PhD-projekt: Disease prevention in poultry production - focus on natural defence mechanisms
Background: The industrialised poultry production can be characterised as a system in which infections are generally eliminated partly by the principle of “everything out – everything in” and partly by very high hygienic standards. The absence of infections implies that the animals do not develop an optimum immune response against potential infections. The utilisation of the animals’ ability to establish a defence against specific infections by means of natural immunisation has instead been provoked by the application of vaccines against the diseases causing most losses.
An alternative way of maintaining this high level of “biosecurity” (vaccination and a high level of hygiene) can be the creation of flocks consisting of animals in different age categories. When young animals are introduced to the flocks at appropriate intervals a permanent, but low infection pressure may exist which stimulates the animals’ own immune response. Recurring introductions of animals may also have an adjuvant effect (further stimulation of the immune response) on the established part of the flock, provided that infection risk and stress are kept at a low and controlled level.
The breeding material of laying hens existing today, has been developed with the purpose of a high production of eggs in battery systems but when these hens are introduced to other systems and mixed with other hens problems often arise, especially healthwise. The reason for this is that during the last 40 or 50 years of breeding animals have primarily been selected for a high egg production registered in systems with individual batteries. Thus, genetically determined disease resistance has not been supported, as manure-determined infection has been almost eliminated. As breeding companies have found it necessary to participate in and develop the very high “biosecurity” level in the breeding nucleus as well as the multiplying chains, the breeding animals have not - for generations – been exposed to infections, which has made it impossible to remove animals with a weak genetic disease resistance. Thus the genetic determined defence mechanisms of the animals are supposedly reduced. This development of the breeding material is especially problematic in connection with free range hens/organic farming because it is difficult to clean and disinfect the areas between different flocks of animals.
A secure application of the proposed principle of repeated compositions of animals in different age categories requires an increased fundamental knowledge about the influence of interval durations between introductions, timing of introductions and finally the age distribution of animals in the flock. Furthermore, it will be necessary to include breeding aspects, including the identification of the hereditary elements which ensure that a hen is able to establish a good immune response in as broad a spectrum as possible and also to examin to which extent the existing breeding material has the required immune system.
Aim: The aim of the project is to elucidate the development and stimulation of the immune system of poultry in relation to
- Fluctuations in infection pressure
- Fluctuations in stress influence
- The genetic background
Responsible: Senior scientist Karin Hjelholt Jensen
Project period: 01.01.2004 - 31.03.2006
Partners:
PhD-student: Liselotte R. Norup
Local supervisor: Karin Hjelholt Jensen
University: The Royal Veterinary and Agricultural University (RVAU)
Last updated: Thursday 21 June 2007 - [email protected]
Tel: +45 8999 1900