Salivary Tannin-binding Proteins Research Articles

The complexity of goats’ feeding behaviour: An overview of the research in the tropical low deciduous forest

This overview describes a series of studies on the feeding behaviour of goats in the low deciduous forest (LDF) and some of the factors that affect such behaviour. Those multidisciplinary studies included field trials as well as controlled pen trials. Field observations were performed with the direct observation method (DOM) and by establishing a bite code grid adapted to the LDF, and the pen studies used a cafeteria strategy using leaves harvested from different plants of the LDF. Studies exploring the selection of feed resources used different selection indexes. Field observations showed that goats consumed >90 plant species from the heterogeneous vegetation, but only a few (7 - 15 species) represented >90% of the daily intake, and that differed between rainy and dry seasons. Although the LDF vegetation allows goats to match their crude protein requirements in both seasons, dietary energy was the limiting factor, and the condensed tannin (CT) content of the harvested diet was always high. Field and cafeteria studies suggested that goats optimize their diet with the resources available as they prefer to consume leaves with lower fibrous content while plant secondary metabolites (PSM) such as condensed tannins (CT) seemed less influential. Field and pen studies confirmed that CT blocking with polyethylene glycol did not modify the intake and selection of the CT-rich foliage which could be related to tannin-binding salivary proteins which were identified as an innate feature of the local goats. While pen studies showed that browsing experience helped goats select feeds of better digestibility and lower PSM content, helping them optimize their nutrition, field studies showed that adult goats consumed more plant species, performed larger bites, at higher strata than kids, while the proportion of life forms consumed was similar. Most field and pen studies showed that goats generally do not consume CT-rich foliage as a therapeutic self-medication strategy against gastrointestinal nematodes (GIN), instead, a prophylactic strategy seemed feasible. This behavioural feature could aim at different goals: (i) to avoid excess nitrogen in the rumen, (ii) to maintain the CP:energy balance (reducing energy loss due to urea urinary excretion), and (iii) to avoid exsheathment of GIN L3 (affecting their life-cycle). The DOM showed that goats consume small quantities of plants containing toxic compounds and they shift from browsing early in the morning to grazing some hours later, and both strategies warrant further research. The DOM also helped to relate plant life forms consumed with the degree of GIN infection, which deepens our understanding of GIN epidemiology in heterogeneous vegetation ecosystems. From these findings on the feeding behaviour of goats in the LDF, new research opportunities were proposed.

Traces of dietary patterns in saliva of hominids: Profiling salivary amino acid fingerprints in great apes and humans

Herbivorous animals that regularly consume tannin-rich food are known to secrete certain tannin-binding salivary proteins (TBSPs), especially proline-rich proteins and histidine-rich proteins, as an effective measure to counteract the antinutritive effects of dietary tannins. Due to their high binding capacity, TBSPs complex with tannins in the oral cavity, and thereby protect dietary proteins and digestive enzymes. Although the natural diet of great apes (Hominidae) is biased toward ripe fruits, analyses of food plants revealed that their natural diet contains considerable amounts of tannins, which is raising the question of possible counter-measures to cope with dietary tannins. In our study, we investigated the salivary amino acid profiles of zoo-housed Pan paniscus, Pan troglodytes, Gorilla gorilla, and Pongo abelii, and compared their results with corresponding data from Homo sapiens. Individual saliva samples of 42 apes and 17 humans were collected and quantitated by amino acid analysis, using cation-exchange chromatography with postcolumn derivatization, following acid hydrolysis. We found species-specific differences in the salivary amino acid profiles with average total salivary protein concentration ranging from 308.8 mg/dL in Po. abelii to 1165.6 mg/dL in G. gorilla. Total salivary protein was consistently higher in ape than in human saliva samples (174 mg/dL). All apes had on average also higher relative proline levels than humans did. Histidine levels had the highest concentration in the samples from Po. abelii followed by P. paniscus. In all ape species, the high salivary concentrations of proline and histidine are considered to be indicative of high concentrations of TBSPs in hominids. Given that the species differences in salivary composition obtained in this study correspond with overall patterns of secondary compound content in the diet of wild populations, we assume that salivary composition is resilient to acute and long-lasting changes in diet composition in general and tannin content in particular.

Seasonal changes in production of tannin-binding salivary proteins by wild boar (Sus scrofa) inhabiting evergreen forest in western Japan

Seasonal changes in production of tannin-binding salivary proteins by wild boar (<i>Sus scrofa</i>) inhabiting evergreen forest in western Japan

Does the Asiatic black bear (Ursus thibetanus) have the ability to secrete tannin-binding salivary proteins?

Does the Asiatic black bear (<i>Ursus thibetanus</i>) have the ability to secrete tannin-binding salivary proteins?

Megaherbivore browsers vs. tannins: is being big enough?

Megaherbivores have been of particular interest to scientists because of the physiological and ecological challenges associated with their extreme body size. Yet, one question that has seldom been explored is how browsing megaherbivores cope with plant secondary metabolites (PSMs), such as tannins, found in their food. It is possible that the sheer body size of these megaherbivores allows them to ingest tannins with no deleterious effects. However, it is plausible that megaherbivores must rely on other mechanisms to cope with PSMs, such as the production of salivary tannin-binding proteins. Thus, we aimed to determine whether megaherbivore browsers produce tannin-binding proteins to further reduce the consequences of ingesting a tannin-rich diet. Using a series of laboratory assays, we explored whether elephants, black rhinoceros, and giraffe had tannin-binding proteins in their saliva. We tested for the presence of proline-rich proteins in the saliva using two different approaches: (1) SDS-PAGE using Laemmli's (Laemmli, Nature 227:680-685, 1970) destaining method, and (2) comparative SDS-PAGE gels using Beeley et al.'s (Beeley et al. Electrophoresis 12:493-499, 1991) method for staining and destaining to probe for proline-rich proteins. Then, to test for the tannin-binding affinity of their saliva, we performed an inhibition assay. We did not observe proline-rich proteins in any of the megaherbivore species, but they did have other protein(s) in their saliva that have a high tannin-binding affinity. Our results highlight that, despite their large body sizes, and their abilities to tolerate low-quality food, browsing megaherbivores have likely evolved tannin-binding proteins as a way of coping with the negative effects of tannins.

Are there phylogenetic differences in salivary tannin-binding proteins between browsers and grazers, and ruminants and hindgut fermenters?

While feeding, mammalian browsers (primarily eat woody plants) encounter secondary metabolites such as tannins. Browsers may bind these tannins using salivary proteins, whereas mammalian grazers (primarily eat grasses that generally lack tannins) likely would not. Ruminant browsers rechew their food (ruminate) to increase the effectiveness of digestion, which may make them more effective at binding tannins than nonruminants. Few studies have included a sufficient number of species to consider possible scaling with body mass or phylogenetic effects on salivary proteins. Controlling for phylogeny, we ran inhibition radial diffusion assays of the saliva of 28 species of African herbivores that varied in size, feeding strategy, and digestive system. We could not detect the presence of salivary proline‐rich proteins that bind tannins in any of these species. However, using the inhibition radial diffusion assay, we found considerable abilities to cope with tannins in all species, albeit to varying degrees. We found no differences between browsers and grazers in the effectiveness of their salivary proteins to bind to and precipitate tannins, nor between ruminants and nonruminants, or scaling with body mass. Three species bound all tannins, but their feeding niches included one browser (gray duiker), one mixed feeder (bush pig), and one grazer (red hartebeest). Five closely related species of small ruminant browsers were very effective in binding tannins. Megaherbivores, considered generalists on account of their large body size, were capable of binding tannins. However, the grazing white rhinoceros was almost as effective at binding tannins as the megaherbivore browsers. We conclude, contrary to earlier predictions, that there were no differences in the relative salivary tannin‐binding capability that was related to common ancestry (phylogeny) or to differences in body size.

Salivary tannin-binding proteins: A foraging advantage for goats?

Tannins are a key chemical defense that plants use against mammalian herbivores. To cope with tannins, many herbivores have evolved salivary tannin-binding proteins that precipitate tannins in forage items, and thus minimize their deleterious effects. In the past, one specific type of salivary tannin-binding protein was identified (proline-rich proteins), and has been found in a range of mammalian species. However, there are other proteins in the saliva of mammalian herbivores that also have a high tannin-binding affinity, which may allow for tolerance of low-quality food resources. Domestic goats (Capra hircus) are able to survive on low quality, tannin-rich food items. However, it has been reported that they do not have proline-rich proteins in their saliva. Thus, the question that arises is, do they have other tannin-binding proteins in their saliva, or do they rely on other physiological mechanisms (e.g. gut microflora) to negate the negative effects of tannins? We explored whether goats had tannin-binding proteins in the saliva by using a series of laboratory assays. As a starting point, we tested for the presence of proline-rich proteins in goat saliva using two different approaches: (1) sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) using Laemmli's (1970) destaining method, and (2) comparative SDS-PAGE gels using Beeley et al. (1991) method for staining and destaining to probe for proline-rich proteins. We found, as in previous studies, that goats did not have proline-rich proteins, but that they did have other proteins in their saliva that have a high tannin-binding affinity. To test for the tannin-binding affinity of goat saliva, we then performed an inhibition assay based on a modified radial diffusion assay. For the inhibition assay, we mixed goat saliva with three tannic acid solutions as well as extracts from seven common South African tree species. To determine whether goat saliva could significantly reduce the amount of tannins left to bind after interacting with the tannin-rich solutions, we used a Wilcoxon test. Our inhibition assays revealed that goat saliva is able to significantly bind to and precipitate tannic acid and tannins in common South African tree species. The presence of these other as yet unclassified proteins, coupled with other physiological mechanisms, helps explain how goats survive on tannin-rich foods, and why they are so successful in areas dominated by highly defended food items.

Salivary tannin-binding proteins are a pervasive strategy used by the folivorous/frugivorous black howler monkey.

Dietary tannins can affect protein digestion and absorption, be toxic, and influence food selection by being astringent and bitter tasting. Animals that usually ingest tannins may regularly secrete tannin-binding salivary proteins (TBSPs) to counteract the negative effects of tannins or TBSPs production can be induced by a tannin-rich diet. In the wild, many primates regularly eat a diet that contains tannin-rich leaves and unripe fruit and it has been speculated that they have the physiological ability to cope with dietary tannins; however, details of their strategy remains unclear. Our research details the salivary protein composition of wild and zoo-living black howler monkeys (Alouatta pigra) feeding on natural versus manufactured low-tannin diets, and examines differences in TBSPs, mainly proline-rich proteins (PRPs), to determine whether production of these proteins is dependent on the tannin content of their food. We measured the pH, flow rate, and concentration of total protein and trichloroacetic acid soluble proteins (an index of PRPs) in saliva. Howler monkeys produced slightly alkaline saliva that may aid in the binding interaction between tannin and salivary proteins. We used gel electrophoresis to describe the salivary protein profile and this analysis along with a tannin-binding assay allowed us to detect several TBSPs in all individuals. We found no differences in the characteristics of saliva between wild and zoo-living monkeys. Our results suggest that black howler monkeys always secrete TBSPs even when fed on foods low in tannins. This strategy of constantly using this salivary anti-tannin defense enables them to obtain nutrients from plants that sometimes contain high levels of tannins and may help immediately to overcome the astringent sensation of their food allowing howler monkeys to eat tanniferous plants.

Incorporating secondary metabolites, tannin-binding proteins, and diet breadth into carrying-capacity models for African elephants

Elephant populations have been historically difficult to manage and have sometimes been subjected to drastic management procedures. One way to monitor elephant populations to estimate a sustainable carrying capacity is through the use of standing-crop carrying-capacity models. Previous carrying-capacity models designed for grazers have posed issues when applied to browsers such as elephants, predicting much higher carrying-capacity estimates than are realized in nature. This might be attributed to the level of plant secondary metabolites, which limit the available nitrogen in browse material that browsers and mixed feeders encounter while foraging. Many browsers and mixed-feeders, including elephants, have a physiological mechanism to tolerate a portion of encountered tannins in the form of salivary tannin-binding proteins. We constructed an optimal-foraging model for carrying capacity for elephants that incorporates the negative effects of plant secondary metabolites and the partial neutralization of these chemicals by the tannin-binding affinity of elephant saliva. In addition, our model includes diet breadth and dietary contribution of browsed species, browse quality, and the available standing crop of browsed species. Ultimately, our model produced more plausible estimates of elephant carrying capacity when compared with estimates that use 100% nitrogen availability and use. Moreover, as the key variables needed for the model can be obtained easily, our model is not site-specific or limited to elephants, but rather can be applied to a wide range of browsing herbivores across a number of reserves of different sizes.

Howler Monkeys (Alouatta palliata mexicana) Produce Tannin-Binding Salivary Proteins

Dietary tannins are ubiquitous in woody plants and may have serious negative effects on herbivores by inducing a loss of dietary protein and producing toxins if they are hydrolyzed in the gut. Many herbivorous mammals counter the negative effects of tannins through tannin-binding salivary proteins (TBSPs) that inactivate tannins by forming insoluble complexes and prevent them from interacting with other more valuable proteins. Howlers are the most folivorous New World primates and ingest foods with varying tannin content. We studied the presence of TBSPs in six wild mantled howlers (Alouatta palliata mexicana) immediately after capture and in captivity when fed on two diets composed of natural ingredients: a mixture of fruit and leaves or only leaves. Protein concentration was determined in whole saliva samples, followed by gel electrophoresis. We identified two protein bands of 17 and 25 kDa that have tannin-binding capacity. Although the monkeys ate almost twice as much condensed tannins in the leaf diet than in the fruits and leaves diet (7 vs. 4 g/d dry matter) the salivary protein concentration did not differ between the two diets (leaf diet: 3.29 ± SE 0.82 vs. fruit and leaves diet: 3.42 ± SE 0.62 mg/ml) and we found no additional protein bands in response to either diet. We suggest that the continuous expression of TBSPs is part of a dietary strategy that enables howlers to consume diets with variable tannin contents, thus partly explaining their dietary flexibility. Although the importance of salivary proteins to arboreal primates is broadly accepted, to our knowledge this is the first report of TBSPs in any Neotropical primate.

Interspecific Differences in Tannin Intakes of Forest-Dwelling Rodents in the Wild Revealed by a new Method Using Fecal Proline Content

Mammalian herbivores adopt various countermeasures against dietary tannins, which are among the most widespread plant secondary metabolites. The large Japanese wood mouse Apodemus speciosus produces proline-rich salivary tannin-binding proteins in response to tannins. Proline-rich proteins (PRPs) react with tannins to form stable complexes that are excreted in the feces. Here, we developed a new method for estimating the tannin intake of free-living small rodents, by measuring fecal proline content, and applied the method to a field investigation. A feeding experiment with artificial diets containing various levels of tannic acid revealed that fecal proline content was clearly related to dietary tannin content in three species (A. speciosus, Apodemus argenteus, and Myodes rufocanus). We then used fecal proline content to estimate the tannin intakes of these three forest-dwelling species in a forest in Hokkaido. In the autumn, estimated tannin intakes increased significantly in the Apodemus species, but not in M. rufocanus. We speculated that an increase in tannin intake during autumn may result from consumption of tannin-rich acorns. This hypothesis was consistent with population fluctuation patterns of the three species, which were well-synchronized with acorn abundance for the Apodemus species but not for M. rufocanus.

Salivary amino acid concentrations in zebus (Bos indicus) and zebu hybrids (Bos indicus x Bos Taurus) fed a tannin-rich diet

Many animals show adaptation to tannins in the form of tannin-binding salivary proteins (1). Among ruminants, such proteins have been demonstrated in saliva of several species (usually browsers and intermediate feeders) (2, 3, 4, 13). There is some circumstantial evidence to suggest that zebu cattle (Bos indicus) are different from temperate cattle breeds with respect to their salivary and digestive physiology. Apart from differences in susceptibility to heat and tropical disease (5), a difference in salivary anti-tannin defenses (and a resulting difference in rumen physiology) could be another reason zebu cattle are particularly suited for agricultural systems in the tropics, where available forages often contain high levels of tannins (6, 7). Although non-proline-rich proteins exist that also have affinity for tannins (1, 8), it is interesting to compare the proline content of different cattle breeds. Here, we report such a screening for a comparison of zebu cattle and zebu-Holstein- Friesian in the Jimma area located at 7°40′N and 36°50′E at 1760 masl in southwest Ethiopia.

No Major Role for Binding by Salivary Proteins as a Defense Against Dietary Tannins in Mediterranean Goats

We investigated whether Mediterranean goats use salivary tannin-binding proteins to cope with tannin-rich forages by determining the affinity of salivary or parotid gland proteins for tannic acid or quebracho tannin. Mixed saliva, sampled from the oral cavity, or parotid gland contents were compared to the intermediate affinity protein bovine serum albumin with a competitive binding assay. Goats that consume tannin-rich browse (Damascus) and goats that tend to avoid tannins (Mamber) were sequentially fed high (Pistacia lentiscus L.), low (vetch hay), or zero (wheat hay) tannin forages. Affinity of salivary proteins for tannins did not differ between goat breeds and did not respond to presence or absence of tannins in the diet. Proteins in mixed saliva had slightly higher affinity for tannins than those in parotid saliva, but neither source contained proteins with higher affinity for tannins than bovine serum albumin. Similarly, 3 months of browsing in a tannin-rich environment had little effect on the affinity of salivary proteins for tannin in adult goats of either breed. We sampled mixed saliva from young kids before they consumed forage and after 3 months of foraging in a tannin-rich environment. Before foraging, the saliva of Mamber kids had higher affinity for tannic acid (but not quebracho tannin) than the saliva of Damascus kids, but there was no difference after 3 months of exposure to tannin-rich browse, and the affinity of the proteins was always similar to the affinity of bovine serum albumin. Our results suggest there is not a major role for salivary tannin-binding proteins in goats. Different tendencies of goat breeds to consume tannin-rich browse does not appear be related to differences in salivary tannin-binding proteins.

Convergent evolution in feeding types: Salivary gland mass differences in wild ruminant species

In the ongoing debate about divergent evolutionary morphophysiological adaptations of grazing and browsing ruminants, the size of the salivary glands has received special attention. Here, we report the most comprehensive dataset on ruminant salivary glands so far, with data on the Glandula parotis (n=62 species), Gl. mandibularis (n=61), Gl. buccalis ventralis (n=44), and Gl. sublingualis (n=30). All four salivary gland complexes showed allometric scaling with body mass (BM); in all cases, the 95% confidence interval for the allometric exponent included 0.75 but did not include 1.0 (linearity); therefore, like other parameters linked to the process of food intake, salivary gland mass appears to be correlated to metabolic body weight (BM0.75), and comparisons of relative salivary gland mass between species should rather be made on the basis of BM0.75 than as a percentage of BM. In the subsequent analyses, the percentage of grass (%grass) in the natural diet was used to characterize the feeding type; the phylogenetic tree used for a controlled statistical evaluation was entirely based on mitochondrial DNA information. Regardless of phylogenetic control in the statistical treatment, there was, for all four gland complexes, a significant positive correlation of BM and gland mass, and a significant negative correlation between %grass in the natural diet and gland mass. If the Gl. parotis was analyzed either for cervid or for bovid species only, the negative correlation of gland mass and %grass was still significant in either case; an inspection of certain ruminant subfamilies, however, suggested that a convergent evolutionary adaptation can only be demonstrated if a sufficient variety of ruminant subfamilies are included in a dataset. The results support the concept that ruminant species that ingest more grass have smaller salivary glands, possibly indicating a reduced requirement for the production of salivary tannin-binding proteins.

Role of Tannin-Binding Salivary Proteins and Tannase-Producing Bacteria in the Acclimation of the Japanese Wood Mouse to Acorn Tannins

We studied the defense mechanisms against the negative effects of tannins in acorns by using the Japanese wood mouse (Apodemus speciosus) and acorns of a Japanese deciduous oak Quercus crispula, which contain 9.9% tannins on a dry weight basis. For the experiment, we allocated 26 wood mice into two groups: acclimated (N = 12) and nonacclimated (N = 14). Mice in the nonacclimated group were fed only acorns for 10 d after 4 wk of receiving a tannin-free diet. In contrast, mice in the acclimated group received ca. 3 g acorns daily in addition to the tannin-free diet for the first 4 wk, then they were fed only acorns for 10 d. Body weight, food intake, and digestibility were monitored. In addition, the amount of salivary proline-rich proteins (PRPs) and abundance of tannase-producing bacteria (TPB) in the feces of mice were measured. Of the 14 mice in the nonacclimated group, 8 died, whereas only 1 of the 12 in the acclimated group died. During the first 5 d of feeding acorns only, mice in the nonacclimated group lost, on average, 17.5% of their body mass, while those in the acclimated group lost only 2.5%. Food intake, dry matter digestibility, and nitrogen digestibility were higher in the acclimated group than in the nonacclimated group. The results indicate that wood mice can mitigate the negative effects of tannins by acclimation. Path analysis revealed that increased secretion of PRPs and abundance of Lactobacillus type of TPB might explain the acclimation to tannins.

Salivary Proteins as a Defense Against Dietary Tannins

Tannins, a diverse group of water-soluble phenolics with high affinity to proteins, are widely distributed in various parts of plants, and have negative effects in herbivores after ingestion. Some mammalian species are thought to counteract tannins by secreting tannin-binding salivary proteins (TBSPs). Several types of TBSPs are found in the saliva of laboratory animals, livestock, and wildlife. Among them, proline-rich proteins (PRPs) and histatins are effective precipitators of tannins. It is widely accepted that, at the least, PRPs act as a first line of defense against tannins. Many observations support this idea: in vitro affinity of PRPs to tannins is far higher than that of other proteins such as bovine serum albumin; complexes formed between PRPs and tannins are stable even under the conditions in the stomach and intestine; and PRP production is induced by ingesting tannins. It is believed that species that usually ingest tannins as part of their natural diets produce high levels of PRPs, whereas species not exposed to tannins produce little or no PRPs. This hypothesis is generally supported, although studies on TBSPs in wildlife are limited. This work stresses the importance of gathering basic information on such items as the characteristics of unidentified TBSPs, and seasonal and geographical variations in PRP production.

Tannin-binding salivary proteins in three captive rhinoceros species

Tannin-binding salivary proteins (TBSP) are considered to be counter-defences acquired in the course of evolution by animals whose natural forage contains such tannins. As tannins mostly occur in browse material but not in grasses, it is assumed that grazers do not have a need for TBSP. Whereas it has been shown in several non-ungulate species that TBSP can be induced by dietary tannins, their presence or absence in ungulates has, so far, been shown to be a species-specific characteristic independent of dietary manipulations. We investigated saliva from three rhinoceros species from zoological gardens fed comparable, conventional zoo diets. As expected, saliva from white rhinoceroses ( Ceratotherum simum, grazer) had lower tannin-binding capacities than that from black rhinoceroses ( Diceros bicornis, browser). Surprisingly, however, Indian rhinoceroses ( Rhinoceros unicornis), commonly regarded as grazers as well, displayed the highest tannin-binding capacities of the three species investigated. It is speculated that this discrepancy might be a result of an evolutionarily recent switch to a grass-dominated diet in Indian rhinoceroses, and that the black rhinoceros, which is closer related to the white rhinoceros than the Indian species, has evolved an inducible mechanism of TBSP production. In separate trials during which the tannin content of the diets of black rhinoceroses was increased by the addition of either tannic acid or quebracho, the tannin-binding capacity of black rhinoceros saliva was increased to levels within the same range as that of Indian rhinoceroses on the conventional diets. While induction trials in white and Indian rhinoceroses remain to be performed for a full understanding of salivary anti-tannin defence in rhinoceroses, these results are the first report of an induced salivary response to increased dietary tannin levels in an ungulate species.

Effects of Acomastylis rossii tannins on a mammalian herbivore, the North American pika, Ochotona princeps.

I investigated the effects of tannin consumption, using plant tannins naturally occurring in the diet, on a herbivorous mammal, the North American pika, Ochotona princeps. The objectives were to determine if a high-tannin diet influenced protein and dry matter apparent digestibility, fiber digestibility and production of detoxification by-products. Additionally, I examined the possibility that pikas produce salivary tannin-binding proteins, a potential mechanism for avoiding detrimental effects of tannins. My results demonstrate that although pikas constitutively produce salivary tannin-binding proteins, animals consuming a high-tannin diet of Acomastylis rossii exhibited lower dry matter, protein and fiber digestion and excreted higher concentrations of detoxification by-products. Thus, A. rossii tannins are potential toxins as well as digestibility reducers. I propose a hypothesis coupling detoxification to reduced fiber digestion that is applicable to pikas as well as other mammalian herbivores consuming phenolic-rich diets.

Comparison of tannin-binding proteins in saliva of Scandinavian and North American moose ( Alces alces)

Differences in the ability of salivary proteins from Scandinavian and North American moose ( Alces alces) to bind tannins from various preferred food plant sources were studied. Both Scandinavian and North American moose produce a salivary tannin-binding protein which binds only condensed tannins common in their diet. The tannins of winter-browsed stems of Pinus sylvestris and Salix pentandra were more effectively bound by salivary tannin-binding protein from North American moose than by those from Scandinavian moose. Tannins of P. sylvestris and S. pentandra stems were also more effective binding agents than tannins from S. caprea and Betula species. The interactions between salivary tannin-binding protein and plant tannins may be one factor affecting food plant choice of moose. The chemical and biochemical characteristics of plant tannins and the ability of salivary tannin-binding proteins to react with tannins should be taken into account in diet selection.

Salivary tannin-binding proteins in root vole ( Microtus oeconomus Pallas)

We demonstrated that the root vole ( Microtus oeconomus Pallas) produces salivary tannin-binding proteins. The ability of the proteins to bind tannins was demonstrated electrophoretically. It is likely that the proteins are proline-rich, based on their staining characteristics. Production of these proteins was not altered by incorporation of 0.1% of birch tannin or 10% birch bark powder to the diets of captive root voles.