View
406
Download
0
Category
Tags:
Preview:
DESCRIPTION
Citation preview
2013 PASA Conference 2/7/2013
Susan Schoenian and Jeff Semler 1
STRATEGIES, TECHNIQUES AND
EXPERIENCE TO FOSTER PARASITE
RESISTANCE & RESILIENCE
SUSAN SCHOENIAN & JEFF SEMLER
UNIVERSITY OF MARYLAND EXTENSION
GASTRO-INTESTINAL PARASITES
� Gastro-intestinal parasites are the primary health problem affecting sheep and goats in warm, moist climates and areas with summer rainfall.
� Sheep and especially goats are more susceptible to the effects of internal parasites than other farm livestock.
Goats are not natural grazers, nor
well-adapted to moist climates.
2013 PASA Conference 2/7/2013
Susan Schoenian and Jeff Semler 2
GASTRO-INTESTINAL PARASITES
• Sheep and goats share the
same internal parasites
(except for coccidia).
• Not all parasites are pathogenic
or equally pathogenic.
• Close grazing facilitates the
ingestion of infective worm
larvae (L3).
• Grazing near fecal pellets also
facilitates ingestion of infective
worm larvae (L3).
GASTRO-INTESTINAL PARASITES
• Sheep and especially goatsare slow to develop immunity to internal parasites and experience a relaxation of immunity around the time of parturition (known as the “periparturient egg rise”).
• Worms have developed varying degrees of resistance to ALL of the dewormers (anthelmintics).
• Drug resistance is inevitable! Worms will eventually develop resistance to any new dewormer, quicker if we over-use it or use it improperly (like we’ve done in the past!).
2013 PASA Conference 2/7/2013
Susan Schoenian and Jeff Semler 3
SHEEP AND GOATS CAN BE AFFECTED BY A
VARIETY OF INTERNAL (AND EXTERNAL) PARASITES
AND IT IS NORMAL FOR THEM TO HAVE SOME
WORMS IN THEIR GUTS AND EGGS IN THEIR FECES.
1. Helminths (worms)
1) Roundworms
(gut, lung, meningeal)
2) Trematodes (tapeworms)
3) Cestodes (flukes)
2. Protozoa (single cell)
1) Coccidia
I have
worms!
Me, too!
PRIMARY PARASITES AFFECTING
SHEEP AND GOATS
• Roundworms, especially Haemonchus contortus (barber pole worm).
• Also, Trichostrongylusspp. and Teladorsagia (Ostertagia).
• Coccidia (Eimeria spp.)
• Other parasites (e.g. meningeal worm) can be a problem on individual farms or in some years.
Barber pole worm
Image from Novartis
Coccidia “nodules” in small intestines
Image from ScienceDirect
2013 PASA Conference 2/7/2013
Susan Schoenian and Jeff Semler 4
0
20
40
60
80
100
6/3 7/7 8/4 9/1
2011
Haemonchus Trichostrongylus Other
0
20
40
60
80
100
6/7 7/1 7/29 8/25
2010
Haemonchus Trichostrongylus Other
0
20
40
60
80
100
6/2 6/28 7/26 8/22
2012
Haemonchus Trichostrongylus Other
0
20
40
60
80
100
6/6 7/1 7/16 7/30 8/13 8/26 9/10 9/26
2009
Haemonchus Trichostrongylus
LARVAE ID (PERCENT HAEMONCHUS IN RED) FROM WESTERN MARYLAND PASTURE-BASED MEAT GOAT PERFORMANCE TEST.
MOST ECONOMICALLY-DEVASTATING PARASITE
IS USUALLY HAEMONCHUS CONTORTUS.
THE BARBER POLE WORM IS
AN INCREDIBLE PARASITE!
• Very pathogenic: kills a
lot of sheep and goats,
especially weanlings.
• Difficult to control• Simple, direct life cycle
• Prolific egg layer
• Undergoes hypobiosis(inhibited developmental stage)
• Adaptable: from the
Tropics to the Artic.
2013 PASA Conference 2/7/2013
Susan Schoenian and Jeff Semler 5
SYMPTOMS IN THE ANIMAL
HAEMONCHOSIS
1. Hyperacute (< 1 week)• “Sudden death”
• No obvious signs
2. Acute (> 1 week)• Anemia
• Edema (bottle jaw)
• Weight loss
• Loss of body condition
• Anorexia
• Loss of stamina
• Diarrhea
3. Chronic (sub-clinical)• Loss of performance
Voracious blood-sucker!
GENETICS OF PARASITES:
TWO TRAITS
RESISTANCE
• Prevent parasitic disease
from establishing.
• Quantified by fecal egg
counts (FECs), which are
an estimate of the
number of worms in the
animal’s gut.
EPG: eggs per gram (of feces)
RESILIENCE
• Tolerate (perform, remain
healthy) despite parasite
burden (could still have
high egg count).
• For barber pole worm,
quantified by packed cell
volume (PCV) and
estimated by FAMACHA©
eye anemia scores.
PCV - percent; FAMACHA© - 1-5
2013 PASA Conference 2/7/2013
Susan Schoenian and Jeff Semler 6
ABOUT FECAL EGG COUNTS (EPG)
• They are “relative”:
a “snapshot” in time.
• A single egg count is not
necessarily a good measure
of the parasite burden in an
individual animal; however, it is a
measure of pasture contamination.
• Fecal egg counts include all
strongyle-type eggs: Haemonchus,
Trichostrongylus, and Teladorsagia:
you must hatch eggs to identify
strongyle species by worm larvae.
• Worms vary in their egg-laying
ability.
McMaster slide
You can learn to do your own FECs.
ABOUT PACKED CELL VOLUME (PCV)
• Is proportion (%) of blood represented
by red blood cells.
• Also known as blood hematocrit.
• 25 to 35 percent is normal in sheep/goats.
• Is usually lower for goats.
• Is estimated by FAMACHA© scores.
McMaster slide
Score Color PCV Tx?
1 Red > 28 No
2 Red-Pink 23-27 No
3 Pink 18-22 ?
4 Pink-White 13-17 Yes
5 White < 12 Yes
2013 PASA Conference 2/7/2013
Susan Schoenian and Jeff Semler 7
OTHER IMPORTANT MEASUREMENTS
OF PARASITE RESILIENCE
• Body condition (1-5)
• Dag score (fecal soiling, 0-5)
• Coat condition
• Weight gain
Weight loss Poor body conditionDagginess
RESISTANCE
• Moderately heritable~0.25 (higher for Katahdins)
• Extremely variable: coefficient of variation is often over 100 percent.
RESILIENCE
• Low heritability
~ 0.10
• Less variability:
coefficient of variation
usually between 20
and 40 percent.
Fecal egg counts are the standard for
improving parasite resistance in sheep.
HERITABILITY (H2) OF
RESISTANCE AND RESILIENCE
Heritability (h2) is the proportion of phenotypic variation due to genetics.
2013 PASA Conference 2/7/2013
Susan Schoenian and Jeff Semler 8
GENETIC RELATIONSHIP BETWEEN
RESISTANCE AND RESILIENCE
• Resistance and resilience are
usually positively correlated,
though measurement numbers
may be negatively related.
e.g. � FEC �PCV and
� FEC � FAMACHA© Score.
• In the Western Maryland
Pasture-Based Meat Goat
Performance Test, FEC and
FAMACHA© scores have had
positive correlations, but they
have not been very strong.
Year Correlation
2007 0.29
2008 0.42
2009 0.18
2010 0.27
2011 0.14
Genetic correlations range from -1 to +1
and are an indication of the amount of
variation that two traits share.
In New Zealand, they found no
correlation between parasite
resistance and parasite resilience.
IN OUR BUCK TEST, WE USE FECAL
EGG COUNTS (FEC) TO EVALUATE
GENETIC RESISTANCE TO PARASITES.
NOT TO MAKE DEWORMING DECISIONS.
2013 PASA Conference 2/7/2013
Susan Schoenian and Jeff Semler 9
WE USE FAMACHA© SCORES TO
ESTIMATE PACKED CELL VOLUME
…AND MAKE DEWORMING DECISIONS.
TWO WAYS TO SELECT FOR PARASITE RESISTANCE AND RESILIENCE
BETWEEN BREED
• Some breeds are naturally
more resistant and resilient to
internal parasites (round-
worms) than others.
• This is well-documented in
sheep; not very well-
documented in goats
(mostly anecdotal).
• Resistant breeds tend to be
those with tropical origins or
landrace breeds that have
naturally adapted to their
environment (“survival of the
fittest”).
WITHIN BREED
• There is as much variation
within a breed as between
breeds.
• The 80-20 rule: it is estimated
that 20-30 percent of the flock
or herd is responsible for
causing 70 to 80 percent of the
pasture contamination
(fecal egg outlay).
• Parasite resistance (FECs) is a
moderately heritable trait.
2013 PASA Conference 2/7/2013
Susan Schoenian and Jeff Semler 10
(MORE) RESISTANT BREEDS
SHEEP
• Landrace hair sheep
1) St. Croix
2) Barbados Blackbelly
3) American Blackbelly
• Composite hair x wool
1) Katahdin
• Medium wool
1) Gulf Coast NativeFlorida Native
• Dorper - not resistant, but maybe more resilient.
• Others (?)
GOATS
• Kiko
• Spanish
• Myotonic
Not
• Boer
• Nubian
• Swiss dairy
St. Croix:
the most
resistant
breed in US.
WITHIN BREED SELECTIONANY BREED (OR POPULATION) CAN BE SELECTED
FOR IMPROVED PARASITE RESISTANCE.
80:20 rule: Fecal egg counts are not evenly dispersed in a herd or flock.
Avg. FEC
2358 epg
2012 Western Maryland Pasture-Based Meat Goat Performance Test
2013 PASA Conference 2/7/2013
Susan Schoenian and Jeff Semler 11
Selection for parasite resistance in Australia
Selection for parasite resistance in Australia
2013 PASA Conference 2/7/2013
Susan Schoenian and Jeff Semler 12
Selection for parasite resistance in Australia
HOW TO SELECT FOR
PARASITE RESISTANCE
• The immune system needs to be stimulated by a worm challenge before genetic differences can be expressed.
• Measure fecal egg counts when animals are between 6 and 12 months of age.
• No sooner than 6 weeks after weaning.
• A high worm load is needed to do the best job of separating resistant vs. susceptible animals;
• Avg. FEC of 500-1000 epgfor barber pole worm
• Less than 10% of animals should have zero egg counts.
2013 PASA Conference 2/7/2013
Susan Schoenian and Jeff Semler 13
PROTOCOL FOR MEASURING
RESISTANCE IN KATAHDINS
Source: NSIP, David Notter, Virginia Tech, 2004
HOW TO SELECT FOR
PARASITE RESISTANCE
• Take all samples on same day.
• Store samples in a cool place to prevent eggs from hatching.
• Compare animals in same contemporary group.
• Compare individual FECs to group average.
• Heritability will be higher if more than one FEC is used for comparison.
2013 PASA Conference 2/7/2013
Susan Schoenian and Jeff Semler 14
Top 10
Bottom 10
1
2
3
4
5
6
7
8
9
10
10
9
8
7
6
5
4
3
2
1
2012 Western Maryland Pasture-Based Meat Goat Performance Test
All goats were triple-dewormed (moxidectin + levamisole + albendazole) on 6/2.
Twelve days later, the average fecal egg count was near zero.
HOW TO SELECT FOR
PARASITE RESILIENCE
• Many criteria can be used
a) Packed cell volume
b) FAMACHA© score
c) Time from fixed point that
deworming is required
d) Number of times dewormed
during specific time period.
e) Body condition score
f) Dag scores (scour worms)
g) Growth rates
• Cull animals that require
frequently deworming.
• Select animals that do not
require deworming and whose
parents don’t require deworming.
2013 PASA Conference 2/7/2013
Susan Schoenian and Jeff Semler 15
Top 10
Bottom 10
123456789
10
10987654321
2012 Western Maryland Pasture-Based Meat Goat Performance Test
All goats were triple-dewormed (moxidectin + levamisole + albendazole) on 6/2.
For the next 8 weeks, the average FAMACHA© score improved and no goat required deworming.
WE WANT BOTH RESISTANCE
AND RESILIENCE!
• You don’t want have to
deworm your stock, but
you also don’t want to
have animals that
deposit a lot of eggs onto
the pasture.
• Heavily-contaminated
pastures lead to clinical
parasitism, as there are
almost always
susceptible animals in
the herd or flock.Fecal egg counts are a measure
of pasture contamination.
Let me
out!
2013 PASA Conference 2/7/2013
Susan Schoenian and Jeff Semler 16
IT IS MOST IMPORTANT THAT THE
MALE BE RESISTANCE TO PARASITES
There are large differences between sires for resistance.
WHAT WILL HAPPEN IF YOU DON’T
PAY ATTENTION TO PARASITES?
• Eventually all the dewormers
will stop working on your farm.
• You will need to feed more so
that your animals can tolerate
parasitic burdens.
• You’ll want to raise your sheep
and goats in complete
confinement so that they are
not exposed to much infective
worm larvae.
• You’ll have to stop raising
sheep and especially goats.
• Your compost pile will get full. Top-performing buck from 2011 TestAvg. FEC: 232 epg; Avg. FAM: 1.7; ADG ratio: 181%
Kiko x Boer
Recommended