Background The lack of dependable, high-quality forage and animal feedstuffs in many areas of the world hampers livestock production. In these regions, farmers often rely on native fodder tree and shrub leaves as a forage source for their animals with little or no information available on nutritional factors of these feedstuffs. In addition, there is a growing need to improve nitrogen use efficiency (NUE) in ruminants, especially in agricultural areas where livestock feedstuffs are limited in quantity and of lower quality. Condensed tannins (CTs) show capability of protecting protein from degradation during both the ensiling process and rumen digestion, producing greater rumen undegradable protein translating into higher ruminant livestock productivity.Results Determination of the concentration of CTs in the leaves of four fodder tree species (Salix nigra, Salix alba, Populus nigra, and Elaeagnus angustifolia), and two shrub species (Hippophae rhamnoides and Rosa webbiana) across seasons from three locations in Pakistan is detailed below. The highest levels of CTs were found in S. nigra and S. alba (seasonal averages of 17.9 and 18.5 mg/g, respectively) and were targeted for purification and characterization. 1H-13C heteronuclear single quantum coherence (HSQC) nuclear magnetic resonance (NMR) spectra of purified CTs indicated the following composition for S. nigra, procyanidin/prodelphinidin ratio = 59/41; cis/trans ratio = 59/41; estimated mean degree of polymerization (mDP) = 8.1. For S. alba, procyanidin/prodelphinidin ratio >= 99/1; cis/trans ratio = 85/15; estimated mDP = 6.9. The CT content of both Salix species trended higher with seasonal growth, with the CT content of S. nigra across seasons statistically significant. The CT content in P. nigra and H. rhamnoides trended lower across all three locations tested but did not reach the level of statistical significance. Insignificant levels of CTs were detected in E. angustifolia and R. webbiana.Conclusion Based on CT literature reports, S. nigra and S. alba likely contain adequate CT levels to bolster NUE in ruminants without exhibiting a detrimental effect on dry matter intake.

Condensed tannins (CTs) in certain leguminous forages can mitigate toxic alkaloid absorption linked to fescue toxicosis due to their high affinity towards various steroidal and protein-like alkaloids. However, their use as feed supplements remains underexplored. This study evaluated the impact of CT-rich sericea lespedeza (Lespedeza cuneata) pellets on the post-ingestive effects of fescue toxicosis. Twelve steers on wild-type endophyte-infected tall fescue pastures received either sericea lespedeza pellets (LES) or LES with polyethylene glycol (LPEG; negative control) for 12 weeks over three consecutive summers. Body weight, hair coat scores, temperatures (rectal and extremity), cortisol levels, and caudal artery lumen area were measured every four weeks. Steers fed LES showed trends toward higher ADG (p = 0.0999) and reduced hair retention (p = 0.0547) compared to those fed LPEG. Steers on LES also showed hotter tail skin temperatures (p = 0.0053) and cooler rectal temperatures (p < 0.0001) compared to those fed LPEG. LES-fed steers had a 21% larger caudal artery lumen area (p < 0.01), suggesting reduced vasoconstriction. Additionally, LES-fed steers tended to have lower hair cortisol (p = 0.0746), indicating reduced chronic stress. These results suggest that supplementation with CTs may alleviate the post-ingestive effects of fescue toxicosis, potentially by improving blood flow and reducing stress. However, further research is needed to determine whether CTs directly reduce alkaloid absorption, as well as to validate the long-term efficacy of CT supplementation.

Sustainable livestock production is essential for meeting the growing global protein demand while minimising environmental impacts. Exploring alternative forages that enhance nutrient utilisation and reduce reliance on imported feeds is a potential strategy. Condensed tannins (CTs) can bind to proteins in the rumen, protecting them from ruminal degradation resulting in decreased ammoniacal N and enhanced nitrogen uptake in the hindgut. This pioneering research is the first to explore the potential of willow (Salix) as an alternative feed for ruminant nutrition. The study involved feeding ewe hoggets a control grass silage (SIL) or a SIL mix containing a 20

Shelf-stable cranberry juice precipitate has not been well characterized. Here, we describe using 1H-13C heteronuclear single quantum coherence-nuclear magnetic resonance (HSQC-NMR) spectroscopy for cranberry juice analysis, focusing on proanthocyanidins and the precipitate. HSQC-NMR cross-peaks from juices were categorized as aliphatic, olefinic, aromatic, carbohydrate backbone, or anomeric signals. An average cranberry juice precipitate had significantly more aromatic and significantly less carbohydrate backbone signals than an average supernatant. The precipitate was a collection of biomolecules held together by a mix of weak and strong intermolecular forces. Proanthocyanidin signals from precipitates of juices showed 22 ± 2 to 29.9 ± 0.7% A-type interflavan linkages and 34 ± 2 to 48 ± 3% of flavan-3-ol units with trans stereochemistry between the C2 and C3 positions. Based on this work, 1H-13C HSQC-NMR is useful to analyze cranberry juice and reveals the complex chemical nature of components in the soluble and insoluble phases.

Tall fescue (Schedonorus arundinaceous (Schreb.) Dumort. nom. cons. Lolium arundinaceum (Schreb.) Darbysh.) toxicosis results from the consumption of alkaloids released by wild-type endophytes (Epichloe coenophiala) that live in symbiosis with the plant. Alkaloid consumption causes significant production and reproductive losses which cost the U.S. beef industry approximately $2 billion every year. Incorporating species that contain condensed tannins (CTs) into forage systems may be an effective strategy to reduce the effects of fescue toxicosis in livestock. It has been hypothesized that stable complexes formed between CTs and toxic alkaloids could help reduce their absorption through the gastrointestinal epithelia, thus reducing their toxic effects. However, it is not yet clear whether CTs are effective in reducing the effects of fescue toxicosis in grazing systems. A comprehensive literature search was carried out using Google Scholar to identify studies relevant to the research question, from which the cited articles were selected. This review covers the value and issues of tall fescue employed as useful forage, summarizes the impact endophyte-infected tall fescue can have on cattle, and sets out the current management strategies implemented to minimize fescue toxicosis. The review continues with a brief summary of tannin structure and the well-documented benefits that CT-containing forages can contribute to the productivity and sustainability of ruminant agriculture. Finally, a summary of the potential forage sources, mechanisms, and benefits of CTs in reducing the negative post-ingestion effects of fescue alkaloids in livestock is provided.

Proanthocyanidins (PAC) are dietary polyphenols with putative anti-inflammatory and immunomodulatory effects. However, whether dietary PAC can regulate type-2 immune function and inflammation at mucosal surfaces remains unclear. Here, we investigated if diets supplemented with purified PAC modulated pulmonary and intestinal mucosal immune responses during infection with the helminth parasite Ascaris suum in pigs. A. suum infection induced a type-2 biased immune response in lung and intestinal tissues, characterized by pulmonary granulocytosis, increased Th2/Th1 T cell ratios in tracheal-bronchial lymph nodes, intestinal eosinophilia, and modulation of genes involved in mucosal barrier function and immunity. Whilst PAC had only minor effects on pulmonary immune responses, RNA-sequencing of intestinal tissues revealed that dietary PAC significantly enhanced transcriptional responses related to immune function and antioxidant responses in the gut of both naive and A. suum-infected animals. A. suum infection and dietary PAC induced distinct changes in gut microbiota composition, primarily in the jejunum and colon, respectively. Notably, PAC consumption substantially increased the abundance of Limosilactobacillus reuteri. In vitro experiments with porcine macrophages and intestinal epithelial cells supported a role for both PAC polymers and PAC-derived microbial metabolites in regulating oxidative stress responses in host tissues. Thus, dietary PAC may have distinct beneficial effects on intestinal health during infection with mucosal pathogens, while having a limited activity to modulate naturally-induced type-2 pulmonary inflammation. Our results shed further light on the mechanisms underlying the health-promoting properties of PAC-rich foods, and may aid in the design of novel dietary supplements to regulate mucosal inflammatory responses in the gastrointestinal tract.

Infections with Cryptosporidium spp. constitute a substantial public health burden and are responsible for widespread production losses in cattle herds. Reducing disease and shedding of Cryptosporidium spp. oocysts is an important One Health goal. There are very few therapeutic options available to treat cryptosporidiosis. Interest in plant bioactive compounds to mitigate the spread of anthelmintic resistance in ruminants has led to investigation of these phytocompounds against other parasitic taxa. Condensed tannins (CTs) are plant secondary metabolites that have shown potential against nematodes in vitro and in vivo but their applicability to Cryptosporidium spp. is comparatively under-explored. Cryptosporidium parvum infected human ileocecal colorectal adenocarcinoma (HCT)-8 cell cultures were treated with escalating doses of highly purified and well-characterized CTs from five plant species, big trefoil (Lotus pedunculatus), black currant (Ribes nigrum), sainfoin (Onobrychis viciifolia), white clover (Trifolium repens) and grapeseed (Vitis vinifera) for 44 h. Quantitative-PCR (qPCR) analysis revealed that none of the CTs examined demonstrated inhibitory potential against the parasite. Substantial inhibition of C. parvum by paromomycin was observed in positive controls in all assays (76.94-90.72% inhibition), proving the validity of the assay. Despite the lack of inhibition, these results represent an important step towards identifying alternative treatment options against this parasite.

Grazing ruminants contribute to global climate change through enteric methane and nitrous oxide emissions. However, animal consumption of the plant polyphenolics, proanthocyanidins, or condensed tannins (CTs) can decrease both methane emissions and urine nitrogen levels, leading to reduced nitrous oxide emissions, and concomitantly increase animal health and production. CTs are largely absent in the foliage of important temperate pasture legumes, such as white clover (Trifolium repens), but found in flowers and seed coats. Attempts at enhancing levels of CT expression in white clover leaves by mutagenesis and breeding have not been successful. However, the transformation of white clover with the TaMYB14-1 transcription factor from Trifolium arvense has resulted in the production of CTs in leaves up to 1.2% of dry matter (DM). In this study, two generations of breeding elevated foliar CTs to >2% of DM. The CTs consisted predominantly of prodelphinidins (PD, 75–93%) and procyanidins (PC, 17–25%) and had a mean degree of polymerization (mDP) of approximately 10 flavan-3-ol subunits. In vitro studies showed that foliar CTs were bound to bovine serum albumin and white clover proteins at pH 6.5 and were released at pH 2.-2.5. Using rumen in vitro assays, white clover leaves containing soluble CTs of 1.6–2.4% of DM significantly reduced methane production by 19% (p ≤0.01) and ammonia production by 60% (p ≤ 0.01) relative to non-transformed wild type (WT) controls after 6 h of incubation. These results provide valuable information for further studies using CT expressing white clover leaves for bloat prevention and reduced greenhouse gas emissions in vivo.

Bioactive dietary components may considerably influence intestinal health and resistance to enteric disease. Proanthocyanidins (PAC) are dietary polyphenols with putative health-promoting activity that have been increasingly studied for their anti-inflammatory and immunomodulatory effects. However, whether dietary PAC can regulate type-2 immune function and inflammation at mucosal surfaces remains unclear. Here, we investigated whether diets supplemented with purified PAC modulated pulmonary and intestinal mucosal immune responses during infection with the helminth parasite Ascaris suum in pigs. A. suum infection induced a type 2-biased immune response in lung and intestinal tissues, characterized by pulmonary granulocytosis, increased Th2/Th1 T cell ratios in tracheal-bronchial lymph nodes, intestinal eosinophilia, and modulation of genes involved in mucosal barrier function and immunity. We observed that PAC had only minor effects on pulmonary immune responses, regardless of concurrent A. suum infection. However, RNA-sequencing of intestinal tissues revealed that dietary PAC significantly enhanced transcriptional responses related to immune function, antioxidant responses, and cellular stress activity, both in uninfected and A. suum -infected animals. A. suum infection and dietary PAC both induced distinct changes in gut microbiota composition, primarily in the jejunum and colon, respectively. Notably, PAC substantially increased Limosilactobacillus reuteri abundance in the colon of both naïve and A. suum -infected animals. Thus, dietary PAC may have distinct beneficial effects on intestinal health during infection with mucosal pathogens, whilst having limited activity to modulate naturally-induced type-2 pulmonary inflammation. Our results shed further light on the mechanisms underlying the health-promoting properties of PAC-rich foods, and may aid in the design of novel dietary supplements to regulate mucosal inflammatory responses in the gastrointestinal tract.

This study aimed to determine the concentration and composition of condensed tannins (CT) in different tissues of purple prairie clover (PPC; Dalea purpurea Vent.) at different maturities and to determine their protein-precipitating capacity. The compositions of CT were elucidated after thiolysis with benzyl mercaptan followed by high-performance liquid-chromatography (HPLC) and 1H–13C heteronuclear single quantum coherence (HSQC) NMR spectroscopy. The results indicated that PPC flowering heads contained the highest CT concentration. Purple prairie clover CT consisted mainly of epicatechin (EC) and epigallocatechin (EGC) subunits. CT in the leaves were composed of more EC and less EGC than CT in stems and flowering heads at both the early flowering (EF) and late flowering (LF) head stages. The mean degree of polymerization was the highest for CT in stems and increased with maturity. CT isolated from PPC leaves at the early flowering head stage exhibited the greatest biological activity in terms of protein precipitation. Overall, the CT in PPC were predominantly procyanidins and the concentration and composition varied among the plant tissues and with maturity.

Research reports involving proanthocyanidins (PAs) in fields ranging from plant breeding to nutritional and health effects are plentiful and expanding. Therefore, improvement of existing and development of new techniques for PA analysis are of paramount importance. This chapter summarizes established and emerging procedures for their isolation/characterization and highlights universal problems associated with PA analysis. Their structural complexities known to influence biological activities are explored. The advantages/disadvantages of techniques for PA analysis are discussed and include several depolymerization/derivatization reactions, nuclear magnetic resonance (NMR: 1H, 13C, 1H-13C heteronuclear single quantum correlation, HSQC; 13C cross polarization/magic angle spinning, CPMAS; and 31P of derivatized PAs) and infrared spectroscopies (IR: Fourier transform, FTIR; near-infrared spectroscopy, NIRS), mass spectrometries (MS: matrix-assisted laser desorption – ionization-time of flight mass spectrometry, MALDI-TOF-MS; liquid chromatography mass spectrometry, LC-MS; ultra-high-performance liquid chromatography – tandem mass spectrometry, UPLC-MS/MS) plus colorimetric methods (4-dimethylaminocinnamaldehyde, Fast Blue Salt B or vanillin reagents). The chapter concludes with a discussion of potential solutions to problems facing scientists conducting PA-related research and suggests the use of multiple methods of PA analysis to ensure accurate assessment of PA concentration and structure.

Proanthocyanidins (PACs) are near-ubiquitous and chemically complex metabolites, prototypical of higher plants. Their roles in food/feed/nutrition and ethnomedicine are widely recognized but poorly understood. With the analysis of evidence that underlies this challenge, this perspective identifies shortcomings in capturing and delineating PAC structures as key factors. While several groups have forwarded new representations, a consensus method that captures PAC structures concisely and offers high integrity for electronic storage is required to reduce confusion in this expansive field. The PAC block arrays (PACBAR) system fills this gap by providing precise and human- and machine-readable structural descriptors that capture PAC metabolomic structural diversity. PACBAR enables communication of PAC structures for the development of precise structure-activity relationships and will assist in advancing PAC research to the next level.

The protein precipitation (PP) of bovine serum albumin (BSA), lysozyme (LYS), and alfalfa leaf protein (ALF) by four procyanidin-rich condensed tannin (CT) samples in both 2-[N-morpholino]ethanesulfonic acid (MES) and a modified Goering-Van Soest (GVS) buffer is described. Purified CT samples examined included Vitis vinifera seed (mean degree of polymerization [mDP] 4.1, 16.5% galloylated), Tilia sp. flowers (B-type linkages, mDP 5.9), Vaccinium macrocarpon berries (mDP 8.7, 31.7% A-type linkages). and Trifolium pratense flowers (B-type linkages, mDP 12.3) and were characterized by 2D NMR (>90% purity). In general, CTs precipitated ALF > LYS ≥ BSA. PP in GVS buffer was 1 to 2.25 times greater than that in MES buffer (25 °C). The GVS buffer system better reflects the results/conclusions from the literature on the impacts mDP, galloylation, and A-type linkages have on PP. Determinations of PP using the MES buffer at 37 °C indicated that some of these differences may be attributed to the temperature at which GVS buffer determinations are conducted. In vitro PP studies using the GVS buffer may offer better guidance when selecting CT-containing forages and amendments for ruminant feeding studies.

Proanthocyanidins (condensed tannins) are important in food chemistry, agriculture, and health, driving demand for improvements in structure determination. We used ultrahigh resolution Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS) methods to determine the exact composition of individual species in heterogeneous mixtures of proanthocyanidin polymers from Sorghum bicolor grain and Neptunia lutea leaves. Fragmentation patterns obtained with FT-ICR ESI MS-MS (electrospray ionization) confirmed structural details from thiolysis-high-performance liquid chromatography (HPLC)-diode array detection (DAD) and 1H-13C heteronuclear single quantum coherence (HSQC) NMR. We found that A-type linkages were characteristic of shorter polymers in predominantly B-linked proanthocyanidin. We suggest that supramolecular complex formation between proanthocyanidins and matrix components such as 2,5-dihydroxybenzoic acid was responsible for anomalous 152 dalton peaks, incorrectly assigned as 3-O-galloylation, when using FT-ICR matrix-assisted laser desorption ionization (MALDI-MS). Our data illustrate the power of the ultrahigh resolution FT-ICR methods but include the caveat that MALDI-MS must be paired with complementary analytical tools to avoid artifacts.

In this study, we optimized the HCl-butanol-acetone-iron (HBAI) assay for the analysis of B-linked procyanidin (PC) and prodelphinidin (PD) condensed tannins (CTs) by direct analysis of whole tissue and sequential analysis of acetone-water extracts and insoluble residues prepared from forage, woody plant, food, and food byproduct samples. Yields of anthocyanidins (cyanidin and delphinidin) were optimized by heating ≤0.25 mg mL-1 CT standards, 1 mg mL-1 tissue, or 1-2 mg mL-1 acetone-water fractioned tissue for 3 h at 70 °C in medium containing 5% concentrated HCl, 6.7% total water, 50% acetone, 42% n-butanol, and 0.15% ammonium iron(III) sulfate dodecahydrate. Accurate quantitation required CT standards of known purity sourced from the same tissue being analyzed. Both analysis methods provided comparable estimates of total CTs for most PD-rich samples, but only the sequential method gave good recovery and accurate estimates of CTs in most PC-rich samples.

As a class of plant polyphenolic compounds contained in some forages (i.e., sainfoin [Onobrychis viciifolia Scop.], big trefoil [Lotus pedunculatus Cav.], birdsfoot trefoil [Lotus corniculatus L.]), condensed tannins (CTs), also referred to as proanthocyanidins (PAs or PACs), exhibit a variety of biological effects on ruminants. The potential positive impact of CTs on the agricultural industry stems from their ability to modulate proteolysis during forage conservation and ruminal digestion, to prevent bloat, to reduce intestinal parasite burdens, to abate methane and ammonia emissions from ruminants, and to inhibit the activity of soil‐nitrifying bacteria. How CTs exert these effects on ruminants focuses on the interaction of CTs with proteins. The structure‐activity relationship in CT–protein interaction is not well understood but is known to be dependent on the structure and properties of both the CT and the protein. The purpose of this perspective is fivefold. First, we provide the reader with a better understanding of the structural diversity of CTs present in plant material and enable the reader to appreciate that not all CTs are the same. Second, we provide examples of how CT structural diversity affects the interaction of CTs with the protein, which, in turn, dictates the biological response from the animal. Third, we describe the hurdles in obtaining highly pure and well‐characterized CTs from natural sources for use in studies to attempt to elucidate how CTs impart each biological effect. We then describe improved and emerging techniques for CT analysis and, finally, we conclude this perspective with questions to address in future investigations and forward a list of recommendations for CT researchers to follow.

The aim of the present study was to define whether elevated rumen-undegradable protein (RUP) and tannin-rich peanut skin (PS) supplementation would affect animal growth performance, average daily gain (ADG), blood metabolites, carcass traits associated with lipogenic and immune-related gene expressions in meat goats grazing winter wheat (WW). Thirty-six Kiko-crossbreed male goats at approximately 6 months of age were blocked by body weight (BW; 25.6 ± 1.1 kg) and randomly assigned to one of the four treatments with two replicates based on a 2 × 2 factorial design. Diets contained PS replacing alfalfa meal (ALM), without or with RUP supplementation. Both PS and ALM were incorporated into grain mix portion of the diet and pelletized, with remaining diets fed ad libitum of WW forage for a period of 51 days. Lipogenic genes examined included SCD, ACLY, YWHAZ, PPIA and FABP4, while immune-related genes examined included ACTB (as a control gene), H3F3A, PPIA, IRF3, STAT2, HERC3 and IFIT3 antibody genes. The meat goats on PS-pellet-supplemented group with or without RUP supplementation grew 38.5% faster ADG (p < .001) when compared to control-supplemented group. When goats received PS diet, empty body weight, hot carcass, cold carcass, shoulder, hind shank, rack, loin and fat thickness were greater (p < .05) than control diet. Animals on PS-pellet had higher ACLY, YWHAZ, PPIA and FABP4 gene expression (p < .05) when compared to ALM-pellet control, with RUP by PS-pellet interactions (p < .01). Goats receiving additional RUP supplementation had increased (p < .05) STAT2 gene expression, whereas goats receiving PS-pellet supplementation showed increased STAT2 (p < .05) and a tendency to increase IRF3 (p = .07) gene expressions. In conclusion, the addition of PS-pellet or RUP supplementation has the potential to improve ADG and altered selected lipogenic and immune-related gene expressions.

Previous studies showed that a series of purified condensed tannins (CTs) from warm-season perennial legumes exhibited high variability in their modulation of methane production during in vitro rumen digestion. The molecular weight differences between these CTs did not provide correlation with either the in vitro CH4 production or the ability to precipitate bovine serum albumin. In an effort to delineate other structure-activity relationships from these methane abatement experiments, the structures of purified CTs from these legumes were assessed with a combination of methanolysis, quantitative thiolysis, 1H-13C HSQC NMR spectroscopy and ultrahigh-resolution MALDI-TOF MS. The composition of these CTs is very diverse: procyanidin/prodelphinidin (PC/PD) ratios ranged from 98/2 to 2/98; cis/trans ratios ranged from 98/2 to 34/66; mean degrees of polymerization ranged from 6 to 39; and % galloylation ranged from 0 to 75%. No strong correlation was observed between methane production and the protein precipitation capabilities of the CT towards three different proteins (BSA, lysozyme, and alfalfa leaf protein) at ruminal pH. However, a strong non-linear correlation was observed for the inhibition of methane production versus the antioxidant activity in plant sample containing typical PC- and PD-type CTs. The modulation of methane production could not be correlated to the CT structure (PC/PD or cis/trans ratios and extent of galloylation). The most active plant in methane abatement was Acacia angustissima, which contained CT, presenting an unusual challenge as it was resistant to standard thiolytic degradation conditions and exhibited an atypical set of cross-peak signals in the 2D NMR. The MALDI analysis supported a 5-deoxy flavan-3-ol-based structure for the CT from this plant.

Sustainable ruminant livestock production could benefit from feedstuffs containing condensed tannin (CT) if they maintained or improved livestock health and productivity while reducing the excretion of urinary nitrogen (N), which can be readily lost to the environment. Such feedstuffs would be most useful if they were easy and inexpensive to grow and could be field dried and pelletized for ease of transport and storage. One feedstuff that may meet these criteria is pelleted sericea lespedeza (SL; Lespedeza cuneata). Therefore, a 4 x 4 Latin square trial was conducted with four mature male sheep fed four proportions of pelleted SL with alfalfa (Medicago sativa) hay cubes, to determine effects on digestion and N excretion, and the fate of the CT during digestion. Pelleted SL contained (g/kg dry matter; DM) 182 CT, 23.3N, 341 aNDF, 227 ADF, 87 ADL and 55 ash, while the cubed alfalfa hay contained (g/kg DM) 28.5N, 381 aNDF, 284 ADF, 78 ADL and 137 ash. The SL pellets were consumed readily, but increasing their proportion in the ration DM from 0 to 0.4 linearly decreased apparent digestibility of DM from 59.7 to 49.9% and N from 74.7 to 53.4%, with associated reductions in urinary N excretion. Evaluation with H-1-C-13 heteronuclear single quantum coherence nuclear magnetic resonance (HSQC NMR) spectroscopy detected trace amounts of intact CT in sheep feces and analysis of the feces from the 0.4 lespedeza pellet ration using the HCl-butanol-acetone-iron assay indicated that 96% of the CT had been modified into non-proanthocyanidin components. Fiber analysis conducted with and without sulfite indicated an accumulation of sulfite-resistant CT-protein complexes in feces which likely contributed to the reduction in digestibility of fiber and N. This study has shown that SL pellets reduced urinary N excretion and diverted feed N to feces, but their inclusion in the diet reduced the apparent digestibility of DM and N. Complexes of CT, protein and fiber were the main contributor to the poor digestibility of aNDF and ADF in diets containing SL pellets. Findings presented here suggest a potential negative effect of these SL pellets on long-term sheep productivity in contrast to short-term productivity improvements due to the ability of the SL pellets to reduce gastrointestinal parasite populations.

Condensed tannins (CT) from purple prairie clover (PPC; Dalea purpurea Vent.) have shown anti-Escherichia coli O157:H7 activity in vitro and in vivo, but the composition and structure of these CT are unknown. The objectives of this study were to determine the concentration and composition of CT in different tissues of PPC at differing maturities and to determine their protein-precipitating capacity. Condensed tannins were extracted from leaf, stem, and flower tissues of PPC harvested at vegetative, early flowering (EF), and late flowering (LF) stages. The structural compositions of CT were elucidated by in situ thiolytic degradation and HPLC–mass spectrometry. The general composition of the CT in PPC obtained from thiolytic degradation was corroborated by 1H-13C heteronuclear single quantum coherence nuclear magnetic resonance spectroscopy. The protein-precipitating capacity of isolated CT was determined by their ability to precipitate BSA and ribulose 1,5-disphosphate carboxylase (RuBisCO). Flowers contained the highest CT concentration followed by leaf and stem tissues. As the plant matured, CT concentration decreased in stem tissue but remained relatively constant in leaf and flower tissues. Regardless of plant tissue or maturity, PPC CT consisted mostly of epicatechin (EC; 70–80%) and epigallocatechin (EGC; 20–30%), with minor amounts of catechin and gallocatechin. Leaf CT consisted of more EC (P < 0.01) but less EGC units (P < 0.01) than CT from stem and flowers at both EF and LF stages. The procyanidin:prodelphinidin (PC:PD) ratio was greater (P < 0.05) for leaf CT than for stem and flower CT. The mean degree of polymerization (mDP) was highest for stem CT and lowest for leaf CT. The PC:PD ratio of stem CT decreased and the mDP increased as the plant matured. Leaf CT had higher BSA-precipitating capacity than stem and flower CT (P < 0.001), with EF leaf CT exhibiting the highest capacity (P < 0.001). Leaf and flower CT had a greater ability to precipitate RuBisCO protein than stem CT (P < 0.05). These results demonstrated that PPC CT were predominantly of the procyanidin type and that the concentration and chemical structure varied with different plant tissues and growth periods. Condensed tannins in PPC at the early flower stage exhibited the greatest protein-precipitation capacity.