Seasonal variation in content of riboflavin and major minerals in bulk milk from three Danish dairies

Milk is an important source of vitamins and minerals in Western diets. Both genetic and management factors influence the mineral content of milk. Furthermore, milk contains relatively high levels of riboflavin. However, little is known about factors influencing variation in riboflavin level in milk. The seasonal variation in the content of riboflavin, calcium, phosphorus and magnesium of bulk tank milk from one organic and two conventional dairies was therefore investigated. Results showed lower mineral contents for milk from the organic dairy compared with milk from the conventional dairies. For all minerals, there was a significant effect of season, whereas the riboflavin content varied only significantly across the year in milk from the organic dairy, resulting in lower levels during summer and higher levels during the indoor winter period. Despite this variation, milk from the organic dairy generally contained more riboflavin than milk from the two conventional dairies.