Influence of condensed tannins on gut morphology in sheep fed Lotus pedunculatus

Abstract

can reduce intestinal absorption of amino acids (AA) and peptides. This experiment tested the hypothesis that CT in Lotus pedunculatus altered small intestinal mucosal morphology reducing absorptive capacity of the gut. Thirteen young Romney wethers were fed ad libitum either Lotus pedunculatus (cv. Grasslands Maku, N = 7) containing 5.5% CT in the dry matter (DM) or white cloverperennial ryegrass pasture (N = 6), which did not contain CT, for 4 wk. The wethers were euthanized at the end of the feeding trial and samples were collected for histological examination from the proximal and distal duodenum, proximal, mid-, and distal jejunum and ileum, and ventral rumen. There was no effect of feeding L. pedunculatus containing 5.5% CT (P > 0.05) on rumen or gut morphological parameters in sheep. The cause of reduced AA absorption in the presence of CT is not known, but this study suggests it is not due to changes in intestinal morphology. L'expérience devait établir si les tannins concentrés qu'on trouve dans Lotus pedunculatus entraînent une modification morphologique de la muqueuse de l'intestin grêle et diminuent la capacité d'absorption de cet organe. Pendant quatre semaines, 13 jeunes béliers castrés Romney ont reçu à satiété du fourrage de L. pedunculatus (cv. Grasslands Maku, N = 7) contenant 5,5 % de tannins dans la matière sèche, ou un mélange de trèfle blanc et d'élyme vivace (N = 6) sans tannin. Les animaux ont ensuite été sacrifiés et on a prélevé des échantillons des parties proximales et distale du duodénum, des parties proximale, intermédiaire et distale du jéjunum et de l'iléon, et du rumen ventral pour les soumettre à un examen histologique. L'absorption de Lotus pedunculatus renfermant 5,5% de tannins n'a aucune incidence (P > 0,05) sur les paramètres morphologiques du rumen ou de l'intestin chez les ovins. On ignore pourquoi les tannins, en grande quantité, réduisent l'absorption des acides aminés, mais les résultats de la présente étude laissent croire qu'une modification de la morphologie de l'intestin n'est pas en cause. Mots clés: Lotus pedunculatus, tannins concentrés, morphologie de l'intestin, ovinsCondensed tannins are polyphenolic compounds commonly found in the seed coats of many plants (e.g., sorghum, alfalfa), and in the foliage of several legumes and grass cultivars (Waghorn 1996). Condensed tannins have been shown to protect plant proteins from degradation in the rumen of sheep. However, the apparent absorption of AA from the small intestine of sheep appears to be impaired by the CT in L. pedunculatus (Waghorn et al. 1994). Condensed tannins fed at low to medium concentrations in DM (up to 4% DM) usually result in increased N retention or AA flow to the intestine, but decreased in N digestibility over the entire digestive tract. The increased N retention is due to a greater supply of protein, and perhaps an improved ratio of nonessential:essential AA available for absorption (Waghorn et al. 1987).Condensed tannins bind to proteins in a pH range of about 5.0-8.0 and dissociate at a pH ...

Adult Trichostrongylus colubriformis infection did not affect protein synthesis rate in whole-body, intestinal, hepatic and skeletal muscle tissues of lambs fed fresh Lucerne (Medicago sativa)

“…However, there were no morphological changes in the duodenum, possibly due to the alkaline environment of the jejunum and ileum (Wang et al 1996;Dawson et al 1999). Similar levels of CT present in fresh Lotus pedunculatus (5.5% CT) had no effect on the morphology of the duodenum, jejunum or ileum in lambs (Walton et al 2001). This suggests that various types of CT may differ in their effects on FSR within the digestive tract as well as on animal production, due to variations in their chemical structure (Aerts et al 1999).…”

Biochemistry of plant secondary metabolites and their effects in animals

“…Decreased voluntary feed intake may be associated with astringency caused by the formation of tannin-salivary protein complexes in the mouth or signals of gut distension resulting from tannin interactions with proteins of the gut wall (D'Mello & Devendra, 1995). Tannins may also inhibit gut enzyme activity and affect gut permeability, causing decreased passage of nutrients through the gut wall (Walton et al 2001). N balance studies have demonstrated an increase in faecal N, often ascribed to undigested complexes between tannins and feed or microbial N. However, in some cases faecal N content is greater than N availability in the feed, and Barry (1989) has suggested a compensatory tannin-induced increase in microbial growth.…”

Morphometry of Organs in Sheep Fed a Diet Containing Tannins and Polyphenols

“…Also there have been findings indicating a trend of decreasing villus height and villus surface area in the proximal duodenum [5]. Conflicting reports on the effects of tannins on the morphometry of the intestine have been attributed to differences in species and to the site of sampling due to the wide variations in intestinal structure along the digestive tract [6].…”

“…There was an indication of these classical effects of tannin-containing feeds in ruminants from a digestibility trial using UTPF with sheep [3]. Higher levels of nitrogen in the faeces indicate lower nitrogen retention, which is a characteristic of dietary tannins, which bind to proteins in the rumen and consequently reduce digestion and absorption in the gut [2,4,5]. There are also reports that tannins may form complexes with carbohydrates and minerals and consequently inhibit microbial and digestive processes in ruminant animals, resulting in depressed rumen digestive function [2,15].…”

“…Tannins interfere with nutrient digestion and promote excretion of endogenous nitrogen in monogastric animals by forming tannin-enzyme complexes [4]. Tannins might also cause physical damage to the digestive system and other vital organs such as the kidney and liver [5,6]. Research has indicated different responses to tannin consumption in various animal species.…”