WHY DOES THAT EGG HAVE FISHY TAINT?

Fishy egg taint is an unpleasant experience both for farmer and customers and also the financial implication of this can be devastating.Some school of thought have proposed that excessive addition of fish meal to diet is the cause of taint,which was quickly discredited because experiment showed that chicken exposed to same feed had different results as only few eggs had the taint and some not exposed to ration with fish meal had eggs with fishy taint. Another school of thought proposed that it was the side effect of rapeseed in layer ration that causes the taint as some others that were not exposed to such rations had tainted eggs.Egg taint has been found to be caused by transfer and excretions of smelling substances resulting from endogenous metabolism in chicken to the eggs.The fishy taint is caused by accumulation of trimethylamine in the yolk. Trimethylamine (TMA) is caused by bacterial fermentation of choline in the small intestine and caeca. The liver converts TMA to non smelly TMA N-oxide, the smelly taint can arise from dietary of TMA or from precursors for TMA formation. The culprit in the taint has been linked to a gene FOM3-gene, hence a hen lacking this gene will not be able to convert TMA to the non smelly TMA N-oxide.This defect has been observed in certain strains of brown layers hence sourcing from genetically tested and proven strains is important.