β-glucuronidase activity and enterolactone concentration in ruminal fluid, plasma, urine, and milk of Holstein cows fed increased levels of flax (Linum usitatissimum) meal
Citation
Schogor, A.L.B., Palin, M.F., Santos, G.T., Benchaar, C., Petit, H.V. (2017). β-glucuronidase activity and enterolactone concentration in ruminal fluid, plasma, urine, and milk of Holstein cows fed increased levels of flax (Linum usitatissimum) meal. Animal Feed Science and Technology, [online] 223 23-29. http://dx.doi.org/10.1016/j.anifeedsci.2016.11.004
Plain language summary
Flax is a well-known source of natural antioxidant compounds, mainly due to the presence of lignans in the outer fibre containing layers of the seed. Flax lignans are mainly converted in the mammalian lignan enterolactone (ENL), a strong antioxidant, by the rumen microbiota. Previous studies have shown that increased dietary levels of flax meal, whole flax seed or flax hulls linearly raise ENL concentration in milk. However, there is no information on the relationships between concentrations of ENL in milk and other body fluids when cows are fed increased proportions of flax meal in the diet. In non-ruminant animals, the activity of beta-glucuronidase was found to play a key role in ENL gut absorption. However, the effect of beta-glucuronidase activity on ENL rumen absorption has never been investigated in dairy cows. Objectives of the present study were (1) to investigate the relationships between concentration of ENL in milk and other body fluids when cows are fed increased proportions of flax meal in the diet and (2) to determine the role of beta-glucuronidase in ENL absorption. The results showed that flax meal supplementation linearly increased concentrations of ENL in urine, ruminal fluid, milk, and plasma. A strong association was observed between ENL concentration in ruminal fluid post-feeding and that in milk. Feeding increased proportions of flax meal in the diet had no effect on beta-glucuronidase activity in ruminal fluids. Results from this study suggest that the activity of beta-glucuronidase is of little importance for the absorption of ENL in the cows’ rumen and its transfer in milk. Additional studies are required to better understand and improve ENL production and absorption, which could contribute to enhance animal health and the transfer of antioxidant components in milk.
Abstract
The main mammalian lignan present in milk of dairy cows fed flax products is enterolactone (EL), but the relationship between EL concentration in milk and body fluids when cows are fed increased proportions of flax meal (FM) is unknown. The objectives were to investigate the effects of increased levels of FM on EL concentration in milk, plasma, urine, and ruminal fluid and the activity of β-glucuronidase in ruminal fluid and feces. Eight rumen-cannulated cows were assigned to a double 4 × 4 Latin square design with four 21 d periods and four diets: control diet with no FM (CON) or a diet with 50, 100 and 150 g/kg of FM. Concentrations of EL in urine, ruminal fluid, milk, and plasma increased linearly with FM supplementation. Spearman's correlation coefficients were significant for all comparisons except that only a trend was observed between concentration of EL in urine and that in ruminal fluid before feeding. The strongest correlation was observed between EL concentration in ruminal fluid post-feeding and that in milk. Feeding increased proportions of FM in the diet had no effect on β-glucuronidase activity. Unlike to what is observed in non-ruminant animals, present results suggest that the activity of β-glucuronidase in the rumen is of little importance for the absorption of EL and its transfer in milk and other physiological fluids. Further studies are required to better understand and improve EL production and absorption, which could contribute to enhance animal health and the transfer of antioxidant components in milk.