Use of Tannin-Binding Chemicals to Assay for Tannis and Their Negative Postingestive Effects in Ruminants

Animal Feed Science and Technology (Impact Factor: 2.09). 04/2001; 91(1):60-81. DOI: 10.1016/S0377-8401(01)00234-6
Source: OAI

ABSTRACT Synthetic polymers such as water-soluble polyvinyl pyrrolidone (PVP), water-insoluble polyvinyl polypyrrolidone (PVPP), and water-soluble polyethylene glycol (PEG) contain sufficient oxygen molecules in a chain to form strong hydrogen bonds with the phenolic and hydroxyl groups in tannins. This review deals with the practical uses of tannin-binding agents, particularly PEG, in tannins assays and for determining the negative effects of tannins on feed intake and digestion in ruminants. A gravimetric method to assay tannins by precipitation with PVPP is specific for tannins and does not require standards. The extractability of tannins from plant tissues can be reduced by drying samples at temperatures above 50°C and is dependent on many other factors, such as content and types of plant proteins. Therefore, it is not feasible to recommend a single, optimal protocol for all plant samples. A method to assay tannins which is based on measuring the amount of binding of PEG to plant samples was shown to be simple and accurate. It can also overcome some of these extractability problems. The following biological effects of tannins were investigated in studies where tannin anti-nutritional effects were partially or completely neutralised by varying levels of PEG supplementation. (1) Effects on appetite: the negative effects of tannins on appetite can occur in the short-term (within 20-60 min) and the long-term (days and weeks), Astringency and adverse postingestive influences of tannins on the epithelium of the oral cavity and the foregut cause short-term effects on food intake. Long-term effects can be related to reduction in the concentration of ammonia and volatile fatty acids (VFA) in rumen fluids, which can in turn serve as metabolic cues for deficiency of nitrogen (ammonia), energy (VFA), or both. (2) Effects on digestion: increasing content of tannins in foliage can be associated with an increase in bound protein and with reduced degradation rate of the degradable matter in the rumen, but there is no corresponding increase of the non-degradable fraction. Consequently, organic matter, protein, and cell wall digestibility are inversely related to tannin concentrations. (3) Inducing digestive responses: if a significant amount of tannins reach the duodenum, they may markedly reduce the intestinal activity of pancreatic enzymes (trypsin and amylase) and amino acids absorption from the intestine. Condensed tannins can also reduce the content of fluid and particulate matter in the rumen, accelerate the passage of liquid from the abomasum, and delay the passage of digesta in the intestine. The overall effect is a delay in the passage of fluid and particulate matter throughout the entire gastrointestinal tract. It is hypothesised that these responses are largely the consequence of the interaction of tannins with digestive enzymes and the epithelium lining the digestive tract.

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    ABSTRACT: The aim of the study was to compare the in vivo anthelmintic activity of sainfoin hay (Onobrychis viciifolia) and carob pod meal (Ceratonia siliqua) against gastrointestinal nematodes. Seven days before infection, 64 naive lambs were assigned to four different groups: Group S received sainfoin hay and group CAR was fed with carob pods. The remaining lambs received lucerne hay (Medicago sativa) and were assigned to positive (non-treated, NT) and negative (treated, T) control groups (treatment with albendazole). On day 0, lambs were artificially trickle infected for 6 weeks, with a mixture of infective larvae of Haemonchus contortus and Trichostrongylus colubriformis. Parasitological and pathophysiological parameters were measured repeatedly during the 2-month study. Compared to the NT group, decreases in egg excretion were observed in the CAR and S groups with significant differences only found for sainfoin (p < 0.05). At necropsy, group S showed decreases in the total worm numbers of both nematode species with significant differences for H. contortus. In contrast, no differences were noticed for the CAR group. Compared to the NT group, lower values for fecundity of female H. contortus were found in the S and CAR groups, however differences were non-significant. No differences in body weight gains were found between groups. Consistent results were found showing significantly higher packed cell volume (PCV) values in the T and S groups compared to NT and CAR groups. Overall, these results confirm a positive effect associated with the feeding of lambs with tanniniferous resources on host resilience (PCV values) and against gastrointestinal parasitic nematodes by affecting some biological traits of worm populations (e.g. eggs per gram of faeces and worm numbers). However, the anthelmintic effects differed between the two tannin-containing resources, which might be associated with the quantity and/or quality of secondary metabolites (condensed tannins and/or other polyphenols). © C. Arroyo-Lopez et al., published by EDP Sciences, 2014.
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    ABSTRACT: The purpose of the study was to evaluate the nutritive value of the forage legume species, Centrosema pascuorum, Lablab purpureus, Macroptilium bracteatum, Macroptilium gracile and Vigna oblongifolia as feed for ruminants in the Capricorn region of Limpopo Province, South Africa. It was hypothesized that forage legumes grown in the Province will be high in fibre and polyphenolics because of the high temperatures and low rainfall in the region. The experimental field was divided into four replications with the five different legume species within each replication, using a randomized complete block design. The plots were hand-harvested 16 weeks after planting, the material sampled, air–dried in the laboratory and analysed for physical parameters, chemical composition and in vitro enzymatic degradability. Lablab purpureus had the highest dry matter (DM) yield of 8 tons/ha followed by C. pascuorum with 2 tons/ha, whilst the other three species had a similar DM yield of approximately 1 ton/ha each. Physical characteristics varied from 2.88 to 4.45 ml/g for packed volume and 6.79 to 9.42 g/g for water retention. The crude protein composition varied from 236.8 to 259.6 g/kg DM, neutral detergent fibre from 418.3 to 505.8 g/kg DM, acid detergent fibre from 335.0 to 374.6 g/kg DM, the DM ruminal degradability from 611.1 to 712.9 g/kg DM and the organic matter (OM) degradability from 586.4 to 688.7 g/kg DM. The concentrations of total phenolics and extracted condensed tannins varied from 19.35 to 48.37 g/kg DM and from 176.6 to 334.5 g/kg DM, respectively. It was concluded that the biotic environment in the Limpopo Province did not impact negatively on the potential nutritive value of these forage legumes since the concentrations of fibre and phenolics were below levels expected to have detrimental effects on animals, and the ruminal degradability of their DM and OM was high.
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    ABSTRACT: Five selected plant species (Balanites maughamii, Breonadia salicina, Dombeya rotundifolia, Hyperacanthus amoenus and Piliostigma thonningii) were extracted using 70 and 100% acetone and the presence of tannins were determined using radial diffusion assay. Our comparative assessment indicated that plant extracted with 100% acetone showed the highest levels of tannins as compared to 70% acetone. The highest tannin levels in both 70 and 100% acetone extracts were recorded for P. thonningii, while no tannins were detected in B. maughamii. However, addition of polyethylene glycol (PEG) and polyvinyl polypyrrolidone (PVPP) to the extraction media resulted in the reduction of tannins in all crude plant extracts, with PEG being more effective than PVPP. 1% PEG removed the highest quantity of tannins in all plant extracts, in comparison with 0.5% PEG (63.3%) and 0.5 and 1% PVPP (24.8 and 49.4%, respectively).
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