饲草中缩合单宁的研究进展

 饲料中高浓度的缩合单宁会降低动物对营养物质的消化利用率,影响自愿采食量,甚至损伤肠胃。适宜含量的缩合单宁,又能阻止臌胀病、肺水肿的发生,降低寄生虫病害的影响,改善肉质品味,提高动物的生产性能。论文概述了缩合单宁的营养作用、抗营养作用,影响饲草缩合单宁含量的因素,以及控制缩合单宁含量的方法,以便在实践中合理应用缩合单宁。     

饲料中添加缩合单宁对凡纳滨对虾生长性能、体成分、血清生化及抗氧化指标的影响

本试验旨在研究饲料中添加缩合单宁对凡纳滨对虾生长性能、体成分、血清生化及抗氧化指标的影响.选择初体重约为1.38 g的凡纳滨对虾600尾,随机分为5组,每组3个重复,每个重复40尾.5组对虾投喂缩合单宁添加量分别为0(CT0组,作为对照组)、0.5(CT 0.5组)、1.0(CT1组)、2.0(CT2组)、4.0 g/...     

Preference for condensed tannins by sheep in response to challenge infection with Haemonchus contortus

Herbivores prefer feeds that supply required nutrients and avoid those with excess nutrients and plant secondary compounds (PSC). Nevertheless, PSC such as condensed tannins can provide beneficial medicinal effects to herbivores as they act against infective diseases such as parasitism. The objectives of this study were to determine: (1) if parasitized lambs increased preference for a tannin-rich feed after they experienced the beneficial antiparasitic effects of condensed tannins relative to parasitized lambs that did not experience such benefits, and (2) if preference for the tannin-rich feed in the former group decreased when parasite burdens subsided. Twenty two lambs were familiarized with beet pulp and beet pulp+8% quebracho tannins (beet pulp+tannins) and choices were given between the two feeds (initial preference tests). Subsequently, all animals were dosed with 10,000 L(3) stage larvae of Haemonchus contortus. Twenty-two days later, animals were exposed to beet pulp (Control group; n=11) or beet pulp+tannins (Treatment group; n=11) during 24 d. After exposure (during a parasitic infection) animals in both groups were given choices between the two feeds. Lastly, animals in both groups received an antiparasitic drench and were again given a choice between both feeds (after a parasitic infection). Lambs preferred beet pulp to beet pulp+tannins throughout the study (P<0.001) and no difference in preference for the tannin-rich feed was detected between groups during initial preference tests (P>0.05). However, during a parasitic infection, intake of and preference for the tannin-rich feed was higher for lambs that experienced the beneficial effects of condensed tannins while parasitized (Treatment) than for lambs that did not (Control) (P<0.05). When parasitic infections were terminated by chemotherapy, differences between groups disappeared (P>0.05). Preference by the Treatment group for the tannin-rich feed was lower after than during a parasite infection (P<0.05). In contrast, preference by the Control group did not change during these periods (P>0.05). Lambs in the Treatment group displayed lower FEC than lambs in the Control group (Group × Sampling Date; P<0.05). These results show lambs learned about the antiparasitic effects of condensed tannins and increased their preference for the tannin-rich feed, which subsided after chemotherapy, indicating preference was due to parasite infection. These findings suggest management that allows animals to select tannin-rich feeds can enable parasitized animals to self-medicate.     

Effects of condensed tannins on established populations and on incoming larvae of Trichostrongylus colubriformis and Teladorsagia circumcincta in goats

The use of tanniferous plants or tannins represents one alternative approach to the control of gastrointestinal parasites in ruminants but most data have been obtained in sheep. The current study was therefore performed in goats with two objectives: firstly, to investigate the effects of condensed tannins (CT) on adult populations of Trichostrongylus colubriformis and Teladorsagia circumcincta; secondly, to examine their effects on the establishment of infective larvae of these two species. In experiment 1, two groups of kids were infected with 6 000 L3 of T. colubriformis and 6 000 L3 of T. circumcincta. After 7 weeks, quebracho extracts were administered per os for 8 days to one group. A comparable group which did not receive tannins was included as the control. The kids were slaughtered on week 11. Parasitological and pathophysiological parameters were measured weekly. Worm counts were assessed and mast cells, globule leukocytes and eosinophils were counted in the abomasal and intestinal mucosae. Tannin administration was associated with a decrease in egg excretion, and a decrease in female fecundity, but with no changes in worm numbers. These changes were associated with an increased number of intestinal mast cells. In experiment 2, 24 goats were used according to a 2 x 2 factorial design, depending on infection and tannin administration. Two groups were either infected with 6 000 L3 of T. colubriformis or T. circumcincta. Within each group, the goats were either drenched or undrenched with tannin extracts. Pathophysiological parameters were measured weekly. Twelve days after the cessation of tannin administration, the goats were slaughtered. Worm counts and female worm fecundity were determined. Tannin consumption was associated with a significant reduction (P < 0.01) of Trichostrongylus populations and a close to significant reduction for Teladorsagia. No effect on fecundity was observed. Our results (1) confirm the consequences of condensed tannins on nematodes in goats as in sheep and (2) indicate divergent effects depending on the parasitic stage exposed to the condensed tannins.     

Polyethylene glycol as a means for reducing the impact of condensed tannins in carob pulp: effects on lamb growth performance and meat quality

We conducted an experiment to evaluate the effects that a diet containing condensed tannins with and without polyethylene glycol (PEG) has on lamb growth and meat quality. Twenty-three male Comisana lambs were introduced to the three experimental diets between 45 and 50 d of age. Eight were given a diet containing 56% of Ceratonia siliqua (carob) pulp (tannin group), another eight received the same diet with a supplement of 40 g of PEG for each kilogram of diet (PEG group), and the remaining seven lambs were given a conventional maize-based diet (maize group). Voluntary feed intake and live weights were measured until slaughter at 105 d of age, and digestibility measurements were undertaken toward the end of the feeding trial. Carcass yield, meat quality characteristics, and a taste panel evaluation were conducted. The tannin-based diet contained 2.5% condensed tannins (DM basis), and lambs given this diet had lower growth rates and poorer feed efficiencies (P < .01) compared with the other treatment groups. Daily gain was similar between the maize and PEG lambs, although the efficiency of feed conversion was highest in the maize group. The digestibility of DM, N, and fiber was reduced (P < .05) by the condensed tannins. Lambs fed the tannin diet had a lower carcass yield (P < .05) and had less fat (P < .05), and the meat had a higher ultimate pH (P < .01) than those given the PEG or maize diets. Condensed tannins affected meat color, which was lighter (L*) than meat from lambs given the PEG-containing diet (P < .01). Sensory evaluation showed that panelists preferred meat from lambs receiving PEG and maize treatments compared with those receiving the tannin diet, and this could be related to differences in meat ultimate pH and carcass fatness. These results show that condensed tannins from carob pulp are very detrimental to feed digestibility and lamb performance. Inclusion of 40 g of PEG/kg diet eliminated the effects of condensed tannins so that lamb performance and meat quality were similar to lambs given a maize-based diet.     

不同氮源添加低水平缩合单宁对延边黄牛瘤胃发酵特性及降解率的影响

试验旨在研究不同氮源饲粮基础上添加低水平缩合单宁（CT）对延边黄牛瘤胃发酵参数及降解率的影响,以期筛选出缩合单宁的最佳添加比例及利用率更高的氮源,为缩合单宁作为反当动物功能性添加剂提供科学依据。试验选用4头延边黄牛（体重452.3 kg±27.1 kg）提供瘤胃液,以不含缩合单宁的6种饲料为氮源（大豆粕、棉籽粕、菜籽粕、紫花苜蓿、红三叶及山野豌豆）,在每种氮源饲料中分别添加不同水平（0（对照组）、0.1%、0.5%、0.9%）缩合单宁,共24组,每组3个重复。采用体外培养法测定不同组合饲粮延边黄牛瘤胃体外发酵pH、氨态氮（NH₃-N）、挥发性脂肪酸（VFA）、产气量以及干物质有效降解率、粗蛋白质有效降解率、中性洗涤纤维有效降解率。结果表明,各试验组的pH、NH₃-N与VFA均在正常范围内变化并且可以满足瘤胃微生物的正常代谢,牧草类0.5%缩合单宁添加组（以下简称0.5%组）与饼粕类0.9%组以上各指标相对较好,且与各自对照组相比,产气量较低;大豆粕0.9%组、菜籽粕0.5%组以及红三叶0.1%组干物质有效降解率均较各自对照组略低（P>0.05）。棉籽粕0.5%组粗蛋白质有效降解率较对照组降低（P<0.05）,3种牧草类0.9%组粗蛋白质有效降解率均低于对照组（P>0.05）。除红三叶0.1%组外,其余5种氮源缩合单宁添加组的中性洗涤纤维有效降解率均显著低于各自对照组（P<0.05）。综合考虑,饼粕类0.9%组、牧草类0.5%组更有利于优化瘤胃发酵环境,可降低瘤胃粗蛋白质降解率,能有效保护过瘤胃蛋白,其中山野豌豆、棉籽粕效果更优。     

Quantification of Enterobacteriaceae in faeces of captive black rhinoceros (Diceros bicornis) in relation to dietary tannin supplementation

Free-ranging browsing herbivores ingest a range of secondary plant compounds, such as tannins, with their natural diet. As many of these substances have been shown to have antibacterial properties, it could be speculated that a lack of such compounds in captive zoo diets could favour the growth of potentially pathogenic intestinal bacteria. The effect of a supplementation of a conventional diet (N, consisting mainly of grass hay and/or lucerne hay and pelleted compound feeds) fed to eight captive black rhinoceroses (Diceros bicornis) from three zoological institutions with either tannic acid (T), a source of hydrolysable tannins, or quebracho (Q), a source of condensed tannins, was investigated. The number of faecal colony forming units (CFU) of Enterobactericeae was determined by colony count of dilution series from fresh faeces applied to MacConkey agar plates. Tannins were added to the diets at approximately 5-15 g/kg dry matter, depending on the varying intake of roughage and compound feeds by the animals. There was no difference in the number of CFU between diets N (95.0 x 10(5) +/- 225.3 x 10(5)/g fresh faeces) and T (164.3 x 10(5) +/- 225.1 x 10(5)/g fresh faeces); in contrast, diet Q led to a significant reduction in CFU (4.3 x 10(5) +/- 6.5 x 10(5)/g fresh faeces) compared with the other diets. These findings suggest that condensed tannins could have the potential to reduce the number of potentially pathogenic intestinal bacteria, and that the deliberate inclusion of tannin sources in the diets of captive wild animals should be further investigated. The fact that tannic acid, shown to have antibacterial effects in various in vitro studies, did not have an effect in this study, emphasizes that the relevance of tannin supplementation for intestinal health must be verified in vivo.     

Analytical approach and effects of condensed tannins in carob pods (Ceratonia siliqua) on feed intake,digestive and metabolic responses of kids

There are contradicting data in the literature regarding condensed tannins content in carobs. In this study, urea (0.5 g/ml) under reflux conditions increased dramatically the yield of condensed tannins to 17% of dry matter, as compared to 3.5% in acidic methanol extraction. This shows that carob pods are rich source of nonextractable condensed tannins. The effect of PEG in diet rich in carob pods on voluntary feed intake, digestibility and growth in weaning kids was studied during 15 days of balance trials in 24 kids distributed into three dietary treatments. The corn grain and wheat bran components in the control diet (diet 1) were replaced by carob in treatments 2 and 3; treatment 3 was supplemented by 3.3% of PEG of molecular weight-4000. Food intake, diet utilization and growth rate of weaning kids fed a diet containing 52% carob pods were decreased considerably in comparison to kids fed the control commercial diet. Supplementing the kids fed the carob-based diet with PEG increased feed intake, crude protein digestibility and growth to the rate obtained with the control diet. The nutritional experiment highlights the following aspects relevant to all mammals consuming carob pods rich diets: (i) tannins increased the variability in feed intake between days, (ii) hypocholesterolemic effect of carob pods is related to lipid binding capacity of nonextractable condensed tannins in the digestive tract, (iii) supplementing high level of carob pods to animals with normal blood cholesterol level may induce hypocholesterolemia.     

不同种质核桃中酚类物质及其抗氧化性的研究

本文以核桃为研究材料,通过采用DPPH自由基清除力、还原力、单宁、总酚和酚类物质为抗氧化指标,对8种不同地域和种质的核桃的抗氧化能力进行了比较。结果表明：陕西纸皮核桃的DPPH自由基清除率最强,河北薄皮核桃最弱;陕西纸皮核桃的还原力最强,山西薄皮最弱;总酚和单宁含量中,河北薄皮核桃最高,新疆纸皮最低; 酚类物质检测中芦丁含量最高。相关性分析结果表明酚类物质含量和核桃的DPPH自由基清除能力、还原力和单宁含量均有较高的相关性,这说明核桃中抗氧化活性物质主要为酚类化合物。此外,河北薄皮核桃和新疆薄皮核桃具有较强的抗氧化能力,益与人体健康,可为其品种选育和适用性的研究提供参考。     

常见芳香族和脂环族化合物在反刍家畜瘤胃内的代谢

芳香族化合物在反刍动物瘤胃的厌氧微生物作用下,通过水解、还原等反应,发生生物转化和矿化。不同的芳香族和脂环族化合物具有各自的代谢特点与途径:羟基桂皮酸经微生物氢化形成的羟基-3-苯丙酸,再经O-脱甲基作用和脱羟基作用转变为3-苯基丙酸;羟基苯甲酸经脱羧和脱甲氧基作用转化为简单酚类;消化道内的微生物对环己烷羧酸转化为苯甲酸的芳香化过程不起作用,仅对奎尼酸和莽草酸转化为环已烷羧酸的过程起作用;氨基酸通过瘤胃微生物降解的可能途径主要是Stickland反应,即氨基酸通过氧化还原机理脱氨;香豆素可能不是哺乳动物体内苯甲酸的前体物质,瘤胃微生物对类黄酮降解的方式与大肠微生物不同;不同类型的单宁降解不同:水解单宁的尿代谢物一般与五倍子酸的分解产物一样,如果缩合单宁单体间稳定耦合链被断裂,那么其代谢途径可能与简单类黄酮的代谢过程类似;木质素单体很容易被生物转化,但木质素低聚体能经受一定程度的解聚作用。     

Antioxidant status of faeces of captive black rhinoceros (Diceros bicornis) in relation to dietary tannin supplementation

In context with the frequent observations of excessive iron (Fe) storage in captive black rhinoceroses (Diceros bicornis), it has been suggested that both an excessive dietary Fe content and a lack of dietary Fe-chelating substances, such as tannins, is the underlying cause. Therefore, studies on the effects of tannin supplementation to captive diet are warranted. Six captive rhinoceroses were fed their normal zoo diet (N), and a similar diet supplemented with either tannic acid (T, hydrolysable tannin) or quebracho (Q, condensed tannins), and the total antioxidant capacity (TAC) was measured as mmol Trolox equivalents per kg fresh faeces. The TAC values on diets N (1.24 +/- 0.39 mmol/kg fresh faeces) and T (1.34 +/- 0.33 mmol/kg fresh faeces) were similar, but significantly higher on diet Q (2.32 +/- 0.61 mmol/kg fresh faeces). In contrast to expectations, faecal TAC increased with increasing faecal Fe, possibly as a result of the fact that the faecal Fe content was positively correlated to the proportion of concentrate feeds in the diet, which also contain antioxidants, such as vitamin E, in addition to Fe. Increased antioxidant status caused by the use of tannin substances could have a beneficial effect on animal health, but if tannins should be incorporated in designed diets, other tannin sources, such as grape pomace should be tested.     

植物单宁及其对动物的作用研究进展

对植物中单宁含量、单宁对动植物的影响及降低单宁含量的方法进行了综述。植物单宁是广泛存在于植物体内的一类多元酚化舍物,是植物进化过程中由碳水化舍物代谢衍生出来的一种自身保护性物质。一般认为单宁在维管植物中有两种存在形式既水解单宁和缩合单宁。单宁的含量与基因、部位、植物生长阶段、植物病虫害等有关;植物含有高度单宁可保护植物...     

CPB-LAR-GFP表达载体的构建及其在紫花苜蓿愈伤组织中的表达

以无色花青素还原酶编码基因LAR为靶序列,构建携带绿色荧光蛋白GFP和抗除草剂bar基因的双标记选择植物表达载体,通过农杆菌介导法对紫花苜蓿进行遗传转化,经PCR检测和PPT筛选出抗性愈伤组织,转基因紫花苜蓿愈伤组织的缩合单宁含量比对照高30.8%。试验证明重组基因已转化至紫花苜蓿愈伤组织中并发挥生理功能,为研究缩合单宁合成与代谢的分子调控机制和培育具有抗除草剂和抗臌胀病的牧草新品种奠定基础。     

Effects of plants containing secondary compounds and plant oils on rumen fermentation and ecology

A number of experiments have been conducted to investigate effects of tropical plants containing condensed tannins and/or saponins present in tropical plants and some plant oils on rumen fermentation and ecology in ruminants. Based on both in vitro and in vivo trials, the results revealed important effects on rumen microorganisms and fermentation including methane production. Incorporation and/or supplementation of these plants containing secondary metabolites have potential for improving rumen ecology and subsequently productivity in ruminants.     

红豆草单宁的研究概况

红豆草是豆科红豆属多年生草本植物,因其营养价值高、适口性好,又具有抗寒、抗旱等特性,故有＂牧草皇后＂之美誉,在世界上被广泛种植。目前,关于红豆草的饲用价值、病害、栽培技术等方面的相关研究和综述已有报道,而对其次生代谢产物的研究相对零散。主要从红豆草含有的多酚类物质——缩合单宁出发,系统综述了不同品种、物候期的红豆草缩合单宁在含量和结构上的差异性,同时整合阐述了红豆草缩合单宁在调控反刍动物营养过程中的应用,尤其是其对养分消化吸收、生产性能、泡沫性瘤胃臌胀病和胃肠道寄生虫等生理过程的影响和作用。     

A comparative histochemical study of plant polyphenols in southern African grasses

Recent anatomical studies have shown that tannin‐like substances (TLS) occur in the epidermal cells of a number of southern African tropical grasses, and the presence of condensed tannins in grasses has been confirmed by chemical analyses. A number of species from four of the five subfamilies of the Poaceae were compared for their responses to a range of histochemical tests which differ in their specificity for phenolic compounds. These included: ferrous sulphate, acidified vanillin, diazotized sulphanilic acid, Fast Blue‐BB, dimethoxybenzaldehyde and nitrous acid, Safranin and Fast Green. In addition, the radial diffusion test for protein precipitation was used. Comparative histochemical tests indicated that most taxa known to contain TLS showed comparable responses to the tests used here, with variations in intensity and hue of the coloured products formed. These qualitative differences suggest the presence of a number of different compounds including oligomeric procyanidins, oligomeric prodelphinidins, monomeric and/or dimeric flavan‐3‐ols and flavan‐3,4‐diols. The presence flavan‐4‐ols has been confirmed in the andropogonoid grasses by previous workers. Histochemical tests are adequate to identify the presence of condensed tannins and their precursors in plant tissue. However, they do not provide a means to identify those compounds which precipitate protein and function as digestibility‐reducing compounds in plant‐herbivore interactions.     

Effect of condensed tannins on egg hatching and larval development of Trichostrongylus colubriformis in vitro

The effects of condensed tannins extracted from seven forages on the viability of the eggs and first stage (L1) larvae of the sheep nematode Trichostrongylus colubriformis were evaluated in in vitro assays. The extracts of condensed tannins were obtained from Lotus pedunculatus (LP), Lotus corniculatus (LC), sulla (Hedysarum coronarium), sainfoin (Onobrychus viciifolia), Dorycnium pentaphylum (DP), Dorycnium rectum (DR) and dock (Rumex obtusifolius). Extracts containing 200 to 500 microg/ml reduced the proportion of eggs that hatched. The larval development assay was used to evaluate the effect of the extracts on the development of either eggs or L1 larvae to L3 infective larvae. Development was allowed to proceed for seven days by which time the larvae in control incubations had reached the infective L3 stage. Extracts containing 200 microg/ml from LP, DP, DR or dock prevented egg development, and only 11, 8 and 2 per cent of the eggs developed to L3 larvae with extracts from LC, sulla and sainfoin, respectively. When the concentration was 400 microg/ml no eggs developed to L3 larvae. The addition of the extracts after hatching also inhibited the development of L1 to L3 larvae; 200 microg/ml extracted from LP, LC, sulla, sainfoin, DP, DR and dock resulted in only 14, 18, 17, 15, 14, 16 and 4 per cent of L1 larvae developing to the L3 stage compared with 85 per cent for controls, and 400 microg/ml further reduced the development of L1 larvae. Statistical analyses showed that when the extracts were added before hatching they were significantly (P<0.001) more effective at inhibiting the larval development than when they were added after hatching. The condensed tannins from dock had the greatest inhibitory effect on egg development followed by the tannins from DR, sainfoin, DP, LP, sulla and LC.     

豆科牧草研究进展

豆科牧草的属间、属内、种间与种内均存在着巨大的遗传变异，利用这种变异，通过育种与选择，已培育出可良好地适应广泛的环境与管理条件的品种，遗传操作为此提供了更为广阔的空间，在豆科牧草固氮方面，对固氮过程、氮向伴生禾草的传送途径及残余氮对后继农作物的价值均有了进一步的理解。对包括施氮、采摘策略和影响混播草地中禾本科－豆科牧草平衡的胁迫等相互作用因素均已给予了阐明。在禾草／白三叶草草地为基础的家畜生产系统中，氮素的损失及其对环境产生的不良作用低于大量施氮的禾草草地系统。与禾草相比，豆科牧草无是用作放牧、青贮或用作干草，其物理、化学和解剖学等方面的特性均可增加家畜的嗜食性和自由采食量。由于豆科牧草的营养价值、可利用营养成分和采食特征，在单一豆科牧草或豆科牧草比重较大的禾草－豆科牧草混播草地上采食的不同种类、不同类型家畜的个体生产性能均优于在禾草草地上采食者。值得注意的是浓缩单宁在动物营养中的有益作用，这类单宁存在于诸如百脉根（Lotus corniculatus）、红豆草（Onobrychis viciifolia）和冠状岩黄芪（Hedys-crum coroharium）等植物中，其防止家畜患膨胀病，通过使较多的氨态氮到达小肠而提高氮的利用，并减轻绵羊肠道中线虫的作用。显然，培育含浓缩单宁的转基因豆科牧草是植物育种者现阶段的主要目标之一。此外，豆科牧草亦有许多其他用途，例如，在葡萄园中用作保护性植被，禾谷类作物的下层植被和为制药业提供次生化合物等。豆科牧草以其植物多态性和花朵的颜色等亦在美化景观和自然保护区中发挥着作用。可以预见，豆科牧草的作用在温带可持续农业中的作用将会增加，充分发掘现有的知识和相关研究成果，及有效的技术将是未来豆科牧草利用的主要特色。     

Silage quality as influenced by concentration and type of tannins present in the material ensiled: A meta‐analysis

Protein degradation during ensiling is a major problem. Tannins are known to prevent or decelerate protein degradation in the rumen and may be able to do so in silages as well. Therefore, the present evaluation aimed to analyse the influence of tannins on silage quality. This was done by integrating from all suitable experiments found in literature on the topic in a meta‐analysis approach. A total of 122 datasets originating from 28 experiments obtained from 16 published articles and one own unpublished experiment were included in the database. Tannins in the silages originated either from the plants ensiled or from supplementations of tanniferous plants or tannins extracted from such plants. Tannin concentrations ranged from 0 to 57.8 g/kg dry matter, and the ensiling period varied from 30 to 130 days. The analysis was based on the linear mixed model methodology in which the different studies were considered as random effects and tannin‐related properties (either concentration or type of tannins) were treated as fixed effects. Results revealed that greater concentrations of tannins were associated with a decrease of butyrate concentration in the silages (p < 0.05). An increasing tannin concentration was also accompanied with smaller proportions of soluble N, free amino acid N, non‐protein nitrogen and NH₃‐N in total silage N (p < 0.05). The relationships between hydrolysable and condensed tannins and the decline in butyrate and NH₃‐N concentrations in the silages were of different magnitude (p < 0.05). A higher tannin concentration was associated with a decline in in vitro dry matter digestibility. It was concluded that tannins apparently have the ability to limit extensive proteolysis which may occur during ensiling and thus may improve the fermentative quality of silages. A desired side effect seems to be given by the tannins' apparent property to limit the activity of the butyrate‐producing microbes.     

The influence of dietary tannin supplementation on digestive performance in captive black rhinoceros (Diceros bicornis)

Free-ranging browsers such as the black rhinoceros (Diceros bicornis) consume a diet that contains tannins, whereas the diets offered to them in captivity consist mostly of items known to contain hardly any such secondary plant compounds. Tannins could have potentially beneficial effects, including the chelation of dietary iron (iron storage disease is a common problem in black rhinos). Here, we tested the acceptance, and the consequences on digestion variables, of a low-dose tannin supplementation in captive animals. Eight black rhinoceroses from three zoological institutions were used. Faecal output was quantified by total faecal collection. Diets fed were regular zoo diets supplemented with either tannic acid (T, hydrolysable tannin) or quebracho (Q, condensed tannins); overall tannin source intake increased at 5-15 g/kg dry matter (DM) in relation to regular zoo diets. Adaptation periods to the new diets were >2 months. Additional data were taken from one hitherto unpublished study. Data were compared to measurements in the same animals on their regular zoo diets. All animals accepted the new diets without hesitation. There was no influence of tannin supplementation on digestion coefficients of DM and its constituents, or faecal concentrations of short-chain fatty acids or lactate. Water intake did not increase during tannin supplementation. Should the inclusion of dietary tannin sources be an objective in the development of diets for captive rhinoceroses, moderate doses such as used in this study are unlikely to cause relevant depressions of digestive efficiency and will not interfere with bacterial fermentation in a relevant way.