In 1973 FAO and UNEP launched their joint studies on the conservation of livestock breeds with a pilot project entitled “Conservation of animal genetic resources”. Its report (1975) made a brief survey of livestock breeds throughout the world which were rare, endangered or vulnerable, and made a special study of cattle breeds in Europe and the Mediterranean countries. This species and this region were chosen because it is the native European and Mediterranean cattle breeds which have suffered most by crossbreeding and replacement. Indeed the report showed that only 33 out of 100 native breeds in this region could be considered stable and not threatened with extinction in the long term.
This decline in local breeds can be summarized as being due to fashion, commercial activity and deliberate policy. As husbandry improves it is possible to keep more productive (but less hardy) breeds. This applies particularly to the dairy breeds. At the same time artificial insemination makes possible a very rapid change-over. The changes in farming structure are also important - the small mountain and upland farmers disappear and with them the local dual- or triple-purpose breeds. Larger farms with improved husbandry no longer use draught animals.
Mediterranean sheep were the subject of the next FAO/UNEP report. “Declining breeds of Mediterranean sheep” by Brooke and Ryder (1978) described 24 breeds (out of a total of about 120) in seven European Mediterranean countries, which are endangered, vulnerable or rare.
In the Western Mediterranean this decline has been due chiefly to crossbreeding with more productive breeds when husbandry could be improved - as for cattle. In the Eastern Mediterranean it is part of a general decline in the sheep industry associated with low returns (e.g. falling wool prices), lack of prestige (hence shortage of shepherds) and spread of tourism on the coasts and in the mountains.
In Europe development has proceeded so far that it is extremely difficult to justify the retention of many disappearing breeds on economic grounds. The big exception is the use of adapted mountain and Mediterranean breeds for commercial crossing with sires of improved breeds (see FAO Report “Mediterranean cattle and sheep in crossbreeding”, 1977). In the developing countries, on the other hand, indigenous breeds predominate. It is therefore, important that they be studied now before they are endangered by crossbreeding with breeds from temperate countries. The pressure for crossbreeding very often comes from the factors of fashion, commercial pressure and prestige rather than real economic advantage - the much more difficult environments in tropical and subtropical countries are often unsuitable for European breeds and even for their crosses.
Accordingly, in 1976 UNEP and FAO initiated a project on “Conservation of animal genetic resources”. Instead of a superficial survey of the whole world it concentrated on developing countries and picked those species, breeds and regions which the pilot survey had suggested were particularly urgent to study because of pressure on local adapted breeds (e.g. Criollo cattle of Latin America, trypanotolerant cattle of West Africa). It also drew attention to neglected local resources. One of these is the sheep of the humid tropics; this is a climatic zone not traditionally associated with sheep but in some of the wet tropics they are extremely important. A special aspect of a few of these populations is that they show a high reproductive rate. Thus the Pilot Project's recommendation was “A mission should be mounted to study the woolless sheep of north-east Brazil and the Caribbean area with particular attention to the Barbados Blackbelly which is known to be highly prolific but whose population is small. Contact should be established with any other sheep projects in the humid tropics, e.g. West Africa, southern India, Java”.
In the current project the aim was enlarged and a coordinating consultant was appointed whose terms of reference were to survey and inventory prolific tropical sheep and other tropical sheep breeds in danger of extinction. This was to be done by a survey of the literature, by visiting the countries concerned, and by recruiting local consultants to help in the collection of information. At the same time a second consultant has been surveying the sheep breeds of Afghanistan, Iran and Turkey and his report is presented separately (see Yalçin, 1979).
As work proceeded it was clear that it is difficult to draw a clear line of distinction between “tropical” and “subtropical”. Therefore, some attention was paid to prolific breeds in subtropical regions. It also became apparent that it was impossible to include all the “other tropical sheep breeds in danger of extinction”. This would have meant visiting all tropical countries in order to study all sheep breeds on the spot and pick out those in the endangered category. However, some regions could immediately be eliminated from the survey, as follows:
North Africa and the Near East, except for prolific breeds, because the sheep of the Arab countries are being surveyed by ACSAD (Arab Centre for Studies on Arid and Dry Lands) and those of Afghanistan, Iran and Turkey by Yalçin (1979).
West and west equatorial Africa (except in search of the origin of American hair sheep) since the sheep of the humid zone at least are included in the report of the FAO/ILCA/ UNEP study on trypanotolerant livestock (1980).
India, since the sheep breeds of India are the subject of a special FAO survey currently in progress.
In addition, eastern and southern Africa were left out because there is no evidence for prolific breeds in this region and no indication that local breeds are in danger of extinction.
This left three main areas to be surveyed in this project:
Tropical America. The coordinating consultant visited Barbados, Brazil, U.S. Virgin Islands, Dominican Republic, Haiti, Jamaica, Cuba and Mexico and received reports from local consultants in Trinidad, Colombia, Venezuela and Brazil.
Southeast Asia. The coordinating consultant visited Indonesia and Sri Lanka and also received reports from local consultants in these countries.
Southwest Asia, and the Mediterranean. The coordinating consultant visited Greece, Morocco and Oman. To complete the picture of this subtropical zone, published accounts of prolific breeds in the same climate zones in the U.S.S.R. and China are also included.
This report takes each of these regions in turn and describes what is known about the prolific breeds. For the two humid tropical regions - tropical America and southeast Asia - it then considers some related or neighbouring breeds and discusses breeding systems and conservation programmes.
The definition of a prolific breed used herein in reference to tropical environments is not so exacting as in Europe. In Europe many breeds have lambing percentages of 150 or more so that it is not until the litter size is over two that a breed is considered to come into the prolific class. In the tropics in general twins are unusual, so that a lambing percentage of over 150 has been chosen as the criterion of prolificacy in this review.
Naturally it was not possible to confine the survey only to known prolific breeds. Related and neighbouring breeds were explored both in the hope of finding other prolific breeds and also to present details of breeds in similar environments which lack the high fertility character. This naturally led to a consideration of the adaptation of sheep to the tropics and particularly to the humid tropics.
The distinction between prolific and non-prolific breeds was particularly difficult to establish among the hair sheep populations of tropical America. Although these sheep are extremely well adapted to their environment and are of vital importance to their owners they have been hithertoo much neglected by research and development services. There is thus comparatively little information available on their characteristics and performance. For these reasons the opportunity has been taken to summarize here all available information about them, not only as a basis for further programmes of research and improvement but also as a source of information for sheep breeders in similar tropical environments elsewhere.
(For references see p. 104).
Note on terminology. A fertile ewe or a fertile mating is one which gives rise to an offspring. Fertility is thus measured as the percentage of mated ewes which produce lambs, i.e. the lambing rate. This may loosely be called the conception rate but in fact it represents the conception rate less any embryonic mortality. In conditions of flock mating where the actual mating may not be observed it is in fact the number of ewes lambing per 100 ewes joined (i.e. put to the ram) which is recorded. Prolificacy is defined as the number of lambs per 100 ewes lambing, i.e. it is another way of expressing the litter size or number of lambs per birth. Fecundity may be used loosely for either fertility or prolificacy. It would be desirable to confine its use to mean number of lambs born per 100 ewes joined i.e. fertility x prolificacy. This may refer to a single lambing season or it may refer to a whole year. In this latter use fecundity = fertility x prolificacy x number of lambings per year.
Although an attempt has been made to use these terms in the ways defined the attempt may not always have been successful because of plurality of authors and quotations from many and varied sources.