Abstract :
In the last decade, numerous studies have been carried out to evaluate the potential
anthelmintic benefit of the consumption of bioactive plants in small ruminants, in order
to reduce the dependence on conventional chemotherapy and supporting a sustainable
control of gastrointestinal (GI) parasitism. This review summarizes the anthelmintic and
nutritional effects of heather (shrub species belonging to the Ericaceae family, such as Erica
spp. or Calluna vulgaris) supplementation in grazing goats naturally infected by GI nematodes.
The experiments were carried out in a mountain area in north-western Spain where
shrubby heather-gorse vegetation is dominant. Some plots were established, in which the
vegetation had been improved by soil ploughed and dressing and sowing perennial ryegrass
(Lolium perenne) and white clover (Trifolium repens), and removing any heather that
was present. Cashmere goats reared outdoors under pasture conditions were used in the
experiments. The trials compared the response to GI nematode infections, animal performance
and nutrition in goats supplemented or not with heather. Interactions between
heather availability and other alternative methods to control GI nematode infections based
on grazing management (stocking rate) or nutrition (energy supply) as well as the potential
adaptation of the rumen microbiota to the consumption of tannins, were also studied. The
results suggest that (i) heather supplementation in grazing goats significantly reduces the
level of GI nematode egg excretion, (ii) the faecal nematode egg count reduction could be
associated with a decrease in worm fertility and/or reduction in the establishment of incoming
third-stage larvae, (iii) consumption of heather is associated with an apparent greater
resilience of goats to GI nematode infections, and (iv) the amount of tannins consumed by
the goats supplemented with heather does not seem to be associated to anti-nutritional
effects which eventually resulted in a better animal performance in the animals incorporating
these shrubs in their diet. Practical application of this knowledge in temperate areas
would support the management of plots integrating improved pastures with high nutritive
value (ryegrass-white clover) with natural vegetation communities.
