Abstract :
The foraging response of goats and sheep to tannin-rich plants (TRP) could be influenced by
their physiological adaptation to eat fodder from a specific ecological niche. The aims of this
study were: (1) to describe the amino acid profile of the protein from whole saliva of adult
goats and hair sheep browsing/grazing native vegetation, (2) to measure the interaction
of whole saliva from goats and hair sheep with tannic acid, (3) to compare the tanninbinding
capacity of lyophilized whole saliva from goats and sheep to precipitate tannins
extracted from the fodder of tropical TRP (Acacia pennatula, Lysiloma latisiliquum, Leucaena
leucocephala and Piscidia piscipula). Fresh whole saliva was obtained from 42 adult goats
and 51 adult hair sheep. A second batch of saliva (obtained from 75 adult goats and 93
adult hair sheep) was lyophilized whole saliva. Protein from whole saliva in both animal
species had a similar pattern of amino acid composition. Histidine and arginine were found,
accounting for 30% and 24% of the amino acid content, respectively. Whole saliva from
goats and sheep showed a linear dose response to increasing concentrations of tannic acid
at each time point measured (P < 0.001). Saliva from goats was able to precipitate higher
quantities of TRP extracts from A. pennatula and L. latisiliquum than from P. piscipula and
L. leucocephala (P < 0.05). Saliva from sheep precipitated higher quantities of L. latisiliquum
and P. piscipula extracts (P < 0.01). Also, salivary proteins from goats had higher capacity
to precipitate tannins from A. pennatula than sheep, while salivary protein from sheep had
higher capacity to precipitate tannins from P. piscipula than goats (P < 0.05). The results
provide evidence of the differences between goats and sheep in the capacity of their saliva
to interact with local sources of tannins, which could explain the different feeding behaviour
of goats and sheep. The presence of histatins may help to explain the in vivo AH effects of
TRP fodder.
