Effects of abomasal infusion of flaxseed (Linum usitatissimum) oil on microbial β-glucuronidase activity and concentration of the mammalian lignan enterolactone in ruminal fluid, plasma, urine and milk of dairy cows

Abstract

Ruminal microbiota plays an important role in the conversion of plant lignans into mammalian lignans. The main mammalian lignan present in the milk of dairy cows fed flax products is enterolactone (EL). The objectives of the present study were to investigate the effects of abomasal infusion of flax oil on the metabolism of flax lignans and concentrations of EL in biological fluids of dairy cows. A total of six rumen-cannulated dairy cows were assigned within a 2 £ 3 factorial arrangement of six treatments utilising flax hulls (0 and 15·9 % of DM) and abomasal infusion of flax oil (0, 250 and 500 g/d). There were six periods of 21 d each. Samples were collected during the last 7 d of each period and subjected to chemical analysis. Flax hull supplementation increased concentrations of EL in ruminal fluid, plasma, urine and milk, while flax oil infusion had no effect. Post-feeding, b-glucuronidase activity in the ruminal fluid of cows infused with 250 g flax oil was significantly lower for cows fed hulls than for those fed the control diet. The present study demonstrated that the presence of a rich source of n-3 fatty acids such as flax oil in the small intestine does not interfere with the absorption of the mammalian lignan EL and that lower ruminal b-glucuronidase activity had no effect on the conversion of flax lignans into EL in the rumen of dairy cows.Key words: Lignan: Enterolactone: b-Glucuronidase activity: FlaxseedThe high level of a-linolenic acid in flaxseed (Linum usitatissimum) makes it a good source of n-3 PUFA from plant origin for humans. Dietary addition of flaxseed increases the n-3:n-6 fatty acid ratio in food, and improvement of the ratio has been recognised as potentially beneficial to human health (1) . Moreover, flaxseed is the richest source of plant lignans which possess antitumour (2) , antioxidant (3) , antithrombic, weakly oestrogenic and anti-oestrogenic (3,4) and anti-atherogenic effects (5) . Plant lignans are polyphenolic compounds concentrated in the outer fibre-containing layers and the lignan secoisolariciresinol diglucoside (SDG) represents over 95 % of the total lignans in flaxseed (6) .The main site for the metabolism of flax lignans in nonruminant animals is the large intestine (7) . On the other hand, recent in vivo results have shown that the rumen is the main site for the metabolism of flax lignans in dairy cows (8) . Under the action of microflora, the plant lignan SDG is converted mainly into the two mammalian lignans enterodiol and enterolactone (EL), and enterodiol and EL are subsequently absorbed into the blood (9) . EL is the main lignan metabolite present in ruminal fluid (8) and milk (10) . In nonruminant animals, mammalian lignans are absorbed in the intestine and under the action of specific enzymes, they are conjugated as sulphate and glucuronide in the intestinal wall

Ruminal Prevotella spp. May Play an Important Role in the Conversion of Plant Lignans into Human Health Beneficial Antioxidants

“…Previous results have demonstrated that the main site of mammalian lignan formation in ruminant animals was the rumen [18]. Indeed, increased levels of the mammalian lignan EL in ruminal fluid of cows supplemented with flax hulls [7], [36] and sheep infused with purified SDG in the rumen [17] have been reported earlier. Feed ingredients such as soy and corn contain lignans [37], [38] also lead to EL production [39], which may explain why EL was present in the rumen of cows fed CON.…”

Flaxseed-enriched diets change milk concentration of the antimicrobial danofloxacin in sheep

“…The increase in the amounts of flaxseed in food has been directly related with a higher concentration of enterolactone in plasma, urine and milk in dairy cattle [ 4 , 32 ]. In this study, we present for the first time a direct correlation between the amount of whole flaxseed added to the diet and the concentration of enterodiol and enterolactone found in sheep plasma.…”

A Review of Lignan Metabolism, Milk Enterolactone Concentration, and Antioxidant Status of Dairy Cows Fed Flaxseed

“…Studies conducted with lactating dairy cows showed no relationship between flaxseed supplementation (FH or FM) and activity of microbial β-glucuronidase in the rumen [8,10,47], thus suggesting that this enzyme has little or no involvement in the ruminal absorption of EL, possibly because conjugation occurs during or after cell uptake of enterolignans [43]. In fact, when the ruminal activity of microbial β-glucuronidase decreased in dairy cows fed FH [48], the concentrations of EL in rumen, plasma, urine, and milk increased compared with the control diet. However, additional research is needed to elucidate the actual mechanisms involved in the absorption of enterolignans in ruminant animals.…”

“…These results [8] imply that ruminal bacteria with predominant β-glucuronidase activity may be more susceptible to the toxic effects of FO than those primarily involved in the conversion of SDG to EL as the concentration of EL in the rumen was not affected by the site of FO supplementation (rumen or abomasum). Compared with the control treatment, fecal β-glucuronidase activity tended to increase in dairy cows fed FH and no change was detected with abomasal infusion of FO in another experiment [48]. In contrast, it was found that feeding FM and infusing sunflower oil (n-6 PUFA source) in the abomasum of lactating dairy cows decreased fecal β-glucuronidase activity relative to the control treatment [47].…”

“…In contrast, it was found that feeding FM and infusing sunflower oil (n-6 PUFA source) in the abomasum of lactating dairy cows decreased fecal β-glucuronidase activity relative to the control treatment [47]. It has been shown that the ruminal microbiota can be modulated by modifying the dietary PUFA profile and similar processes may also take place in the large intestine of ruminants, which may explain to a certain extent these inconsistent results in fecal β-glucuronidase activity [8,47,48]. Changes (increase or decrease) in 16S rRNA copy numbers of ruminal microorganisms such as Butyrivibrio , ciliate protozoa, methanogens, Selenomonas ruminantium , and Streptococcus bovis were detected during an in vitro rumen simulation technique study in which fermenters were dosed with diets rich in n-6 PUFA (i.e., sunflower oil) or a n-6/n-3 PUFA mix (i.e., sunflower oil plus fish and algae oil) [52].…”