Relationship between intake of tannin-containing tropical tree forage, PEG supplementation, and salivary haze development in hair sheep and goats

• Variation in TBSP expression of sheep and goats modifies tannin intake from foliage.
• Foliage fiber or protein content are better predictor of intake than tannin content.
• Sheep and goats’ supplementation with PEG does not modify preference.
• Sheep and goat salivary protein content is not affected by foliage intake or PEG.

The objective of this study was to estimate the relationship between tannin binding salivary protein (TBSP) and condensed tannins (CT) intake in hair sheep and creole goats. Foliage was obtained from trees with different levels of CT content; animals were offered foliage ad libitum, with or without polyethylene glycol (PEG). Saliva haze development (SHD) was evaluated as evidence for TBSP. PEG consumption did not affect dry matter intake (DMI) (P > 0.05). Lignin (R = −0.714, P < 0.001) and Crude Protein (CP) (R = 0.622, P < 0.001) contents had a stronger association with DMI than CT (R = 0.622, P < 0.011) in sheep; no significant association was found in goats. The positive relationship between tannin intake and SHD (P < 0.05) was not confirmed after PEG supplementation in sheep (P > 0.09), but remained significant for goats (P < 0.01), except for those fed Lysiloma latisiliquum (P = 0.07). Foliage lignin or CP contents are better predictors of foliage intake than CT. Sheep and goats fed with tropical tree forages containing different levels of tannins exhibited differences in intake behavior; moreover, individual variations in TBSP expression helps explaining foliage DMI.