Agriculture Reference
In-Depth Information
overlooked cause of weight loss is tooth wear. Front and
side teeth need to be examined to establish if this is the
cause, especially in older goats.
Many diseases resulting in ill thrift cause obvious signs.
For instance, a goat with foot rot will walk less and forage
less due to the pain of the infection. Other diseases are less
obvious, and the signs will be hidden. Organ failure (liver
or kidney), chronic infections (chronic pneumonia), or
damage to viscera from previous disease (intestinal damage
from parasites) will all result in the symptom of ill thrift.
In adult females, these are all commonly lumped into the
diagnosis of “Thin Doe Syndrome.”
One of the most common infectious diseases causing ill
thrift in adult goats is internal abscessation due to CL (see
the Subcutaneous Swellings section). CAE is less common
and has obvious signs (see Lameness). Paratuberculosis
(Johne's Disease) (see Digestive Disorders) is primarily a
problem of dairy goats. It is a dangerous bacterial disease
because it can be introduced by buying apparently normal
goats that carry the disease.
In some countries, protozoan diseases like anaplasmo-
sis, babesiosis, theileriosis, eperythrozoonosis, and try-
panosomiasis can cause severe anemia, emaciation, and
death. Bacteria like mycoplasmosis and leptospirosis
(a bacterial disease that can affect the kidneys) would
also have to be considered. It needs to be emphasized
that any long-term infection or parasitism is accom-
panied by weight loss, and the primary cause must be
identifi ed.
parasites, for the most part, are a nuisance and can cause
production loss simply because the animal spends more
time and energy combating them than feeding. Physical
injury occurs when irritation and scratching result in open
wounds that then can become infected or subject to infes-
tation with fl y larvae.
The effects of parasitic infection can be infl uenced by
the nutritional status of the host. It is also true that parasites
interfere with the ability of the host to use nutrients effi -
ciently. The well-fed animal is able to tolerate increasing
infection levels, but eventually a point may be reached
where parasitism overwhelms the host's ability to function
properly. Depending on the host's age and sex, season of
the year, and exposure to various potential infectious
agents (parasitic and otherwise), nutrients are partitioned
for growth, breeding, pregnancy, lactation, immunity, etc.
The ability of the host to maintain a proper balance of this
partitioning ensures that nutrients are used appropriately.
Overall, inadequate feeding will lead to loss of productiv-
ity unless the balance is restored.
GASTROINTESTINAL
NEMATODES (WORMS)
There are a number of worms found in goats, and this
section will concentrate on the predominant and usually
the most pathogenic ones.
General Life Cycle of Roundworms
The life cycle of worms consists of part of their life being
spent inside the animal and part of their life on the pasture
(Figure 11.1). Worms mate in the host, and females lay
eggs that pass out in the feces. The eggs hatch and develop
to infective larvae while remaining in the feces. The infec-
tive larvae then move out of the feces onto the surrounding
forage where they can be consumed during grazing thus
completing the cycle. The time from ingestion of infective
larvae to egg-laying adults, called the prepatent period, is
about 2-3 weeks, and the time for development from egg
to infective larvae can be as short as 7-10 days (especially
during the summer months). Therefore, continual pasture
contamination can lead to rapid transmission and reinfec-
tion. During the colder months, larval development on
pasture is delayed and may take up to a month or two to
reach the infective larvae stage, thus pasture contamination
and reinfection is minimized. The infective larvae have a
protective sheath making them relatively resistant to
adverse environmental conditions, which allows them to
survive for months, thus extending transmission potential.
As long as temperature and moisture conditions remain
GOAT PARASITES
Parasitism, and gastrointestinal nematode parasitism in
particular, is a serious constraint affecting small ruminant
production worldwide. Economic losses are caused by
decreased production, cost of prevention, cost of treat-
ment, and the death of infected animals. Problems with
nematode parasitism are often classifi ed as production
disease (chronic and subclinical conditions affecting
productivity such as weight loss, reduced weight gain,
reproductive ineffi ciency, etc.). This is more so the case
when goats are managed as grazers or in confi nement
rather than browsers. The nematode of particular concern
is the Barber-pole worm (
Haemonchus contortus
). The
tremendous egg-laying capacity of this worm is main-
tained by feeding on blood by both immature and mature
stages. Severe blood loss can occur, resulting in anemia,
loss of appetite, depression, loss of condition, and even-
tual death. Other worms contribute to “production disease”
because they usually do not kill but affect the animal's
ability to increase and/or maintain production. External
