Interactions of flavin containing monooxygenase 3 (FMO3) genotype and feeding of field beans and rapeseed cake on the trimethylamine (TMA) content in egg yolks of laying hens

The aim of the present study was to evaluate the relationship between Flavincontaining monooxygenase 3 (FMO3) genotype and dietary FMO3 inhibitors on trimethylamine (TMA)-N content in egg yolks of laying hens. Fishy taint is characteristic for the tertiary amine TMA. Rhode Island Red pure breed hens and Lohmann Brown commercial layers were genotyped for non-synonymous A to T polymorphism at position nt1034 of the cDNA of the FMO3 gene. This polymorphism is associated with variation in TMA-N levels in egg yolks. Hens of the FMO3 genotype AA, AT and TT were used for the experiments. Genotypes were equally distributed among the varying experimental diets. As dietary FMO3 inhibitors natural or hydrothermally treated field beans (100 g/kg diet) or rapeseed cake (0, 100 and 300 g/kg diet) were incorporated in the diets. Field beans contain tannins, vicine and convicine as antinutritive substances. Rapeseed cake contains the TMA-precursors glucosinolates and sinapine. TMA was extracted from egg yolks with trichloroacetic acid and analysed as TMA-N by a photometric method. The performance parameters number of laid eggs, egg weight, laying intensity, egg mass, daily feed intake and feed-to-egg-mass ratio were recorded. High amount of TMA-N was found in egg yolk of TT-hens when fed with the experimental diets. In contrast, hens of the AA-genotype and heterozygous AT-hens only exhibited low levels of TMA-N. 300 g rapeseed cake/kg diet reduced performance of hens. No negative effect on performance could be found in the experimental groups fed on natural and hydrothermally treated field beans, respectively. It can be concluded both field beans and rape seed cake at concentrations of antinutritive substances used in this experiment can be fed to brown egg layer hens of the FMO3 genotypes AA and AT without leading to fishy tainted eggs.