Evolution of fat soluble vitamin content of ewe’s milk from conventional semi-extensive and organic production systems

Summary

During a 12-month study, bulk-tank milk was collected once a month from organic (O) (n=3) and conventional semi-extensive (CSE) (n=5) ewe’s dairy farms in the Castile and León region (northwest Spain). CSE is the most similar conventional production system to the organic one because they are both part-time grazing system. Milk samples were analysed for retinol, -tocopherol and -tocopherol. The production system and the sampling month affecting the milk fat vitamin content were investigated. Results show that organic ewe’s milk showed significantly higher contents of -tocopherol and -tocopherol and consequently of total tocopherol possibly due to the higher green pasture intake (1,02 vs 0.48 kg sheep-1 day-1) and the lower milk yield (53.5 vs 88.7). Although milk from CSE showed slightly higher values for retinol there were not statistically significant differences between CSE and O. Sampling month significantly affected retinol that tended to increase from February to May, and -tocopherol contents that were higher in autumn and winter months. During these months organic samples showed higher -tocopherol contents than conventional ones. A strong effect of season was observed for -tocopherol only for organic samples that showed a strong increase from March up to June.