A review of morphological characteristics relating to the production and reproduction of fat-tailed sheep breeds

The purpose of this study is to survey the literature pertinent to some morphological traits which are related with the production and reproduction of fat-tailed sheep breeds. The fat-tailed breeds were identified according to Food and Agriculture Organization databases. Articles referring to all these sheep breeds were evaluated. The morphology of udders and their measurable variables were collected and described. The particularities of pelt and fleece features which are important from an economic point of view were summarized. Linear, planar, and spatial parameters of body, slaughter, and carcass factors were compared at various ages of breeding. Testicular dimensions and semen characteristics were recorded. Their relationships with productive and reproductive performance were discussed. The pattern of ovarian follicle development and the involution of the genital tract were assessed from the anatomical point of view in normal and untreated animals. The data presented here provide useful baseline information on the normal morphological aspects which are important in the animal production of these breeds.     

中国绵羊肉用性能及其遗传参数研究进展

绵羊业是中国畜牧业的重要组成部分,其主要产品羊肉以丰富的营养价值受到人们的青睐。因此,了解现今中国绵羊品种的产肉性能及肉质、遗传特性等,是了解绵羊种质特性和绵羊选育研究的基础。作者综述了中国绵羊产肉性能及其遗传研究概况,以期为优质绵羊育种工作提供理论基础。     

Populations and production of fat-tailed and fat-rumped sheep in the Horn of Africa

The six countries comprising the Horn of Africa are Djibouti, Eritrea, Ethiopia, Kenya, Sudan and Somalia. Together, they cover an area of just under 5 million square kilometres and support a human population of 17.7 million at an average density of 38.15 people per square kilometre (although in the purely pastoral areas population density is probably of the order of 15–16 people per square kilometre). The Horn is a major repository of domestic animal biodiversity and genetic resources and is home to 15 million one-humped camels, 110 million cattle, 94 million goats and 102 million sheep. A list of 72 sheep “breeds” of which 23 can be considered fat-tailed or fat-rumped has been compiled for the area, although many of these are merely subtypes of a larger grouping and several are not native to the Horn. This paper provides information, where such is available, on the distribution, numbers and production parameters of the fat-tailed and fat-rumped sheep that occupy the Horn.     

Biodiversity of Domestic Livestock in the Republic of Yemen

This paper describes the domestic livestock of the Republic of Yemen and aspires to complement earlier sources listing or partially describing `breeds'. It attempts to cover all species and provide indications of production parameters through a literature review and via field observations made by the author in 1999. Information is provided on livestock numbers and the economic importance of animal production. Most animals are kept in sedentary mixed crop–livestock production systems; transhumant systems have the next greatest number of stock; with nomadic systems being of least and declining importance. Yemen's livestock appear to comprise at least 11 breeds of sheep, 5 breeds of goat, 2 breeds of cattle, 4 breeds of camel, 2 breeds of donkey and 1 breed of horse. There are no data on breeds of poultry but domestic fowl (where clearly considerable diversity exists) and pigeons are kept. There is little formal information on the history and relationships of most breeds. Some appear to be of ancient local origin, whereas others show affinities with those of neighbouring and other countries. None of the identified types is considered endangered, so conservation would be premature. A more formal and detailed genetic characterization, to add to the largely morphological and traditional classification, may, however, reveal such a need.     

畜禽遗传资源保存研究进展

世界上70％的遗传资源分布在发展中国家，因战乱、政策、环境等因素，致使这些丰富的种质资源面临生存危机；发达国家家禽品种本身就比较单一，遗传资源贫乏，加之过份追求经济性状的遗传和集约化生产，因而原本就十分少有的地方品种也同样面临消亡的危机。本文比较系统地综述了全球畜禽品种资源而临的危机及其原因，以及世界各地采取的应对措施，同时还对畜禽遗传资源保存的技术方法进行了总结。     

Genetic diversity and population structure of the endangered Namaqua Afrikaner sheep

The Namaqua Afrikaner is an endangered sheep breed indigenous to South Africa, primarily used in smallholder farming systems. Genetic characterization is essential for the breed’s conservation and utilization. In this study, a genetic characterization was performed on 144 Namaqua Afrikaner sheep kept at the Karakul Experimental Station (KES), Carnarvon Experimental Station (CES), and a private farm Welgeluk (WGK) using 22 microsatellite markers. The mean number of alleles observed was low (3.7 for KES, 3.9 for CES, and 4.2 for WGK). Expected heterozygosity values across loci ranged between 46 % for WGK, 48 % for KES, and 55 % for CES, indicating low to moderate genetic variation. The analysis of molecular variance revealed that 89.5 % of the genetic variation was due to differences within populations. The population structure confirmed the differentiation of three clusters with high relationships between the CES and WGK populations. In the population structure comparison with Pedi and South African Mutton Merino sheep, limited hybridization between the Namaqua Afrikaner sheep and both of these breeds was observed. The results of this study will serve as a reference for genetic management and conservation of Namaqua Afrikaner sheep.     

Assessing carcass and meat characteristics of Damara, Dorper and Australian Merino lambs under restricted feeding

Seasonal weight loss (SWL) is the most pressing constraint in ruminant production systems in tropical climates. SWL is controlled using supplementation, which is costly and difficult to implement in extensive systems, or using breeds adapted to tropical hot dry climates, like the Damara and Dorper. Albeit 15 years in Australia, little is known on how these sheep compare to Australian Merino. Here, the responses of the Damara, Dorper and Merino breeds to nutritional stress were compared. Seventy-two 6-month-old ram lambs, 24 from each breed, were allocated to growth (gaining 100 g/day) or restricted diets (losing 100 g/day, 85 % of maintenance needs). Animals were weighed and carcass and meat characteristics determined. Results point out to the existence of important differences between the three genotypes, in particular between the Merino and the Southern African breeds. Additionally, Merino ram lambs seem to have been more influenced by SWL than the other two, with consequences on meat characteristics.     

A review on prolificacy genes in sheep

Ovulation rate and litter size are important reproduction traits in sheep and are of high economic value. Reproduction traits typically have low to medium heritabilities and do not exhibit a noticeable response to phenotypic selection. Therefore, inclusion of genetic information of the genes associated with reproductive ability could efficiently enhance the selection response. The most important major genes affecting prolificacy and their genetic diversities in different sheep breeds were reviewed. Different causative mutations with major effects on reproductive traits including ovulation rate and litter size have been found in various sheep breeds around the world. A general overview of the studies on main prolificacy genes showed that some alleles may express different phenotypic effects in different breeds, and thus, further studies on epistatic effects are necessary for more understanding of genetic control of reproductivity in sheep. Regarding the polygenic control of fertility traits, application of new high‐throughput technologies to find new variants is essential for future studies. Moreover, genomewide association studies and genomic best linear unbiased predictions of breeding values are likely to be effective tools for genetic improvement of sheep reproductive performance traits.     

Present status of the conservation of livestock genetic resources in Brazil

Brazil has various species of domestic animals, which developed from breeds brought by the Portuguese settlers soon after the discovery of the country. After being submitted to a long process of natural selection, these breeds present characteristics adapted to specific Brazilian environmental conditions, and are known as “criollo”, “local” or naturalized breeds. From the beginning of the 20th century, some exotic breeds, selected in temperate regions, have begun to be imported, and, although more productive, they do not have adaptive traits, such as resistance to disease and parasites found in the naturalized breeds. Even so, they gradually replaced the native breeds, to such an extent that the latter are in danger of extinction. To avoid further loss of this important genetic material, in 1983 the National Research Center for Genetic Resources and Biotechnology (Cenargen) of the Brazilian Agricultural Research Corporation (Embrapa) decided to include conservation of animal genetic resources among its priorities. The conservation activities have been conducted under the Brazilian Genetic Resources Network — Renargen, and is carried out by various research centres of Embrapa, universities and State research institutions, as well as by private farmers, with a single coordinator at national level, Cenargen. The in situ conservation of cattle, horses, buffaloes, donkeys, goats, sheep and pigs is being carried out by Conservation Nuclei, located in the animal's original habitat. Ex situ conservation is centred at the Brazilian Animal Germplasm Bank (AGB), kept at Cenargen. This is responsible for the storage of semen and embryos of various breeds of domestic animals threatened with extinction. Presently the AGB has almost 60,000 doses of semen and more than 250 embryos, as well as over 7000 DNA samples. An important challenge for this program is to increase awareness within the different segments of society in terms of the importance of the conservation of animal genetic resources. The development and evolution of Renargen and its efforts to facilitate the conservation of genetic resources of livestock in Brazil are described in this paper.     

Molecular evidence for fat-tailed sheep domestication

The sheep is one of the most successful and widely spread domestic animals. Archaeological evidence traces the first domestic sheep back to the Near East region around 9,000 years ago. It is also known that soon after, the domesticated sheep started to flow out of the centre of origin and spread all over the ancient world following the expansion of agriculture. Throughout time, herders, nature elements and eventually some hybridization with different wild relatives produced a multitude of breeds. However, until the advent of the molecular genetics field, very little was known about the origins of most of those breeds. Two decades after the first genetic studies, we have gathered considerable information on the origins, phylogenetic relationships and patterns of genetic diversity of the sheep across the world. Indeed, the genetic studies confirmed the Near East region as the main centre of origin and also revealed other contributions from other regions. Specifically about the fat-tailed sheep, molecular genetics was also able to link their maternal origin to a specific group. So far, modern sheep have originated from five different maternal origins. Nonetheless, the technological advances of the DNA sequencing techniques are bringing more data that is showing the complexity of the domestication process.     

Possible consequences of the Nagoya Protocol for animal breeding and the worldwide exchange of animal genetic resources

The paper discusses animal genetic resources in the context of the Nagoya Protocol, providing an overview of the distinctive features and practices in this sector of genetic resources. It presents how animal genetic resources are utilized, who are the users and providers, and what are the trends in gene flow of these resources. The paper reflects on current access measures and arrangements for local breeds and for international commercial breeds. Key benefits arising from the international exchange of animal genetic resources for research and livestock production and current developments in the sector supporting the implementation of the Nagoya Protocol are presented. References to the scope and application of EU ABS legislation are also made. The paper underlines the importance of continuous undisturbed access to animal genetic resources for research and breeding to facilitate further development within the global livestock sector.     

Allelic polymorphism in the second exon of Ovar-DRB1 in fat-tailed sheep

Ovar-DRB1 is one of the most important response genes in the major histocompatibility complex (MHC) class II region of sheep. Gene polymorphism in the second exon of Ovar-DRB1 in three different Iranian fat-tailed sheep breeds (Lori-Bakhtiari, Shaul and Zandi) was analyzed by either restriction fragment length polymorphisms (RFLP) or direct sequencing. A total of 92 Lori-Bakhtiari, 40 Shaul, and 47 Zandi sheep were examined. PCR-RFLP identified 17 genotypes in Lori-Bakhtiari sheep, 12 in Shaul sheep and 11 in Zandi sheep. Collectively, 24 different genotypes could be found for Iranian fat-tailed sheep. Using direct sequencing, seven new sequences in exon 2 of the Ovar-DRB1 gene were identified. Generalized linear modeling with a multinomial error structure showed that the sheep populations had significantly different allele frequencies.     

Renal excretion of urea in the Merino and Steppe fat-tailed breeds of sheep after a short period of fasting

Urea excretion was studied in an experiment with two sheep breeds (steppe fat-tailed and merino) on the second day of fasting when the urea concentration in blood increases in fasting animals. The control group in the two breeds was given free-choice feed and water while fasting sheep were given ad libitum only water. Diuresis in both breeds was steady during the experiment. Glomerular filtration rate was not found to vary, in comparison with the control, although the plasma urea concentration rose in fat-tailed sheep (P less than 0.01) as well as in the sheep of merino breed (P less than 0.001). Fractional excretion of urea decreased in fat-tailed sheep (P less than 0.05) and also in the sheep of merino breed (P less than 0.02) while total output of urea remained steady in fat-tailed sheep but it increased in merino sheep (P less than 0.02). Tubular reabsorption of urea on the second day of fasting was observed to be higher by 65% in merino sheep (P less than 0.001), but in steppe fat-tailed sheep the increase was much higher--by up to 180% (P less than 0.001), in comparison with the control. It was demonstrated by the results that the increased tubular reabsorption of urea contributes to the rise of plasma urea concentration in sheep on the second day of fasting.     

Population structure and genetic characterization of two native Danish sheep breeds

ABSTRACT

Genetic diversity in livestock animals has become recognized as important genetic resource for future sustainable livestock production. Especially native breeds, adapted to their local environment, are of considerable interest. Here, we report a genome-wide characterization of two native Danish sheep breeds, the Danish Landrace sheep and the Danish White-Headed Marsh sheep. We investigated the genetic diversity both at national and European breed level using a European-derived reference panel. The native Danish breeds are genetically distinct from other Nordic breeds. Their closest relatives are Border Leicester, Galway, and Texel. Apart from gene flow between native Danish breeds, Texel admixture was most dominant. For Danish Landrace sheep, a population split into two genetically distinct sub-populations was detected. Compared to other livestock species, genomic inbreeding was moderate. However, among European-derived sheep the native Danish breeds were among the 10 most inbred investigated, illustrating the need for sustainable management strategies to preserve genetic diversity.     

An international panorama of goat selection and breeds

The preservation of the biodiversity of animal breeds is an important condition to maintain the ability of animal production to adapt to the changing conditions of breeding and production systems in the future. The decrease of the number of animal breeds has been observed both for sheep, cattle and goats in relation with the standardisation and intensification of animal production systems.Goats are mainly concerned by the situation as they have the biggest increase in livestock numbers in 20 years. A global overlook of goats worldwide is showing a contradictory situation: On one hand, small but well organised sectors have developed in a few countries for milk and cheese, meat and fibre production. On the other hand, most of the goats are mostly still used for auto consumption of milk meat and skin or fibres in village herds. The present goat genetic situation is the direct consequence of this evolution with the high specialisation of a small number of selected and well characterised breeds for milk, meat and fibres and a majority of not well defined populations and local breeds, generally without selection schemes and organisation.A global panorama of the main families and breeds is presented. A special consideration is then pointed on the necessary financial and logistic conditions to achieve successively these selection objectives. After having observed that in many cases these conditions are not present, this report concludes by some proposals to control better the possibilities of success and express with more efficiency the genetic potentiality of this interesting species.     

A critical review of the value of genetic distance studies in conservation of animal genetic resources

There has been a veritable explosion of projects in recent years aiming to calculate genetic distances between domesticated breeds of animals and the number of such projects is still increasing. The extent of this can be appreciated by a glance at the recent proceedings of the 26th International Conference on Animal Genetics (ISAG 1998). All domesticated species are being targeted, using breeds from both developed and developing countries and projects are now almost exclusively based on microsatellite marker loci. Although the goal in a few cases is to provide insights into the history of animal domestication (see, for example, M ac H ugh et al. 1997; L au et al. 1998), the most common justification for genetic distancing projects is their importance for helping the decision-makers to identify genetically unique breeds so that they may be prioritized for breed conservation purposes (e.g. H all and B radley 1995; M oazami -G uodarzi et al. 1997; C rawford and L ittlejohn 1998). On a world-wide basis there are roughly 3000 breeds and breed varieties of the seven major mammalian species – cattle, pig, sheep, goat, horse, donkey and buffalo (FAO 1995). Of those with population data, 23% are either endangered or critical (FAO 1995). In addition, in the current century it is estimated that at least 600 breeds have been lost (H all and R uane 1993). On the poultry side, the picture is even worse as over half the breeds of the five major species (chicken, domestic duck, muscovy duck, goose and turkey) are thought to be endangered or critical (FAO 1995). At the same time, there is often a lack of even the most rudimentary information on many of these breeds. Basic phenotypic data, including approximate figures for population sizes, are currently available on only 50% of the world’s animal genetic resources (AGR) (H ammond 1998). There is therefore an urgent need to act now to prevent the rapid erosion of AGR. This is especially true for breeds in developing countries, where many will be lost without ever having been adequately characterized or studied (K& ouml ; hler -R ollefson 1997). However, resources (both in terms of available manpower and finances) are limited in this area and appropriate use of these resources is therefore of vital importance. Given the large amount of current activity in the area of genetic distancing of domestic breeds, the aim of this article is to critically examine the value that genetic distance projects have for breed conservation.     

Amino acid profiles of muscle and liver tissues of Australian Merino,Damara and Dorper lambs under restricted feeding

Seasonal weight loss (SWL) is a major constraint in extensive animal production systems in the tropics and Mediterranean. The objective of this study was to characterize the amino acid profile of muscle and hepatic tissues of Australian Merino, Damara and Dorper lambs under restricted feeding to evaluate the impact of SWL at the metabolic and physiological levels. SWL induced generalized muscle protein breakdown among restricted groups of all breeds, with varying intensity. Dorper breed mobilized less muscle amino acids when under these conditions, with the Damara having frequent significant differences, namely by having lower amino acid concentrations in the muscle of restricted lambs. Damara lambs showed greater ability to catabolize branched‐chain amino acids in the muscle tissue, which indicates yet another mechanism that provides the Damara with the necessary tools to endure harsh conditions. Overall, the Damara breed mobilized more muscle amino acids than the other breeds, with a better capacity to catabolize branched‐chain amino acids in the muscle, while maintaining muscle structural integrity.     

微卫星标记ILSTS011在3个绵羊品种中的遗传多样性分析

为了分析微卫星标记ILSTS011的遗传多态性,研究以河南省地方绵羊品种大尾寒羊、小尾寒羊和豫西脂尾羊为研究对象,采用聚丙烯酰胺凝胶电泳技术分离微卫星标记的带型.结果表明:在3个绵羊品种中均检测到微卫星标记ILSTS011有3个等位基因,微卫星标记ILSTS011的平均杂合度为0.614 1,平均有效等位基因数为2.614 0,平均多态信息含量为0.551 3.说明ILSTS011为高度多态基因座,可作为有效的遗传标记用于大尾寒羊、小尾寒羊和豫西脂尾羊的遗传多样性分析.     

开发利用陇东草地资源 大力发展农区养羊业

针对陇东地区草地资源丰富,适于发展养羊业的特点,在分析草地资源,羊品种资源和优势的基础上,提出２０００年后,养羊是该区发展草食家畜,调整畜牧业产生结构的一个主攻方向,并提出了加快草地资源开发利用,发展以养羊为中心的创汇畜牧业的具体措施。     

Genetic diversity of Afrikaner cattle in southern Africa

The Afrikaner is an indigenous South African breed of “Sanga” type beef cattle along with breeds such as the Drakensberger and Nguni. Six composite breeds have been developed from crosses with the Afrikaner. Additionally, Afrikaner has been the base from which exotic breeds were established in South Africa through backcrossing. The study examined genetic diversity of Afrikaner cattle by genotyping 1257 animals from 27 herds in different geographic areas of South Africa and Namibia using 11 microsatellite markers. Multiple-locus assignment, performed using the Bayesian clustering algorithm of STRUCTURE, revealed three underlying genotypic groups. These groups were not geographically localized. Across herds and markers, the proportion of unbiased heterozygosity ranged from 0.49 to 0.72 averaging 0.57; mean number of alleles per locus ranged from 3.18 to 7.09, averaging 4.81; and allelic richness ranged from 2.35 to 3.38, averaging 2.67. It is concluded that a low inbreeding level of 2.7% and a moderate to high degree of variation still persists within the Afrikaner cattle breed, despite the recent decline in numbers of animals.