Received 8 August 2013, Revised 20 September 2013, Accepted 1 October 2013, Available online 15 October 2013
Bovine milk samples were collected from 30 Dutch farms and analysed by gas chromatography-mass spectrometry for phytanic acid (PHY), pristanic acid (PA) and SRR/RRR-diastereomers ratio of PHY. The samples differed in the percentage of fresh grass in the cows' daily ration (0–94%) fed either indoors or via grazing (daytime grazing or continuous grazing). Six samples were from organic/biodynamic farms. PHY and PA concentrations were not significantly higher in organic/biodynamic compared with conventional milk, nor were they correlated with the amount of fresh grass in the diet. The SRR/RRR-diastereomers ratio was correlated with the percentage of fresh grass in the diet and was lower in organic milk than in conventional milk, although the difference was not significant (p = 0.057). These results indicate that PHY and PA contents are not suitable indicators of pasture grazing or organic/biodynamic farming, whereas the SRR/RRR-diastereomers ratio may be useful for indicating fresh grass feeding and organic farming.