Effects of condensed tannins on goats experimentally infected with Haemonchus contortus.

Summary

Although the use of tanniferous plants or condensed tannins as an alternative to anthelmintics to
control gastrointestinal nematodes has been largely documented in sheep, studies remain scarce in
goats. The objective of this study was therefore to assess the possible impact of condensed tannins
in goats infected with adult Haemonchus contortus. Two groups of cull goats were experimentally
infected with 10.000 L3 of H. contortus. After 4 weeks, quebracho extracts, representing 5%
of the diet DM, were administered for 8 days to one of the two groups. Goats of the second
group remained as controls. One week after the end of quebracho administration, the goats were
euthanised. Individual egg excretion and pathophysiological parameters were measured weekly
during the study. At the end of the study, worm counts were assessed and histological samples
from the abomasa were taken to count the numbers of mucosal mast cells, globule leukocytes
and eosinophils. The administration of tannins was associated with a significant decrease in egg
excretion, which persisted until the end of experiment. This reduction was not associated with
any difference in worm number but with a significant decrease in female fecundity. No significant
changes in the mucosal density of the three inflammatory cell types were detected between the
two groups. These results indicate that the major consequence of tannin consumption in goats is a
reduction in worm fecundity and egg output, which does not seem related to significant changes in
the local mucosal response.