Effects of the supplementation of plant-based formulations on microbial fermentation and predicted metabolic function in vitro.

This study aimed at testing the effects of three different formulations of feed supplements based on three different combinations of plant derived alkaloids, prebiotics, tannins, vitamins and minerals on rumen fermentation and the microbiome in vitro. A Rusitec experiment was conducted in 2 identical runs using a complete randomized design with 3 replicates per treatment resulting in total of 6 treatment combinations (n = 6). Each run lasted 12 d with sampling occurring in the last 5 d. Diets were a standard dairy ration (60:40; concentrate:forage) supplemented with one of 3 different plant-based combinations (PI, PII, and PIII) at a level of 100 mg/l and a non-supplemented control (basal diet, control). Microbial DNA samples were taken on the last day of each run and the 16S rRNA target gene sequenced using Illumina MiSeq technology. The supplementations had no effect on the pH, methane and carbon dioxide production. However, both total SCFA (P = 0.08) and molar concentrations of acetate (P = 0.06) tended to be increased in the treatment groups in comparison to control, with PII having the highest overall values (102.7 mmol/L and 43.3 mmol/L, respectively). Alpha diversity indices Shannon, Simpson and Chao1 showed no effect of supplementations or combinations. The addition of PII increased the relative abundance of Bacteroidetes compared to all other treatments (P = 0.05). Supplementation with plant-based combinations reduced the relative abundance of Pyramidobacter from the family Dethiosulfovibrionaceae in comparison with the control diet (P = 0.05). Evaluation of predicted gene function through PICRUSt analysis showed variation in predicted cellular function and metabolism between bacterial communities supplemented with plant-based combinations compared to the control diet. This shows that the addition of plant-based combinations can have the potential to modulate the metabolic function of rumen microbes, and likely the production of small-sized rumen metabolites, without disrupting the rumen microbial community structure and diversity.

Bioavailability of Quercetin from Onion Extracts after Intraruminal Application in Cows.

The aim of the present study was to investigate the bioavailability of quercetin from onion bulb (OB) and onion skin (OS) extracts in ruminants. Three non-lactating cows equipped with a permanent rumen fistula intraruminally received equimolar amounts of quercetin as either aglycone, rutin, or OB or OS extract, respectively, at a dose of 50 mg of quercetin equivalents/kg of body weight. Blood samples were drawn before and frequently within the 24 h period after application of the respective substance. Quercetin and quercetin metabolites with an intact flavonol structure (kaempferol, isorhamnetin, and tamarixetin) were analyzed in plasma samples by high-performance liquid chromatography with fluorescence detection. All quercetin sources administered resulted in a fast increase of the plasma concentrations of quercetin and total flavonols (sum of quercetin and its metabolites), followed by a rapid decline, whereby significant higher concentrations occurred with OB extract and rutin compared to quercetin aglycone and OS extract, respectively. The results clearly demonstrate a higher systemic availability of quercetin from OB extract and rutin. Taken together, OB extract with a high content of quercetin glucosides is an interesting source for the application of quercetin to ruminants.

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.