The lack of protective effects of tea supplementation on liver and jejunal epithelium in adult rats exposed to cadmium and lead

Bioactive compounds, antibiotics and heavy metals: effects on the intestinal structure and microbiome of monogastric animals – a non-systematic review

The intestinal structure and gut microbiota are essential for the animals‘ health. Chemical components taken with food provide the right environment for a specific microbiome which, together with its metabolites and the products of digestion, create an environment, which in turn is affects the population size of specific bacteria. Disturbances in the composition of the gut microbiota can be a reason for the malformation of guts, which has a decisive impact on the animal‘ health. This review aimed to analyse scientific literature, published over the past 20 years, concerning the effect of nutritional factors on gut health, determined by the intestinal structure and microbiota of monogastric animals. Several topics have been investigated: bioactive compounds (probiotics, prebiotics, organic acids, and herbal active substances), antibiotics and heavy metals (essentaial minerals and toxic heavy metals).

Effect of Raw Chickpea in the Broiler Chicken Diet on Intestinal Histomorphology and Intestinal Microbial Populations

The aim of the study was to determine the effect of partial replacement of SBM protein with CPR-derived protein in the broiler rearing period from 22 to 42 days of age on the intestinal histomorphology and the composition of the intestinal microbial population. Male broiler chicks aged 1 day were assigned to two groups with different nutrition schemes (n = 100 in each, 5 cages of 20 chicks in each). The chickens were reared for 42 days. All birds were fed isonitrogenous and isoenergetic diets: starter (1 to 21 d), grower (22 to 35 d), and finisher (36 to 42 d). From rearing day 22, different diets were provided to the birds: the SBM group received feed with 100% soybean meal protein, and the diet of the CPR group the protein originated from soybean meal was replaced by 50% chickpea protein. The study results indicated a significant impact of the inclusion of CPR in the diet on the basic intestinal structures (thickness of myenteron: submucosa, jejunum and duodenum mucosa, and jejunum transversal lamina). The addition of CPR led to shortening of intestinal villi, an increase in villus thickness, and reduced intestine absorptive surface in the duodenum and jejunum. The CPR group exhibited a significantly lower villus length-to-crypt depth ratio in the jejunum (p < 0.001). The inclusion of chickpeas in the diet increased the total count of mesophilic bacteria and coliforms in the intestinal contents (p < 0.05). In summary, it has been demonstrated that the inclusion of CPR in the diet induced considerable disturbances in metabolism and intestinal structure. Although CPR is a cheap protein source, its use in poultry diet does not ensure development of the intestinal structure comparable to that in the case of an SBM-only diet.

Distinct fatty acid redistribution and textural changes in the brain tissue upon the static magnetic field exposure

We observed different outcomes upon the subacute exposure to the 128 mT highly homogeneous static magnetic field (SMF) when its orientation was (i) aligned with the vertical component of the geomagnetic field; (ii) in the opposite direction. We employed the fatty acids (FA) composition and digital image analyses (DIA) to provide insights into the underlying processes and examine the possible weak SMF effects. Swiss-Webster male mice were whole-body exposed for 1 h/day over five days. Brain tissue's thin liquid chromatography resulted in brain FA composition, indicating a possible sequence of changes due to the SMF exposure. Quantitative DIA accurately assessed different image parameters. Delicate textural changes were revealed in the group where pathohistological or biochemical alterations have not been detected. DIA-based biological markers seem to be very promising for studying delicate tissue changes, which results from the high sensitivity and wide availability of DIA.

Antagonistic effect of selenium on lead-induced neutrophil apoptosis in chickens via miR-16-5p targeting of PiK3R1 and IGF1R

Environmental contamination by heavy metals, such as lead (Pb), can lead to severe immune dysfunction. MicroRNAs (miRNAs) are involved in regulating immunity. Whether Pb can regulate neutrophil apoptosis through miRNA, and whether selenium (Se) can antagonize this response are still unknown. We treated neutrophils with 12.5 μM (CH₃OO)₂Pb and 1 μM Na₂SeO₃ for 3 h, after which apoptosis was evaluated using acrideine orange/ethidium bromide (AO/EB) dual fluorescent staining and flow cytometry. The results showed that neutrophil apoptosis was significantly increased following Pb exposure, and that this response was prevented upon Se addition. Pb up-regulates miR-16-5p and leads to the subsequent down-regulation of the target genes phosphoinositide-3-kinase regulatory subunit 1 (PiK3R1), insulin-like growth factor 1 receptor (IGF1R), and phosphatidylinositol 3 kinase (Pi3K)-protein kinase B (AKT), followed by activation of the tumor protein P53 (P53)-B-cell lymphoma-2 (Bcl-2)/Bcl-2-Associated X protein (Bax)-cytochrome c (Cytc)-Caspase 9 (mitochondrial apoptotic pathway) and the tumor necrosis factor receptor superfamily member 6 (Fas)-Fas-associated death domain protein (Fadd)-Caspase 8 (death receptor pathway). Pb also triggered oxidative stress and indirectly activated the mitochondrial apoptotic pathway. We conclude that miR-16-5p plays a key role in the apoptosis of neutrophils exposed to Pb by down-regulating the expression of PiK3R1 and IGFR1, thereby activating the mitochondrial apoptotic pathway and death receptor pathway. Se can prevent Pb-induced apoptosis.

Bacillus coagulans R11 maintained intestinal villus health and decreased intestinal injury in lead-exposed mice by regulating the intestinal microbiota and influenced the function of faecal microRNAs

Lead contamination is an environmental problem, especially in developing countries; due to the nondegradable characteristics of lead, it is easily deposited in human and animal bodies by the food chain. Probiotics are regarded as a good tool to remove lead ions in the intestine and maintain gut health conditions, but previous studies failed to elucidate the relationship among probiotics, the host and the gut microbiota. In the present study, B. coagulans R11 was employed as the "lead removal tool" in lead-exposed mouse, and the effects of B. coagulans R11 on intestinal cells, the microbiota and faecal microRNAs were tested. The results indicated that B. coagulans R11 had no negative effects on mouse intestine model cells and helped keep cells in a normal proliferation ratio and reduce the reactive oxygen species and apoptosis ratios under lead exposure conditions. An in vivo mouse experiment also showed that B. coagulans R11 feeding could reduce the intestinal villi damage caused by lead through adjusting the microbiota structure and function, such as increasing the genus abundance of Akkermansia and Alistipes, decreasing the genus abundance of Alloprevotella, Lachnospiraceae, Parabacteroides and Ruminiclostridium, and keeping the protein dltD existing. Host faecal microRNAs may be influenced by lead and B. coagulans R11, which may change the microbiota structure. Thus, B. coagulans R11 has the potential to be developed and considered as the probiotic that protects the host gut against villi damage and gut microbiota structure and function disorders during lead exposure.

Intestinal mucosa develops in a sex-dependent manner in Japanese quail (Coturnix japonica) fed Saccharomyces cerevisiae

1. The aim of study was to investigate whether the impact of the yeast Saccharomyces cerevisiae on the histological structure of the intestine, innervation of the small intestine wall, and basal biochemical serum parameters in Japanese quail was sex dependent. 2. One-day-old healthy male and female Japanese quail were fed either a basal diet containing no yeast (control group) or the basal diet plus 1.5% (15 g/kg of diet) of yeast (S. cerevisiae inactivated by drying). Samples from the duodenum and jejunum were taken from each bird at the age of 42 days. Blood samples were collected at this age and the concentrations of glucose, total protein, creatinine, uric acid, lipid profile (total cholesterol, low density lipoproteins (LDL), high density lipoproteins (HDL) and triacylglycerols (TG)), alanine aminotransferase (ALAT), aspartate aminotransferase (AspAT), lactate dehydrogenase (LDH), amylase (AMY), calcium, phosphorus and iron were determined. 3. Female quail fed diets supplemented with yeast had significantly lower total cholesterol and amylase activity than the control females. The concentration of HDL was higher in the male quail than in the females, irrespective of the treatment. An opposite effect was observed in LDL. The diet treatments influenced the activity of AspAT, which was significantly less in the male quail fed diets with 1.5% yeast. 4. Supplementation with S. cerevisiae increased the myenteron, submucosa and mucosa thickness, villus length and thickness and size of absorptive surface, while the number of villi and enterocytes were decreased in the duodenum in males. Female quail showed an increased absorptive surface in the jejunum. The Meissner (submucosal) plexuses were influenced by the feeding and sex to a greater extent than the Auerbach plexus (in the muscularis propria). 5. The results demonstrated that S. cerevisiae (1.5%) in the diet caused significant positive effects in Japanese quail, exerting an effect on the morphology of the small intestine in a sex-dependent manner.

White Tea is More Effective in Preservation of Bone Loss in Adult Rats Co-Exposed to Lead and Cadmium Compared to Black, Red or Green Tea

Lead (Pb) and cadmium (Cd) are toxic metals occurring commonly in the human environment that show mutagenic, genotoxic and carcinogenic effects. Dietary components could prevent heavy metals intoxication by reducing their accumulation in the body. The purpose of the study was to check possible protective effect of regular consumption of white, black, red, or green tea on bone metabolism during long-term exposure to Pb and Cd in adult rats. The 12 week-long exposure to Pb and Cd (50 mg Pb and 7 mg Cd/kg of the diet) in a rat model was studied. Twelve-week-old adult male Wistar rats were randomly divided into a negative control group (Pb and Cd exposure without tea), a control (without Pb and Cd and teas), and groups co-exposed to Pb and Cd and supplemented with green, red, black, or white tea (n=12 each group). The experiment lasted for 12 weeks. The co-exposure to Pb and Cd led to the increase of bone resorption depending on the tea treatment, which was confirmed by the mechanical testing and histomorphometrical examination of cancellous bone. Pb and Cd influenced mechanical strength, reduced the densitometric and geometric parameters and the thickness of growth plate and articular cartilages. Concluding, white tea exerted the best protective effect on bone tissue and hyaline cartilage against heavy metal action.

The influence of dietary replacement of soybean meal with high-tannin faba beans on gut-bone axis and metabolic response in broiler chickens

Faba bean (FB) seeds can be a good protein-energy component in animal feed. However, the presence of anti-nutritional substances is a negative feature of FB seeds. The aim of this study was to examine the influence of different levels of unprocessed FB seeds in feed on the gut-bone axis and metabolic profile in broilers. Ninety six, 1-day-old Ross 308 broiler chickens were randomly selected to one of the 3 dietary treatments (32 chickens in each, divided into 8 pens with 4 birds per each pen): the control group fed standard diet with soybean meal and without FB seeds, group I fed 8/15% (starter/grower) of high-tannin FB seeds, and group II fed 16/22% of high-tannin FB seeds. Bone mechanical examination, hematological and serum biochemical analysis as well histomorphometry of small intestine and liver tissue were performed. The intake of high-tannin FB seeds, irrespective of their amount, did not alter the bone geometric, mechanical and densitometric parameters nor influenced basal hematological parameters, however it resulted in: decreased serum concentration of total cholesterol and calcium; a reduced longitudinal myenteron of small intestine; increased mucosa and villus epithelium thickness, villus length, thickness and absorptive surface in duodenum; increased number of active crypts in jejunum; unchanged collagen area, intercellular space, and total cell number in the liver; decreased number of multinuclear hepatocyte cells. Moreover, the livers of birds fed the higher dose of high-tannin FB seeds had lymphocytic infiltrates in portal tracts and sinusoids. Feeding of unprocessed high-tannin FB seeds exerted an influence on the gastrointestinal tract by increased absorptive surface. In conclusion, the dietary inclusion of unprocessed high-tannin FB seeds had no negative effects on broiler growth, tibial bone mechanical properties and intestinal characteristics. Unprocessed high-tannin FB seeds may be used in broiler diets, but their dietary levels should not be higher than those discussed.

Chloramphenicol-Induced Alterations in the Liver and Small Intestine Epithelium in Pigs

An effect of the exposure to chloramphenicol (CAP) at doses used therapeutically was studied in pigs at the age of slaughter. Pigs were treated with CAP intramuscularly (20 mg/kg b.w. two times every 24 hours). Histomorphometrical and immunohistochemical analyses of small intestine and liver were done. CAP increased the thickness of myenteron and submucosa, and the length of villi; decreased the depth of crypts in the duodenum and jejunum. CAP influenced the Auerbach plexus. A decrease in cell proliferation, an increase in the number of apoptotic cells and T lymphocytes in the CAP-treated pigs were observed. CAP induces hepatotoxicity, neurotoxicity and disturbed intestinal epithelium. It can be concluded that short exposure of pigs to CAP at doses used therapeutically results in disturbed digestion and absorption process in the intestine.

Gut-bone axis response to dietary replacement of soybean meal with raw low-tannin faba bean seeds in broiler chickens

It seems that faba bean (FB) seeds could be a good protein-energy component in animal feed, but the presence of anti-nutritional substances limits their use as a substitute of soybean meal. The aim of the study was to examine the influence of different concentrations of raw, low-tannin, FB seeds on the gut-bone axis in Ross 308 broilers. One-day old chickens were randomly subjected to one of the 3 dietary treatments: the control group was fed standard diet based on soybean meal and without FB seeds, and two groups were fed 8%/15% and 16%/22% of raw low-tannin FB seeds in the starter and grower, respectively. On the 35th day, hematological and serum biochemical analyses as well histomorphometry of the small intestine and liver tissue and bone mechanical tests were performed. The diet type had no effect on the body weight gain and feed conversion ratio. However, the basal intestinal structures were significantly reduced in birds fed the lower concentration of FB. The enlargement of nerve plexuses was dependent on the concentration used in the diet and, additionally, on the kind of plexus and location in the intestinal tract. The liver was characterized by an increase in non-hepatocytes. There was no influence of the low-tannin FB seeds on most of the analyzed serum parameters in the 35-day-old broiler chickens, except the decreased concentration of total cholesterol and Ca in both experimental groups, triglycerides in group I, and P and uric acid in group II. Furthermore, the increasing concentration of the dietary low-tannin FB did not influence the activities of AspAT (except the group fed the higher amount of FB), ALAT, and LDH. The broiler chickens had no visible leg lesions and no problem in the locomotor function, but the tibiae were lighter mainly in birds fed the higher concentration of FB seeds. Geometric analysis revealed reduction of the cross section area and wall thickness, indicating a decline in the bone midshaft, which influenced the densitometric parameters and the results of mechanical tests. In conclusion, the dietary inclusion of raw low-tannin FB seeds had no negative effects on broiler growth, but disturbed the intestine structure and tibia characteristics. Therefore, all these negative effects necessitate additional examinations before inclusion of raw low-tannin FB seed into poultry diet.

Selenium Antagonizes the Lead-Induced Apoptosis of Chicken Splenic Lymphocytes In Vitro by Activating the PI3K/Akt Pathway

Lead (Pb) pollution has become one of the most serious global ecological problems. In animals, Pb ingestion induces apoptosis in many tissues. However, the mechanisms by which Pb induces apoptosis in chicken splenic lymphocytes in vitro via the PI3K/Akt pathway and the antagonistic effect of selenium (Se) on Pb remain unclear. Therefore, we established the in vitro Se-Pb interaction model in chicken splenic lymphocytes and examined the frequency of apoptotic cells using acridine orange/ethidium bromide (AO/EB) staining and the TdT-mediated dUTP nick end labeling assay and detected the activities of glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase (CAT), as well as the levels of malondialdehyde (MDA) and reactive oxygen species (ROS). The expression of PI3K/Akt pathway-related genes was also examined by qRT-PCR and western blotting. MDA and ROS levels were markedly increased, whereas the activities of GPx, SOD, and CAT were significantly decreased; the levels of the PI3K, Akt, and Bcl-2 messenger RNAs (mRNAs) and proteins were decreased; and the levels of the p53, Bax, cytochrome c (Cyt-c), caspase 3, and caspase 9 mRNAs and proteins were increased in the Pb group. In addition, the frequency of apoptotic cells was also significantly increased by the Pb treatment. However, Se supplementation during Pb exposure observably attenuated Pb-induced apoptosis; increased the levels of the PI3K, Akt, and Bcl-2 mRNAs and proteins; and decrease the levels of the p53, Bax, Cyt-c, caspase 3, and caspase 9 mRNAs and proteins in the chicken spleen. In conclusion, Pb exposure causes oxidative stress, inhibits the PI3K/Akt pathway, and subsequently induces apoptosis in chicken splenic lymphocytes in vitro, and these effects are partially attenuated by Se supplementation. To the best of our knowledge, this study is the first to reveal the antagonistic effect of Se on Pb-induced apoptosis of chicken splenic lymphocytes in vitro via the activation of the PI3K/Akt pathway.

Protective effects of proanthocyanidins against cadmium-induced testicular injury through the modification of Nrf2-Keap1 signal path in rats

The purpose of this study was to evaluate the potential chemoprotective effects of proanthocyanidins (PAs) against cadmium (Cd)-induced oxidative damage of testes via Nrf2-Keap1 signal pathway in rats. Briefly, by using biochemical histological analysis, as well as the real time PCR and western blot approach, oxidative damage in rat testicular tissue was observed after exposure to Cd. In addition, significant down-regulations of mRNA and protein levels of nuclear erythroid 2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1), γ-glutamyl cysteine synthetase (γ-GCS), glutathione peroxidase (GSH-Px) and quinone oxidoreductase 1 (NQO1), as well as a significant up-regulation of Kelch sample related protein-1 (Keap1) levels in testicular tissue were observed after Cd exposure. Notably, these alterations were reverted back to near normalcy in Cd+PAs group rats. In conclusion, PAs exhibited a significant chemopreventive potential against Cd-induced testicular oxidative damage in rats, possibly through the modification of Nrf2-Keap1 signal path.

The effect of tannic acid on bone mechanical and geometric properties, bone density, and trabecular histomorphometry as well as the morphology of articular and growth cartilages in rats co-exposed to cadmium and lead is dose dependent

Cadmium (Cd) and lead (Pb) are toxic elements that accumulate to the largest extent in bones. Rats were used to investigate whether tannic acid (TA; 0.5%, 1.0%, 1.5%. 2.0%, or 2.5%) would have a protective effect on the structure and properties of bones in the case of exposure to Cd and Pb (diet: 7 mg Cd/kg and 50 mg Pb/kg) for 6 weeks. The effects of administration of TA in Cd- and Pb-poisoned rats on bone characteristics and the morphology of articular and growth cartilages were determined. All the rats administered Cd and Pb had an enhanced Cd and Pb concentration in blood plasma and bone and reduced bone Ca content irrespective of the TA administration. Cd and Pb alone reduced the mechanical endurance and histomorphometric parameters of trabecular bone and the thickness of the growth plate and articular cartilage. Tannic acid improved cancellous bone parameters in the rat exposed to Cd and Pb. A diet rich in TA improved articular cartilage constituents in heavy metal-poisoned rats. These results suggest that alimentary TA supplementation can counteract in a dose-dependent manner some of the destructive changes evoked by Cd and Pb possibly by reducing the exposure.

Synergistic effect of aluminum and ionizing radiation upon ultrastructure, oxidative stress and apoptotic alterations in Paneth cells of rat intestine

Environmental and occupational exposure to aluminum along with ionizing radiation results in serious health problems. This study was planned to investigate the impact of oxidative stress provoked by exposure to ionizing radiation with aluminum administration upon cellular ultra structure and apoptotic changes in Paneth cells of rat small intestine . Animals received daily aluminum chloride by gastric gavage at a dose 0.5 mg/Kg BW for 4 weeks. Whole body gamma irradiation was applied at a dose 2 Gy/week up to 8 Gy. Ileum malondialdehyde, advanced oxidative protein products, protein carbonyl and tumor necrosis factor-alpha were assessed as biomarkers of lipid peroxidation, protein oxidation and inflammation respectively along with superoxide dismutase, catalase, and glutathione peroxidase activities as enzymatic antioxidants. Moreover, analyses of cell cycle division and apoptotic changes were evaluated by flow cytometry. Intestinal cellular ultra structure was investigated using transmission electron microscope.Oxidative and inflammatory stresses assessment in the ileum of rats revealed that aluminum and ionizing radiation exposures exhibited a significant effect upon the increase in oxidative stress biomarkers along with the inflammatory marker tumor necrosis factor-α accompanied by a significant decreases in the antioxidant enzyme activities. Flow cytometric analyses showed significant alterations in the percentage of cells during cell cycle division phases along with significant increase in apoptotic cells. Ultra structurally, intestinal cellular alterations with marked injury in Paneth cells at the sites of bacterial translocation in the crypt of lumens were recorded. The results of this study have clearly showed that aluminum and ionizing radiation exposures induced apoptosis with oxidative and inflammatory disturbance in the Paneth cells of rat intestine, which appeared to play a major role in the pathogenesis of cellular damage. Furthermore, the interaction of these two intestinal toxic routes was found to be synergistic.

Hematological, biochemical, and toxicopathic effects of subchronic acetamiprid toxicity in Wistar rats

Acetamiprid is one of the most widely used neonicotinoids. This study investigates toxic effects of repeated oral administration of three doses of acetamiprid (1/20, 1/10, and 1/5 of LD₅₀) during 60 days. For this, male Wistar rats were divided into four different groups. Hematological, biochemical, and toxicopathic effects of acetamiprid were evaluated. According to the results, a significant decrease in the body weight gain at the highest dose 1/5 of LD₅₀ of acetamiprid was noticed. An increase in the relative liver weight was also observed at this dose level. The hematological constituents were affected. A significant decrease in RBC, HGB, and HCT in rats treated with higher doses of acetamiprid (1/10 and 1/5 of LD₅₀) was noted. However, a significant increase in WBC and PLT were observed at the same doses. Furthermore, acetamiprid induced liver toxicity measured by the increased activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphates (ALPs), and lactate dehydrogenase (LDH) which may be due to the loss of hepatic membrane architecture and hepatocellular damage. In addition, exposure to acetamiprid resulted in a significant decrease in the levels of superoxide dismutase and catalase activities (p ≤ 0.01) with concomitant increase in lipid peroxidation in rat liver. These findings highlight the subchronic hepatotoxicity of acetamiprid.

Cerebral ganglion ultrastructure and differential proteins revealed using proteomics in the aplysiid (Notarcus leachii cirrosus Stimpson) under cadmium and lead stress

Cadmium (Cd) and lead (Pb) are both highly toxic metals in environments. However the toxicological mechanism is not clear. In this study, the aplysiid, Notarcus leachii cirrosus Stimpson (NLCS) was subjected to Cd (NLCS-Cd) or Pb (NLCS-Pb). The cerebral ganglion of NLCS was investigated with a transmission electron microscope. Next the differential proteins were separated and identified using proteomic approaches. Eighteen protein spots in NLCS-Cd and seventeen protein spots in NLCS-Pb were observed to be significantly changed. These protein spots were further excised in gels and identified. A hypothetical pathway was drawn to show the correlation between the partially identified proteins. The results indicated that damage to the cerebral ganglion was follows: cell apoptosis, lysosomes proliferation, cytoskeleton disruption, and oxidative stress. These phenomena and data indicated potential biomarkers for evaluating the contamination levels of Cd and Pb. This study provided positive insights into the mechanisms of Cd and Pb toxicity.

Alteration in bone geometric and mechanical properties, histomorphometrical parameters of trabecular bone, articular cartilage, and growth plate in adolescent rats after chronic co-exposure to cadmium and lead in the case of supplementation with green, black, red and white tea

Adolescent male Wistar rats were used to check whether regular consumption of black, red, white, or green tea would have a protective effect on femur development during 12-week exposure to Cd and Pb (7mg Cd and 50mg Pb in 1kg of the diet). The animals were randomly divided (n=12) into a positive control (without Cd, Pb and teas), a negative control group (Cd and Pb), and groups supplemented additionally with green (GT), black (BT), red (RT), and white tea (WT). Heavy metals reduced the geometric and densitometric parameters and the total thickness of articular cartilage irrespective of tea administration and influenced mechanical endurance, growth plate thickness, and trabecular histomorphometry depending on the tea type. It is difficult to indicate which tea has the best protective effects on bone and hyaline cartilage against heavy metal action.

Systemic Absorption of Catechins after Intraruminal or Intraduodenal Application of a Green Tea Extract in Cows

Green tea catechins have various potential health benefits in humans including anti-inflammatory, anti-oxidative and hepato-protective effects. If present in the circulation, they might have similar effects in ruminants, which are exposed to oxidative stress and fatty liver disease such as dairy cows during the periparturient phase. However, the bioavailability of a substance is a prerequisite for any post absorptive effect in vivo. This study aimed to investigate the appearance of catechins from a green tea extract (GTE) in cattle plasma after intraruminal and intraduodenal administration because absorption is of major importance regarding the bioavailability of catechins. The studies were performed in 5 rumen-fistulated non-lactating heifers and 6 duodenally fistulated lactating dairy cows, respectively, equipped with indwelling catheters placed in a jugular vein. The GTE was applied intraruminally (10 and 50 mg/kg BW, heifers) or duodenally (10, 20 and 30 mg/kg BW, dairy cows) in a cross-over design with a 2 d washout period between different dosages. Blood samples were drawn following the GTE administration at various pre-defined time intervals. The concentration of the major GTE catechins (gallocatechin, epigallocatechin, catechin, epicatechin, epigallocatechin-gallate, epicatechin-gallate) in plasma samples were analysed by HPLC with electrochemical detection. Irrespective of the dose, almost none of the catechins originally contained in the GTE were detected in plasma samples after intraruminal application. In contrast, intraduodenal administration of GTE resulted in increased plasma concentrations of epicatechin, epigallocatechin, epigallocatechin gallate in a dose-dependent manner. Thus, we can conclude that intraruminally or orally administered catechins are intensively metabolized by ruminal microorganisms.