Carotenoids for ruminants:: From forages to dairy products

Carotenoids are involved in the nutritional and sensory characteristics of dairy products, and are potential biomarkers for traceability of cows' feeding management. We review general and recent knowledge on carotenoids from forage to milk and dairy products in ruminants. Nearly 10 carotenoids (i.e., xanthophylls and carotene) have been quantified in forages, and their concentrations vary highly according to development stage and length of conservation. Sensitivity of beta-carotene to ruminal degradation varies among studies, depending on its dietary source. Data suggest that carotenoid digestion would be linked to dietary lipids for transit, and to specific transporters of lipophilic molecules for absorption. Among ruminants, only bovines accumulate high concentrations of carotenoids, mainly beta-carotene, possibly due to lower Vitamin A synthesis efficiencies in enterocytes. Carotenoid flows in plasma and tissues in dairy cows remain to be investigated, especially the ability of adipose tissue to release beta-carotene in depleted or underfed animals. Carotenoids in cows' milk mainly consist of all-trans-p-carotene and, to a lesser extent, lutein. In milk, concentration is more variable for beta-carotene than for retinol, for which the plasma concentration is well regulated. Milk concentration of beta-carotene depends on its dietary supply. Both animal and feeding factors that affect milk yield (i.e., breed, parity, physiological stage, level of intake) generally also control milk beta-carotene concentration by concentration/dilution mechanisms, and by efficiency of extraction from plasma. The beta-carotene concentration in cheese is highly linked to milk concentration, whereas high losses of retinol occur during cheese-making. The color of dairy products highly depends on their carotenoid concentration, suggesting that color may be a promising rapid measurement tool for traceability of feeding conditions. Feeding management of dairy cows allows efficient control of carotenoid concentration and color in dairy products. (c) 2006 Elsevier B.V. All rights reserved.