H. Narjisse et al., EFFECTS OF OAK (QUERCUS-ILEX) TANNINS ON DIGESTION AND NITROGEN-BALANCE IN SHEEP AND GOATS, Small ruminant research, 18(3), 1995, pp. 201-206
Sheep and goats exhibited different levels of tolerance to the effects
of tannins extracted from oak leaves (Quercus ilex). Feed intake, N b
alance, and rumen ammonia concentrations decreased by 8%, 159% and 50%
, respectively, in sheep infused intraruminally with tannins (P < 0.05
). Similar measurements were not depressed (P > 0.05) in goats althoug
h mean rumen ammonia content was 39% less. In vivo DM digestibility wa
s not significantly different for either sheep or goats. Averaged in v
itro fermentation capacity was depressed 10% by tannin (8-12% concentr
ation) in the rumen fluid from non-infused sheep given the same diet,
but was improved by 9% for goats. Finally, tannin-infused goats lost i
n urine only 17% of the N ingested, while tannin-infused sheep excrete
d as much as 44%. The superiority of oats in dealing with tannin might
result from the greater ability of their microbial population to degr
ade tannins, and/or their higher urea recycling and salivary secretion
capabilities. Results derived from this study indicate that goats may
be more suitable for grazing in oak woodland, especially during the s
eason when alternative forage availability is scarce.