Secoisolariciresinol diglucoside is the main flax (Linum usitatissimum) lignan that is converted to the mammalian lignans enterodiol (ED) and enterolactone (EL) by gastrointestinal microbiota. The objectives of the present study were to investigate the role of ruminal microbiota and the effects of flax oil on in vivo metabolism of flax lignans and concentration of EL in biological fluids. Four rumen-cannulated dairy cows were used in a 4 £ 4 Latin square design. There were four periods of 21 d each and four treatments utilising flax hulls (1800 g/d) and oil (400 g/d) supplements. The treatments were: (1) oil and hulls administered in the rumen and abomasal infusion of water; (2) oil and hulls administered in the abomasum; (3) oil infused in the abomasum and hulls placed in the rumen; (4) oil placed in the rumen and hulls administered in the abomasum. Samples were collected during the last week of each period and subjected to chemical analysis. The site of supplementation of oil and hulls had no effect on ruminal EL concentration. Supplementing flax oil in the rumen and the abomasum led to similar EL concentrations in urine, plasma and milk. Concentrations of EL were higher in the urine, plasma and milk of cows supplemented with hulls in the rumen than in those placed with hulls in the abomasum. The present study demonstrated that ruminal microbiota play an important role in the metabolism of flax lignans.

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RESUMO.Foi realizada análise bromatológica da casca do grão de soja (CGS), farelo de soja, milho moído e farelo de trigo; ensaio de digestibilidade in vitro da matéria seca (DIVMS) e da parede celular (DIVPC) dos referidos alimentos; e degradabilidade in situ da matéria seca (MS), matéria orgânica (MO) e energia bruta (EB), da CGS moída (CSM) ou peletizada (CSP). Para a determinação da DIVMS e DIVPC, foram realizadas três coletas de líquido ruminal, com intervalos de uma semana. Para a determinação da degradabilidade in situ da MS, MO e EB, foram utilizadas três vacas munidas de fistula ruminal. Os tempos de incubação foram: 3, 6, 12, 24 e 48 horas, sendo que o tempo zero foi realizado no laboratório. Foram determinadas as percentagens de degradação e das degradabilidades efetivas para MS, MO e EB. A partir dos resultados encontrados, conclui-se que a CGS pode ser utilizada como um alimento alternativo nas rações de bovinos. Palavras-chave: composição química, bovinos, degradabilidade in situ, digestibilidade in vitro.ABSTRACT. Nutritional value of soybean hulls, soybean meal, ground corn and wheat meal for cattle. The experiment was divided into three parts: composition analysis of soybean hulls (SH), soybean meal, ground corn and wheat meal; in vitro digestibility of dry matter (IVDDM) and cellular wall (IVDCW) of the feeds mentioned above; in situ degradation of dry matter (ISDDM), organic matter (ISDOM) and gross energy (ISDGE), of milled (MSH) or pelleted (PSH) soybean hulls. Three collections of rumen liquid were undertaken for IVDDM and IVDCW at weekly intervals. Three rumen fistulated cows were utilized for the estimates of ISDDM, ISDOM and ISDGE. Incubation periods were 3, 6, 12, 24, 48 hours, whereas zero time was achieved in the laboratory. Degradation percentages and the percentages of real degradability for dry matter, organic matter and gross energy were reported. Results showed that SH could be used as an alternative food in cattle rations.

Four ruminally lactating Holstein cows averaging 602+/-25 kg of body weight and 64+/-6 d in milk at the beginning of the experiment were randomly assigned to a 4 x 4 Latin square design to determine the effects of feeding whole flaxseed and calcium salts of flaxseed oil on dry matter intake, digestibility, ruminal fermentation, milk production and composition, and milk fatty acid profile. The treatments were a control with no flaxseed products (CON) or a diet (on a dry matter basis) of 4.2% whole flaxseed (FLA), 1.9% calcium salts of flaxseed oil (SAL), or 2.3% whole flaxseed and 0.8% calcium salts of flaxseed oil (MIX). The 4 isonitrogenous and isoenergetic diets were fed for ad libitum intake. Experimental periods consisted of 21 d of diet adaptation and 7 d of data collection and sampling. Dry matter intake, digestibility, milk production, and milk concentrations of protein, lactose, urea N, and total solids did not differ among treatments. Ruminal pH was reduced for cows fed the CON diet compared with those fed the SAL diet. Propionate proportion was higher in ruminal fluid of cows fed CON than in that of those fed SAL, and cows fed the SAL and CON diets had ruminal propionate concentrations similar to those of cows fed the FLA and MIX diets. Butyrate concentration was numerically higher for cows fed the SAL diet compared with those fed the FLA diet. Milk fat concentration was lower for cows fed SAL than for those fed CON, and there was no difference between cows fed CON and those fed FLA and MIX. Milk yields of protein, fat, lactose, and total solids were similar among treatments. Concentrations of cis-9 18:1 and of intermediates of ruminal biohydrogenation of fatty acids such as trans-9 18:1 were higher in milk fat of cows fed SAL and MIX than for those fed the CON diet. Concentration of rumenic acid (cis-9, trans-11 18:2) in milk fat was increased by 63% when feeding SAL compared with FLA. Concentration of alpha-linolenic acid was higher in milk fat of cows fed SAL and MIX than in milk of cows fed CON (75 and 61%, respectively), whereas there was no difference between FLA and CON. Flaxseed products (FLA, SAL, and MIX diets) decreased the n-6 to n-3 fatty acid ratio in milk fat. Results confirm that flax products supplying 0.7 to 1.4% supplemental fat in the diet can slightly improve the nutritive value of milk fat for better human health.

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Aims:  To determine the in vitro conversion of plant lignans from two flax products (hull and seed) into the mammalian lignans, enterolactone and enterodiol, by bovine ruminal and faecal microbiota. Methods and Results:  Flax seeds and hulls were incubated in vitro over a 96‐h time course with ruminal or faecal inoculum. Plant lignans in flax seeds and hulls averaged 9·2 and 32·0 nmol mg−1, respectively. The highest net production of enterodiol at 72 and 96 h of incubation was obtained with flax hulls incubated with faecal microbiota. There was no difference in net production of enterodiol between flax products within the first 24 h of incubation. In general, net production of enterolactone over the 96‐h time course was significantly higher for flax products incubated with ruminal than with faecal microbiota. Net production of enterolactone at 72 and 96 h of incubation was greater for flax hulls than flax seeds. Conclusions:  Results of the present experiment suggest that, of the metabolites studied, the main mammalian lignan metabolite produced from flax hulls and seeds by ruminal microbiota is enterolactone while faecal microbiota leads mainly to the net production of enterodiol. Significance and Impact of the Study:  This research will improve the understanding of the metabolic pathway of mammalian lignans in dairy cows, in order to enable targeted manipulation of their quantities in milk.

The effects of flax meal (FM) on the activity of antioxidant enzymes (superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (CAT)) in the blood, mammary tissue and ruminal fluid, and oxidative stress indicators (thiobarbituric acid-reactive substances (TBARS) and 1,1-diphenyl-2-picrylhydrazyl-scavenging activity) in the milk, plasma and ruminal fluid of dairy cows were determined. The mRNA abundance of the antioxidant enzymes and oxidative stress-related genes was assessed in mammary tissue. A total of eight Holstein cows were used in a double 4 £ 4 Latin square design. There were four treatments in the diet: control with no FM (CON) or 5 % FM (5FM), 10 % FM (10FM) and 15 % FM (15FM). There was an interaction between treatment and time for plasma GPx and CAT activities. Cows supplemented with FM had a linear reduction in TBARS at 2 h after feeding, and there was no treatment effect at 0, 4 and 6 h after feeding. TBARS production decreased in the milk of cows fed the 5FM and 10FM diets. There was a linear increase in nuclear factor (erythroid-derived 2)-like 2 (NFE2L2) mRNA abundance in mammary tissue with FM supplementation. A linear trend for increased mRNA abundance of the CAT gene was observed with higher concentrations of FM. The mRNA abundance of CAT, GPx1, GPx3, SOD1, SOD2, SOD3 and nuclear factor of k light polypeptide gene enhancer in B-cells (NFKB) genes was not affected by the treatment. These findings suggest that FM supplementation can improve the oxidative status of Holstein cows as suggested by decreased TBARS production in ruminal fluid 2 h post-feeding and increased NFE2L2/nuclear factor-E2-related factor 2 (Nrf2) mRNA abundance in mammary tissue.Key words: Catalase: 1,1-Diphenyl-2-picrylhydrazyl: Glutathione peroxidase: Superoxide dismutase: Thiobarbituric acid-reactive substances High-yielding dairy cows are prone to oxidative stress due to intensive metabolic demands for maintenance and production. This condition can be exacerbated under certain environmental, physiological and dietary factors (1,2) . Although lipid supplementation of ruminant diets with n-3 PUFA is a strategy to improve the nutritional quality of dairy products, this approach could increase the risk of plasma peroxidation with deleterious consequences on animal health (3) . Peroxidation results from oxidative metabolism, which is essential for the survival of cells. However, a side effect of this phenomenon is the production of free radicals and other reactive oxygen species that can cause oxidative damage (2) . Normally, the body is protected by a wide range of antioxidant systems working in concert with intracellular enzymes such as superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (CAT), which remove superoxides and peroxides before they react with metal catalysts to form more reactive compounds (4) . Lactation performance and antioxidant status of cows fed oxidised fat are enhanced when antioxidants are included in the diet (5) , which may be due to the scavenging of peroxides a...