Chicken breeder Lohmann Tierzucht worked on the problem with Finland's MTT Agrifood Research,whose researchers announced yesterday they had identified a genetic defect in brown-coloured chickens that leads them to produce the fishy smelling eggs.
White chickens do not carry the genetic mutation, said Johanna Vilkki, the principal research scientist at MTT and leader of the research team.
"Furthermore, the eggs of brown chickens do not smell unless chickens which have inherited the genetic defect have been given feed containing an ingredient which triggers the taint, forexample rapeseed," she said.
About five to 10 per cent of brown chickens that consume such feed produce tainted eggs.
"The fishy taint occurring in brown eggs has caused major problems for chicken breeders, producers and trade in the EU, where most hens' eggs consumed are of the brown variety,"MTT said in a statement. " In Finland, however, brown eggs account for less than 10 per cent of all eggs sold. At worst, the smell of rotting fish can be so strong that it persists even the cooking of eggs. When trade buyers find tainted eggs through spot checks, the producer faces significant loss as the entire batch must be withdrawn from sale. The problem is most severe incentral Europe."
After the discovery the MTT research team developed a procedure to test for the defect. Lohmann Tierzucht is already using the procedure to produce chickens free of the defective gene. The company,which is based in Germany, plans to market the first chicken parent stock free of the defect at the end of the year.
Usually genetic testing is done from taking blood samples, which is not only complicated and expensive, but may also be traumatic for chickens, Vilkki said. MTT's testing procedure only requirestaking a sample from one feather to produce an unequivocal result. Cells from the feather shaft indicate whether a chicken has the genetic defect.
The procedure, which is being patented, makes it possible for breeders to select brown chicken lines for crossbreeding. The selection ensures that they produce progeny without the genetic defect.
Lohmann Tierzucht is one of only three chicken breeding companies supplying the international market. The company holds a 25 per cent share of the world market for stock chickens and is theEuropean market leader. It supplies about 70 per cent of the Finnish market.