Abstract :
Livestock production systems worldwide rely largely on conventional feedstuffs. The current
world food crisis highlights the need to improve the use of local resources for animal
nutrition, such as fodder trees and shrubs. The detrimental effects of tropical tannin-rich
plants (TRP) on animal production have been frequently described. In contrast, their potential
benefits have long been neglected. This paper presents the potential positive effects
of tropical TRP on small ruminants either as source of feed or as nutraceuticals with
anthelmintic (AH) properties. It also analyses the host behavioral and physiological adaptations
associated with exploitation of those tannin-rich resources. Both sheep and goats
preferred a mixture of plants even when tannin-free forage was available. Moreover, the
preference for TRP by goats and hair sheep were mainly associated with the digestible
fraction of fiber and to a less extent with tannin content, which implies that they do not
necessarily select against TRP. The addition of polyethylene glycol did not modify the preference
or intake of TRP by goats and sheep. Evidence of physiological adaptation to TRP
is presented and discussed. Both, experienced hair sheep and goats had saliva with tannin
binding capacity, enabling both species to eat higher quantities of TRP which could lead
to a higher availability of tannins in the gastrointestinal tract. Tannins in the gastrointestinal
tract could be an AH against gastrointestinal nematodes (GIN). Indeed, in vitro and in
vivo studies have shown AH effects of tannins from TRP, suggesting their possible use as
natural anthelmintics against GIN. This paper supports the change in the current view of
tannins in TRP as anti-nutritional compounds. If adequately managed, TRP can be a valuable
component of sustainable small ruminant production systems.
