Phytanic acid content and SRR/RRR diastereomer ratio in milk from organic and conventional farms at low and high level of fodder input

Abstract

Milk quality has an important role in organic farming due to the obligation to a maximum use of pasturage for herbivores. Markers should be identified to confirm the authenticity of organic milk production. The concentration and SRR/RRR diastereomer ratio of phytanic acid were investigated as potential markers to discriminate different feeding strategies. In a two-factorial design, 80 farm milk samples were compared for their ‘origin’ and ‘level of intensification’, both during the grazing season and the indoor season. In all groups the concentration of phytanic acid in winter was about 50 % lower than in summer. A strong negative correlation was found between the sum amount of concentrates plus maize silage in the cow’s diet and the phytanic acid level. In winter, cows fed with hay had lower phytanic acid levels than cows fed grass silage. The differentiation of low-input and high-input systems was more consistent than the differentiation between biodynamic and conventional samples based on the combination of phytanic acid and SRR/RRR ratio. The SRR/RRR ratio was an indication for the factor ‘intensification’, whereas the concentration of phytanic acid reflected the factor ‘origin’. The SRR/RRR ratio is therefore a marker for the grazing policy in summer and the differentiation between hay versus grass plus maize silage in winter diets. Organic farming could lose its characteristic features reflected in several aspects of milk fat quality if grazing during summer is reduced and replaced by larger amounts of concentrate and maize silage.