Do goats have a salivary constitutive response to tannins?

Abstract

The effect of tannin-rich fodder (TRF) consumption on the saliva response of Criollo goats without previous browsing experience was determined. Eighteen kids were allocated into three treatments (n = 6 each): control group (CG), short-term tannin stimulus (TS) and long-term tannin stimulus (TL). Three experimental periods were used: adaptation (two weeks) in which the three treatment groups were fed Pennisetum purpureum grass and supplemented with a balanced feed. In period 1 (five weeks), TS and TL treatments were fed TRF (Lysiloma latisiliquum) with 55.5 g/kg DM condensed tannins (CT), grass and balanced feed. In period 2 (three weeks), L. latisiliquum fodder was withdrawn from the TS group. Thus, both the TS and the CG kids were only offered grass and balanced feed, while TL kids continued to receive TRF. In each period, saliva samples were collected to measure the tannin–protein interaction, salivary protein and protein turbidity index (PTI). The salivary protein was similar in all treatments and periods (P > .10). The goats’ saliva reacted similarly when mixed with either tannic acid or L. latisiliquum water-acetone extract. Although the PTI tended to increase in the TL group compared to CG and TS with time, such difference was not significant. Thus, TRF intake failed to further increase the salivary response or PTI. Therefore, the saliva of goats from Yucatan, without previous browsing experience do have a constitutive response as it can block tannins irrespective of TRF stimulus.