction in the rate of inbreeding. The magnitude of this difference depends on the proportion of breeding females in the nucleus that are introduced from the base herds. This proportion of breeding females introduced from base herds itself depends on the accuracies of selection in the nucleus and the base. As the accuracy of selection of females in the base decreases relative to that in the nucleus, then the optimum proportion of females from the base also decreases. In the extreme, if the relative accuracy of the base test is very poor, then no females should be introduced to the nucleus from the base. This means that if the nucleus size is constrained for whatever reason, additional effort should be devoted to increasing the accuracy of base testing, so that a higher proportion of females can be introduced from the base, and inbreeding minimized in the nucleus.
Even so, the continued screening of the base herds in most programmes will be at relatively low levels of accuracy. For this reason, nucleus size must be sufficient to maintain the rate of inbreeding to an acceptable level and to allow adequate selection intensity. These two words “acceptable” and “adequate” will have to be quantified for each programme, taking into account all factors and constraints affecting that programme.
6.3 Sampling of population to set-up nucleus
Open nucleus systems are usually initiated with a screening of all animals in the base herds to select the best males and females for the nucleus. Optimally, “best” in this sense means those animals that have highest performance for the defined selection criteria. However, objective records for these criteria generally will not be available in the base herds. Even in this case, some selection gain can usually be achieved. The number of animals required for the nucleus is only a small proportion of the total population, so that only extreme animals are required. Thus the subjective evaluation by owners of the base herd animals can be valuable. Discussions with the owners in this context can be a very useful part of the process of gaining their confidence in and support for the whole breeding programme, and confirming their support for the defined breeding objectives. In addition, where no records exist, some indication of merit can be gained, for example, by measuring body weights, or milk yield over one or two days. Such sample measurements can also provide the basis for development of measurement procedures for later selection of females from the base herds.
6.4 Environment and management practices of the nucleus
As the aim of the breeding programme is to improve performance in farmers' herds, selection in the nucleus should be done in the same environment as that of the base herds. This means in the same region, exposed to the same climate, and under the same management levels as the base herds. Thus for example, treatment for a disease or parasite should not be given unless the same treatment is freely and practically available in the base herds.
Although care is necessary in exercising it, there is one possible modification to this specification of same environment. When an open nucleus system is fully operational and rates of genetic gain stabilize, the base herds will lag two generations behind the nucleus in average genetic merit. Thus the environment for evaluation and selection in the nucleus could be one which it is anticipated will be that of the base herds in 2–3 generations.
6.5 Ownership and access to material
The development of an open nucleus scheme for any breed in the developing countries will likely involve government organizations in one (or more) countries, the farmers who are owners of the base herd animals and one (or more) international agencies. All will be contributing - either expertise, funds or animals. The animals in the nucleus may be purchased from the base herds, or they may continue to be owned by the farmers and loaned for use in the nucleus.
Further, while the primary aim of the programme is to make genetic improvement in the base herds, the superior animals in the nucleus are a resource that could be used for improvement of other populations of the same breed (perhaps in another country) or for crossbreeding (in the same or another country).
These possibilities must be recognized when the programme is being set-up, and clear and specific agreements made as to ownership of the animals present in the nucleus at any time, ownership of genetic material (e.g. frozen semen), and possible use of both outside the herds that constitute the breeding population.
6.6 Storage of germplasm
The continuous introduction of females to the nucleus clearly involves health risks. Policies, therefore, must be defined to protect the nucleus as much as possible, and all procedures for movement of animals strictly adhered to. Further, breeding objectives may change over time. For both of these reasons, consideration should be given to the desirability of germplasm preservation. This storage will normally be frozen semen, but for some species may include now or in the future, frozen embryos. The questions to be considered include:
7 Application of open nucleus breeding systems - successes and failures
Open nucleus breeding systems are in operation in a number of countries such as the Australia, Denmark, New Zealand, Poland, and the U.K. In some cases, these schemes include the additional technology of multiple ovulation and egg transfer (MOET), but they also depend on existing recording programmes and other infrastructure. They are, therefore, less relevant as examples for breed improvement in developing countries.
However, FAO has been interested in the possibilities of ONBS for some years, and already has sponsored two meetings on this topic (Polish Academy of Sciences 1990, Steane and Alexiev 1990). Further, starting in 1987, FAO initiated an open nucleus breeding system for Awassi sheep in Turkey, Syria, Iraq and Jordan, aimed at the genetic improvement of milk yield in this breed. This project can be considered a pilot scheme for the development of ONBS in developing countries, and preliminary results are very encouraging (Table 2).
Schemes have also been initiated in Djallonke sheep and, very recently, in D'Nama cattle. In addition, in India a scheme is being developed based on the use of the urban dairy animal (usually milked for only one lactation) in which the best of these will be purchased for use in a MOET scheme.
While these ONBS schemes are already being developed, it is useful to consider past breeding schemes used in developing countries to see what can be learned from them. Most schemes involved the use of an exotic breed imported to provide immediate and hopefully spectacular gains. Frequently the F1 performed successfully and the programmes continued to use the exotic.
Table 2. Nucleus-control comparisons (year 1)
|Lactation yield (kg)||231||170||91||55|
|Nucleus superiority (%)||36||65|
from Jasiorowski (1990).
There are a number of reviews documenting the results, most of which indicate that the F1 out performed all other crosses when overall performance rather than one specific trait was considered. Valuable reports and reviews include Vaccaro (1979), McDowell (1983), FAO (1987) and Bondoc, Smith and Gibson (1989). However, even where the F1 are superior, careful consideration must be given to what is feasible. In particular, is the infrastructure adequate to maintain continuous production of F1 animals? How are the F1 to be used as far as further breeding is concerned? This latter is very important, but is often forgotten, and either backcrossing or inter se mating among the F1 may be quite undesirable.
Essentially, past failures can be attributed to inadequate information and poor definition of objectives, for example:
8 Biodiversity, conservation and genetic improvement
The major emphasis here has been on identification of priority breeds and considerations necessary for the specification of appropriate breeding programmes for these breeds. However, it would be remiss not to give consideration to longer term aspects of the breeds. However, it would be remiss not to give consideration to longer term aspects of the utilization of animal genetic resources.
The question of the identification of breeds for future development programmes was introduced earlier. The suggestion then was made that a start should be made now in the planning of comparative evaluation studies. But given the wealth of breeds, strains and geographical populations that exist within each species, it obviously will not be possible to evaluate all of them with the limited resources available. In essence, the existing biodiversity is too great; the scope of the problem must be reduced.
One solution to this dilemma (Barker 1980, 1985) is to determine the genetic relationships among the breeds, strains or populations of each species of livestock, so that they may be grouped into sets that are genetically similar, and then to include in evaluation studies one representative from each set.
The genetic relationships may be determined using biochemical genetic and/or molecular markers, and these studies can usefully be coordinated with genome mapping, further extending their value. Such studies should be seen as an essential component of work that is necessary to both understand and utilize existing biodiversity; the question that needs to be resolved relates to the proportion of available resources (financial, human expertise) that should be devoted to immediate development of priority breeds on the one hand, and identification of diversity for future use on the other.
Such studies of the genetic relationships among strains and geographical populations of a particular species can also be valuable in determining the population to be chosen as the base for a genetic improvement programme. For swamp buffalo, alpaca, West African pigs and species of poultry, the problem was noted earlier that breeds are not recognized, so that some particular local population (or populations) has to be chosen if a development programme is to be initiated. If all populations were closely related (i.e. high genetic similarity or small genetic distances among them), it would not matter which population was chosen, as all would provide a similar genetic base. However, what should be done if there are significant genetic differences among the populations, as has been found for swamp buffalo populations in southeast Asia (Mukherjee et al. 1991). Although the populations have been shown to be genetically different for biochemical markers, they are presumed also to differ genetically for production traits. In the absence of comparative evaluation data, the choice of population will have to be pragmatic as noted earlier. But in this case, the breeding programme should be designed to include introduction of genetic material (males or semen) from other populations, both to broaden the genetic base for selection and genetic improvement, and with appropriate planning and design, to gain information on the comparative genetic merit of different populations.
Barker, J.S.F. 1980. Animal genetic resources in Asia and Oceania - The perspective. Proceedings of the SABRAO Workshop on Animal Genetic Resources in Asia and Oceania. Tropical Agriculture Research Center, Tsukuba, Japan. pp. 13–19.
Barker, J.S.F. 1985. Identifying the breeds to be evaluated. In Copland, J.W. (ed.) Evaluation of Large Ruminants for the Tropics: proceedings of an international workshop held at CSIRO, Rockhampton, Qld., Australia, 19–23 March, 1984. Canberra: ACIAR Proceedings No. 5: 161–166.
Bondoc, O.L., Smith, C. and Gibson, J.B. 1989. A review of breeding strategies for genetic improvement of dairy cattle in developing countries. Anim. Breed. Abst. 57: 819–829.
FAO 1981. Animal Genetic Resources Conservation and Management. FAO Animal Production and Health Paper No. 24. FAO, Rome. 387 pp.
FAO 1986a. Animal Genetic Resources Data Banks. Volume 1: Computer systems study for regional data banks. FAO Animal Production and Health Paper 59/1.
FAO 1986b. Animal Genetic Resources Data Banks. Volume 2: Descriptor lists for cattle, buffalo, pigs, sheep and goats. FAO Animal Production and Health Paper 59/2.
FAO 1986c. Animal Genetic Resources Data Banks. Volume 3: Descriptor lists for poultry. FAO Animal Production and Health Paper 59/3.
FAO 1987. Crossbreeding Bos indicus and Bos taurus for milk production in the tropics. FAO Animal Production and Health Paper No. 68. FAO, Rome. 90pp.
Hodges, J. 1989. Review of the animal gene banks and recommendations from Hannover Workshop on associated topics raised by the Tenth Committee on Agriculture. FAO Animal Production and Health Paper 80: 51–59.
Hodges, J. 1990a. Manual on establishment and operation of animal gene banks. FAO Animal Production and Health Paper. FAO, Rome, 67 pp.
Hodges, J. 1990b. Animal genetic resources. A decade of progress, 1980–1990. FAO Animal Production and Health Paper. FAO, Rome, 44 pp.
James, J.W. 1977. Open nucleus breeding systems. Anim. Prod. 24: 287–305.
Jasiorowski, H.A. 1990. Open nucleus breeding schemes - New challenge for the developing countries. In Polish Academy of Sciences, 1990, pp. 7–12.
McDowell, R.E. 1983. Strategy for improving beef and dairy cattle in the tropics. Cornell International Agriculture Mimeo No. 100. Cornell University, Ithaca, N.Y.
Mukherjee, T.K., Barker, J.S.F., Tan, S.G., Selvaraj, O.S., Panandam, J.M., Yushayati, Y., and Sreetharan, K. 1991. Genetic relationships among populations of swamp buffaloes in southeast Asia. ACIAR Proceedings 34: 34–40.
Polish Academy of Sciences 1990. Proceedings of the FAO Conference on Open Nucleus Breeding Systems, held at Bialobrzegi, Poland, June 11–19, 1989. Animal Science Papers and Reports, 6. Polish Scientific Publishers, Warszawa.
Steane, D.E. and Alexiev, A.I. (Eds) 1990. Proceedings of FAO Workshop on Buffalo Open Nucleus Breeding Schemes (ONBS), held at Buffalo Research Institute with Biotechnology Centre, Shumen, Bulgaria, November 18–23, 1990. FAO, Rome.
Vaccaro, L.P. de 1979. The performance of dairy cattle breeds in tropical Latin America and programmes for their improvement. In Balaine, D.S. (ed.) Dairy Cattle Breeding in the Humid Tropics. Haryana Agricultural University, Hissar, India. pp. 159–182.