Alfa-tocopherol and beta-carotene in roughages and milk in organic dairy herds

Summary

The aim of the present study was to increase our knowledge about the vitamin content in roughage at harvest and during storage on organic commercial farms and to analyze the vitamin content in the milk. Roughages produced at the five organic dairy farms were monitored from harvest when the silage was laid in the silo and until the roughage was fed during the winter. The roughages had average α-tocopherol and β-carotene contents during the feeding period of, respectively, 30 mg and 21 mg per kg DM in grass-clover silage (after 281 days at storage), 13 mg and 8 mg per kg DM in maize wholecrop silage (stored for 194 days) and 28 mg and 9 mg per kg DM in cereal wholecrop silage (after 210 days from ensiling to feeding).
The average daily intake of α-tocopherol was 876 mg per cow of which the 520 mg came from the feed, hereof 83% from roughage, and the remaining 356 mg came from a vitamin mixture. The average daily milk production during the winter period was 25.9 kg energy corrected milk (ECM) with an average content of 0.82 μg/ml α-tocopherol and 0.17 μg/ml β-carotene.
The highest concentration of vitamins was found in the grass-clover silage with high digestibility of organic matter and high energy content per kg DM. For grass-clover silage, there were generally no losses of vitamins during the ensiling process and during storage but there were huge variations between farms. The highest concentration of vitamins in cereal wholecrop silage was found in silage with a high content of legumes and weeds and a relatively low content of cereals. For wholecrop silage crop there was a loss of vitamins during the ensiling process, whereas there were no further losses during the feeding period. The output of vitamins in milk was with-in farm positively correlated to supply of vitamins from roughage.