Carotenoids, ergosterol and tocopherols in fresh and preserved herbage and their transfer to bovine milk fat and adipose tissues: A review
2012
Kalac, P., Jihoceska Univ., Ceske Budejovice (Czech Republic). Katedra Aplikovane Chemie
The requirements of cattle for the fat-soluble vitamins A, D and E, their provitamins and some carotenoids have increased under conditions of intensive husbandry with insufficient provision of fresh forage, their cheapest natural source. Moreover, bovine milk fat and adipose tissues participate in the intake of these micronutrients by humans. Four major carotenoids occurring in forage crops are lutein, all-trans-beta-carotene, zeaxanthin and epilutein. Fresh forage is their richest source. Losses are significantly higher in hay as compared with silage, particularly if prepared from unwilted herbage. Maize silage is a poor source of carotenoids as compared with ensiled grasses and legumes. Ergosterol contents in forages increase under environmental conditions favourable for the growing of moulds, particularly at higher humidity and lower temperatures. Credible data on changes of ergosterol during herbage preservation, particularly drying and ensiling, have been lacking. Alpha-tocopherol is the most important among eight related compounds marked as vitamin E. It is vulnerable to oxidation and herbage ensiling is thus a safer preservation method than haymaking. As with carotenoids, maize silage is a poor source of alpha-tocopherol. Overall, information on factors affecting the content of ergosterol and tocopherols in fresh herbage, on changes during forage preservation and on transfer to bovine fats has been much more limited than data for beta-carotene.
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