Impact of variation in structure of condensed tannins from sainfoin (Onobrychis viciifolia) on in vitro ruminal methan production and fermentation characteristics

Our study investigated the effects of condensed tannins (CT) on rumen in vitro methane (CH4) production and fermentation characteristics by incubating lucerne in buffered rumen fluid in combination with different CT extracts at 0 (control), 40, 80 and 120 g CT/kg of substrate DM. Condensed tannins were extracted from four sainfoin accessions: Rees ‘A’, CPI63763, Cotswold Common and CPI63767. Gas production (GP) was measured using a fully automated GP apparatus with CH4 measured at distinct time points. Condensed tannins differed substantially in terms of polymer size and varied from 13 (Rees ‘A’) to 73 (CPI63767) mean degree of polymerization, but had relatively similar characteristics in terms of CT content, procyanidin: prodelphinidin (PC: PD) and cis:trans ratios. Compared to control, addition of CT from CPI63767 and CPI63763 at 80 and 120 g CT/kg of substrate DM reduced CH4 by 43% and 65%, and by 23% and 57%, respectively, after 24-h incubation. Similarly, CT from Rees ‘A’ and Cotswold Common reduced CH4 by 26% and 46%, and by 28% and 46% respectively. Addition of increasing level of CT linearly reduced the maximum rates of GP and CH4 production, and the estimated in vitro organic matter digestibility. There was a negative linear and quadratic (p < 0.01) relation between CT concentration and total volatile fatty acid (VFA) production. Inclusion of 80 and 120 g CT/kg of substrate DM reduced (p < 0.001) branched-chain VFA production and acetate: propionate ratio and was lowest for CPI63767. A decrease in proteolytic activity as indirectly shown by a change in VFA composition favouring a shift towards propionate and reduction in branched-chain VFA production varied with type of CT and was highest for CPI63767. In conclusion, these results suggest that tannin polymer size is an important factor affecting in vitro CH4 production which may be linked to the CT interaction with dietary substrate or microbial cells

Facile purification of milligram to gram quantities of condensed tannins according to mean degree of polymerization and flavan-3-ol subunit composition

Unambiguous investigation of condensed tannin (CT) structure-activity relationships in biological systems requires well-characterized, high-purity CTs. Sephadex LH-20 and Toyopearl HW-50F resins were compared for separating CTs from acetone/water extracts and column fractions analyzed for flavan-3-ol subunits, mean degree of polymerization (mDP) and purity. Toyopearl HW-50F generated fractions with higher mDP values and better separation of procyanidins (PC) and prodelphinidins (PD) but required a pre-purification step, more time for large scale purifications and gave poorer recoveries. Therefore, two gradient elution schemes were developed for CT purification on Sephadex LH-20 providing 146 - 2000 mg/fraction. Fractions were analyzed by thiolysis and NMR spectroscopy. In general, PC/PD ratios decreased and mDP increased during elution. 1H NMR spectroscopy served as a rapid screening tool to qualitatively determine CT enrichment and carbohydrate impurities present, guiding fractionation towards re-purification or 1H-13C HSQC NMR spectroscopy and thiolysis. These protocols provide options for preparing highly pure CT samples

The effects of tannin-containing ground pine bark diet upon nutrient digestion, nitrogen balance, and mineral retention in meat goats

Background Pine bark is a rich source of phytochemical compounds including tannins, phenolic acids, anthocyanins, and fatty acids. These phytochemicals have potential to significantly impact on animal health and animal production. The goal of this work is to measure the effects of tannins in ground pine bark as a partial feed replacement on feed intake, dietary apparent digestibility, nitrogen balance, and mineral retention in meat goats. Results Eighteen Kiko cross goats (initial BW = 31.8 ± 1.49 kg) were randomly assigned to three treatment groups (n = 6). Dietary treatments were tested: control (0 % pine bark powder (PB) and 30 % wheat straw (WS)); 15 % PB and 15 % WS, and 30 % PB and 0 % WS. Although dry matter (DM) intake and digestibility were not affected (P > 0.10) by feeding PB, neutral detergent fiber (linear; P = 0.01), acid detergent fiber (linear; P = 0.001) and lignin digestibility (linear; P = 0.01) decreased, and crude protein (CP) digestibility tended to decrease (P = 0.09) as PB increased in the diet, apparent retention of Ca (P = 0.09), P (P = 0.03), Mg (P = 0.01), Mn (P = 0.01), Zn (P = 0.01) and Fe (P = 0.09) also increased linearly. Nitrogen intake and fecal N excretion were not affected (P > 0.05) by addition of PB in the diet, but N balance in the body was quadratically increased (P < 0.01) in the 15 % PB diet compared to other diets. This may be due to more rumen escape protein and less excreted N in the urine with the 15 % PB diet. The study showed that a moderate level of tannin-containing pine bark supplementation could improve gastrointestinal nitrogen balance with the aim of improving animal performance. Conclusion These results suggest that tannin-containing PB has negative impact on fiber, lignin, and protein digestibility, but positively impacted on N-balance

Analysis of sainfoin (Onobrychis viciifolia) proanthocyanidins by complementary and newly developed techniques

Sainfoin proanthocyanidins (PAs) are complex mixtures of homo- and hetero- polymers consisting of B-type procyanidins and prodelphinidins. Direct analysis by thiolytic degradation revealed a wide range of PA contents and compositions within the HealthyHay germplasm collection (46 accessions). PA contents varied from 0.57% to 2.80% (g PAl100g freeze-dried samples). PAs polymer size ranged from 12 to 84 flavan-3-ol units in terms of their mean degree of polymerisation. Prodelphinidin/procyanidin ratios ranged from 53/47 to 95/5 and trans/cis ratios varied from 12/88 to 34/66. Purified PAs fractions from 4 selected accessions showed a positive correlation between polymer size and prodelphinidin content within each accession (R2 from 0.69 to 0.92). Careful selection of MALDI-TOF MS matrices and analytical conditions made it possible to detect PAs up to 12 subunits and also ion signals that could be assigned to A-type and rarely reported glycosylated A-type PAs. For detecting and confirming the polymer size of underivatised higher molecular weight PAs a new HPLC-GPC technique consisting in a single calibration curve for galloyl glucoses, ellagitannins and PAs was developed. Peak-average molecular weights of sainfoin PA fractions were overestimated by 42.0% at 2436 Dalton and underestimated by 13.9% at 8318 Dalton. Number-average molecular weights were overestimated by 30.0% and underestimated by 25.8%, respectively. Cluster analysis of the HealthyHay germplasm collection revealed that accessions clustered into two main clusters, Western Europe and Eastern Europe/Asia, and that accessions from Armenia, Canada and USA clustered into another group. This seems to be in agreement with the strong links between geographic origin and accession performance found in the HealthyHay sainfoin germplasm. This research made significant contributions to the fields of PA analysis and germplasm screening in terms of novel analytical techniques for determining the average molecular weight distribution, content, subunit composition and linkages, purification and fractionation of proanthocyanidins in sainfoin.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Mean flow structure in thermal convection in a cylindrical cell of aspect ratio one half

In this paper we propose a simple model that, by comparing different time scales, allows a prediction for the mean flow structure and its dynamics in confined thermal convection in a cylindrical cell of aspect ratio (diameter over cell height) $\Gamma\,{=}\,1/2$. It is shown that the break-up of the mean elongated recirculation into two counter-rotating unity-aspect-ratio rolls, sometimes referred to as flow bimodality, occurs only in a narrow range of Rayleigh numbers whose extrema depend on the Prandtl number. The predictions of the present model are consistent with the published literature, according to which the dual mean flow structure has been observed in numerical simulations at $\hbox{\it Pr}\,{=}\,0.7$ and experiments in gaseous helium ($\hbox{\it Pr}\,{\approx}\,0.7$) but never in water at ‘ambient’ temperature ($\hbox{\it Pr} \,{\approx}\,5$) and only once in water at T\,{=}\,80\,^\circC ($\hbox{\it Pr}\,{=}\,2$). Another prediction of the model is that the thermal properties of the sidewall affect the mean flow unsteadiness and, sometimes, prevent transitions via a subtle anchoring mechanism that has been identified and verified by ad hoc numerical simulations

Transitional regimes and rotation effects in Rayleigh–Bénard convection in a slender cylindrical cell

In this paper we analyze transitional regimes and mean flow structures for the thermally driven convective flow in a cylindrical cell of aspect-ratio (diameter over cell height) Γ=1/2. The investigation is carried out through the numerical integration of the three-dimensional unsteady Navier–Stokes equations with the Boussinesq approximation. In particular the critical Rayleigh numbers for the onset of convection, for the unsteady, chaotic and turbulent regimes are computed for two values of the Prandtl number and comparisons with cylindrical cells of larger aspect-ratio are performed. The effect of the background rotation on the flow dynamics is also described showing that the heat transfer increase, already evidenced in the literature, is only obtained for a range of rotation rates. The rotation can enhance or inhibit the heat transfer and, at low Rayleigh numbers, it is a very effective way to inhibit vertical motions and to prevent horizontal thermal gradients. This is highly desirable in solidification and crystal growth processes where thermally induced motions cause material defects and crystal inhomogeneities