Effect of feed block supply on the ruminal ecosystem of goats grazing shrub land in Tunisia

Six male goats, fitted with ruminal cannulae, were used to study effects of feed block supplementation on the ruminal ecosystem of browsing goats during spring. Ruminal fermentation parameters (i.e. pH, ammonia N, and volatile fatty acids (VFA)) in rumen liquor were measured monthly three times in a day (i.e. 0, 2 and 6 h after starting shrub land pasturing). A rumen in situ technique was used to examine disappearance of dry matter (DMD), crude protein (CPD), and organic matter (OMD), and rate and extent of gas production was studied. The browse species evaluated were Arbutus unedo, Calycotum villosa, Cistus salvifolius, Erica arborea, Phillyrea angustifolia, Pistacia lentiscus, Myrtus communis, and Quercus suber. There were no effects of feed blocks on ruminal pH, NH3–N and VFA concentrations. Browse species varied widely in CP (55–221 g/kg DM) and condensed tannin contents (10–383 g/kg DM), but DMD, OMD and CPD did not differ in unsupplemented vs. supplemented goats. There was also no effect of the origin of the rumen inoculum (i.e. from unsupplemented vs. supplemented goats) on patterns of gas production. Feed block supplementation did not affect the ruminal ecosystem of goats browsing on shrub land during the growing season due to either sufficient nutrients consumed without supplementation, or the inability of feed block supplementation to inactivate tannins in the browse species.