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close this bookAnimal Husbandry - Initial Environmental Assessment Series No. 2 (NORAD, 1994)
close this folderPart I: General account
close this folder3 Possible environmental impacts
View the document(introduction...)
View the document3.1 Overgrazing and soil erosion
View the document3.2 Pollution of air, soil and water
View the document3.3 Special impacts of livestock-based industries and transportation
View the document3.4 Loss of valuable genes
View the document3.5 Infection pressure and diseases, and impacts of medication
View the document3.6 Other ecological impacts, and consequences for landscapes
View the document3.7 Social impacts
View the document3.8 Impacts of other existing or planned activities

3.4 Loss of valuable genes

Increased efficiency in agriculture and animal husbandry may lead to loss of valuable genes. The focus has particularly been directed towards genetic resources in plants. This is due to the fact that many cultivated plants are self-fertile or clones being marketed as homogeneous lines or hybrids. When these supplant local varieties from a cultivated area, reduced genetic variation and loss of valuable genes may be the result. For a more detailed account of this, "The convention on biological diversity" (UNEP 1992) can be consulted.

In general, the risk of losing genes of domestic animals is smaller, as domestic animals are cross-fertilizers. Loss of genes can happen if imported exotic breeds totally replace local ones. Commercial poultry production is especially vulnerable, because some local poultry breeds are in danger of becoming extinct. Such standardizing of production systems creates a form of monoculture, reducing the possibilities of subsequent alterations, which might be desirable. Experience, by FAO for example, shows that subsistence households and hobby producers often take great interest in local poultry breeds, and that these breeds will therefore be preserved. One should nevertheless note that The World Poultry Science Association has appealed to FAO to take initiatives to preserve genetic resources in poultry. Replacement of local swine breeds by improved swine breeds from the industrialized countries is widespread wherever commercial pork production is established in developing countries. Measures may be called for to preserve local swine breeds. An alternative to preserving local breeds is to improve them by crossing in imported breeds, as well as making selections in the new mixed population under current environmental conditions. Crossing and selection will make it possible to preserve valuable genes in the population, provided they do not have a strongly negative effect on the properties which selection is meant to improve. The frequency of local genes may become lowered, but research has shown that the decline takes place slowly and that loss of important production and resistance properties, being governed by many genes, will not happen for generations. Such improved and upgraded local breeds are also likely to become valuable elements in a three or four breed crossing programme aimed at efficient and economical pork and poultry production in developing countries.

Introduction of new cattle, goat and sheep breeds in developing countries generally takes place through crossing with local breeds, not through substitution by new pure breeds. Such crossing and subsequent selection under local environmental conditions will preserve valuable local genes. FAO (1992) has recommended that selection in order to improve and preserve local breeds should take place in a so-called Open Nucleus Breeding System, where it is allowed to cross in animals of the same breeds or of other breeds having the desired properties. In many industrialized countries, a high degree of standardization of cattle breeds over large areas and between countries is taking place. This development, however, is still not common in most developing countries.