ANSC 420: Critical thinking
in Animal Science
Susan Schoenian
Sheep and Goat Specialist
Western Maryland Research & Education Center
University of Maryland Cooperative Extension
www.sheepandgoat.com – sschoen@umd.edu
Critical thinking is learning to think for yourself
and to develop your own independent opinions,
backed by sound reasoning and support.
Critical thinking is the process of evaluating
what other people say or write to determine
whether to believe their statements.
Critical thinkers gather information from all senses,
verbal and/or written expressions, reflection,
observation, experience, and reasoning.
. . . to form a solid judgment that reconciles
scientific evidence with common sense.
Lecture/Discussion topic
(Internal) parasite control
in small ruminants
Small ruminants
• Ruminant
–
–
–
–
Even-toed hoofed animal
Cud-chewing
4 compartment stomach
Bovidae (hollow horns) family
• Caprinea sub family
– Ovis aries (54 chromosomes)
– Capra hircus (60 chromosomes
• Small
– sheep, goat, cervids (deer)
Sheep and goats
•
Multi-purpose animals
1)
2)
3)
4)
5)
6)
7)
8)
Meat
Dairy
Fiber
Vegetation control
Research and biomedical
Hobby
Youth projects (4-H, FFA)
Pets
Sheep vs. goats
 More similarities than
differences.
 Same problems,
same opportunities
 Mostly the same
diseases and health
issues.
Sheep and goats in Maryland
2002 Ag Census: 22,702 sheep (655 farms) and 9,601 goats (702 farms)
• Some large farms
– 200-300 females
– Over 500
– Largest farm has 1,600 sheep for
bleeding
– Only 4 certified dairy goat farms;
no sheep dairies
– A lot of small fiber flocks
• Mostly small farms
– Average flock size is less than 30
– A lot of niche marketing of lamb
and wool products.
• Some commercial production
• Mostly hobby, 4-H, tax advantage
Parasite
An animal or plant that lives in or on a host (another animal or plant) and
obtains nourishment from the host without benefiting or killing the host.
Internal parasite
An organism which lives in an animal and derives its
nutriment from the host animal often causing death or
damage to the host. This term is usually reserved for worms.
Internal parasites (worms)
• Primary health
problem affecting
small ruminants in
warm, moist climates
like Maryland.
• Sheep are goats are
more susceptible to
the effects of internal
parasites than most
other livestock.
Why more susceptible?
•
•
•
•
•
•
•
•
•
•
•
Close grazing
Goats forced to graze
Small fecal pellets
Graze close to feces and each
other.
Slower to develop immunity
Incomplete immunity (goats)
Temporary relaxing of
immunity at lambing/kidding.
Lack of veterinary expertise
Lack of FDA-approved drugs
Worms have become resistant
to most dewormers (drugs).
Main parasite is a blood
sucker and killer!
Lack of veterinary expertise
• Many veterinarians will not
work with farm livestock.
• Many veterinarians lack
technical and/or practical
knowledge of sheep and goat
health issues.
• The cost of treating a sheep or
goat often exceeds its value.
• There is often a disconnect
between veterinarians and
producers.
• Most sheep and goat
producers learn to do their own
veterinary work.
– They are often in violation of
extra-label drug laws (they
have no choice!).
Lack of FDA-approved drugs
•
Three families (chemistries) of
anthelmintics.
1) Benzimidazoles
2) Nicotinic agonists
3) Macrolytic lactones
•
1-2 drugs in each family are FDAapproved for use in sheep.
1) Valbazen®
2) Levamisol ®
3) Ivermectin ® and Cydectin ®
•
Only two drugs are FDA-approved
for use in goats.
1) Safeguard ®
2) Rumatel ®
•
•
U.S. Organic standards do not
permit deworming of meat animals.
There is growing public scrutiny
regarding the use of drugs in food
animal production.
Therapeutic  Medical use
Lack of anthelmintic efficacy
• Overuse (therapeutic) and
sometimes misuse (e.g. pourons and injectables,
underdosing) has lead to the
emergence of drug-resistant
worms in all three anthelmintic
classes.
• Highest levels of resistance
have been reported in the
benzimidazoles and
ivermectins.
• Drug resistance is determined
using a fecal egg count
reduction test or DrenchRite®
larval assay test.
• Resistance is permanent
(levamisole ?).
Slowing drug resistance
The FAMACHA© system
• A color eye chart showing
varying degrees of anemia
(symptom of barber pole worm
infection).
• Identifies animals that require
deworming and those that do
not.
• Results in fewer animals being
treated.
• Results in more refugia (worms
that have not been exposed to
the drug).
• Slows the development of drugresist worms and prolongs the
effectiveness of anthelmintics.
Non-chemical “dewormers”
• Nematode-trapping
fungus
• Copper oxide wire
particles
• Condensed tannins
(Sericea lespedeza)
• Natural dewormers are
currently be evaluated by
researchers:
–
–
–
–
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Garlic juice
Pumpkin seeds
Wormwood
Diatomaceous earth
Oregano oil (coccidiosis)
• A vaccine is under
development.
The internal parasites of
sheep and goats
 Stomach worms
• Tapeworms
• Lungworms
• Liver flukes
 Coccidia
• Meningeal worm
The “other” parasites
These parasites tend to cause less problems than the others
• Tapeworms
– Tend to be non-pathogenic
– No beneficial effect of
treatment
• Lungworms
– Difficult to diagnose
• Liver fluke
– Not thought to be a problem
in Maryland
• Meningeal worm
– Parasite of the white tail deer
(sheep and goats are
abnormal hosts)
– Requires intermediate host
(snail, slug)
– Causes neurological damage.
Coccidia
Eimeria sp.
• Single-cell protozoa
• Species-specific
• Permanently
damages lining of the
small intestines.
Coccidia life cycle
2 to 3 weeks
oxygen, moisture, warmth
Diagnosing coccidia
• Affects mostly young
lambs and kids, 1 to 6
months of age.
• Diarrhea is the most
common symptom. It
often contains blood or
mucous.
• Other symptoms: loss of
appetite, rough hair coat,
poor growth, ill thrift, loss
of body condition,
dehydration.
• Fecal egg flotation*
Treating coccidiosis
• Amprolium (Corid)*
• Sulfa drugs*
• Must individually
treat each animal.
• Must treat each
animal in pen.
• Cannot reverse
permanent damage.
* Not FDA-approved for goats
Prevention of coccidiosis
• Some level of “infection”
is normal.
• Most fecal tests will be
“positive” for coccidia
eggs.
• Young animals require
low level of exposure to
develop immunity.
• Prevention starts with
good sanitation and
management.
– Clean pens
– Feed and water that is free
from fecal matter
– Avoid overstocking
Prevention of coccidiosis
• Coccidiostats aid in the prevention of coccidiosis and
can be put in the feed, mineral, or drinking water.
Feed/mineral
– Monensin (Rumensin®1)
– Lasalocid (Bovatec®2)
– Decoquinate (Deccox®12)
– Oregano oil (experimental)
Drinking water
– Amprolium (Corid)
1
FDA-approved for goats
2 FDA-approved for sheep
Coccidiostats
Inhibit growth but do not kill coccidia
• Reduce coccidia in the
environment
– Start 30 days before
lambing/kidding
– Continue through weaning
– Include in lamb and kid
rations
• Have many other
beneficial effects
– Feed efficiency, rate-ofgain, aid in prevention of
toxoplasmosis and bloat
 Can be toxic to equines
Gastro-intestinal worms
The barber pole worm and its relatives
 Haemonchus contortus
Barber pole worm
• Ostertagia circumcincta
•
Medium or small brown stomach worm
Trichostrongylus
Bankrupt or hair worm
Barber Pole Worm
Rough hair coat
Symptoms
–
–
–
–
–
Pale mucous membranes
Edema (bottle jaw)
Not diarrhea (scours)
Sudden DEATH
Fecal egg flotation (?)
Weight loss, unthrifty
Is difficult to control because . .
– Short, direct life cycle
– Prolific egg producer
– Can go into “hypobiotic”
(arrested) state during winter
to survive.
– Can survive on pasture for a
long time.
Bottle jaw
Pale membranes
Stomach worm life cycle
2-3 weeks
Eggs require
warmth (60°F)
and humidity to
hatch to first
stage larvae.
Infective larvae on pasture
(if no treatment)
Lambing Rise
Spring Rise
Fecal egg counts
Ewes
Lambs
Lambing
Weaning
F
M
A
Spring
M
J
J
A
Summer
S
O
Fall
N
D
J
Winter
F
Integrated Parasite
Management (IPM)
Goal is not to create parasite-free animals. It is normal
for sheep and goats to have parasites. Goal is to prevent
clinical disease and production losses.
Parasite control begins with good
management and common sense
• Good sanitation
• Feeders which prevent
wastage and
contamination.
• Clean water, free from
fecal matter.
• Not overstocking pens
and pastures.
• Isolation and
deworming of new
animals.
The primary cause of internal parasitism is overstocking.
Use “clean or safe” pastures
What is a safe pasture?
•
•
•
•
•
•
•
•
New pasture
Pasture that has been renovated
with tillage
A pasture that has not been
grazed by sheep or goats for the
past 6 to 12 months.
Pasture grazed by horses and/or
cattle for the past 6 to 12
months.
Pasture in which a hay or silage
crop has been removed.
Pasture that has been rotated
with row crops.
Burnt pasture
Severely overgrazed pasture????
Cleaner, safer pastures are a more realistic goal for most producers.
Graze multiple species
• Sheep and goats share the
same internal parasites, but
they are different from the
parasites that affect cattle and
horses.
• Producers who graze multiple
species of livestock report
fewer parasite problems.
• Cattle and horses“vacuum”
sheep/goat pastures.
• There are other benefits to
mixed species grazing, such as
complimentary grazing habits.
Pasture Rest and Rotation
•
•
•
•
Pasture rotation is a
recommended strategy for
controlling internal parasites
because it allows the use of safe
or safer pastures.
BUT, intensive rotational grazing
generally does not help to reduce
parasitism unless rest periods are
long enough.
In a rotational grazing system,
ideally, sheep/goats should not be
returned to the same pasture for
2 to 3 months.
Due to increased stocking rates,
management intensive grazing
may increase internal parasite
problems in sheep and goats.
Alternative forages
• Livestock that browse
have fewer parasite
problems.
• Livestock grazing tallgrowing forages will
have less parasite
problems.
– 80% of parasites live
in the first 2 inches of
the vegetation.
• Grazing some hightannin forages may
reduce the effects of
parasitism.
Forage
Chicory
Sericea Lespedeza
Birdsfoot
Trefoil
Chicory, birdsfoot trefoil,
and Sericea Lespedeza
have been shown to
reduce fecal egg counts
and/or larval
development.
Nutritional Management
• Animals on a high plane of
nutrition and in better body
condition are better able to
withstand worm burdens.
• Nutrition in early pregnancy
(fat stores) can affect the
immune response to internal
parasites.
• Sheep receiving higher levels
of protein prior to lambing
have lower fecal egg counts.
• Supplementing lambs with
protein has been shown to
reduce fecal egg counts.
“Zero” grazing
• Sheep/goats raised
in confinement or
dry lot (zero
grazing) have fewer
stomach worm
problems.
• Sheep/goats put in
confinement or dry
lot do not usually get
re-infected with
stomach worms.
• Coccidiosis could still
be a problem.
Genetics and worms
Two important traits: resistance and resilience
Resistance
– Ability of host to limit infection
– Assessed by fecal egg counts
(FEC)
Resilience
– Ability of host to withstand
challenge and/or infection, and
thus maintain health and
productivity.
– Assessed by blood
hematocrit/packed cell volume
(PCV) and eye anemia score.
Moderately heritable – 20-40 percent
“Resistant” Breeds
Some sheep and goat breeds are more resistant to worms.
Sheep
•
•
Gulf Coast Native
Hair sheep
– Barbados
Blackbelly
– St. Croix
– Katahdin
– Royal White (?)
– Select populations
of other breeds(?)
NOT
•
•
Traditional wooled
breeds
Dorper
Goats
•
•
•
•
•
Spanish/Brush
Myotonic/Tennessee
Kiko
Pygmy?
Savannah????
NOT
•
•
•
Boer goats
Dairy goats
Angora goats
“Resistant” Individuals
Parasite resistance varies between individual animals of the same breed type.
•
•
•
20-30 percent of flock shed most
of the parasite eggs.
Focusing deworming on
susceptible animals will
significantly reduce pasture
contamination.
Culling worm-susceptible animals
will increase flock resistance and
reduce pasture contamination.
Heritability of FEC and PCV
FEC
(resistance)
PCV
(resilience)
Ewes
0.31
0.15
Lambs
0.10
0.39
2004, Vanimisetti, Andrew, Zazac, Notter
Selection for parasite resistance is
possible and will not adversely affect
growth of lambs and fertility of ewes.
Comparison of Genetic and Nongenetic Control Strategies
Strategy
Reduction in FEC’s
Genetic Selection
69%
Protein supplementation
35%
Strategic deworming
28%
Experimental vaccine
0%
Australia, 2002
•Monitor sheep, run in the plots after the end of the experiment had
lower FEC’s when run in the plots previously grazed by
supplemented sheep (35%) or selected sheep (46%).
•The largest and most persistent effect on FEC’s and worm
contamination of pasture was achieved by genetic selection.
Maximize the effect of a
single treatment
• Give proper dose;do not
underdose.
• Dose orally (all formulations)
• Put dewormer in back of mouth
behind tongue.
• Restrict feed 12-24 hours
before administering a
benzimidazole or ivermectin or
administer two treatments 1224 hours apart.
• Use higher dose for goats than
listed on label. Goats usually
require 1.5-2X the sheep/cattle
dose. (Consult with
veterinarian for proper dose for
goats).
• Use two different drugs.
Slowing Down Drug Resistance
• DO NOT overuse drugs,
especially Levamisole and
Moxidectin.
• DO NOT introduce resistant
worms to your farm
– Isolate new animals and
deworm them aggressively
• DO NOT underdose
– Weigh animals or dose for
heaviest animals in group.
• DO NOT rotate dewormers
after each treatment
– Rotate dewormers annually
– Rotate among drug families
– Use specific dewormers for
specific situations.
• DO NOT treat everybody
– Leave some animals untreated
“Refugia” –
in refuge from the drug
What is refugia?
– Worms not exposed to
drug;therefore still
susceptible to treatment.
The goal
– Increase the population of
susceptible worms.
How?
– Selective treatment –
leave some animals
untreated.
– After deworming, do not
move animals to a clean
pasture.
You do not have to deworm every animal.
Parents
How We Select for
Drug resistance
Resistant
Resistant
Drug Treatment Next Generation
FAMACHA©
Treatment Recommendations
Deworm adults at scores 4 and 5*
Treat lambs and kids at
categories 3, 4, and 5
*South Africa recommends goats
be treated at categories 3, 4, and 5
Clinical
Category
Eye Lid
Color
Packed
Cell
Volume
Deworm?
1
Red
> 28
No
2
Red-Pink
23-27
No
3
Pink
18-22
?
4
Pink-White
13-17
Yes
5
White
< 12
Yes
Using the FAMACHA© system to control
internal parasites in grazing lambs
3.5
60
Avg FAMACHA Score
# Lambs Dewormed
3
1.2%
1.2%
4.8%
6
5
4
7.1%
3
16.7%
2
30
41.7%
1
20
26.2%
0
50
2.5
40
% Lambs/
No. times treated
2
1.5
1
10
0.5
•
-S
ep
30
-S
ep
19
ep
2-S
g
-A
u
19
ug
5-A
l
22
-Ju
l
-Ju
11
-Ju
24
-Ju
10
•
•
•
n
0
n
0
84 hair x wool crossbred lambs, 3 months old
June 10-Sept 30 (112-day grazing period)
Lambs scoring 3, 4, or 5 on the FAMACHA© scale were
dewormed with moxidectin or levamisole
Lambs gained 0.3 lbs. per day, 57 lbs. → 87 lbs.
Western Maryland Research & Education
Center, Keedysville, MD
Fecal Egg Counting
Qualitative Analysis
– Shows presence or
absence of eggs
– Identify egg types
– Shows general trends
Quantitative Analysis
– Shows specific number
of eggs per gram of
feces (epg)
– Use known quantity of
feces and flotation
solution.
What do fecal egg counts tell you?
• Potential pasture
contamination
• Fecal egg counts are not
mathematically correlated
to worm numbers or the
severity of parasitic disease.
• Monitor and maintain low
egg counts; deworm when
appropriate to keep
contamination of pasture
low.
• Determine the efficacy of
anthelmintic treatment by
comparing paired samples
from the same animals
(treatment and control
group).
Next Wednesday’s farm visit
• Small meat goat farm in Clarksburg
(typical operation for Maryland)
• Evaluate overall health management, with
specific attention to the control of internal
parasites (worms and coccidia).
– Reduce morbidity and mortality
– Minimize cost
– Minimize use of drugs
Sanitation
Pasture and grazing
management
Management
Internal parasites
Worms
Coccidia
Equipment and
facilities
Genetics and
selection
Feeding and
nutrition