Whole-Farm Approaches to Parasite Prevention and Control on Organic Dairy and Livestock Farms Farms

April 9 & 10, 2008  
Presented by  Dr. Ann Wells, DVM
(Spring Pond Holistic Animal Health Prairie Grove, Arkansas)

Workshop description:  A whole-farm management approach is required to control internal  parasites in organic livestock.  In the absence of chemical controls, keeping organic animals healthy and productive during the  grazing season requires a good understanding of parasite-host  interactions, grazing management strategies and animal selection.   Dr. Wells is a nationally recognized expert and workshop presenter on parasite control and prevention in organic  systems.


GOATS:  generally goats in dry lots with good sanitation don’t have parasite problems, but when they go out on pasture they will have problems particularly if in a wet climate and there is not a parasite pasture prevention system.  Goats are adapted to dry climate and have little or no immunity to parasites.  Goats do better in browse than in pasture because they don’t pick up parasites when browsing high off the ground.  Also some of the browse plants help with parasite management.

SHEEP: have more immunity to parasites than goats but are more susceptible than cattle.  Their grazing habits (they like to graze short) make them very likely to become infected by parasites.

DAIRY CATTLE AND BEEF ANIMALS: generally shouldn’t have any problems with parasites but young animals may have problems in wet climates without a pasture prevention program.  With good grazing management, good selection and good nutrition most farms should never have to deworm any animals.  In very humid temperate climates (like Vermont) there may be problems in young stock if pasture management isn’t excellent.



Worms and coccidian and other organisms are developing resistance to multiple chemicals so even if you are not organic it is advised that you start looking at alternatives to routine deworming.

OVERVIEW OF THE ORGANISMS:  coccidia (single celled organism) and “worms”

COCCIDIA:  This is a very different organism than the “worms”.  This is a single celled organism which can effect calves, lambs, kids is what this is most likely to be a problem in.  This is a management issue and can be completely prevented by good sanitation.

  • Management disease which is easily prevented and can be difficult to treat
  • Sanitation is the key to prevention
  • Overcrowding makes it more likely to occur
  • Most likely to be a problem on farms which have been reliant an coccidiostats who discontinue them when transitioning to organic.  Note that coccidiostats are losing their effectiveness.
  • Homeopathic ipecacuanha is being used by some producers, but good management/sanitation is most effective

Coccidia is a single celled organism which damages the lining of the gut.  If they don’t get reinfected it lasts 21 days, but without good sanitation they will get reinfected.

Coccidia can occur on pasture in certain conditions… if animals are returning to a shade area  or feeders or barnyard where they are “camping” out and isn’t dry and clean then young animals may have problems even when on pasture.

All species of livestock have their own species of coccidian so chickens can NOT give your sheep or cows coccidia.  Sheep and goats do share the same coccidia however.

PARASITES OR ‘WORMS’ are a symptom that there is a sickness within the farm… it is a disease in individual animals but it is also an indication of imbalance/problem on the farm.  Parasites are best addressed by prevention and management.

Holistic Animal Health

  • Animals:  immune system (low dose exposure) low dose is needed for them to develop immunity.  You are most likely to have problems with new animals being brought in to a new area or in young animals which have not yet developed immunity.  This immunity doesn’t kill them but it does keep the animal healthy and they will be shedding fewer eggs and not contaminating the pastures as much.
  • Weather: cold, humidity:  weather has a big effect on parasite survival in the pastures.  High humidity is parasite paradise.  Hot and dry weather will reduce the number of infective parasites in the pasture.  In hot southern climates they can “sterilize” pastures of parasites by grazing it and letting it sit in the sun/heat
  • Forages:  height, species, by pass protein/condensed tannins:  Most of the larvae that infect livestock are in the bottom 2 inches of pasture so don’t graze too short.  Plants which are higher in by pass protein
  • Soil: Dung Beetles, earthworms, nematophagous Fungi:  Unhealthy soils have fewer of the beneficial organisms which can kill parasites and reduce infection rates in the pasture.  Soil organisms kill the parasites.


  • Treatment needs to be the last resort… this includes alternative and pharmaceutical treatment materials.
  • Dr Wells has not found any of the alternative treatments which works as well as the pharmaceutical treatments so management/prevention is even more important for organic producers and for conventional producers who are dealing with increasing in levels of parasites which are resistant to the chemical dewormers.

Management/treatment options

  • Chemical treatment is considered to be effective if it kills over 90% of the worms.
  • Good rotational grazing can give you 30% control.
  • If you add selection of animals which do well you get even more effective control.
  • If you also have a dry grazing season you’ll be able to get very effective control.
  • However in a wet year you may still have significant problems.
  • The alternative treatments can be a useful method when added onto good animal selection and grazing prevention but are not going to treat serious problems on farms where they do not have a grazing systems for prevention and animal selection for resilience/resistance and good nutrition for prevention

IVERMECTIN:  is the only one that is allowed in organic production.  It can NOT be used in slaughter stock.  It requires a 90 day milk withholding for diary animals.  It DOES kill dung beetles.  Dr wells said she can tell if a farm is using ivermectin by looking at the manure in the pastures.

STRONGYLES (nematodes/worms):  adult worms in abomasums lay eggs which pass out in manure and hatch in the pastures.  Infective stage will be in dew drops on base of pasture plants where it is eaten.  That is the ONLY stage which is infective.  The strangles includes the Haeomochus (most common sheep parasite)

  • Main gastrointenstinal nematodes (strongyles) of cattle
    • Ostertagia
    • Haemonchus
    • Trichostrongyus
    • Less impor
  • Main gastrointestinal nematodes of small ruminants
    • Haemonchus conturtus is the one of greatest concern
    • Trichostrongyus
    • Teladorsagia

Other Parasites

    • Usually not a problem for small ruminants but it can be a serious problem for cattle.  Dictyocaulus viviparous (cattle) Dictyocaulus filarial (sheep and goats).
    • Symptoms are bronchitis and pneumonia
    • Older animals will develop immunity
    • Requires a baerman technique for diagnosis.  Harder to diagnose than the other strongyles
    • LIVER FLUKES (fasciola hepatica) have a snail as an intermediate host.  Control measures include removal from snail infested areas.  Animals will gain immunity to liver flukes.  Generally not a problem in this part of the country.

ANIMAL SELECTION:  what is resistance and what is resilience?

  • Resistance:  genetic componant:  the ability of an animal to prevent establishment and maintenance of a parasite population in the GI tract
  • Resilience:  ability of the host to maintain a relatively undepressed level of production during a parasite challenge.
    • Resilience is what most producers are trying to select for.  For example, don’t keep the calves from a cow who always produces calves that have worm problems.  This is MOST critical for sheep and goat producers to select for and they can change the entire make up of their flock and how they are impacted by parasites in one year.  For Cattle/dairy producers this resilience is likely to be one of several traits that are being selected for.
    • GOAL is to:
      •  decrease parasite eggs on the pasture
      • And select for animals that perform like we want even with parasites.


  • Fecal egg counts.
    • Simple flotation is probably not helpful to most of us.  Ask your vet which technique she is using or learn how to do it yourself. (info on how to order the mcmasters kit to do this is included in these notes.  Also contact carol Delaney or chet parsons with UVM Extension to learn about workshops to teach you how to do these yourself)
    • Wisconsin sugar fecal egg flotation technique requires a centrifuge.  Is more sensitive for lower egg counts so can be better for cattle producers who will have lower counts.
    • Modified mcmasters technique  is easier to do yourself.
      • Cattle 200 to 300 epg
      • Sheep/goat 5000+ epg
    • McMaster fecal egg count is quick easy to perform and can be done by the farmer on the farm.  You buy the slides/kit from Chalex Corporation
    • Mcmasters slides http://www.vetslides.com
    • ONLY for sheep and goat producers… does NOT apply to cattle
    • Veterinarians can purchase FAMACHA cards by making requests tofamach@vet.uga.edu.
      • This ONLY works for sheep and goats.  It is a test for anemia to show the amount of Haemonchus in the animal/flock.
      • Famacha is best used to determine which animals NOT to treat.  It can significantly reduce the number of treatments given when compared with conventional drenching practices and should significantly decrease the rate of development of anthelmintic resistance.
      • Used as a guide to determine which animals are most affected.
        • It can help you significantly reduce the number of treatments given when compared with conventional drenching practices
        • It should significantly decrease the rate of resistance.

Contact chet parsons if you are interested in attending the FAMACHA workshops in Vermont or New Hampshire this summer chester.parsons@uvm.edu

Famacha classes scheduled for Aug 15 at Shelburne Farms, Aug 22 at Windham Foundation in Grafton and Aug 29 at the Cope Farm in Bath NH.


      • Most important parasitic disease in cattle.  Two types of this disease
      • TYPE 1:
        • Primarily young cattle, first season of grazing from immature adults, diarrhea, anorexia, dehydration, late summer, early fall they get picked up in larger numbers and young animals get sick in late summer/fall
      • TYPE 2:
        • Usually occurs the next spring.
        • Hypobiosis is a dormant form that the parasite will over winter in the animal.
        • Spring time highest incidence when the parasites all emerge at once.
    • TEMPERATURES effect mortality of parasites on the pastures.  70 degrees is ideal for ostertagia.  At 104 degrees they will live only 1 to 2 days!  So in our climate they may survive in the pasture for many months.
        • You get a natural spring spike in egg count in spring and fall.  Its good to do counts over a season so you can see when it peaks on your farm.  Its good to do at least 10 % of the herd and do the same animals each time over the year.  If you can do all the animals then you can CULL OUT ALL THE HIGH EGG SHEDDERS and quickly improve the health of the herd because by the next spring there will be fewer eggs to infect they young animals.
      • Manage to leave a 2 to 4 inch residual behind to minimize parasite infection.
      • Manage to maximize DMI and nutritional quality and consistency
      • Rotate pastures:  this improves the nutrition going into the animals, it improves the pastures, it can prevent them from grazing too short if done correctly
      • Stock density is important… lower density = fewer problems
      • Height of forage is critical.  Take the animals off the pasture before they graze it down to shorter than 2 inches.
      • Frequency of Rotation is important and should be determined by the height of the forage.
      • Grazing with multiple species can be helpful.  Goats will graze around cattle manure and cows will graze around goat manure and they are a deadend host for each others parasites.  Chickens will also consume some of the parasites.
      • For sheep they have found that never grazing sheep after sheep in a pasture makes a big improvement.  Ann grazes cattle after the sheep in the rotation.
    • HERBAL LEYS  otherwise known as a weedy pasture – can be a useful part of parasite management system.
      • Mixtures of grasses, legumes, forbs
        • Nutritional.  Many have a deep tap root and provide minerals not found in equally high levels in the grasses
        • Medicinal
        • Palatable
      • Persistence of forbs requires long rest periods.  These plants are so palatable they will get selected out by grazing animals quickly.
      • Important compounds
        • Phenols — eugenol, condensed tannins
        • Terpenes – sesquiterpines, lactones


  • In one study cattle were moved ONCE to a new pasture during the grazing season and not dewormed and the second group was continuously grazed and dewormed monthly.  Cleary shows the benefit of even very minimal rotation.
  • Dairy calf study (NCSU) found that weaning age didn’t have an effect but did show that rotational grazing improved performance.  This seems to contradict the results which farmers in the Northeast are reporting from feeding milk to an older age… needs more research up here.  Milk does change gut pH and seems to have an effect on parasites.


  • Birdsfoot Trefoil – grows well in VT but slow to establish
  • Serecea lespedeza – not being grown up here
  • Dock (yellow dock, curly dock –rumex)
  • Chicory which does grow well here.  Puna chicory is being grown in Vermont successfully
    • These plants affect the survival/migration of infective larvae in the sward.
    • Tannin content has a direct toxic effect on the parasite and/or parasite egg production
    • Improve the protein an/or mineral status of grazed sheep thereby enhancing their growth and potentially the immune response corresponding to an improved resilience
    • Animals eating high tannin forages on a regular basis will have much lower or ZERO egg counts.


    • Wormwood – Artemisia Absinthium
    • Epazote – Chenopodium ambriosoides (whole plant shows promise… oil extract by itself did not show effect in trials)
    • African basil – ocimum gratissimum
    • Holy Basil – Ocimum Sanctum
    • Garlic Barrier  (research being done on this now) www.garlicbarrier.com
    • Hoeggers (trials show it to be non effective so far)
    • Molly’s herbal formula also not showing effectiveness in trials so far.  Was labor intensive and perhaps too low a dose
    • Mollys weekly formula and tonic – not any results showing it works yet
    • Paradex – no research that shows it works yet
    • Neema tox and Vermi Tox from Agridynamics (new products) not tested yet but may show some promise

Herbal Dewormer research has been done on.  Do any of these work?

  • Hoeggers
  • Mollys Finest
  • Garlic, wormwood, pumplin seed
  • Natures finest
  • Garlic Barrier research:
    • third year of use in research now on sheep and goats.  No cattle research done yet.
    • Used as a drench.
    • They are using a 50 cc drench now and they are not yet sure this dose is large enough.
    • Clinical improvement, FEC not significantly changed but famacha scores do improve.
    • May aid the animals but not a substitute for good management.
    • It is proven to be very anti bacterial but not anti parasitic so it may be preventing/treating secondary bacterial infection.
    • It MAY have some effect on lungworm?  But data isn’t clear
    • It may be just working as a tonic to improve gut health and prevent secondary infection.
  • Pyrethrum
  • Oil of chenopodium
  • African marigold in alcohol (may be promising)
  • Molly’s finest research did not show promising results with dairy and meat goats
  • Papaya research:  some preliminary research showed that it has some deworming effect.  Seeds vs whole fruit puree research showed the seeds worked better.  Dose in research was 3 tbs seeds/day for 3 days.


  • DE (Diatomaceous Earth) research in IA, MN, VA, TX all show that it has no impact on internal parasites but many producers still use it and claim it is working.  There may be a mineral content which helps the livestock?  One study showed there may be a larval effect but it wasn’t repeated.  It DOES work on external parasites.  Wear a mask so you don’t breath in the dust
  • Nematode trapping fungi:
    • You can feed it to animals, it passes into the manure and kills the parasites.  Source of this in commercially available form is currently in limbo but it is promising.
    • Duddingtonia flagrans
    • Is a commercial product which is a bolus fed to sheep which kills eggs in the manure.  Research was done at LSU.
    • This is a fungi found in healthy soils
  • Copper Oxide Wire particles:
    • Research on hair sheep shows that it reduces fecal egg counts.  No liver toxicity was observed and research is being continued.  It effects the existing worm population in the gut but not new infections so it may work better in combination with a rotational grazing system to prevent re infection.  The sheep research has been done on hair sheep which have a higher tolerance for copper (not a higher requirement… just a higher tolerance)
    • There is a copper product sold in this country for cattle but it is not available in this country for sheep at this time.
    • This doesn’t work well if they are constantly being reinfected.
    • Research of this product on goats have shown mixed results… some showed no effect and some showed some benefit.
  • Copper sulfate feeding is being done in the North East.
    • There is a risk of toxicity particularly in sheep.  The best way to determine if you have high levels is to test some of the livers when you slaughter some lambs.  Soils are copper deficient here which is probably why farmers can feed this here and are not observing copper toxicity symptoms.

One recent research project:

  • 4 groups of lambs – all were rotationally grazed.
  • Control
  • Chicory pasture grazing
  • Papaya seeds as needed
  • Garlic barrier as needed

Results:  papaya seed was the only treatment which seemed to show some effect BUT the chicory grazing group had much lower mortality rates.  They were grazed in chicory 7 days out of each month.  Ann wells thinks the chicory shows enough promise to be worth experimenting with.  And grazing chicory is much lower labor than drenching or admistering boluses to animals!  This study also showed sire effects… it is clearly worth selecting sires which are resilient and shed fewer eggs.

Overall the benefits of good grazing management was most clear


Multi Faceted Approach

  • Each farm will be different
  • What is getting the credit?  Its probably not some product you are using…  its probably good prevention management that should be getting the credit
  • Good management, good breeding, good nutrition is what should be getting the credit?

When using chemical anthelmintics

  • Anemia takes up to 3 weeks to go away so keep watching/observing the animals
  • If animals gets no worse, give TLC, not more dewormer
  • Be careful to use chemical dewormers in a way that does not increase the levels of resistance
    • Use the same dewormer til it no longer works
    • When one dewormer quits working, change classes of drugs


This is weather dependent, but they do seem to live 3 to 4 months or longer.  They may live for a year or longer in some situations.  In hotter drier climates they will live for a shorter period of time.  In more humid and temperate climates they will live longer in that pasture.

TAPEWORM is different than the other parasites.  It’s lifecycle is different.  It is NOT killed by Ivermectin.  It is generally NOT a problem in an animal unless the animal is run down or debilitated.

OBSERVATION to know which animals need treatment and see how effective your prevention system is before problems become serious:

  • Famacha to see level of anemia
  • Depressed
  • Not eating
  • Not chewing cud
  • Listless
  • No rumen fill

CULLING SELECTION criteria used at heifer ranch

  • Cull anything that
    • Requires deworming
    • Is a late breeder
    • Has general health problems
    • Produces lambs that require assistance
    • Has high egg counts (which contaminates the pastures)
    • Doesn’t produce multiple lambs
    • Doesn’t produce lambs with good weight gains



  • Grazing management to prevent infection
  • Selection of dams/sires so that lambs/calves are more resilient to parasites and fewer eggs are shed to reduce pasture contamination
  • Good nutrition is essential
  • Ample mineral supplementation

Early observation – catch the early symptoms


  • Can’t use alternative treatments the same way you can use chemical dewormers
  • Treatment is the option of last resort


  • Don’t graze forage height below 2 inches
  • Don’t force animals to graze close to manure
  • Use weather to help decrease larval survival times
  • Keep pasture diversity high
  • Select for resilient dams and sires
  • Use multiple animals species and different classes of animals (example.  Use dry cows to clean the pastures – as a dead end host – if they are not under stress
  • Rotation of pastures is a must
  • Be aware in wet weather that animals are affected very quickly
  • Rotational grazing has the biggest impact
  • Selecting resilient parents is critical
  • Leader follower with cattle is very helpful
  • FAMACHA scoring for small ruminants necessary every two weeks during summer months, especially with high rainfall
  • Chicory appears to have an effect
  • Papaya needs more testing
  • Garlic is useful as a tonic, less as a treatment
  • High rainfall will create more parasite problems.


And you may never get as complete a control as an effective chemical dewormer

Most promising treatments we know of now include

  • Papaya
  • Basil
  • Wormwood
  • Pumpkin seed
  • Garlic ONLY as a tonic/support but don’t expect it to work as a dewormer


  • Must take time
  • Look at records
    • Grazing decisions
    • Culling decisions
  • Plan
    • For next year
  • Monitor the plan
    • Observations important
    • As season weather and animals change
  • Make Adjustments
    • Change grazing frequency
    • Change paddock size
    • Change treatment strategies


  • What is the time of year – learn when you are most likely to have problems
  • What are livestock body condition scores
  • What does the hair coat look like
  • What is the nutritional status of the animal


  • The first question to ask yourself is
    • how many animals do you have on the farm?
    • How small of an area are they in?


www.scsrpc.org  southern consortium for small ruminant parasite control

www.sheepwormcontro.com sustainable control of internal parasites of sheep

Sustainable Control of Internal Parasites in Ruminants – 1997 NZ book from Animal Industries Workshop Lincoln University


  • You could have a really sick pasture because it is really contaminated.  You need to figure out how to get your animals off that pasture
  • Rotate to new pastures daily so the grass is the correct height when they get turned it, are not grazing any shorter than 2 inches, and they are getting excellent nutrition.
  • Most critical time… make sure that animals going into winter are in good condition.
  • For cattle #1 improve nutrition.  Adding some herbal products may be helpful but its not proven yet.  The artemesia family may be most useful but will likely require drenching to get in an adequately sized dose.  Ann is about to start doing some research on verma tox and neema tox.  Garlic also has a tonic effect which can be helpful… but seems to be working as a tonic not as a treatment.
  • Rotational grazing:  don’t let cattle graze it shorter than 3 inches.  Pregrazing height of 10 inches  is good.  Its difficult to manage to prevent them from grazing too short if you are not moving them to new pasture daily.  They will graze some areas short if they are left in an area.  Watch out for spot grazing.  Multiple species can be helpful by using cattle to clean up a sheep pasture or sheep to clean up a sheep pasture.  You can also put the animals with the  highest nutritional needs in the highest quality (and taller) pastures.  Can then follow them with the animals with lower nutritional needs such as dry animals which are also less susceptible to the parasites.
  • Look at availablility of forage and amount of parasite infectivity in a pasture and balance that with the nutritional needs and parasite susceptibility of the different groups of animals.
  • St Croix sheep do seem to have natural resistance to parasites and they function as a dead end host for parasites on the farm.   Barbados also seem to have some resistance also.  Dorpers don’t seem to have parasite resistance.  Katadins seem to vary a lot but most don’t seem to have significant resistance.  Resistance in wool breeds varies a lot.


Farmers who have improved parasite problems attribute their improvements to:

  • Added hay land into the pasture rotation to provide clean pasture and decrease overall stocking density
  • Improved the pasture rotation to improve pregrazing height and maintain a higher post grazing height
  • Changed the mineral feeding mix to address deficiencies particularly of trace minerals.  This is extra important for animals receiving little or no grain since they aren’t getting all the minerals they need from grain
  • Improved forage and pasture quality so cows were in better condition
  • One beef producer said that most of the improvement was from better quality pasture, improved nutrition and correcting mineral deficiencies including selenium.  They fed garlic, geobond (for micotoxins), mineral mix and kelp.
  • Other ideas discussed during the meeting included weaning time… is it possible to wean later?  This is challenging due to weather.  Discussion of how to reduce weaning time stress by practices such as fence line weaning.  Make as few changes a possible at weaning time to minimize stress
  • Dragging at the end of the season can be helpful when it is dry can help reduce fly and possibly parasite levels in the pasture, but in WET climates like Vermont the dragging, particularly during the wet grazing season may just spread the parasites around more.
  • Suggestions included looking at copper levels.  You can do soil tests as well as liver biopsy
  • Turn 6 month old heifers out to ‘clean’ pastures if possible.
  • If putting young calves out to pasture… put them in a pasture with a low level parasites to give them a low dose exposure and let them begin to develop immunity.  If you wean them and then put them out onto a contaminated calf/heifer pasture they get a large risk of infection when they do not  yet have a good immunity (or any immunity) to the parasites.
  • Find a way to gradually transition them from winter heifer rations to pasture so they don’t have a 2 week adjustment period when they have to learn how to graze and may have a depressed immune function.  Watch their rumen fill.  Are they eating enough?  This may be a good time to feed some probiotics.  The more healthy you can keep the gut functioning the better the animal will do and the less accommodating habitat there will be for the parasites.
  • Dairy farmers who are now feeding whole milk for 4 months instead of 2 months are seeing fewer problems in their calves and heifers.
  • Cows don’t shed as many eggs so they can be used to clean up pastures which (after they regrow) can then be grazed by the more susceptible heifers.  This is better than grazing the heifers on a pasture which was previously grazed by heifers.
  • For lama and alpaca farms looking for information on the menengial worm look at the Ohio State University research.  Ann Wells recommends that you NOT deworm every month and look for the recommendations which suggest a twice a year deworming based on an understanding of the lifecycle of the worm.

Other comments & notes

STOCKING RATE.  By lowering the stocking rate you decrease the overall infectivity rate of the farm.  A lower stocking rate allows you to have more areas that you can rest for longer and have more ‘clean’ pastures.

SHEEP like to graze short so even if you turn them into tall pasture they may be selectively grazing the short plants between the tall plants.  St Croix and Barbados appear to be the only breeds that still have a good level of resilience/resistance to parasites.  Much of the parasite resistance in other breeds which previously were selected for resistance has been lost.  This includes katadins and polypays… most of these sheep seem to be quite susceptible to parasites.

SHADE:  if the animals are returning to the shade or barnyard daily… then even if they are on a ‘clean’ pasture grazing, they will be re-infecting themselves.  This is difficult to avoid if the weather requires you to provide shade

NUTRITION:  Ann observed that increasing the concentrates through nutrition doesn’t seem to work as well as high quality forages.

OVERWINTERING LARVAE:  they seem to become infective as soon as the grass begins to turn green.

HAYING a pasture is one way to remove many of the parasites from the pastures.  So for dairy heifers in the summer they can be moved into a hayfield after its grown back following first cut of hay as a way to graze them in a ‘clean’ pasture to reduce their level of infection to prevent fall “crash” in heifer  health when they come in from pasture.