Everything Horse magazine Everything Horse UK Magazine, November 2014 | Page 34

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n the last issue we looked at different
parasites which live inside the horse
and the best way to diagnose that the
horse has a burden. Most species gain
access to the horse after being passed
out in faeces on pasture either as larvae
or eggs which later hatch and are then
swallowed by the horse and its herd mates
whilst they are grazing. Domesticated
horses are more often than not confined
to undersized paddocks with varying
degrees of an available food sources,
resulting in overgrazed areas that have a
high concentration of droppings (Lamoot,
et al. 2004). The horse’s environment has a
huge influence upon the risk of it becoming
infected and the owner can control many
of these areas through good pasture
management.

Assessing the risk: Q&A
What is stocking density and why is it
important?
Assessing the amount of land available and
the number of horses grazing it is essential
to calculate the stocking density. The British
Horse Society recommends a ratio of two
horses per hectare on permanent grazing
(1-1.5 acres per horse) although this can
vary according to the pasture quality
and the type of animals grazing it. It is
not unusual to see much higher stocking
densities, especially on commercial
enterprises where space is at a premium.
However, this will increase the likelihood of
the horse ingesting worm larvae, as most
species will migrate up to one metre from
each droppings pile. Where areas of the

field have been churned up, grazing areas
will be concentrated.

horses had the highest parasite burdens
which contradicted what was expected.

Are other co-grazing species at risk?
All grazing animals are at risk of parasite
infection, but most worms have a
preference for one species. This can be
used to your advantage if you have access
to cows, sheep, goats or other grazers
who can share the acreage as they act as
‘biohoovers’ – taking in larvae from the
pasture which then do not complete their
life cycle and thus reducing the overall
worm burden on the pasture and in your
horse! It is noteworthy to mention that
these co-grazers will still need their own
worming treatment plan, and will need to
be accounted for in the stocking density.

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What about poo picking?
Whilst it can be a laborious task, there is
evidence to suggest that regular removal
of droppings from pasture is an effective
strategy to reduce parasite burdens.
Corbett, et al. (2014) investigated the effect
of three modes of pasture management;
no removal (group 1), manual removal
of faeces twice weekly (group 2) and
automatic removal of faeces twice weekly
(group 3). They found that both removal
methods resulted in a significant reduction
in the eggs per gram when compared to
group 1.

I haven’t got enough grass – should I put
hay out in the field?
Feeding supplementary forage can be a
useful way of making sure that horses
still have something to eat BUT this may
be exposing them to high numbers of
parasites. BSc (Hons) Equine Science
student Adam Taft investigated the effect
of dominance on parasite burdens in a
group of horses at Reaseheath College.
Results showed that when hay was fed in
one area of the field, the most dominant

www.equetech.com

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Pasture Management
Parasitism

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WELCOME TO OUT NOW
ECTION NOVEMBER’S MAGAZINE
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Take home message….
Ultimately parasite management should
follow a strategic approach – judicious use
of wormers linked to season and diagnosis
of a burden, coupled with a pasture
management strategic which works for the
yard in question.
Reduced reliance on wormer chemicals will
help to combat resistance with financial
benefits to the horse owner and health
benefits to the horse!
Written by Kate Douglas-Dala

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Everything Horse UK Magazine • Issue 14 • November 2014

November 2014 • Issue 14 • Everything Horse UK Magazine

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