Antioxidants and dairy production: The example of flax

This manuscript reports on the main problems decreasing productivity of dairy cows (e.g. fatty liver syndrome and poor fertility) and how antioxidants could enhance it. High producing dairy cows are prone to oxidative stress, and the situation can be exacerbated under certain environmental, physiological, and dietary conditions. Antioxidants have important effects on the expression of genes involved in the antioxidant status, which may enhance animal health and reproduction. Moreover, antioxidants may contribute to decrease the incidence of spontaneous oxidized flavour in milk enriched in polyunsaturated fatty acids. Plant lignans are strong antioxidants and flax is the richest source of plant lignans. Flax lignans are converted in the mammalian lignans enterolactone and enterodiol. The main mammalian lignan in milk is enterolactone and flax lignans are converted in enterolactone mainly under the action of ruminal microbiota. Therefore, ruminal microbiota may be the most important flora to target for plant lignan metabolism in order to increase concentration of mammalian lignan antioxidants in milk of dairy cows. However, more research is required to improve our knowledge on metabolism of other antioxidants in dairy cows and how they can contribute in decreasing milk oxidation. © 2009 Sociedade Brasileira de Zootecnia.