Health Management, Diseases, and Parasites - Goat Science and Production - page 232

for a long time) will more highly contaminate the new
pasture with resistant worm larvae.

work has shown that COWP effectively removes substan-
tial numbers of H. contortus in goats (Burke et al., 2007).
Copper toxicity, which is common in sheep, may not be
much of an issue in goats because they are not as sensitive
to excess copper intake. Thus, more extensive use of
COWP during haemonchosis season may be useful in
goats.

Non - Drug Approach
M IXED /A LTERNATE L IVESTOCK S PECIES G RAZING
For the most part, each livestock species harbors its own
parasite fauna except that small ruminants have the same
parasites. Cattle and goats can be grazed together where
each consumes the parasites of the other. As an alternative
to co-grazing, cattle and goats can graze alternately on the
same pastures. Either way, pasture contamination and re-
infestation will decrease over time, thus both (or one)
species should gain from this (Jordan et al., 1988).

C ONDENSED T ANNIN - C ONTAINING F ORAGE
There is growing evidence that plants containing con-
densed tannins (CT) can reduce FEC and adult worms in
the abomasum and small intestine. In addition, larval
development in feces may be hindered. There are a number
of CT-containing forage products; and in the U.S., sericea
lespedeza (SL, Lespedeza cuneata ), a perennial warm-
season legume, has been shown to reduce FEC (primarily
H. contortus ) in grazing sheep and goats and when fed as
hay, ground hay or pellets in confi nement (Min et al., 2005;
Terrill et al., 2007). Similar results have been observed
with quebracho extract for both abomasal and small intes-
tinal worms (Athanasiadou et al., 2000).

P ASTURE R OTATION
The value of pasture rotation to break the parasite cycle
has been discussed for years (Levine et al., 1975; Colvin
et al., 2008). The main reason to use pasture rotation is not
for parasite control but to provide the most nutritious
forage for animal growth and development. Many forage
products reach the most nutritious stage about 30 days after
animals have been removed, so rotation schemes usually
have the animals returning to pastures at around 30-day
intervals. Unfortunately, this 30-day interval is also about
the same time necessary for newly deposited eggs to
develop into the highest level of infectivity for the next
grazing group. Thus, this rotation scheme may actually
lead to increased worm parasite load. Rotation schemes of
2-3 months have been shown to have some effect on
reducing pasture infectivity in tropical and subtropical
environments; but in more temperate environments, infec-
tivity can extend out to 8-12 months depending on the
conditions. It is usually impractical to leave pastures
ungrazed for such extended periods of time; therefore,
being aware of the possible problems associated with
whatever rotation scheme being used is important. Some
success at reducing infectivity can be achieved by cutting
pasture for hay between grazing periods. It should also be
emphasized that when rotation schemes are used, stocking
rate is usually high and the resultant increase in contamina-
tion may also make the problem worse.

G ENETIC I MPROVEMENT
Part of the ability of the host to resist worm infection is
under genetic control. Resistance is based on inheritance
of genes, which play a primary role in expression of host
immunity. Under survival of the fi ttest management condi-
tions, several sheep and goat (East African Dwarf and
Saanan) breeds have been shown to be relatively resistant
to infection (Preston and Allonby, 1978; Baker et al., 1998;
Amarante et al., 2004). Using resistant breeds exclusively
or in crossbreeding programs could lead to improved resis-
tance to worm infection, but some level of production
might be sacrifi ced. While this strategy may be acceptable,
selection for resistant animals within a breed is also an
option. Within breed, animals usually become more resis-
tant to infection with age as their immune system matures.
However, some animals do not develop this immunity as
well as others and remain relatively susceptible to infec-
tion. It is well known that the majority of the worm popula-
tion resides in a minority of the animal population. It
would make sense, then, to encourage culling practices
(based on FEC, PCV, FAMACHA, etc.) where these
minority “parasitized” animals are eliminated, thus retain-
ing more resistant stock. Using sires that throw relatively
resistant offspring and/or using genetic markers to identify
resistant animals would speed up this process. This
approach has been used successfully (Crawford et al.,
2006; Hunt et al., 2008), but it may take quite a long time
to achieve satisfactory results. The real benefi t to this

C OPPER O XIDE W IRE P ARTICLES
Copper oxide wire particles (COWP) are marketed as
a supplement for cattle being managed in copper-
defi cient areas. It is also known that copper has some
anthelmintic activity against abomasal worms, but not
other gastrointestinal worms. That makes it a very narrow
spectrum product. But, in view of the potentially devastat-
ing problem of anthelmintic resistant H. contortus , recent