PAPERS PRESENTED AT THE EXPERT CONSULTATION (Contd.)

C. PRACTICAL ISSUES FOR THE CONSERVATION AND IMPROVEMENT OF PRIORITY BREEDS WITH GLOBAL REVIEWS OF SPECIES (Contd.)

A GLOBAL REVIEW OF THE GENETIC RESOURCES OF CATTLE

J. Philipsson¹

1 Introduction

Effective use of the modern reproduction technologies of frozen semen and embryo transfer has contributed not only to successful genetic programmes with highly productive breeds in developed countries, but also to a wide-spread use of such germplasm around the world. In many parts of developing countries the use of semen of these “exotic” breeds has greatly enhanced the production of milk and beef, mainly by crossbreeding with indigenous cattle breeds. Areas or farms with high management standards and little climatic stress in the tropics have gained good results with pure or high grade exotic breeds, for example in Kenya. However, the more common experience under less favourable tropical conditions has been the use of a temperate breed to crossbreed with the indigenous cattle, thus producing positive results with F1 animals. Grades higher than 5/8 usually give poorer results. This effect is often due to less resistance and adaptability to various climatic, disease and other stress factors which cause health or reproduction problems and result eventually in a higher rate of loss.

Despite these well known facts there is a continuous use of semen of exotic bulls in the tropics for the production of superior crossbreds, while the preconditions for a successful long term breeding strategy are neglected. This type of indiscriminate crossbreeding, which at first sight gives very promising results, has become the greatest threat to some indigenous cattle breeds, especially those which show the highest potential for continuous crossbreeding.

An illustrative example of such a case is the Sahiwal breed in Pakistan and India. Crosses with Holstein and some other exotics have been so successful for milk production that few purebred females were retained. Consequently the pure Sahiwal population very rapidly decreased in numbers. The Kenana breed in Sudan is another example. When AI was introduced, only the imported semen of Holstein bulls was available. When the more progressive farmers joined the AI scheme they were extremely satisfied with the results of their F1 animals. However, they were not so satisfied with the 3/4 or 7/8 Holstein crosses, which were less resistant to diseases and climatic stress. Since the AI service did not offer anything other than imported Holstein semen, the lack of long term breeding strategy at farm level meant that the more progressive farmers had to quit the AI service.

¹ Swedish University of Agricultural Sciences, S-750 07 Uppsala, Sweden.

These two examples illustrate the importance of sound long term breeding strategies to make efficient use of modern biotechnology in animal breeding, as well as providing the basis for a sustainable breeding programme using valuable indigenous breed resources. Although some indigenous breeds with unique characteristics for a given environment are threatened with extinction in this way due to their highly competitive F1 progeny, there are other indigenous breeds that retain their competitive position as pure breeds. However to stay competitive in the long run, improvement and conservation schemes need to be applied, whereby different reproductive technologies might prove their usefulness, especially when a breed expansion is desirable.

The objective of this paper is to identify and review a number of cattle breeds, recognized for unique characteristics or proven to be of such importance, whose future survival justifies the use of improvement and conservation schemes. To some extent also studies supporting the conservation and improvement schemes of the selected breeds are proposed.

First the development of cattle populations and types of cattle breeds in the various regions of the world are briefly reviewed. Criteria for choice of breeds for conservation and improvement programmes are proposed; this is followed by a review of six breeds considered to have high priority.

2 Cattle populations by region

The cattle population of the world amounts to nearly 1,300 million head according to the most recent FAO statistics (FAO, 1991). Of these, nearly 900 million head are found in developing countries. Their distribution by region is given in table 1.

Table 1. Cattle populations of developing or tropical countries by region

Source: (1) FAO yearbook, 1990;
(2) Maule, 1990

In the last decade the cattle population in the developing countries increased by some 85 million head or 10% (table 2) according to FAO statistics. By contrast cattle numbers in the developed countries decreased about 6%. The increase in the tropics has been most rapid in the Far East. Also Africa has had a continuous growth despite some severe droughts. The highest ratio of cattle to the human population is found in the Americas, where it is twice as high as the ratio in Africa, which in turn has a ratio which is more than twice as high as that of Asia. On the other hand, in relation to land area, Africa has a little less than half the numbers of cattle compared with the other two regions.

Table 2. Development of cattle populations by regions

Total milk production increased in the last decade by 41% in the developing countries of which those in the Far East show the sharpest increase. This is also true per cow (table 3). Latin America shows the highest annual yield per cow, but a slower total production development (+17%) than the human population growth (+24%), a situation which is even more pronounced for the Near East region (+9% vs. +32%).

Table 3. Development of milk production by region. The corresponding change in human population size is given with brackets

3 Main types of tropical breeds

The cattle breeds in the tropics may, according to Maule (1990), be divided into three distinct main groups:

3.1 Humped cattle

1. Zebu (Bos indicus)
2. Sanga (Zebu × Humpless Longhorn)

3.2 Humpless (Bos taurus)

1. West African Humpless
2. Middle East Shorthorn
3. Criollo of Latin America
4. Far East Humpless types

3.3 Humped × Humpless

1. Zebu × West African Humpless
2. Zebu × Bos brachyceros
3. Zebu × Bos taurus

4 General characteristics of the different breed types

4.1 Humped cattle

The zebu is the dominant tropical cattle breed with its main location in Asia. It has long been well represented in all tropical regions due to its adaptation to hot and harsh environments. The different breeds vary considerably in size and are, with few exceptions, rather low producers of milk. A relatively high resistance to tropical cattle diseases has made the zebu an important part of most crossbreeding programmes in the tropics, as well as a foundation component of many synthetic breeds. A generally slow reproductive rate, including high ages at puberty and calving, is noticeable.

The Sanga type of cattle is unique to the southern and eastern parts of Africa. They are distinguished from the zebus by their long horns and the position of the commonly smaller hump.

4.2 Humpless cattle

Breeds of this type fall mainly into four groups which are of importance for the tropics. Their area of domestication, Asia, is still very important. The West African Longhorn type includes the N'Dama breed, which is known for its tolerance against trypanosomiasis in the tse-tse infested areas of the humid central and western parts of Africa.

The Criollo type breeds have proven to be of specific importance to the Americas. These cattle, originating from the Iberian peninsula, gradually became the dominant type of cattle throughout Latin America. Later, Criollos have to a large extent been replaced in Latin America either by zebus or European breeds or crosses.

4.3 Humped × Humpless

Numerous breeds are the result of crossbreeding Bos taurus and Bos indicus. These may be divided into three groups. The first include established indigenous breeds of rather ancient origin. These are numerous in Africa and South East Asia.

Breeds of the second group are still at a formative stage and are intermediate, while the third group includes breeds of recent origin resulting from planned crossbreeding to produce synthetic breeds such as the Jamaica Hope and Santa Gertrudis. The characteristics of these crossbreds vary considerably depending on the parental origin. The oldest ones have developed into breeds which are well adapted to their usually harsh environments, while the last group of breeds usually has developed a higher production potential.

In Payne (1990) a detailed classification is given of the tropical breeds, categorized as above, by world region.

5 Criteria for choice of breeds and pilot conservation and improvement schemes

A number of indigenous breeds of ancient as well as more recent origin, is apparently threatened with extinction, despite or just because of, some very good characteristics relating to their adaptation to tropical climate and harsh conditions. Equally well some indigenous breeds have been identified that possess characteristics needed for long term planned cross-breeding with exotic breeds and which will result in desired and adaptable crosses.

Some indigenous breeds show characteristics that prove themselves to be highly competitive with any crossbreds or exotic breeds, but they are not fully utilized in the tropics, nor is their genetic potential utilized in a breeding programme for further improvements. When choosing 5–6 breeds for global pilot conservation and improvement schemes which will be of the greatest benefit to their users and which will also contribute experience in the management of the pilot schemes, the following criteria are desirable:

1. The breed should have some unique characteristics that are considered to be of specific importance for food production in a large tropical area

2. The breed is either endangered or is not efficiently utilized

3. The breeds should be of different types and cover some different needs

4. The breeds should cover different tropical regions

5. The infrastructure, some basic resources of the country where the pilot scheme is to be conducted and the personnel competencies should be of an acceptable level to support the anticipated performance of the pilot scheme.

6 Selected breeds and proposed schemes

On the basis of the above criteria the following breeds have been selected in priority order. Reasons for their choice, some more detailed facts about the breeds and features of proposed studies and conservation and improvement schemes will be given.

1. Sahiwal (Asia, Africa, Humped, very productive, dual purpose)
2. N'Dama (West Africa, Humpless, trypanotolerant)
3. Criollo (Latin America, Humpless, dual purpose)
4. Kenana (Africa, Humped, milk)
5. E. Boran (Africa, Humped, beef)
6. F. Guzera (Latin America, Humped, triple purpose)

Due to the fact that Sahiwals cover two continents, and that synthetic breeds with a component of Sahiwal are utilized in two more continents this breed will be given somewhat more consideration than the others in this paper. Ongoing FAO supported research concerning Sahiwal also calls for more evaluation.

7 Sahiwal

7.1 Origin, habitat and distribution

The Sahiwal breed originated in the central and southern parts of Punjab, Pakistan, primarily in the districts of Sahiwal and Okara. This area is characterized by a subtropical and arid climate. According to Hasnain & Shah (1985) there is no authentic record of the early development of the breed but most probably it derived from a mixture of strains that migrated from the south of India and north of Pakistan and the adjoining territory of Afghanistan. There is an apparent similarity with the Gir breed, which has had a great influence on other breeds in India such as the Red Sindhi. This one is also considered to be a possible parental breed of the Sahiwal cattle.

7.1.1 Pakistan and India

Sahiwal cattle were the main livestock in the original habitat in Pakistan throughout the last century. The introduction of a canal irrigation system at the beginning of this century changed the entire ecology and agriculture from pastoral livestock production into intensive crop production. The dairy qualities of the Sahiwals were then challenged by the buffaloes, which produce a higher fat milk. In addition Sahiwal bullocks, being slow workers and lethargic, were found to be inadequate for farm operations in the new production system. Thus, the Sahiwal breed lost its old status and was to a great extent replaced by other better work animals.

The number of pure Sahiwal animals declined drastically and the process was further accelerated by the introduction of AI and crossbreeding with temperate dairy breeds. Crosses with Sahiwal have been extremely successful under the prevailing conditions and much more in demand than the pure breed. To preserve and improve the breed several large governmental and grantee Sahiwal herds have been built up in Pakistan since 1920. These farms, which practice milk recording with registrations of pedigree and performance data, now form the only effective breeding population of the Sahiwal breed in Pakistan. Around 2,000 pure Sahiwal breeding females are found on such farms out of a total of about 10,000 in the whole country (see table 4). The most well known of these farms are the privately run Jehangirabad (nearly 400 cows) and Allahdad farms (about 250 cows), the governmental experimental stations Bahadurnagar (about 500 cows including its tenant farms) and Qadirabad, which has the AI station.

In Pakistan a progeny testing programme started in 1981/82 comprising four farms (Bahadurnagar, Jehangirabad, Allahdad and Fazilpur) with almost 1,000 cows. Around 100– 150 cows are considered as elite cows and used for the production of breeding bulls, whereas the remaining cows are used for testing of young bulls. A batch of 5–7 bulls is tested every second year and bulls with a positive breeding value, calculated on a contemporary comparison basis, are used for breeding the elite cows.

In India, the Sahiwal breeding herds are found almost exclusively at various institutions and military farms in the northern parts of the country. The best known being at the National Dairy Research Institute at Karnal. A cooperative progeny testing programme was established in 1982/83 between 9 institutional herds (Bhat & Taneja, 1987). These farms have around 900 cows and according to the plan 6–8 young bulls in each set are progeny tested of which one or two will be selected.

Table 4. Estimated population size, effective breeding population (number of registered cows) and crosses of the Sahiwal breed

Sources (1) Hodges, 1987;
(2) estimation by author;
(3) Hodges, 1984

7.1.2 Kenya

Sahiwal cattle were first imported in 1939 from the Pusa herd of India followed by further imports from Pakistan after World War II. A total of 60 bulls and 12 cows were imported following which the Kenya Sahiwal stock was closed for nearly 30 years.

Sahiwal herds are owned both by the government and by a few private breeders. These herds are found mainly in the central and eastern parts of the country at high altitudes but also in the humid coastal areas. In general the Sahiwals and their crosses are kept in grazing areas where the environmental conditions are rather harsh.

To establish an effective national breeding programme a national stud herd was founded at Naivasha in 1962. An intensive selection programme has been applied since then in this herd of some 500 cows of which about 180 are kept in an elite group. These regularly produce some AI bulls, which are selected on pedigree and growth rate followed by a progeny test for milk yield. According to the plan around 10 young bulls are progeny tested each year in the national stud herd and of these, two are later selected as proven bulls for further breeding.

The usefulness of Sahiwal as a dairy breed, with good potential also for beef, for improvement of local stock in tropical and sub tropical regions by crossbreeding is well recognized. As a result the breed has been introduced to many more countries in addition to Kenya including Australia, Tanzania, Thailand and Zambia. The world demand of frozen semen of pure Sahiwal bulls has been larger than the supply.

Several new breeds have developed from crosses between Bos taurus and Sahiwal such as the Jamaica Hope (Jamaica), Karan Swiss (India), AMZ and AFS (both Australia), and a synthetic cross with Ayrshire and Brown Swiss at the Kilifi plantation in the coastal region of Kenya.

7.2 Characteristics

The Sahiwal is considered to be one of the pre-eminent productive zebu breeds for milk production in the tropics. It was first recognized as a potentially useful dairy breed when the Pusa herd was established in 1912 in Bihar State in India. During a period of 20 years the average daily milk yield increased rapidly from 2.6 to 8.5 kg/day.

It is also one of the largest zebu breeds, heavily built with deep body and strong legs. The mature weight of cows is around 340–400 kg and of bulls up to 700 kg. The coat colour is usually reddish but other colours like pale red, dark brown, or almost black with white patches may also occur. The cows have large, sometimes pendulous udders and big teats. The horns are very short and thick and loose horns are common in the female. The bulls have a large, massive hump which frequently falls to one side. The sheath is quite pendulous and the dewlap is also large and heavy. The lethargic temperament has also given bulls of the breed a reputation as slow breeders. This has been reported by Philipsson et al. (1989) to be a problem of the Sahiwal AI service in Kenya.

Some research has been carried out to characterize the Sahiwal breed, mainly in India and Pakistan, but also in Kenya and some other countries. In general most studies have been based on fairly small data sets (less than 1,000 animals) or on data including very long time spans, in some cases more than 50 years.

Two comprehensive reviews on performance and other characteristics of the Sahiwal breed in Pakistan, India and Kenya have been published by Kimenye (1985a) and Hasnain & Shah (1985). Table 5 shows an extract of their findings together with some other results.

According to the literature, average lactation yields are in the range of 1,500 to 2,000 kg. with individual results reaching double this. Lactation lengths are 260 to 300 days. Kenyan data are often at the lower limit for milk yield. However, there is a common belief in Pakistan and India that short lactations (the limit varies between 70 and 200 days) are abnormal and should be rejected from the analysis; this practice may have biased the quoted means upwards. Studies in Pakistan and India show a negative annual genetic trend in milk yield (Chaudhry, 1988; Bhat & Taneja, 1987). This is commonly explained by poor breeding bulls and inbreeding. In Kenya a moderate improvement of 0.28%/year has been observed (-Wakhungu et al., 1991).

Age at first calving and calving intervals are given a high priority in Pakistan. Generally, the calving age is around 37 to 45 months and calving intervals are 390 to 490 days.

Table 5. Results from the literature characterizing the Sahiwal breed

(1) I=India;
K=Kenya
P=Pakistan

A special characteristic reported in Sahiwal cows, compared to most other zebu breeds, is that there are rather few milk let down problems, despite the fact that the calves are reared separated from their dams. This is thought to be a result of selection over many years.

7.3 Ongoing research

As a result of an FAO consultancy report by Philipsson (1985) a joint initial programme for the rehabilitation of the Sahiwal breed in Pakistan has been established between FAO, the Pakistan Agricultural Research Council (PARC) and the Swedish University of Agricultural Sciences. The programme started in 1987 and data were collected from 12 governmental/grantee farms of almost 6,000 pure Sahiwal cows born in 1964 and later with more than 20,000 calving records. The material contains information on pedigree, dairy and fertility traits, stillbirths, growth rate, longevity, health problems etc. This data set is unique and constitutes almost all recorded Sahiwal cows in Pakistan during the time period in question. The following analyses are under way (Olsson, 1992):

1. Population structure, inbreeding and generation intervals.

2. Estimation of genetic and phenotypic parameters for various traits of milk production, live weight and reproduction.

3. Estimation of breeding values and genetic trends.

In table 6 overall means, standard deviations and coefficients of variation are listed for some traits, based on the data analyzed. Short lactations were not excluded from these data.

Some other main results extracted from the analyses are:

• Generation intervals for the four paths were estimated to roughly 6 years except for the path dam/son which was 8.3 years.

• Most Sahiwal herds have to a great extent been closed and inbreeding coefficients are fairly high, on average 5%; in some small farms they are even more than 10% on average.

• Preliminary REML estimates of the heritability for total yield in first lactation was 0.17 and for 305 day yield 0.20.

• Preliminary breeding values have been estimated for all animals with a BLUP animal model. The estimated genetic trend was slightly positive (+2,5 kg/year) for the population of breeding bulls, but negative (-1 kg/year) for the cows. The majority of all bulls with large progeny groups had negative breeding values indicating the use of inadequate selection criteria.

The results of the analyses will form the basis for:

• development of a procedure (BLUP animal model) for continuous genetic evaluations of Sahiwal cattle in Pakistan

• studies of alternative breeding plans for the Sahiwal breed in Pakistan.

Table 6. Overall means of various traits of Sahiwal cattle in Pakistan recorded during 1964–1987 (Olsson, 1992)

7.4 Needs and plans for conservation

According to the results presented here and to several other authors, including Maule, 1990, the Sahiwal breed is one of the best zebu milk breeds in the tropics. Its qualities, not only for dairy but also for beef, have been exploited especially in crossbreeding programmes in developing countries. However, the success in crossbreeding has become a real threat to the breed. The replacement of purebred Sahiwals have been neglected for a long period and the population size has decreased continuously. It is presently estimated at only 10,000 pure Sahiwals in Pakistan or 15,000 in the whole world, of which about 4,000 constitute the active breeding population which is divided into three sub-populations which are genetically isolated from each other. If the decline is not stopped the number will, within a few decades, reach such a low level that the genetic base will be too narrow for any significant improvement of the breed in the future. A strong increase in the inbreeding coefficient could then be anticipated and the breed would certainly be in danger of extinction.

There are several reasons why a long term conservation plan is needed. One is the lack of genetic progress during the last 40 years; another is a deterioration of the Pakistan cow population, most probably caused by inbreeding, and a lack of adequately defined breeding objectives and efficient breeding programmes. The Sahiwal breed with its sub-populations in Pakistan, India and Kenya, meets all the criteria of a breed to be selected for a pilot conservation and improvement scheme with global implications. If successful the Sahiwal breed should be more extensively used in an expanded area of the Near East in order to increase cattle productivity.

It is therefore an urgent matter to complete the studies outlined for the Sahiwal of Pakistan and also to include data from Kenya and India. This will give a basis for a joint analysis of alternative strategies for a global approach to conserve, improve and better utilize this breed resource.

Presently, there is almost no exchange of genetic material (Sahiwal semen or bulls) between Pakistan, India and Kenya. Such an exchange should be facilitated not only as a measure to prevent inbreeding, but also because there is a great demand for Sahiwal semen for crossbreeding, especially in Africa. Sahiwal semen is regularly being produced at Qadirabad in Pakistan but infrastructural problems seem to hamper the export of semen. In Kenya it seems urgent to try alternative methods of rearing the young bulls and train them for semen collection.

In summary the conservation scheme for the Sahiwal breed should include the following steps:

1. Studies on population structure of the three sub-populations in Pakistan, India and Kenya.

2. Establishment of a procedure to exchange semen regularly between the countries.

3. Development of a BLUP animal model procedure for continuous evaluation of dairy, growth and reproductive traits to be applied in the nucleus populations of all three countries.

4. Definition of the breeding objectives utilizing dairy, growth and reproductive traits into a single index for selection of bull dams and young bulls for AI service and use in the nucleus herds.

5. Studies of alternative selection strategies for sustainable improvement, considering the possibilities of a global breeding programme with a controlled development of inbreeding and relationships.

6. Implementation of the most attractive and realistic breeding plan according to resources available in the nucleus herds and AI schemes of Pakistan, India and Kenya.

7. Production of Sahiwal semen for crossbreeding purposes on a global scale in tropical and subtropical countries.

Results from studies in Kenya and Pakistan, already published or in progress, indicate good possibilities of success with an FAO supported scheme for this breed, given the resources available in recorded herds at governmental and some other farms, as well as developed AI services and research competence.

8 N'Dama

8.1 Origin, habitat and distribution

Around one third of the African continent, mainly West and Central Africa, is infected with tse-tse flies which transmit trypanosomiasis disease to domestic animals. This disease severely limits food production from domestic animals in some of the best watered and fertile lands of Africa. However, the N'Dama cattle, introduced to the continent some five to seven thousand years ago, has during this long period of time developed a high degree of resistance to trypanosomiasis. The development of the breed and its characteristics have been reviewed extensively by Starkey (1984).

The N'Dama is a humpless (Bos taurus) breed of the Hamitic Longhorn type. Its ancestors were probably the first domesticated cattle in Africa. According to a recent ILRAD (1989) report, the N'Dama cattle population is thought to number about 4.9 million of which the majority is in Guinea. Other countries with large N'Dama populations are Senegal, Mali and The Gambia. The breed apparently increased in numbers during the last century. The N'Dama constitute about half of all the trypanotolerant cattle in West and Central Africa, that is cattle that are able to resist the pathogenic effects of trypanosomiasis and to remain productive in tse-tse infected areas where other breeds cannot survive. Thus, the N'Dama cattle, which is well adapted to conditions of both humid and dry tropical areas, constitute the principal wealth of many West African villagers.

8.2 Characteristics

The typical N'Dama is a small humpless animal with a straight top line, well muscled hindquarters and short, fine limbs. The coat is usually yellow, fawn, light red or dun in colour, although there are black and pied animals with black or fawn on a white background. The head is short and broad. The horns are lyre shaped. The dewlap and umbilical fold are rather small as well as the udder of the females. Cows weigh on average about 230 kg and bulls 370 kg. Wither height is to about 110 cm. Despite its small size the N'Dama is mainly used for beef, producing meat of good quality. Milk production is relatively low. The N'Dama cattle are also used for draft purposes. The normal range of performance of the N'Dama breed is given in table 7 from a thorough FAO study of 1980.

The single most important characteristic of the N'Dama breed is its inherited trypanotolerance which contrasts with the zebu breeds of Africa. Due to this fact much research has been directed towards the N'Dama breed to understand better both the effects of trypanosomiasis and the biology of its resistance (e.g. FAO, 1980; ILRAD, 1989). Studies have also shown that the N'Dama breed, when kept in non tse-tse infected areas, shows much better performance and is quite comparable to common zebu breeds in those areas. Also considerable benefits have been seen from improved management of the cattle in their normal habitats.

8.3 Needs and plans for conservation

The situation of the N'Dama breed is quite different from most of the other breeds proposed for conservation. The population size is large and even increasing. However, its habitat in a densely populated area of Africa that permits few other cattle breeds to survive and produce, is a serious call for effective schemes to guarantee the future existence of the breed and to improve its productivity. Any improvement would be significant to the human food supply. A significantly increased output might also be obtained by improved management.

Table 7. Normal range of N'Dama performance levels under traditional and improved management (FAO, 1980)

The N'Dama was chosen as a prospect for a conservation programme by FAO in 1980. Improvement schemes based on nucleus herds at research or government stations, where performance recording easily can be applied are suggested. Selected bulls from the nucleus herds should regularly be distributed to the villages. Improved management would then ensure the future development of the breed and its advantages in tse-tse infested areas. It could be an appropriate strategy for ILCA and ILRAD to include these aspects into the research networks already operating for studies of the trypanotolerance of the N'Dama breed in cooperation with governments and research institutes of West and Central Africa.

9 Criollo

9.1 Origin, habitat and distribution

The Criollo cattle of the Americas are defined as descendants of the Bos taurus cattle that were brought originally from the Iberian peninsula and the Canary Islands by Christopher Columbus on his second voyage in 1493 and subsequently. Probably less than 1,000 head were landed within a 50 year period in the Caribbean islands and were then rapidly dispersed throughout South and Central America as well as the south western parts of the United States. The cattle originated from different parts of Spain and Portugal. They could certainly not be described as simply one breed but rather comprised various unselected populations of cattle from different parts of a limited geographical area.

In the early parts of the 16th century this cattle population grew very rapidly. The quick multiplication of animals continued over large areas, in a great variety of environments of South and Central America during the next centuries and has been described as a biological wonder (de Alba, 1978). By the beginning of the 19th century the original population had increased to millions.

During the second half of the 19th century Indian zebu cattle were brought to Brazil and Bos taurus breeds from North America were introduced to Argentina and Uruguay. Later the American Brahman was introduced as well. A period of crossbreeding these breeds with the various types of Criollos started. In the temperate zones crossing with Holstein and Brown Swiss was successful for dairy production and in tropical areas crosses with zebu led to increased productivity. These results encouraged further massive importations, which resulted in a rapid decline of the pure Criollo types of cattle. A detailed account of the history of Criollo cattle, their development and later decline may be found in Rouse (1977).

The present types and distribution of Criollo cattle in Latin America have been reviewed by Wilkins (1984) and by de Alba (1987). The latter distinguished the following main Criollo types of cattle:

1. Lowland tropical beef Criollos
2. Mountain ecotypes of Criollo
3. Temperate climate or subtropical Criollo ecotypes
4. Blanco Orejinegro, a unique external parasite resistant breed
5. Tropical milking Criollos

Table 8 from de Alba (1987) summarizes the various Criollo type breeds recognized in different countries according to the classification above. Population trends and an indication of some research facts about the breeds are also given. Mariante (1992) has suggested that the Brazilian Criollos Pantaneiro belonging to the first group and Criollo Lageano of the second group are of significant importance, although they now exist only in small numbers.

9.2 Characteristics

The origin of Criollos and their development in various parts of Latin America easily explains the number of distinct breeds found in different ecozones. The typical Criollo is almost of any colour and pattern. However, where selection has been practised within some of the sub-populations for a long time a considerable uniformity is found, for example in colour. Despite some heterogeneity in characteristics between different Criollo breeds it seems that they have several important traits in common. One is the docility of the animals, which has been cited as a great advantage of Criollo cattle compared with the zebus and their crosses. Other typical traits are resistance to ticks and biting flies, good fertility and longevity. They are generally considered as dual purpose cattle, which often produce 1,000– 2,000 kg of milk in a lactation. Cows weigh 350–400 kg and bulls up to 700 kg. The present state of knowledge on the characteristics of some 27 Criollo breeds has been well documented by de Alba (1987) in his review paper of the Criollos presented at the second meeting of the FAO/UNEP Expert Panel on Animal Genetic Resources Conservation and Management.

Table 8. Locations, population trends and amount of knowledge of Criollo breeds (de Alba, 1987)

9.3 Needs and plans for conservation

Indiscriminate crossbreeding has taken place for several reasons. The successful results from crossing Criollos with improved breeds of European origin for milk production and with zebus in the tropical regions mainly for beef production have been principle attractions.

The different Criollo types of cattle, with their common characteristics of docility, productivity and adaptation to a range of ecological zones in Latin America where pure temperate breeds cannot contribute, certainly have certainly played an important strategic role for food production in these areas.

Awareness of the need for specific efforts to conserve a number of Criollo breeds exists in several Latin American countries. There are various projects to preserve or conserve Criollo breeds, for example in Argentina, Bolivia, Brazil, Colombia and Venezuela. The National Research Centre for Genetic Resources and Biotechnology (CENARGEN) in Brazil started in 1981 to document and evaluate information about various Criollo breeds and to identify those in danger of extinction (Mariante & Trovo, 1989). In 1987, when FAO decided to create two Regional Animal Gene Banks in South America, CENARGEN was chosen as the site of one due to the work in this area already started at the Centre. These include reproducing populations as well as freezing of semen and embryos. A data bank is kept for storage and retrieval of information on the threatened breeds.

In Bolivia Wilkins & Rojas (1989) have reported a progressive commercial scheme for the improvement of Criollo cattle for the humid lowlands. The procedure, which could serve as a model for more areas and breeds, involves fairly thorough investigations of the problems in the local livestock industry, the potential role of different genotypes and economics of alternative breeding programmes. These aim at multiplication of the breed under conservation in order to provide the producers with continuously selected bulls. Interest in the breed and its further improvement schemes are gradually taken over by a newly formed breed society.

Conservation programmes of Criollo cattle have two different purposes. The main one is to produce bulls for crossbreeding programmes in a number of different environments, either with temperate breeds for dairy production or with zebus for beef production. The benefits of the latter type of cross, according to Plasse (1989), is clearly increased fertility, reduced calf mortality and heterotic effects for growth rate.

The other purpose, which also seems very important, is to conserve pure Criollo cattle adapted to certain adverse environments for use in remote areas where crossbreeding might have no advantages or be difficult to realize due to small herds and lack of AI service. Such adapted breeds might produce 1,500–2,000 kg of milk per cow for support of both a calf and a family.

It seems important that future efforts of FAO should include conservation and continuous improvement schemes for a number of pure Criollo breeds in Latin America. The Regional Animal Gene Banks that are now to be enlarged seem to offer a logical structure for coordination of these. The work should include detailed evaluations of the different Criollo breeds or strains, and of their potential role as pure breeds as well as sources for crossbreeding; this should be followed by conservation of closely recorded nucleus herds for production and selection of improved bulls.

10 Kenana

10.1 Origin, habitat and distribution

This Sudanese breed is named after the semi-nomadic Kenana tribe who live on the western bank of the Blue Nile. The home land of the breed is mainly between the Blue and White Nile rivers within the savannah ecological region of Sudan south of Khartoum. The area is characterized by low rainfall and high temperatures.

The Kenana breed is a true zebu belonging to the Northern Sudan Shorthorn Zebu group of cattle. The exact origin is not known, although most likely it migrated in early years from Asia. However, the other main type of Sudanese cattle, the Nilotic Sanga cattle in the south, have undoubtedly been native to Sudan for a much longer period according to Osman (1985).

In an FAO study of the population structure and alternative strategies of conserving the Kenana breed, the total population including the White Nile type, was estimated at about 3 million (Cunningham, 1987). The production systems involving the Kenana breed are quite variable and range from pure nomadic in stressful, arid environments to more settled systems producing milk for urban areas. The latter certainly utilize exotic breeds in various degrees of crossbreeding with the Kenana cattle to increase production. Proper crossbreeding ensures the availability of cattle that are well adapted to the environment.

10.2 Characteristics

The Kenana, and the related Butana breed, have the general reputation of being among the better, if not the most productive indigenous African milk breeds. In a small number of herds Kenana cattle have long been selected for milk production. Table 9 summarizes some data of the breed. The results refer only to experimental farms, while field data are scarcely to be found. However, the institutional herds provide much better feed and environmental conditions than can be obtained under nomadic conditions.

Kenana cattle are white or steel gray in colour with shadings on the neck, shoulders and tail. Calves are born reddish brown but turn grey at about 6 months of age. Horns vary greatly in size and direction. Polled animals are common. The Kenana cattle are considered docile and are fairly tall. Mature bulls weigh 500–550 kg and cows around 400 kg (Osman, 1985). Calving intervals, as well as age at first calving, have been reported to be quite variable, indicating a large influence of environment and especially an effect due to nutritional status. As an example the better fed group of heifers in an experiment calved at 32 months of age compared with 47 months for the controls.

Recent genetic studies show a heritability of 0.21 for milk yield, while it was close to zero for lactation length and calving interval (Ageeb & Hillers, 1991).

10.3 Needs and plans for conservation

As a zebu breed the Kenana apparently has an outstanding potential for milk production adapted to arid and semi-arid conditions. Results also indicate that it would respond to selection for milk production and in addition, reproductive traits would respond to environmental improvements.

Table 9. Some characteristics of the Kenana breed in Sudan

The development of more intensive settled production systems near urban areas of Sudan results from a great need to improve the food supply. This calls for the use of exotic breeds in crossbreeding with the Kenana. However, the lack of a long term strategy for crossbreeding might in a relatively short period threaten the breed with extinction. As a result of such a situation the crossbreeding programme will collapse.

Due to its extremely good genetic potential and the importance for milk production in rather variable hot environments, the Kenana breed deserves being conserved and further improved. The related Butana breed has similar potential and characteristics and could also be considered. However, the Kenana breed was deemed more important and given the highest priority in the FAO study earlier reported.

The conservation plan of the Kenana breed should satisfy the two fold objectives:

1. to conserve and consistently to improve the pure breed taking into consideration all important traits including milk production, growth, udder conformation, beef and reproductive traits.

2. to produce continuously pure and crossbred bulls to be used in long term crossbreeding programmes with exotic breeds applied in semi intensive systems of milk production.

Cunningham (1987) proposed a detailed strategy to utilize the herd of the Umbenein Research Centre as an open nucleus herd. It was suggested that 200 cows should be kept in this herd and that some 20 outstanding cows of village herds in the country should be recruited annually to the nucleus. The best selected cows should produce bulls for both AI and natural service in other herds. Such a scheme could be enhanced by the use of the embryo transfer (ET) technique. However, before investing in such a technique it is essential that effective genetic evaluation techniques are first applied for selection of bull dams and that the nutritional status is such that good technical results of ET could be anticipated.

The conservation plan earlier proposed in the FAO study is highly recommended. It assumes preceding studies for more exact definition of the breeding objectives, the mode of recording the desired traits in a fairly detailed manner in the nucleus herd and in a more extensive way in the village herds. It also assumes application of an appropriate procedure for genetic evaluations of the cattle in the nucleus herd.

By establishing an open nucleus herd as the basis for the conservation plan at an experimental station, sufficient infrastructure and personnel competence to conduct the project with the assistance of FAO should be guaranteed.

Although the Kenana breed is fairly well documented, mainly at the Gezira and the Umbenein research stations, data from the field is still scarce. Various supportive studies to the conservation plan are thus needed, and were also proposed in the FAO study, in order to make the most efficient long term use of the breed and to ensure its existence.

11 Boran

11.1 Origin, habitat and distribution

There are two distinct types of Boran cattle which is an East African Shorthorn Zebu. The indigenous type is found in the Borana Province of southern Ethiopia from where it spread to western Somalia and northern and central Kenya. The other type is the improved Boran developed in Kenya under ranch conditions for beef production.

The Ethiopian Borana cattle are kept under nomadic semi dry conditions by the Borana tribe, known for their high husbandry capabilities and which depend to a large extent upon the milk produced by their cattle. There are large numbers of the indigenous type in Somalia known as Avai cattle, which are similar to the Ethiopian type; in northern Kenya cattle of the same type as the Avai are known as the Tanaland Borana.

The improved type of Boran, bred in the semi arid uplands of Kenya, is the result of six to seven decades of selection for conformation and size, fertility and mothering ability under commercial ranching conditions. Some literature indicate that an early inclusion of imported European cattle in the 1920's, mainly Hereford, might have occurred. The improved Boran cattle in Kenya today play the role of a predominant beef breed in Eastern Africa and it is now being exported to a number of countries outside the main original areas.

The development of the Kenya Boran cattle has been supported by the improvement programme undertaken by the Borana Cattle Breeders Society founded in 1951 in Kenya. Development in Ethiopia has gained from the research and breeding programmes used at the Adamitulu and Abernossa pure breeding and crossbreeding ranches (e.g. Kassa-Mersha & Arnason, 1986).

There is no accurate census of the Boran cattle but Kebede (1985) in a breed review indicated a figure of some 820,000 animals.

11.2 Characteristics

The Ethiopian Borana are rather large, long-legged cattle with good body conformation. They are normally white or grey, but brown or pied colours occur. Horns are short and thick at the base. The hump is well defined and the thorax usually large and sometimes folded on one side, especially in bulls.

The improved Kenya Boran cattle are characterized by well developed hind quarters and they produce carcasses that suit the export market. Weights of mature cows are reported to 400–550 kg while adult bulls weigh 550–750 kg. The Ethiopian Borana weigh a little less. Cows and bulls are frequently reported to weigh 300–400 kg and 550–675 kg respectively.

On good grazing Kenya Boran steers are ready for slaughter at three to three and a half years of age giving a carcass of 220–250 kg. In a number of studies Boran cattle have shown a surprisingly good potential also for milk production. In the review by Kimenye (1985b) lactation yields of 1,000–1,600 kg have frequently been found.

The specific characteristics of the Boran cattle that contribute to its leading role as a highly productive, indigenous breed may be summarized from the extensive studies and reports published about the breed. These are according to Maule (1990):

1. ability to walk long distances in search of grass and water and to do without water for two days, possibly longer;

2. strong herd instinct and good mothering ability;

3. adaptability to a wide range of environmental conditions;

4. high fertility - up to 90 per cent - and low calf mortality (3 per cent);

5. longevity - cows will breed up to 20 years; seven calves in 10 years is a reasonable expectation.

The good performance of Boran cattle in adverse environments also lies in its generally good resistance to endemic diseases. However, Kenya ranchers usually practice dipping to prevent tick born diseases. Unlike the small East African Zebus the Boran cattle are quite susceptible to East Coast Fever.

11.3 Needs and plans for conservation

The Boran breed has undoubted value, especially beef production but also milk, under quite variable tropical conditions. The breed was chosen in 1980 by FAO as meriting special attention for future conservation and improvement. It certainly is a high potential breed which should be multiplied into more areas and thereby increase food production. There is already a fairly good infrastructure. Research stations and the beef recording scheme established in 1973 in Kenya should provide excellent data for the breeding programme.

An FAO supported conservation and improvement programme for this breed should therefore aim to support the existing activities with emphasis on analyses of records and their use for selection purposes. A further component should aim at increased semen production in Kenya for domestic as well as export purposes. An increased export of live animals of the improved Kenya Borans to neighbouring countries might also be important as part of the programme.

12 Guzera

12.1 Origin, habitat and distribution

The Guzera is a Brazilian selected population of Bos indicus cattle originating from India, where it is named Kankrej. The breed has been well known in its home area probably for more than five thousand years. The introduction of the Guzera breed to Brazil, when it was named after its home province Gujerat, started in 1895. Due to its superiority in producing highly productive crossbreds with Holstein Friesian the number of pure Guzera has reduced to some ten thousand registered cows (Madalena, 1983). Annually three to four thousand female calves are registered by the breeder's herd book association, that was formed in 1936.

The Guzera breed has been used as the foundation of several new Brazilian breeds, such as the Pitangueiras (Red Poll cross), Lavinia (Brown Swiss cross), Riopardense (Holstein Friesian cross) and Indo-Brasil (Guzera, Gir and Nellore synthetic), besides having had a strong influence on the foundation of the Brahman breed.

12.2 Characteristics

The Guzera is a triple purpose breed (draft, milk and meat). It is well recognized by its stature (135 cm withers height of cows) and lyre shaped horns. It is reported to have very good draft power in its country of origin. Milk yield in Brazil has been reported to be between 1,155 kg and 2,134 kg per lactation in the official recording scheme.

The following average weights were, according to Madalena (1992), obtained in the national performance recording scheme, adjusted to ages 205, 365 and 550 days, respectively: 128 kg (n = 7,568), 195 kg (n = 3,951) and 250 kg (n = 1,812). In a study in seven commercial farms, cows of second and higher parities weighed about 440 kg. The range of body weights of bulls in AI studs is 900 to 1,140 kg.

The crosses of Guzera with the Holstein Friesian have very good dairy characteristics. The F1 crosses have outperformed the purebred Holstein Friesians in a wide range of management systems, producing between 1,730 and 2,450 kg milk per lactation.

12.3 Needs and plans for conservation

The Guzera breed has proven its value in Brazil both as a pure breed and in crossbreeding. It certainly deserves serious attention since the population is small and needs to be conserved by management for the future. A nucleus breeding scheme has already been initiated involving 17 private breeders and one experimental farm according to Madalena (1992). The better cows (in the owner's judgement) are sent to a central farm for milk recording and embryo production for sale. The average production of the first 100 cows with completed lactations was 3,100 kg with 4.1% fat content. Feeding of these cows was based on elephant grass hay, natural pastures, dried whole plant maize, yuca residues and cottonseed meal. The scheme has technical support from the School of Veterinary Science, Federal University of Minas Gerais, and the Federal and State research organizations (EMBRAPA and EPAMIG). However, extra funds and organization are needed for milk recording and better evaluation of cows and bulls in order to allow full use to be made of the genetic improvement which is potentially available by capitalizing on present activities and infrastructure.

13 Conclusions

A number of very important indigenous cattle breeds in tropical countries show a fairly high production potential combined with adaptability to tropical and often adverse environments. Several of these breeds are endangered due to indiscriminate crossbreeding programmes lacking long term strategies for selection. These indigenous breeds need to be conserved and further improved in order to guarantee possibilities of long term crossbreeding programmes and of more widespread use as pure breeds.

Six priority breeds or breed types are proposed for practical conservation and improvement programmes. They cover different regions of the world and different types of cattle with unique characteristics which are deemed important for either milk or beef production. They are adapted to a range of tropical or subtropical environments. Finally, the conservation and improvement programmes cover different stages of development and, therefore, they may also serve as pilot schemes for other similar cases.

14 References

Ageeb, A.G. & Hillers, J.K. 1991. Production and reproduction characteristics of Butana and Kenana cattle of the Sudan. Wld. Anim. Rev. 67, 49–56.

Ahmad, Z., Ahmad, M.D., Sial, M.B. & Latif, A. 1971. Influence of age at first calving on production performance in Sahiwal cows. Pak. J. Agri. Sci. 8 (3–4):32–35.

Basu, S.B., Bhatnagar, D.S., Taneja, V.K., Rao, V.P. 1979. Comparative performance of Indian dairy breeds. Indian J. Dairy Sci. 32(4):497–499.

Bhat, P.N. & Chandramohan, K.K. 1982. Note on factors affecting birth weight in Sahiwal cattle. Indian J. Anim. Sci. 52(7):561–564.

Bhat, P.N. & Taneja, V.K. 1987. Principles of indigenous animal improvement in the tropics - the programmes for India. In: FAO Animal Production and Health Paper No. 66. Animal Genetic Resources. Strategies for improved use and conservation. FAO, Rome.

Bhatnagar, D.S., Taneja, V.K., Basu, S.B., Murthy, K.M.K. 1983. Genetic parameters for some economic traits in Sahiwal cattle. Indian J. Dairy Sci. 36 (4):402–406.

Chaudhry, M.Z. 1988. Progeny testing of Sahiwal bulls. Journal of Animal Health and Production (Pakistan), 8(1–4):64–71.

Chawla, D.S. & Mishra, R.R. 1976. Variation and inheritance of protein content in Karan Swiss (Brown Swiss cross), Sahiwal and Red Sindhi cattle. Indian J. Anim. Sci. 46(6):293–296.

Cunningham, E.P. 1987. Conservation of the Kenana Breed in Sudan. In: FAO Animal Production and Health Paper No. 66. Animal Genetic Resources. Strategies for improved use and conservation. FAO, Rome.

de Alba, J. 1978. Progress in the selection of the Latin American Criollo. Wld. Anim. Rev. 28, 26–30.

de Alba, J. 1987. Criollo cattle of Latin America. In: FAO Animal Production and Health Paper No 66. Animal Genetic Resources. Strategies for improved use and conservation. FAO, Rome.

Fangaly, O.A.I. 1980. Reproduction and milk yield of Kenana and Butana cattle in the Sudan. M.Sc. thesis, Univ. of Khartoum.

FAO. 1980. Trypanotolerant livestock in west and central Africa, vol. 1 - General study, FAO Animal Production and Health Paper No. 20/1. FAO, Rome.

FAO. 1991. FAO Production Yearbook, vol. 44, 1990.

Hasnain, H.U. & Shah, S.K. 1985. The Sahiwal Cattle of Pakistan. Pakistan Agricultural Research Council, Islamabad, Pakistan

Hodges, J. 1984. Breeding plans for improvement of indigenous breeds and species -the Sahiwal. In: FAO Animal Production and Health Paper No. 44, Vol 1. FAO, Rome.

Hodges, J. 1987. Sahiwal in Kenya and Pakistan. In: FAO Animal Production and Health Paper No. 66. FAO, Rome.

ILRAD. 1989. N'Dama Cattle: Managing Africa's Genetic Resources. In: ILRAD Reports October 1989. pp. 1–6.

Iqbal, Z. & Qureshi, M.J. 1968. Studies on the composition of Sahiwal cow's milk at West Pakistan Agric. University Dairy Farm. West Pakistan Journal of Agric. Research. 6(2):98–106.

Ishaq, S.M. & Shah, S.K. 1975. Comparative performance of buffaloes and Sahiwal cows as dairy animals. Agric. Pakistan, 26(1):75–88.

Kassa-Mersha, H. & Arnason, T. 1986. Non-genetic factors affecting growth of Ethiopian Boran cattle. World Rev. Anim. Prod. 22(2):45–55.

Kebede, B. 1985. Review of the Ethiopian Borana breed. In: Animal genetic resources in Africa. High potential and endangered livestock. Second OAU Expert Committee Meeting on Animal Genetic Resources in Africa, 24–28 November, 1983, Bulawayo, Zimbabwe.

Kimenye, D. 1981. Production traits of Kenya Sahiwal cattle. Bull. Anim. Hlth. Prod. Afr. 29(2):121–124.

Kimenye, D. 1985a. Review of the Sahiwal in Kenya. In: Animal genetic resources in Africa. High potential and endangered livestock. Second OAU Expert Committee Meeting on Animal Genetic Resources in Africa, 24–28 November, 1983, Bulawayo, Zimbabwe.

Kimenye, D. 1985b. Review of the Boran in Kenya. In: Animal genetic resources in Africa. High potential and endangered livestock. Second OAU Expert Committee Meeting on Animal Genetic Resources in Africa, 24–28 November, 1983, Bulawayo, Zimbabwe.

Madalena, F.E. 1983. Conservation of genetic resources through commercial utilization. A case for the improvement of the Brazilian milking zebu breeds. FAO Animal Production and Health Paper No. 44/1. FAO, Rome.

Mariante, A. da S. & Trovo, J.B. de F. 1989. The Brazilian genetic resources conservation programme. Rev. Brazil. Genet. 12,3 - Suppl. 241–256.

Maule, J.P. 1990. The cattle of the tropics. University of Edinburgh Centre for Tropical Veterinary Medicine. Edinburgh, UK. 225 pp.

Meyn, K. & Wilkins, J.V. 1974. Breeding for milk in Kenya, with particular reference to the Sahiwal Stud. Wld. Anim. Rev. 11, 24–30.

Muhammad, F. & Ahmad, M.D. 1968. Heritability estimates of age at first calving and calving interval in Sahiwal cows. Pak. J. Agri. Sci. 5(3–4):257–263.

Olsson, A. 1992. Personal communication. The Swedish University of Agricultural Sciences, Uppsala, Sweden.

Osman, A.H. 1985. The review of Butana and Kenana breeds. In: Animal genetic resources in Africa. High potential and endangered livestock. Second OAU Expert Committee Meeting on Animal Genetic Resources in Africa, 24–28 November, 1983. Bulawayo, Zimbabwe.

Payne, W.J.A. 1990. An Introduction to animal husbandry in the tropics (4th edn). Longman: London.

Philipsson, J. 1985. International cooperation for genetic improvement of the Sahiwal breed. Consultancy report on study of the Sahiwal breed in Pakistan. FAO, January 1985. 20 pp.

Philipsson, J., Mosi, R.O., Mwangi, J.L.N., Rege, J.E.O. 1989. Kenya artificial insemination rehabilitation programme. Consultancy report on the breeding programme. 60 pp.

Plasse, D. 1989. Results from crossbreeding Bos taurus and Bos indicus in tropical Latin America. Rev. Brazil. Genet. 12, 3-Suppl. 163–181.

Rao, M.K. & Sundaresan, D. 1979. Influence of environment and heredity on the shape of lactation curves in Sahiwal cows. J. Agric. Sci. Camb. 92(2):393–401.

Reddy, K.M. & Nagarcenkar, R. 1988a. Effect of inbreeding level and generation number on age at first calving of Sahiwal cows. Asian J. Dairy Res. 7(3):142–146.

Reddy, K.M. & Nagarcenkar, R. 1988b. Studies on production traits in Sahiwal cattle. Indian J. Dairy Sci. 41(3):298–311.

Rouse, J.E. 1977. The Criollo. University of Oklahoma Press. Norman, Okla. 580 pp.

Shah, S.K. & Shah. I.H. 1983. Factors affecting service period in Sahiwal cows. Pakistan Vet. J. 3(4):179–182.

Shah, I.H. & Zafar, A.H. 1986. Inheritance of age at first calving and first lactation yield in Sahiwal cows. Pakistan Vet. J. 6(2):60–62.

Sharma, K.N.S., Jain, D.K. Bhatnagar, D.S. & Sharma, R.C. 1983. Estimation of milk fat, solids-not-fat and total solids production in Zebu and their Brown Swiss crosses. Anim. Prod. 36:383–387.

Starkey, P.H. 1984. N'Dama cattle - A productive trypanotolerant breed. Wld. Anim. Rev. 50. 2–15.

Taneja, V.K., Basu, S.B., Bhatnagar, D.S. & Rao, V.P. 1979. Comparative study of body weights in Indian dairy breeds. Indian J. Dairy Sci. 32(3), 326–327.

Trail, J.C.M. & Gregory, K.E. 1981. Characterization of the Boran and Sahiwal breeds of cattle for economic characters. J. Anim. Sci. 52(6):1286–1293.

Wakhungu, J.W., Rege, J.E.O. & Itulya, S. 1991. Genetic and phenotypic parameters and trends in production and reproductive performance of the Kenya Sahiwal cattle. Bull. Anim. Hlth. Prod. Afr. 39(4):365–372.

Wilkins, J.V. 1984. Criollo cattle of the Americas. In: FAO Animal genetic resources information 1/84. FAO, Rome.

Wilkins, J.V. & Rojas, F. 1989. Criollo cattle utilization for dairy production in Bolivia. Rev. Brazil. Genet. 12, 3 - Suppl. 221–230.

Wilson, R.T., Ward, P.N., Saeed, A.M. & Light, D. 1987. Milk production characteristics of the Kenana breed of Bos indicus cattle in Sudan. J. Dairy Sci. 70:2673–2679.