CHAPTER 12
CENETIC TYPES FOR DIFFERENT ENVIRONMSNTS

by

A.H. Osman
Breeding and Genetios Expert
FAO/Middle and Near East Regional Animal
Production and Health Project "MINEADEP"
P.O. Box 2048 Alwiyah, Baghdad, IRAQ

Summary

Livestock populations in the world frequently occur in a wide variety of environ-ments to which they nave become well adaptad through natural and artificial selection. Consequently there are many genetic types which vary a great deal in their physioal and functional charaoteristica as well as in their productivity.

By and large the majority of livestock in developing countries are found in the tropios and eub-tropics, The animals themselves, although well adapted to the various ecologioal zonas which range from desert to tropical foreste, have relatively low potential for high production.

In order to improve domestic livestock production many governments of developing countries have therefore embarked on livestock improvement programmes involving large importations of exotic breeds from developed countries. In many instances such programmes do not include the genetic improvement of the indigenous stock. At their best, these programmes are designed to upgrade the indigenous breeds to the exotic breeds at the great risk of the disappearance of the former.

This paper deals with the animal genetic resources available in the Middle and Near East and looks into their adaptability and production potentialities under the different environmental oonditions prevailing in the region. An attempt is made to esimate indireotly the amount of genetic variation available as well as to identify local livestock breeds and types of prospeotive merit.

12.1 Introduction

Livestock populations in the world occur in a wide variety of environments to which they have been well adapted through natural and artificial selection. Consequently there are many genetic types which vary a greal deal in their physical and functional character-istias as well as in their productivity.

By and large the majority of livestock in developing countries are found in the tropics and sub-tropios. The animals themselves, although well adapted to the various ecologioal zones which range from desert to tropical forests, have relatively low potential for high production. In order to improve domestic livestock production many governments of developing countries have therefore embarked on livestock improvement programmes involving large importations of exotic breeds from developed countries. In many instanoes such programmes do not include the genetic improvement of the indigenous stock. At their best, these programmes are designed to upgrade the indigenous breeds to the exotic breeds at the great risk of the disappearance of the former. The question then arises: What are the most suitable genetic types and breeding systems to use in any specific environment?

The discussion which follows will be concerned mainly with the Middle and Near East region for two main reasons. The first is that the author has visited most countries of this region; therefore first hand inforraation when available can be given. Secondly its site in Asia and Africa and the range of environments, both ecological and social, as well as the genetic resources and breeding methods, which are present in the region, are typical of most developing countries.

Enphasis has specially been placed on cattle and sheep, not only because of their economic and social importancs in the region, but also because in these two species conservation of genetic resources is of the greatest importancs.

The purpose of this paper is to highüght the genetic types available under Middle and Near East conditions, look into the adaptability and production potentialities of the various genetic types which have evolved under different environmental conditions and thereby estimate indirectly the amount of genetic variation available, as well as identify local livestock types of prospectivo merit.

12.2 The Environment

The Middle and Near East region is a vast area and stretches from the Maghreb countries in the west to Afghanistan and Pakistan in the east and from Somalia and Sudan in the south to Turkey in the north. Because it covers an enormous area, there are wide variations in climatic and topographic conditions as well as in agricultural and animal husbandry practices. The region is inhabited by different ethnic groups with different social structures and habits.

For most of the region (except for two sub-regions one in the extreme north, the other in the extreme south) the climate is characterized by long dry summers, and winter rain which is erratic and in many places does not exceed 100mm per annum. Summers are very hot with mean maximum temperatures rising several degrees above mammalian body temperature. In many countries of the region high summer temperatures alternate with very low winter temperatures. In the Gulf states the ill-effects of high summer temperatures are compounded by high humidities. Consequently livestock are under physiological stress over the greater part of the year in the region.

Due to erratic rains and the nature of the soils of the region which is characterized by the prevalence of exeessively light soils, soils with deficient organic content and tendency to salinization when continuously irrigated, the natural range and pasture potential falls far short of the feeding and nutritional requirements of the animals. There is a marked fluctuation in feeding and nutrition in different seasons and years. Qnly in the Sudan and Somalia does the grassland and wooded savannah of Africa form good range resources for livestock development. Livestock in the rest of the region depend on meagre range and natural pasture resources, and crop residuos of small tracts of irrigated lands. Ohfortunately livestock and crop production are not well integrated in most parts of the region.

Because of aridity and marked seasonality in water supply and feed resources, the main pattern of animal husbandry is nomadic or semi-nomadic. Nomadism, which is the regular movement of whole families with their animals in search of grazing and water, is characteristic of Bedouin tribes in Saudi Arabia, Syria and Iraq, and also of Iran, Afghanistan, Somalia and of the Baggara of the Sudan.

Semi-nomadism or transhumance involves the regular movement of people and their animals between winter grazing areas in valleys and plains to summer grazing areas on the mountains. This is characteristic of pastoralism in Jordan, northern Iraq and the North Western Frontier Province of Pakistan. In Southern Sudan a different form of trans­humance exists where cattle, sheep and goats are moved northward during the rainy season to escape biting flies in the south.

The animal health situation is far from satisfactory. Beside nutritional diseases resulting from malnutrition, many epizootic and enzootio diseases prevail in all classes of animals. Rinderpest, foot-and-raouth diseaee and contagious bovine pleuro-pneumonia are the main diseases of cattle, while sheap and goat pox, enterotoxaemia, various forme of pneumonía, anthrax, haemorrhagic Bepticaemia and parasitic infestations are the main diseases of sheep and goats, Both cattle and sheep suffer from tick-borne diseases, including theileriosis and also tripanosomiasis in Southern Sudan.

12.3 Cattle Breed Types

Indigenous cattle: The cattle population, of the region of which there are about 68 million head, are distributed over the entire region, but about two-thirds are found in Sudan, Pakistan and Turkey. Several indigenous breeds and types exist which differ in form and function. One the one hand there are the straight-backed taurus types in Maghreb countries, on the other the typical zebu in Pakistan. Intermedíate types between these two extremes are found in Egypt, Cyprus and Syria (Shami cattle). The latter group of cattle is known as Near East type. They all have long legs, high withers, sloping rumps and sleek coats.

The majority of indigenous cattle are nondescript and unimproved. But they are well adapted to the harsh environmental conditions prevailing in most parts of the region. They are characterized by low milk production (Table 12.1), slow growth rate and small body size, In many instances the effect of their low genetic potential is confounded by the low standards of management in which indigenous cattle are usually kept.

However, there are a few indigenous breeds in the region which oan respond very well to good feeding and management. Boyns (1974) reported average milk production of 2006 kg for a group of Butana cows collected from nomadic tribes in Sudan and kept at a government farm. Other promising breeds for milk production in the region include Kenana cattle of Sudan, Shami (Damascus), Domietta of Bgypt, Red Sindhi and Sahiwal cattle.

Exotic cattlet The low production potentialities of indigenous cattle and the high demand for animal products especially dairy produots, together with the marked improvement in the control of epizootic diseases during the post-World Vfer II era, have encouraged countries of the region to import temperate cattle. The majority of these cattle were from the European dairy breeds with Friesian topping the list. They were mainly used for cross-breeding with indigenous cattle but few purebred herds were kept.

Where good feeding and management were provided in institutional herds the resulte were encouraging. European cattle and their crosses with native cattle excelled purebred native cattle in both milk production and earliness of maturity (Tables 12.1 and 2).

Crossbreeding in Sudan was started in Belgravia Dairy near Khartoum in 1925. The cattle are kept in open yards with trees providing shade. The performance of this herd was studied by Osman and Russell (1974). The total lifetime milk production of indigenous cows was 2906 litres in 110 weeks compared to 15 949 litres in 276 weeks for crossbred cows. Total milk yield increased with percentage of European blood up to a maximum of 75 percent. High-grade cows had high milk yield per year of productiva life, but a shorter total productivo life and higher death rates and infertility problems. The conclusions drawn from this study were that European cattle and their crosses are suitable for use in Sudan so long as they are provided with suitable feeding and management.

An interesting study on the effect of the cliraate on the health and productivity of Friesian cattle and management techniques to alleviate the situation was reoently made by Ansell (1976) at Digdaga Farm, United Arab Emirates. The author had the opportunity to visit this herd in July 1978, at a time when shade temperature was well above 40°C and relative humidity was near saturation point. The cattle were kept during the day in shelter yards with high elevated roofs. At night the cows stayed out in open yards. During the summer cattle are fed mainly at night and with feeds with low content of orude fibre. In Ansell's study, using these and other techniques of management, the productivity of 19 Friesian heifers oompleting their first lactation was 3253 kg on a 305-day basis and mortality was very low.

A marked feature in recent years has been the development in Borne countries in the region of large-scale projects involving the importation of high-producing, exotic dairy breeds (mainly Friesian) as the basis of more intensivo and prouctive dairy industry. Eramples of such projects are those recently (about 1976) established in Iraq. Three large-ecale dairy projects each consist of a farra carrying about 800 Friesian cows imported from Europa as pregnant heifers. Thay have been developed on a turn-key basiB by expatriate firms whose contraete also include irrigation and forage development as well as training of local staff.

The author visited one of these projects (7 April Farm) last year. The cows are zero-grazed and kept in air-cooled (desert coolers) barns all year round. However, each barn has a small open yard attached to it for cows to stay out at night or when the weather allows during spring days. Summer temperaturas in Iraq can be very high, exceeding 50°^c in the shade in certain days. By the use of desert coolers, the temperature inside the barn can be brought down to 36°C with 20% RH. Bvrery pracaution has been taken to spray the cattle twice during the summer as precautionary measure againBt tick-borne diseases (Theileria annulata) which is quite coramon in Iraq and many oountries of the region. The author was told by expatriate technical manager that first calvers averaged 4000 kg in a lactation. One group of second calvers was giving about 25 kg/day. Acoording to his experience, under the present expatriate management conditions the general adaptability of the cows is good, no problems with calving or calf rearing. The problem is with conception.

During winter the number of services per conception was two, while during summer it was six. It seems that high ambient temperaturas have more ill-effects on fertility than on milk production. SI Deesouky et al. (1977) found that the average sarvice period in purebred Friesian cows kept in cooled barns in Iraq was 126.5 days compared to 253.4 days for the control group.

Effects of environment and adaptations of cattle; The distribution of different types and breeds of cattle in the region does not indicate a pattern related directly to geography or climate. Sven though températe type cattle are found in Maghreb countries and typical zebu are found in Pakistan, there are zebu cattle in Africa and the Arabian Peninsula. Suropean cattle have been imported recently in larga numbers to the region. Now there is a significant population of Suropean cattle and their croases in praotically all countries of the region. Acoording to Mason (1975) the present distribution of cattle types throughout the world has been influenced. primarily by human migration and secondarily by the development of local adaptations in the cattle which have been brought to a given area.

It must be noted, however, that by and large zebu type cattle are concentrated in the arid/hot parta of the region while temperate type cattle are found mainly in the relatively cooler areas, namely in countries bordering the Mediterranean Sea. This cannot be a coincidence; zebu cattle are known to be more resistant than temperate cattle to high temperaturas, to water shortage, low nutrition, to many parasites and diseases including theileriasis, which is endemic in the hot parts of the region.

Zebu cattle are specially well adapted to live and reproduce under range conditions. There is evidence from USA that while Brahman and Brahman croases grow more rapidly in summer on pasture than the European breed (Hereford), the latter gains faster on feed lot and in winter. In another study it was found that the corssbreds between large European breeds and the local zebu (Boran) were no better than pure Borans on the low and medium concentrate ration, but they grow 30% faster on the high concentrate ration.

There is ampie evidence in the literature indicating genetic differences in resistance to diseases, espeoially parasitio diseases. But this subject will be covered in another part of this Symposium. Suffioe it to mention here that the Australian Milking Zebu (ANZ) was developed from zebu, mainly Sahiwal, and temperate cattle (Jersey) in order to combine the heat toleranoe and tick resistance of the former and the high milk production of the latter.

It is therefore reasonable to assume that the majority of indigenous breeds of the region are well adapted to the local environment which is harsh and in many ways not optimal for high levels of production. Only when this harsh environment is ameliorated, either by natural factors, like proximity from sea or high altitude, or through good management, including housing, better feeding and disease control, exotic stock and their crossbreds can thrive and produce, With the present scarcity of animal products and the resulting high prices espeoially of milk and dairy products, the cost of environment amelioration and improvement can be economical in certain parts of the region. However, in the long run, and oonsidering the limited financial resouroes available at present in most countries of the region, it is more rational to put the greatest emphasis on the improvement of the well adapted local stock. This policy will pay the greatest dividends when the most promising breeds in the region are identified, studied and improved.

In some speoies, however, like the water buffalo, there are no temperate breeds that could be used for grading-up local breeds. Therefore improvement of indigenous buffaloes by selection is the only available means.

Beef cattle on the other hand are raised under extensivo conditions, where feeding and veterinary conditions are not optimum. Therefore the local breeds do better than the exotic stock, although where pastures are improved and reasonably good veterinary services are available, croases between Buropean cattle and Boran or other African zebu are superior to pure zebu strains. Beef production in developing countries will therefore have to rely to a large extent on the local well-adapted strains, and it is important that these should be systematically evaluated.

12.4 Sheep Breed Types

Indigenous breedst: The sheep population of the region, estimated at about 193 million head in 1976, is distributed in all countries with the largest concentrations in Turkey, Iran, Pakistan, Afghanistan and Sudan.

There are more than 40 indigenous breeds. They vary a great deal in physical as well as in physiological characteristics. The majority of the breeds are fat-tailed, while a significant number have thin taxis. There are many intermedíate types. The sheep in the region also vary in their fleece types; sorae have carpet wool, while many others are woolless (hair).

The objectives of sheep breeding also vary from one part of the region to another. Fbr instance, while in the majority of countries sheep are raised for meat, other countries put a great emphasis on milk and wool also. Therefore there is an array of indigenous breeds each adapted to its own environment and satisfying certain objectives. Sxamples of sheep breeds in the region are shown in Table 12.3.

Sheep products and produotiont The chief sheep products in the region are meat, milk_f wool, and ekine. Tablee 12.4, 12.5 and 12.6 sumraarize the productivity of the local breeds of the region. Seemingly there is a great variability in degree of productivity and quality and type of products.

One oharacteristic of raeat in the Middle East is the presence of the fat tail on the caroass which is highly desired in the local markets. Therefore this strong consumer preference limits genetic improvement of fat-tailed sheep to selection within breed or crossing different breeds of the same tail type.

Sheep provide about one-fifth of the total milk produced in the region. Even though not all sheep are milked, there are a number of good milk sheep in the region, for instanoe Awassi and Chios.

The most important wool in the region is the carpet-wool which comes from the fat-tailed sheep. It forma the basis for the carpet industry in the Near Sast. Though exact specifications of this wool have not been determined, wool traditionally used for carpets has a high fibre diameter (30 /u), a high percentage (35%) of medullated fibres and average length of at least 10.2 cm. The content of kemp should not exceed 4% by weight. White wool is generally preferred over pigmented wool specially for machine-made carpet. But pigmented wool can still be used in hand-woven carpets.

Sheep skins have not been well studied in the region. But it is well known that Sudanese Desert sheep produce some of the world's best glove leather.

The environment and sheep breeds; As in the case of cattle, the distribution of sheep breeds in the region does not fit into any climatic or ecological pattern. For instance there are wooled sheep in hot dry areas (Awassi in central Iraq, Arabi in southern Iraq) as well as in relatively cool areas (Barbary in Libya and Tunis, Barki in Egypt). There are thin-tailed sheep in hot arid areas (Dongola in northem Sudan), but there are also thin-tailed sheep in relatively cool areas (Ben Alisen, Tadmit, Thibar).

However, by and large, hair (woolless) sheep occur mainly in the hot (and sometimes wet) areas, for instance in Sudan and Somalia» However both Nejdi and Hejazi sheep in Saudi Arabia are hair sheep. It is therefore reasonable to assume that present-day breeds in the region are a result of several factors including breeders' selection, migration and adaptation to the local environments.

Many countries have imported foreign sheep breeds into the region. The main objective was to improve wool production. However more recently interest in the foreign prolific breeds has grown tremendously. In contrast to cattle, the adaptation of exotic sheep was even more difficult. Chamen et al. (1963) and Gaial et al, (1974) compared the fertility and survival of the local Egyptian sheep (Barki) and some imported breeds. The results are shown in Table 12.7.

The performance of Finnish sheep imported to Iraq recently is shown in Table 12.8.

According to Mason (1977) the superiority of the local breeds in the Near Sast region lies in the heat tolerance, adaptation to poor nutrition, resistance to drought, parasites and diseases, rather than in presence of fat tail which is characteristic of most breeds of the region. Injid et al. (1977) have shown that docking fat-tailed sheep improved their semen quality.

In the hot and humid parts of the world there was no interest in developing wool for clothing, and it seems that wool has an advantage for sheep only in dry climate and direct sun, Experiments in Iraq (Eyal, 1963) and Saudi Arabia (Ramadan, 1974) have shown that shearing shsep during hot season has incrwaaed body temperatura and respiration rate in sun, but not in shade or at night. Sheep lose heat chiefly by pulmonary evaporation.

12.5 Amount of Genetio Variation Available

Tablas 12.9 and 12.10 provide some estimates of variation in performance levels in cattle and sheep in the Middle and Near Eest region.

The above variation may reflect both genetic and enviroriniental factors. But judging by the range of breeds available, it is quite evident that there is enough genetic variation to support programmes of genetic improvement using breed resources in the region.

Within-breed variation in dairy traits was studied in Sudanese cattle by Alim (1960, 2962), Osman (1970) and Osman and Elamin (1971). These studies have given heritalility estimates of milk yield in the range of 22 to 26 percent.

Evidence of within-breed genetic variation in Awassi sheep was indicated in an experiment carried out by the Arab Centre for the Studies of Arid Zones and Dry Lands (ACSAD) in Syria. A comparison was made of milk production of daughters of four Awassi rams, two of which were importad from Cyprus and Terbol Station in Lebanon. The results obtained are shown in Table 12.11.

A study of between-breed variation was reportad by Fox et al. (1971) where Awassi ewes were crossed with Chios rams in Terbol Lebanon to improve fertility. Results are shown in Table 12.12.

12.6 References

Alim, K.A. (1960). Reproduotive ratas and milk yields of Kenana cattle in the Sudan. J. Agrie. Sci., Camb. 55:183-188,

Alim, K.A. (1962). Snvironmental and genetic of factors affecting milk production of Butana cattle in the Sudan. J. Dairy Sci. 45:242-247.

Ansell, R.H. (1976). Maintaining European dairy cattle in the Near East. World Animal Rev., 20:1-7.

Boyns, B.M. (1947). Sudanese cattle as milk producers. Enp-J. Exp. Agrie., 15/57):27-41.

El Dessouky, F.I., L. Enmark, M.H. Al Salman and S.A. Al Doori (1977). Alleviating heat stress on a group of imported Friesian cows in their first lactation. Iraqi J. Agrie. Sci., 12:143.155.

Eyal, S. (1963). Shorn and unshorn Awassi sheep. J. Agric. Sci., 60:159-163.

Fox, C., R. Chaaban, W. Hardison, S. Badawi, Dr. Choueiri and M. Maalouf (1971). Selection and breeding programmes of Awassi and Chios sheep. Instituto de Recherohes Agronomiques, Liban, Magon No. 36.

Galal, E.S.E., M.M. Mabrouk, Y.S. Ghanem and H.A. El Oksh (1974). The effect of cross-broeding and other factors on livability of lamba raised under send-arid conditions. Zeitschrift für Tierzuchtung und Züchtungsbiologie.

Ghanem, Y.S., M.H. Fahray, A.M. Sooudi and M.F.A. Parid (1963). Some obeervations on the reproductivo behaviour of local and imported breeds of sheep under desert conditions. Paper for 4th Egyptian Vet. Congress, Cairo, April 1963. 8 pp. Mimeograph.

Injid, M.H., K.H. Juma, A.J. Alchalabi and J. Eliya (1977). On some semen characteristics of Merino and Awassi rams. Iraqi J. Agrie. Sci., 12:157-174.

Mason, I.L. (1975). Factors influencing the world distribution of beef cattle. Inter­national Aspects of Beef Production.

Mason , I.L, (1977). Sheep breeds of the Arab Countries. Paper presentad at Trairdng Course in Sheep Production in Arid Zones. Tripoli, Libya.

Osman, A.H. (1970). Genetic analysis of daily milk yield in a diary herd of northern Sudan zebu cattle. Trop. Agrie. Trin., 47:205-213.

Osman, A.H. and F.M. Elamin (1971). Some dairy characteristics of northern Sudan zebu cattle. II. Inheritance of some reproductivo and milk production traits. Trop. Agrie. Trin., 48:201.208.

Osman, A.H. and W.S. Russel (1974). Comparativo performance of different grades of European-Zebu crossbrod cattle at Ghurashi Dairy Farm, Sudan. Trop. Agrie. Trin., 51: 549-558.

Ramadan, M.Y. (1974). A note on the effect of shearing, shade, and water spraying on the heat tolorance of Nejdi sheep. Ministry of Agriculture, Saudi Arabia and University College of North Wales, Bangor. Publication No. 28.

Des Types Génétiques pour Différents Ehvironnements
Résumé

1. Préambulo. Le bétail dans le monde est élevé dans des conditions d'environnement et d'exploitation extremement variables et auxquelles il a été très bien adapté par une sélection naturelle ou artificielle. Les objectifs de la sélection animale sont tout aussi divers.

Aussi exite-t-il de multiples types génétiques qui varient considérablement en ce qui concerne aussi bien leurs caractéristiques physiques et fonctionnelles que leur rendement.

Dans l'ensemble, la plus grande partie du bétail des pays en développement se trouve dans des régions tropicales et subtropicales. Quoique bien adaptées à l'environnement local, les betes ont en général un potentiel trop faible pour permettre une production élevée.

Afin d'accroítre la production nationale de l'élevage, de nombreux gouvernemonts de pays en développement ont mis en route des programmes d'anélioration du cheptel impliquant des iraportations nombreuses d'animaux de races étrangères en provenance de pays développés. Malheureusement, il n'a pas encore été mis en oeuvre de prograrames efficaces et comparables en vue d'améliorer le potentiel génétiques deB races indigènes.

Le présent document portera principalement sur la région du Moyen-Orient et du Proche-Orient pour deux raisons: d'abord, l'auteur s'est rendu dans la plupart des pays de cette région; ensuite, cette région s'étend à la fois sur l'Asie et l'Afrique et l'éventail des environnements, tant écologiqueB que sociaux, ainsi que les ressources génétiques et les méthodes d'élevage qu'on observe dans la ràgion, sont typiques de ce qui se passe dans la plupart des pays en développement.

On s'est efforcé de mettre en évidence les types génétiques disponibles compte tenu des conditions qui regnent au Moyen-Orient et au Proche-Orient, d'étudier les facultés d'adapta-tion et les potentiels de production des divers types génétiques qui ont évolué dans différentes oonditions d'environnement, et de la sorte d'estimer l'ampleur de la variation génétique disponible en chercbant á repérer les types locaux qui offrent des perspectives encourageantes.

2. L'environnement. La région du Moyen-Orient et du Proche-Orient est très vaste et s'étend des pays du Maghreb à. l'ouest jusqu'a l'Afghanistan et au Pakistan a l'est et du Soudan et de la Somalie au sud jusqu'à la Turquie au nord. II existe donc une grande diversité de conditions climatiques et topographiques, ainsi que des pratiques agricoles et zootechniques tr&s variables. La région est habitée par différents groupes ethniques dont les structures et les habitudes sociales sont fort diverses.

Dans la majeure partie de cette région (à l'exception de deux sous-régions, l'une dans l'extre'me nord, l'autre dans 1'extrême sud), le climat est caractérisé par des étés longs et secs et des pluies d'hiver qui sont irrégulieres et, en maints endroits ne dépassent pas 100 mm par an. Les étés sont très chauds, la moyenne des températures maximales dépassant de plusieurs degrés la température du corps chez les mammiferes. Dans les Stats du Oolfe et dans certaines parties du Pakistan, les effets nocifs des températures élevées de l'été sont aggravés par la forte humidité.

En raison de l'aridité et du caractere très saisonnier de l'approvisionnement en eau et des ressources fourragères, l'élevage est principalement du type nomade ou serai—nómade,

Sur le plan de la santé anímale, la situation est loin d'Stre satisfaisante. Outre les maladies nutritionnelles résultant de la malnutrition, toutes les catégories d'animaux souffrent de maladies épizootiques et enzootiques.

3. Effets de 1'environnement et adaptations

Bovins. Dans leur majorité les bovins indigenes de la région du Proche-Orient sont caractérisés par une faible production laitiere, un taux de croissance lent et une petite taille. Pourtant, il n'existe que peu de races indigènes dans la région qui réagissent vraiment bien à de meilleures conditions d'affouragement et d'exploitation (tableau 12.i).

Quand 1'environnement est amélioré, soit par suite de facteurs naturels coame la proximité de la mer ou l'altitude élevée, soit par de bonnes conditionB d'exploitation, de logement, d'alimentation et de lutte contre la maladie, les bovins étrangers et leurs produits de croisement peuvent donner une meilleure production que les bovins indigenes (tableau 12.2). Toutefois, il ressort d'études faites a. la laiterie Belgravia de Khartoum (Soudan) et à l'exploitation laitiere thale-danoise en ThaSlande que, dans de telles conditions, les bovins européens de haute qualité ont des taux de mortalité et d'infertilité plus eleves.

Ovins. II existe plus de 40 races indigenes dans la région. Blles varient considéra-blement quant à leurs caractéristiques physiques aussi bien que physiologiques. II s'agit dans la plupart de cas de races à grosse queue, mais il y a aussi un nombre non négligeable de raoes à queue mince. On trouve aussi de nombreux types intermédiares. Ces ovins sont également variables quant aux types de toison; certains fournissent de la laine à matelas, tandis que beaucoup d'autres ne produisent pas de vraie laine (poils). (Tableau 12.3).

II semble que l'importance du rÔle joué par le type de laine et de queue dans 1'adapta-tion des ovins dans la région du Proche-Qrient varie selon l'environnement. La laine ne constitue apparemment un avantage qu'en cas de climat sec et d'ensoleillement direct. Des études faites en Arabie saoudite et en Iraq ont révelé que la tonte des moutons pendant la saison chaude produit une augmentation de la température et de la vitesse de respiration au soleil mais non a l'ombre ni la nuit. Chez les ovins, la déperdition de chaleur s'effectue surtout par évaporation pulmonaire. On a observé que le fait de raccouroir les queues des moutons à grosse queue améliorait la qualité du sperme.

4. Ampleur de la variation génétique disponible. Les tableaux 12.9 et 12,10 donnent quelques estimations de la variation des niveaux des performances ohez les bovins et les ovins de la région du Proche-Orient. Cette variation peut refléter des facteurs aussi bien génétiques que liés à l'environnement, mais, si l'on en juge d'après l'éventail des races (tableaux 12.1 et 12.3), il existe de toute évidence une variation génétique suffisante pour autoriser des programmes d'amélioration génétique faisant appel aux races existant dans la région.

Une expérience menée en Syrie par l'ACSAD (Centre arabe d'étude des terres arides et non irriguées) a revelé l'existence possible d'une variation génétique intraraciale chez les ovins Awassi. On a comparé la production laitière des filies de quatre béliers Awassi, dont deux étaient importés de Chypre et de la station de Terbol au Liban (tableaux 12.11 et 12.12).

Tipos Geneticos en Ambientes Distintos
Resumen

1. Preámbulo. Las poblaciones de ganado del mundo se mantienen en condiciones ecológicas y de manejo extremadamente variadas a las que se han adaptado bien por medio de una selección natural y artificial. Los objetivos de la cría de animales son asimismo diversos.

Por ello, existen muchos tipos genéticos que varían en gran medida por sus caracterís­ticas físicas y funcionales, así como por su productividad.

En general, la mayor parte del ganado de los países en desarrollo se encuentra en las regiones tropicales y subtropicales. Estos animales, aunque se hayan adaptado bien al medio ambiente local, tienen un potencial relativamente bajo de alta producción.

Para mejorar su producción ganadera, muchos gobiernos de países en desarrollo han iniciado programas de mejora pecuaria que suponen grandes importaciones de razas exóticas provenientes de países desarrollados. Desgraciadamente, hasta ahora no se han implantado programas eficaces y comparables para mejorar el potencial genético de las razes indígenas.

El presente documento se refiere ante todo a la región del Medio y Cercano Oriente, por dos razones principales: primeramente, porque el autor ha visitado la mayor parte de los países de esta región y en segunda debido a la localización de dicha región en Asia y Africa, presenta una variedad de ambientes ecológicos y sociales así como por los recursos genéticos y los métodos de cría utilizados en la región, y que son característicos de lo que está ocurriendo en la mayor parte de los países en desarrollo.

Se ha intentado hacer resaltar los tipos genéticos disponibles en el marco de las condiciones del Medio y del Cercano Oriente, analizar las posibilidades de adaptabilidad y de producción de los diversos tipos genéticos que han evolucionado en condiciones ambientales diferentes y, con ello, estimar la cantidad de variación genéitica disponible, así como identifioar tipos locales de posible interéis.

2. El medio ambiente. La regi6n del Medio y Gercano Oriente constituye una vasta zona que se extiende desde los países del Maghreb, al oeste, hasta AfganiBtáin y Pakistán, al este, y desde Sudán y Somalia, al sur, hasta Turquía, al norte. Por ello existen grandeB variaciones en lo que respecta a las condiciones climátieas y topográficas asf como en las explotaciones agrícolas y ganaderas. La región está habitada por distintos grupos étnicos, de diferentes estructuras sociales y costumbres.

En la mayor parte de la región (excepto en dos subregiones, una al extremo norte otra al extremo sur) el clima se caracteriza por veranos largos y secos, y por irregulares lluvias invernales que en muchos lugares no exceden de 100 mm anuales. Los veranos son muy calientes con temperaturas máximas medias que superan en varios grados la temperature corporal de los mamíferos. Eh los BstadoB del Golfo y en ciertas partes de Pakistán a los inconvenientes de las altas temperaturas del verano vienen a sumarse el alto grado de humedad.

A causa de la aridez y del carácter marcadamente estacional del abastecimiento de agua y recursos forrajeros, la ganadería es predominantemente nómada o semin6mada.

La sanidad animal se encuentra en una situaói6n lejos de ser satisfactoria. Junto a las enfermedades nutricionales debidas a mala nutrici6n, en todas las clases de animales imperan numerosas enfermedades epizo6ticas y enzoófticas.

3. Efeotos del medio ambiente y adaptaciones

Ganado vacuno. La mayor parte del ganado vacuno indígena de la region del Oercano Oriente se caracteriza por una baja producción de leche, lento índice de crecimiento y pequeno tamano corporal. Sin embargo, existen en la región algunas razas indígenas que pueden responder satisfactoriamente a un buen sistema de alimentación y manejo (Cuadro 12.1).

Cuando mejora el medio ambiente, bien por factores naturales como la proximidad al mar, o por la gran altura o un buen manejo incluyendo disponibilidad de alojamientos, mejor alimentación y actividades de lucha contra las enfermedades, el ganado vacuno importado y sus cruzas pueden tener un mejor rendimiento que el ganado indígena (Cuadro 12.2;. Sin embargo, los estudios llevados a cabo en la finca Belgravia, de Khartoum, Sudan, y en la finca tailodanesa de Thailandia, han demostrado que el ganado vacuno europeo de buena raza tenía en estas condiciones tasas más altas de mortalidad e infertilidad.

Ganado lanar. Existen en la región más de 40 razas indígenas. Varían mucho en sus características físicas y fisiol6gicas. La mayoría de las razas son de cola gruesa, mientras que un número considerable presentan una cola delgada. Existen muchos tipos intermedíos. Los ovinos también se diferencian por sus tipos de lana. Algunos producen lana para tapices, mientras que muchos otros carecen de lana (pelo). ?er cuadro 12.3.

La importanoia del tipo de lana y del tipo de cola en la adaptación de las ovejas a la regi6n del Cercano Oriente parece variar con el medio ambiente dominante. Aparententente, la lana tiene ventajas solamente en climas secos, de sol fuerte. Los estudios efectuados en la Arabia Saudita y en Iraq han demostrado que la esquila de las ovejas durante la estación cáilida aumenta la temperatura y la frecuencia respiratoria cuando quedan expuestas directamente al sol. Esto no ocurre a la sombra ni durante la noche. El ganado lanar elimina el calor principalmente por evaporación pulraonar. La amputación de la cola en los ovinos de cola gruesa mejora la calidad del semen.

4. Variaciones genéticas disponibles. Los cuadros 12.9 y 12.10 ofrecen algunas estimaciones de la variación de los niveles de conformación en ganado vacuno y lanar de la regi6n del Cercano Oriente. Esta variación puede corresponder tanto a factores genéticos como del medio ambiente. Pero a juzgar por la variedad de razas (cuadros 12.1 y 12.3) resulta evidente que existen suficientes variaciones genéiticas para apoyar programas de mejoramiento genético, que utilioen los recursos de razas disponibles en la regi6n.

Eh un experimento llevado a cabo por el ACSAD en Siria, se obtuvieron pruebas evidentes de la variación genética dentro de una raza empleando las ovejas Awassi. El estudio consistió en comparar la producción de leche de las hijas de cuatro carneros Awassi, dos de lob cuales habïan sido importados de Chipre y de la Estación Terbol de Líbano. Ver cuadros 12.11 y 12.12.

APPENDIX

BREEDING ADD DEVELOPMEHT MODELS