Healthy chickens the natural way
The Danish organic chicken, the Hellevad chicken, contains the key to egg production without the use of preventive medicine. Scientists from Aarhus University are mapping the genetic basis for the chicken's robustness. The research-based knowledge can be used commercially worldwide.
Denmark has an organic superhen, the Hellevad chicken, which is bursting with natural health. Researchers from Aarhus University and the American broiler breeding company Cobb-Vantress have joined forces to investigate the genetic background for why the Hellevad chicken is so unusually healthy and robust. The aim is to breed highly productive chickens with a high natural health status. This will benefit both the birds' welfare and the farmer's economy.
Generation after generation, the Wolf family at the Hellevad hatchery has removed the most inferior chickens in the chicken yard. Sick birds and hens that dared to lay their eggs outside the nesting box were given the red card. This has resulted in a chicken line that is unusually robust and does all the right things when laying eggs. Preventive medicine is not used in the hatchery, and the only vaccination carried out is the statutory one against Newcastle Disease.
The Hellevad chicken's are primarily sold to organic farms and backyard breeders, but now scientists from Aarhus University and Cobb-Vantress have put the chicken under the microscope. They wanted to examine the background for the excellent health- related traits and expect that the knowledge can be transferred to large commercial breeds.
MBL is good for the immune system
The research project was initiated in 2010 (Less antibiotic dependence via breeding), and the scientists have already achieved some interesting results. It all has to do with mannose-binding lectin (MBL).
MBL is a protein that binds to sugars on the surface of pathogens. When this happens, the immune system is activated and starts the fight against the pathogens. Scientists have previously found that the Hellevad chicken contains two to three times as much MBL in the blood as commercial laying hens, so they assumed that this could be the key to their high degree of health and robustness.
- MBL is especially important in the early part of life, explains senior scientist Helle R. Juul-Madsen, Aarhus University, and leader of the project.
MBL levels affect the immune defence in several species.
- In humans, low levels of MBL are associated with more frequent incidences of disease because the immune system is less active. In pigs, the gene for MBL has been found to reside on the same chromosome as other genes that influence the immune defence. In chickens, a low level of MBL means that chicken's with an E. coli infection have lower weight gain and that diseases such as Infectious Bronchitis virus and Pasteurellosis proceed more severely because of decreased immune function, says Helle R. Juul-Madsen.
The gene has been found
The project participants have localized the gene for a high level of MBL on the chromosome. Hereafter, they have examined the parental lines to the Hellevad chicken. The chicken is in fact a cross between Skalborg and New Hampshire breeds. The results show that none of the studied animals had the genotype that causes low levels of MBL. This means that the high level of immunity exists already in the parental lines and is passed on to the offspring.
In the broilers from Cobb, on the other hand, the aforementioned genotype for low MBL levels was found in all the lines studied, with varying frequency.
- Our results support the theory that the Hellevad chicken has a special robustness, says Helle R. Juul-Madsen.
The next step in the project is to investigate whether there is a correlation to disease for the Cobb lines – similar to the results already published. If so, Cobb will use the information to increase the levels of MBL in their pure lines as part of their programme on disease prevention. Scientists at Aarhus University have also started to develop test methods that can perform genotyping quickly and easily, so it can be done routinely.
The project is supported by the Danish Poultry Council, Cobb-Vantress and the Danish Council for Strategic Research.
Further information: Senior scientist Helle R. Juul-Madsen, Department of Animal Science, email: Helle.JuulMadsen@agrsci.dk, telephone: (+45) 8715 7837
Text: Janne Hansen