Progress and prospects in selecting for resistance to diseases

摘要

For many years, breeding companies have been expressing that there is little chance that they can do anything on improving the disease resistance in their birds. Traditional methods seem not to be very effective and reliable, so the focus remained at the economic traits gain and FCR. Does molecular genetics help to make progress in selecting for disease resistance? Genetic resistance to disease has long been recognised as a valid strategy for disease prevention. It avoids the use of drugs or vaccines and, once achieved, may provide long-term protection. However, as Dr. Urs Kuhnlein, from the Department of Animal Sciences at McGill University in Montreal, Canada, pointed out, the only method available until the emergence of molecular genetics was "phenotypic selection." This involves actually exposing large populations of birds to the specific disease and selecting those that survive. A variety of modifications of this procedure have been developed, and some have been applied to commercial breeding. But the process is difficu primary breeding populations are usually kept in isolation and elaborate methods are used to limit disease incidence. So direct selection must be carried out with satellite populations and only relatives of resistant birds or families can be used as ancestors for future generations. Another shortcoming of these methods is that they tell us nothing about the actual mechanisms of disease resistance which are being selected. Such mechanisms may provide clues for disease prevention by management, nutrition or pharmacological intervention.