Utility of the browser’s behavioural and physiological strategies in coping with dietary tannins: Are exogenous tannin-inactivating treatments necessary?

Abstract

The desire to reduce feeding costs in small-ruminant production systems has led to increased reliance on non-conventional locally available browse products as protein supplements. Browse products contain variable quantities of tannins, whose nutritional effects on the animal can be positive or negative. Because of the lack of rapid evaluation techniques and methods that can differentiate, accurately, between potentially beneficial and harmful tannins, most researchers employ a 'safety first' approach in which tannin-inactivating treatments are applied to browse products to protect the animal and enhance feed utilization. This is despite the fact that browsing herbivores are known to have various behavioural and physiological strategies to cope with a number of anti-nutritional plant compounds, which include tannins. In this paper, the authors explore the rationale behind recommending the use of tannin-neutralization strategies when feeding animals with browse leaves and fruits. Are browsing herbivores' own coping strategies sufficient to protect them from suboptimal nutrition and possible toxicity caused by tannins or is intervention always required? In an attempt to answer this question, this review presents the current state of knowledge of tannins in ruminant nutrition before summarizing the strategies that browsing herbivores use to cope with tannins and their potential utility in various rearing systems. Finally, the utility of exogenous tannin inactivation strategies and the animals' own coping strategies are compared. Feeding scenarios are identified in which exogenous inactivation strategies may be worthwhile.

Comparative nutritional studies of sheep and goats fed cultivated tree legumes mixture under desert condition

“…On the other hand, animals fed G1 showed higher (P<0.05) overall DM, OM and NFE digestibility than those fed G2 (73.21 vs. 66.55, 74.12 vs. 68.21 and 77.56 vs. 68.61 %, respectively) but overall CP, CF and EE digestibility were similar between both treatments. The lower values in digestibility of tree legumes mixture may be attributed to high content of tannins [48,49]. Tannins could can be reduce digestibility of crude protein and carbohydrate by inhibiting digestive enzymes and by altering permeability of the gut wall [50,51].…”

Influence of harvesting site on chemical composition and potential protein value of Acacia erioloba, A. nilotica and Ziziphus mucronata leaves for ruminants

“…While browse trees are widely accepted as potential sources of protein for ruminants and non‐ruminant herbivores, they also contain secondary plant compounds whose effects on animal production and health are rather equivocal. Of major concern is the high concentration of phenolic compounds such as tannins, which are produced by plants for various purposes (Mlambo et al., ). In some plants, biosynthesis of these secondary plant metabolites, although largely constitutive, can be induced and enhanced by biotic and abiotic environmental stress factors (Harbone, ) such as herbivory or moisture stress.…”

Potential of oak acorn with and without polyethylene glycol as an alternative to corn in broiler diets

“…PEG can form complexes with tannins, thereby preventing the binding of tannins with dietary nutrients (Mansoori et al, 2007b). The beneficial effects of PEG in reducing the negative effects of tannins in ruminants have been indicated (Mlambo et al, 2015). However, supplementation with PEG increased the nitrogen digestibility in chicks fed high-tannin sorghum (Ford & Hewitt, 1979).…”