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Worms can build resistance to the Chemical wormers. Usually this happens because the wormer being used, is used over a long period of time and at improper dosages. The amount of wormer used is not enough to kill all the worms, but enough to help many of them build resistance. Also, over a long period of time, using the same chemical wormer, there are bound to be "strong" worms that survive the worming, these guys for, some reason, have built a resistance to that particular wormer and pass this on to their offspring (survival of the fittest). So, if a chemical wormer is used for over a long period of time, there is bound to be resistance. How long a period is totally dependant on the particular situation and management practices.

Goats have worms. It's a fact. There is no shame in this for the breeder. It's the amount of worms that is the issue. A healthy animal can resist a worm infestation because his system resources are strong and fight the worms and the worms cannot get a foothold. It is when the animal is poorly managed, or under some sort of stress (which contributes to illness and disease) that the worms get a foothold and cause an infestation.

This is where herbal remedies differ from chemical ones. Herbs work with the body, to build and strengthen system resources, and so the body is strong and can resist and fight disease. Herbal wormers not only expel worms, but they also strengthen the body so that worms cannot get a foothold.

How old the animals are when they are brought to your property really does not make a difference to the worms or their resistance, even if you have never had animals on your property before. Even a 1 month old kid is going to be carrying worms of some sort and these worms came from somewhere. It is good practice to worm all animals immediately when they are brought onto your property, so as to reduce the worms that they are bound to shed and let loose on your property. As a practice of "polite management", I always worm every animal I sell the day they are to leave my farm to go to their new home.

 

Symptoms of worms:

• pale (or white) gums
• dull coat
• diarrhea
• lower milk production
• clumpy stools
• off feed
• fluffed hair
• listlessness
• subnormal or slightly elevated temperature
• rumen failure
• dehydration
• chronic coughing (lung worms)- dry cough, especially after running or other exercise.
• "bottle jaw" (severe infestation)- swelling under the jaw.

We do not worm pregnant does with chemical wormers unless absolutely necessary. If it is necessary, we use Ivomec, since this is proven safe for pregnant does.

Control of internal parasites, especially of Haemonchus contortus (barber pole worm, stomach worm), is a primary concern for the majority of sheep and goat producers. These parasites have become more
difficult to manage because of increasing resistance to nearly all available dewormers. A severe infection of barber pole worm causes anemia, bottle jaw, and—if not treated—death of infected sheep and goats. Mature parasites breed inside the host and “lay eggs,” which pass through the host and are shed in the feces. After the eggs pass out of the host, they hatch into larvae. Warm, humid conditions encourage hatching of the eggs and development into infective larvae. The larvae need moisture, such as dew or rain, to break open the fecal pellet and move. They migrate out of the feces and up blades of grass (usually 1 to 3 inches). When an animal (sheep or goat) grazes, they may take in parasite larvae along with the grass blade. Parasite numbers increase over time when conditions are favorable (warm, wet). Parasites are now developing resistance to anthelmintics (dewormers). Drug resistance is the ability of worms in a population to survive drug (Deworming) treatment of the animal at the prescribed dosage. Over-use of dewormers has led to resistance, and many available dewormers are now ineffective.

Producers can no longer rely on anthelmintics alone to control internal parasites. It is important to use multiple management practices to control internal parasites. The following are tools that can be used to manage internal parasites. For more information

see ATTRA’s Managing Internal
Parasites in Sheep and Goats.

Maintain forage height greater than 3 inches (beware of patch grazing) Provide areas of browse (brush, shrubs, small trees, etc.) Maintain low stocking rate Graze sheep and goats with cattle, or in a rotation with cattle or horses Provide tannin-rich forages, such as sericea lespedeza Harvest hay from pastures Avoid wet patches in pasture, such as from a leaky water trough.

Selective Deworming

Use a visual system (FAMACHA©) for classifying animals based on levels of anemia from FAMACHA© chart is only effective for diagnosing infection by H. contortus (barber pole worm)

o Treat only animals that are anemic (a sign of parasitism)
o Reduces the use of dewormers
o Helps slow down drug resistance problems
o Saves money

Selecting Resistant Animals

Several breeds show resistance to internal parasites (that is, when exposed to parasites, the animal immune system does not allow the parasites to be established in its body). Select a resistant breed if it fits your system.

Select individual animals that demonstrate resistance to parasites Resilient animals can host a parasite burden and not be negatively affected by the parasites (don’t show signs of parasitism, and they remain productive); however, they may be shedding high numbers of parasite eggs and causing illness in other animals.

Cull animals that are most susceptible to parasites and those that contribute most to pasture contamination.

Alternative Treatments

Tannins

Tannins are plant compounds that bind to proteins and other molecules. Tannin is related to “tanning”, as in preserving hides, and tannins are found in many plants.

There are two main types of tannins; hydrolyzable (HT), some of which may have toxic effects on animals, and condensed tannins (CT), which are found in forage legumes (including sericea lespedeza) and other plants.

Effects of tannins vary depending on type of tannin, concentration, and on the animal consuming the tannins. Negative effects may include reduced intake and reduced digestibility, leading to a decline in animal productivity.

Negative effects are seen more often when CT concentration is high (above 55 g CT/kg DM in the forage). (Min et al., 2003)

Positive effects may include an increase in by-pass protein (causing the animal to use protein more efficiently), a reduction in bloating, increased milk production, and a reduction in internal parasite numbers, egg output, and hatchability.

For more information on tannins, see the references listed at the end of this publication and the Resources section, especially <www.ansci.cornell.edu/plants/toxicagents/ tannin>.

According to Min et al. (2003), low concentrations of CT (20-45 g CT/kg DM) are helpful to animals, while high forage CT concentrations (>55 g CT/kg DM) may have negative effects. Results vary according to CT concentration and structure and the animal that is grazing the forage, however.

Researchers have shown that big trefoil, sulla, sanfoin, and sericea lespedeza are useful in controlling internal parasite infection in sheep and goats. Providing condensed-tannin-containing forages is one way to boost the health of sheep or goats.

Forage CT, g/kg of DM %DM
Birdsfoot trefoil 48 4.8
Big trefoil 77 7.7
Sanfoin 29 2.9
Sulla 51–84 5.1–8.4
Lucerne (alfalfa) 0.5 .05
Sericea lespedeza 46-152 4.6–15.2
Perennial ryegrass 1.8 0.18
Chicory 3.1 0.31
Crabgrass/tall fescue mixture 3.2 0.32

Table 1. Condensed tannin (CT) content in diff erent forage species.*

(Adapted from Min and Hart, 2003 and Min et al., 2005).

*The standard used for analysis will affect the results. For these studies, a Quebracho standard was used.

Sericea Lespedeza

Sericea lespedeza is a high-tannin forage (4–15% DM) that has been scientifically proven to reduce parasite loads in sheep and goats. The mechanism of action is not yet known. Researchers believe that the plant tannins may affect parasites either directly or indirectly (or both). Tannins may react directly with adult worms by attaching to their “skin”, causing them distress, or indirectly by improving protein nutrition of the goat and boosting the immune system. In addition, tannins appear to reduce the hatching of fecal eggs and development of larvae, perhaps by binding to the larvae. (Min et al., 2005). The tannins could also bind with feed nutrients and possibly prevent bacterial growth in the feces (larva feed on bacteria) and so limit the feed available for larval growth, or in some other way inhibit larvae growth and movement. Adult worms residing in animals that are grazing sericea lespedeza shed fewer eggs, and the eggs that are produced have reduced hatching ability.

However, when animals are moved off sericea lespedeza pastures and on to other forages, egg counts go back up, indicating that mature worms were inhibited but not killed in the short term. As animals are fed with sericea for longer periods of time, research has shown a reduction in mature worms as well (Min et al., 2005, Shaik et al., 2006, Lange et al., 2006). Reducing pasture contamination and animal worm burdens will help sheep and goats to be healthier and more productive

Things you should know about Sericea Lespedeza

Sericea lespedeza is a legume that grows in low fertility and acid soils and was widely planted to rebuild eroded and depleted soils. It is one of the most commonly used species for planting on surface mine spoils, road banks, and other disturbed or eroding areas. Sericea is listed as a noxious weed in some states (Colorado and Kansas, at the time of this writing) and may become invasive or weedy in some areas. Where sericea is considered a noxious or invasive weed, sheep and goat grazing can help to control the plant while also helping sheep or goat parasite problems. It will not be invasive when grazed and prevented from producing seed.

Sheep and goats may need time to adjust to grazing sericea if they are not familiar with the forage; however, they will graze it readily once they go through the adjustment period. Cattle will graze sericea if it is not too mature. No adjustment period is needed for feeding sericea hay, as it is readily consumed by all classes of livestock. Researchers are investigating the performance of animals grazing sericea or being fed sericea hay or supplement. Research has shown that sericea is effective against internal parasites when grazed or when fed in dried forms, such as hay or pellets.

Using Sericea Lespedeza

Producers should not rely on sericea as the sole method for controlling internal parasites. However, sericea can be useful as one part of a complete parasite management strategy. Sericea has been shown to reduce hatchability and fecundity (egg laying ability) of internal parasites, and in that way it will help reduce pasture contamination with larvae. Also, when used for longer periods of time, it can reduce the number of adult worms. Researchers are working to determine the most effective and economical ways to use sericea lespedeza as a substitute for anthelmintics, or as a “deworming pasture.” More information will be available as the research is done. Continue to check the Southern Consortium for Small Ruminant Parasite Control Web site at www.scsrpc.org for updates.

Copper Oxide Wire Particles (COWP) boluses

It should be noted that COWP has been found to be effective on reducing abomasal (H. contortus) only and not intestinal worms. COWP has been found to be effective against H. contortus in mature goats most of the time, though sometimes marginally effective. Other control strategies may be more effective in mature animals. As with all anthelmintic treatments, it is important to work with your veterinarian.

COWP should not be the only method used for controlling internal parasites. COWP boluses should be thought of as one component of a complete parasite management strategy. COWP boluses should be used selectively, treating only the animals that need it. Using the FAMACHA© system is one way to determine animals that should receive a COWP bolus. Selective treatment is advised to reduce the risk of worms developing resistance to COWP. Other parasite management techniques are mentioned earlier in this publication. The use of COWP can also help slow the development of anthelmintic drug resistance, as fewer anthelmintics are used.

COWP Results

There have been several research trials studying the effects of COWP on internal parasites in sheep and goats.

Summary

Copper oxide wire particles (COWP) have been proven to be an effective method of controlling H. contortus (barber pole worm) in sheep and goats. While COWP have shown positive results in reducing parasite loads, they should not be the only method of parasite control used. Research continues on the use of COWP to determine the most effective treatments for sheep and goats. COWP can be an effective component of a holistic parasite management strategy.

Garlic and other botanical materials and formulations (being tested)

Nematode-trapping fungus (not commercially available yet)

Condensed-tannin (CT)-containing supplements (such as sericea hay)

Condensed tannins and, in particular, the high-CT forage sericea lespedeza are discussed in this paper. An overview of current research on the topic, as well as additional resources and references, are provided. Producers can use this information to keep their animals healthier.

WORM MANAGEMENT

Sustainable control of goat worms involves a combination of planned stock and farm management, monitoring worm levels using worm egg counts, regular drench resistance testing, maximizing the use of non-chemical worm management strategies, the strategic timing of effective drenches and breeding worm resistant goats.

Without sustainable worm management, drench resistant worms will keep increasing and economic loss will be greater.

The aim  is to reduce drenching and minimize the onset of drench resistance while increasing animal productivity and profitability.

When this happens, there are less larvae on the pastures, waiting for your goats to ingest them!

Worm larvae in dew drop waiting to be ingested

Worm egg counting

This is one of the most useful worm management tools a goat producer can use.

A worm egg count is a count of the number of worm eggs in a sample of goat dung.

The result is usually expressed as 'eggs per gram' (EPG) of dung with the main results often divided between strongyles (including most of the significant worm species such as barbers pole worm, brown stomach and black scour worm) and Nematodirus eggs.

The actual number at which the worms become a problem varies with the worm species present.

For example, a worm egg count of 500 eggs per gram (EPG) of barbers pole worms is not as significant as 300 EPG of  Trichostrongylus vitrinus, one of the scour worms.

Conducting a larval culture which will identify all the species present in the sample, can further refine this result.

Worm egg counts are an important practical tool to estimate the burden of adult worms in monitored goats.

A worm egg count is a much more accurate diagnostic tool than visual assessment and will identify an emerging problem long before any visual symptoms appear.

Worm egg counts are a useful guide to check the overall worm status of a mob to decide if treatment is necessary, to decide if previous treatments were effective or to assess the levels of worm contamination being put into paddocks.

Individual goats worm egg counts can also be used as the basis for selecting worm resistant goats.

Worm egg counts (WEC)

Collecting the sample:
There are 2 ways dung samples can be collected - freshly deposited dung off the ground or directly from the rectum of the goat.

If collecting for normal monitoring of a mob, the goats can be quietly held against a fence for 10 – 20 minutes, allowed to walk off and fresh dung collected off the ground, taking care not to collect too much dirt and other debris with the sample.

Often goats are 'on camp' in the early afternoon (noon to 1.00pm) and this is a good time to quietly approach the mob, get them to stand for a short time before moving them off camp and then collect samples from the fresh dung piles.

Fecals samples can be collected directly from the rectum of individual goats with a gloved finger.

This is the preferred technique when it is important to have individually identified samples, such as when selecting animals for worm resistance, and when collecting post-treatment during a Fecals Egg Count Reduction Test (FECRT or resistance test) so that exact groups of origin are known.

The collected samples should be sent to the laboratory as soon as possible after collection. Contact your local veterinarian, goat consultant or laboratory to discuss specific sampling and laboratory requirements for worm egg count.

Doing the count:
When the samples arrive at the laboratory, a carefully weighed sub-sample will be taken from each of the samples.

This is mixed with a saturated salt solution. A sample of this mixture is placed on a special microscope slide (Whitlock Universal or Whitlock McMaster). The saturated salt solution makes the worm eggs float to the top of the mixture in the slide where they are counted. The number of eggs is multiplied by a sample weight and dilution factor to arrive at the 'eggs per gram' (EPG) figure in the results.

Worm typing (larval culture and differentiation)

It is difficult to differentiate the eggs of many common species of goat worms during a worm egg count.

When it is important to know exactly which species of strongyles worms are present (e.g. when the presence of barber’s pole worm is being checked or after a drench resistance test) a worm larval culture and species differentiation is carried out.

The collected dung remaining after the worm egg count has been completed is bulked together in a jar, mixed with a substance called vermiculite to help aerate the dung and then incubated in an oven for a few days to allow the eggs to hatch and develop into worm larvae. Trained laboratory technicians can then tell the species of the worm larvae and give a result describing the proportion of each worm species in the dung samples that were from the different worm species.

Do your own worm egg counts

Some farmers do their own worm egg counts. Learning to do worm egg counts is not difficult. You will need a laboratory microscope (hobby ones are not suitable), an egg-counting chamber, some beakers and mixing implements and a supply of saturated salt solution.

Training is available through some state Departments and other training organizations. You will also need the discipline to regularly collect the required number of samples and to sit down and follow the correct procedures on each sample if you are going to get a credible result. However, it is a fact that most goat producers who start out doing their own worm egg counting go back to paying for a professional service.

There are also commercially available worm egg counting kits. You should check the accuracy of your worm egg counts by conducting comparison testing which is available from some accredited laboratories.

If you want to know the species of worms present, you will have to send dung samples to a laboratory offering that service.

Total worm counts

The only way to get a direct measurement of the actual burden of worms inside a goat is by doing a total worm count.

The goat is killed and specific portions of gut are removed and processed to collect the contents, including immature and adult worms.

A trained technician can then count the worm larvae and adults. This is a time consuming task and so it is usually used for research or situations when a diagnosis of a worm problem is urgently required.

Pasture larval counts

Counting of worm larvae on pasture is also possible, giving a measure of the likely challenge to goats put in the paddock.

At present, this technique is limited to research as it requires a lot of time and labor to collect and process pasture samples.

Research is being carried out to try to refine the technique and to make it less costly.

Drench resistance

In most goats, knowing the drench resistance status of your property is essential if you are going to be able to effectively manage worms. If you do not have any drench resistance information, you should seek professional advice on how to have it done as soon as possible.

Theoretically, drench resistance occurs once a population of a species of worm can survive a dose of a drench that would have previously killed it. Worms killed by a drench are said to be susceptible to the treatment.

The currently accepted industry definition of drench resistance, as measured in a Fecals Egg Count Reduction test (FECRT), is a reduction in worm egg count of less than 95 percent.

This definition is important to understand, because at this level of efficacy drench resistance would most likely not be causing clinical worm problems, such as scouring and obvious weight loss. However it could be associated with loss of sheep production. By the time that obvious drench failure occurs then resistance is very well established within the worm population. This is one of the reasons why it is unlikely that resistance can be reversed, even if the drench group is not used for a long period of time. Preventing or reducing the onset of drench resistance is the best option.

Drench resistance is genetic (controlled by genes). Resistance to each group of drenches is controlled by different genes, meaning that resistance develops to each drench group separately. Being a genetic trait, drench resistance is also heritable (can be passed on from one generation of worms to the next).

Initially, resistant worms are rare in a population of worms. When a goat is treated the resistant worms survive and, if they find a mate, can reproduce. The resultant offspring are resistant and if they survive as larvae on the pasture and infect another goat they will make up a greater proportion of the worm population than their parents did. Over time, and with continued treatment, the overall resistance level to the treatment within the worm population increases.

The rate of development of drench resistance can be influenced by many factors such as:

• The chemical group and persistency of the product involved
• The frequency of treatments
• The worm species involved
• Environmental factors such as climate

Drench resistance testing

When planning worm treatments it is critical to know the efficacy of the various drench options on your property. Knowing which drenches are effective on your property is essential if you are going to choose the correct drench to kill the worms present in your goats.

The main way to assess drench efficacy is using a drench resistance test or fecals egg count reduction test (FECRT). You should contact your local veterinarian, goat consultant  when planning this test to ensure that the work involved yields the most useful results possible. They will give good advice on mob and drench selection for the test and other local requirements such as the number of animals and fecals sample collection techniques that are necessary.

A drench resistance test is best carried out on a group of wormy, young, un-drenched goats such as kids approaching weaning age. If testing is only possible using goats older than about six months of age then seek professional advice first to modify the methodology used.

An initial worm egg count of the selected goat is important before the main test is started to check that sufficient worms of the necessary species are present to make the test worthwhile. A worm egg count of at least 300 eggs per gram (EPG) is the general rule, but check this with your local veterinarian or goat consultant. Once a suitable mob of test animals has been found they are randomly drafted in to groups of 15 animals.

One group is randomly allocated to each of the drench groups to be tested and an additional group is needed to provide untreated control animals. Goats should be adequately identified to their groups and then receive an individual dose of their respective products. This is carefully calculated and checked on the heaviest individual within each group. Goats in the control group remain untreated. After treatment all of the goats can be run together or as part of any other mob of goats until it is time for post-treatment sampling.

Between 10 and 14 days after treatment (this timing is critical for a good result) the goats should be re-mustered and individual fecals samples collected from each group, including the controls. Individual worm egg counts for each sampled sheep and a bulk larval culture for each group should be carried out using the collected samples.

The results (drench efficacies) are obtained by comparing, for each worm species present in the test, the average number of eggs in the treated group sheep with the average number of eggs in the control group goats.

The Drenchrite™ Drench Resistance Test is a product that allowed assessment of resistance to the BZ, Lev and BZ/Lev combination products by measuring the effects of these products on worm larvae.

This test is not used widely any more as it has difficulty in detecting ML resistance but ongoing development is continuing and it might become available again in the future.

Another test using worm larvae is available, through NSW Department of Primary Industries, to assess Closantel efficacy.

It is also possible to get a 'quick and dirty' estimate of drench efficacy if a full drench resistance test is not possible at the time, by checking the worm egg count of a treated group of goats before and after the drench.

Larval culture results before and after treatment can also add more value to the results obtained this way

Control without drench

Producers often over emphasize the importance of drenching within a worm management program.
The need to treat can be markedly reduced by developing and implementing non-chemical worm management strategies.

This has a number of benefits:

• Reduced labor and drench costs
• Reduced onset of drench resistance
• Increased animal productivity

A well thought out non-chemical worm management program incorporating a number of non-chemical strategies can, over time, reduce the need to drench at all.
A professional adviser will help you to develop the best strategies for your property.

Smart Grazing for winter rainfall districts

Smart grazing is an improved, yet simple and reliable, strategy for the control of worms in weanling goats during their first winter. It can counter the negative effects of summer rainfall that reduce the effectiveness of the 'two-summer treatment strategy' in one in three summers in the winter rainfall areas southern United States.

The strategy hasn't been evaluated in the summer rainfall areas.

The why and how of 'Smart grazing'
Merino weanlings are very susceptible to worms in their first winter. Consequently, they need to graze pastures that have as few worm larvae as is practicable. 'Smart grazing' combines intensive grazing for 30 days with each of the two 'summer' drenches to ensure that virtually no worm eggs are deposited on a chosen pasture from the first summer drench (November) until after the autumn break (March-April), when the weanlings are put into these pastures.

Intensive grazing means using 2.5-3 times the normal stocking rate, for no longer than 30 days after each of the summer drenches is given. Not exceeding 30 days is critical because it takes three weeks for a worm larvae (eaten off pasture) to develop into an egg-laying adult in the goats. After the intensive grazing period, the paddocks are de-stocked to allow the pastures to re-grow. This means that the total stocking pressure for the 'Smart grazed' paddock will be the same as that for a paddock continuously stocked at the farms normal stocking rate (Figure 1).

The intensive grazing will reduce pasture residues to around 800-1000 kg DM/ha after the first summer drench, and around 600 kg DM/ ha after the second. If there is insufficient feed, the periods of intensive grazing can be reduced. Alternatively, if there is excess feed the summer drenches can be 'staggered' for different mobs so as to provide a longer intensive grazing period.

Finally, the weanlings must be drenched with an effective drench before they start grazing the 'Smart grazed' paddock after the autumn break.

Smart grazing on a typical farm
A typical self-replacing flock of 5,000 DSEs in southern United States is made up of 1,500 does, 1,500 wethers and 1,000 weanlings, running at a winter stocking rate of 15 DSE/ Ha.

70 Ha of 'Smart grazed' paddocks must be prepared for the weanlings. Thus, 2600 DSE (70 x 15 x 2.5) are needed to stock the 70 Ha at 2.5 times the normal stocking rate for each of the two intensive grazing periods - this is all of the wethers and 70% of the does on the farm.

A typical timetable for 'Smart grazing'
 

Why does smart grazing work?
The intensive grazing periods:

• Reduce the amount of pasture dry matter, making the pasture less suitable for the survival of worm larvae.
• Ensure that there is no deposition of worm eggs on the pasture from the time of the first summer drench until the autumn break.
• Probably allow the drenched goats to 'vacuum' up infective larvae, in much the same way as cattle do when they are used in alternate grazing programs with goats.
• Have the same cumulative stocking pressure from November to March as set-stocked paddocks grazed continuously by wethers.
• Are quite flexible. What must not be changed is the need (i) not to exceed 30 days grazing after each summer drench, and (ii) for a fully effective compound at the summer drenches.

What are the benefits?
Results from a controlled experiment over 2 years in United States show that, compared to weanlings grazing paddocks prepared the usual way (grazed by wethers over the summer/ early autumn), weanlings grazing 'Smart grazing' plots:

• Were 3 kg heavier in October (46.5 vs. 43.2 kg).

During winter, the egg counts from the 'Smart grazed' weanlings didn't go higher than 250 epg, a trigger for drenching weanlings used by many farmers and their advisers. In contrast, the weanlings on the paddocks prepared by set-stocked wethers exceeded 400 epg in both years.

The numbers of worm larvae on the 'Smart grazed' pastures in winter were from one-half to a one-third of those on pastures in paddocks prepared by grazing with set-stocked wethers.

Preparing winter weanling paddocks by 'Smart grazing'

Figure 1

Cross grazing with other species

Cross grazing with cattle and equine

Alternating grazing between cattle and sheep has been demonstrated to be an effective means of reducing worm infection.

This process relies on the fact that most worms are host specific, that is, most worms are only able to successfully infect either goats or cattle, not both, and ingestion by the non-preferred host results in death of the larvae.

A notable exception is the ability of barbers pole worm worm and stomach hairworm (T axei) to successfully reproduce within goats and young cattle (ie. pre-weaning). Using adult cattle for cross grazing is preferable.

Scientists have demonstrated the benefits of alternating goats grazing with cattle.

Grazing with cattle for the six months prior to goats grazing reduced numbers of barbers pole worm and black scour worm recovered from animals at post mortem by 94% and 98% respectively. The benefits of alternating goats and cattle grazing on weight gain.

Grazing goats on pastures that had been grazed by cattle for the previous 6 months increased annual weight gain by 25% (0.7kg) respectively.

Similar results highlighting the benefits of alternating grazing have been demonstrated with periods of alternation between goats and cattle as brief as 6 weeks. Prior grazing with cattle for the six week period January – mid February has been shown to reduce numbers of most of the important worms in goats over the following month with the exception of brown stomach (Ostertagia) worm.

The total number of worms recovered from the sheep which grazed pastures that had prior cattle grazing was 2158 compared to 14,842 worms from sheep that grazed on pastures grazed by goats for the previous six weeks. Note that the six weeks during January – February also took advantage of the time of year when conditions may have been least conducive for survival of larvae on pasture. In addition to the use of different ruminant species for alternating grazing, differences in parasite immunity between classes of animal within a species may be exploited to assist with the control of worms.

With this system, grazing management is planned so that pastures prepared for grazing by susceptible classes (e.g. recently weaned kids) are previously grazed by more resistant classes (e.g. adult dry goats). The length and timing of grazing by resistant goats is critical to the success of this strategy.

Based on the results from goats – cattle alternations, it is reasonable to assume that in the summer rainfall region, best results from grazing with resistant goats would occur if grazing were timed to occur for at least the three months prior to January.

However, alternate grazing with cattle has been shown to be superior.

Spelling

Short term spelling is of little use in worm control. Some time ago it was believed that short term spelling for three weeks or so would reduce the numbers of infective worm larvae on a pasture.

These are the spelling periods typically seen in rotational or cell grazing strategies, or when leaving pastures un-stocked after the autumn break in winter rainfall areas ('autumn saving').

However, studies in the 1960s clearly showed that this was not the case. Following these studies, it was shown that unless pastures were spelled for more than 10 weeks in autumn/winter there was no useful reduction in numbers of worm larvae.

The two influencing factors are:

In both winter and summer rainfall areas we now know that larvae from eggs deposited in the late summer and autumn can remain on the pasture in quite high numbers and infect goats right up until mid-spring (when rising temperatures and increased sunlight finally kill them).

Knowing this, the 'Smart Grazing' strategy was developed for winter rainfall areas to give more reliable worm control in weanlings during their first winter grazing period.

In summer rainfall areas, intermittent storms may occur in October and November. The intervals between storms are often hot and dry. Larvae released from dung pellets by the storms have a very short life expectancy under these conditions. Spelling paddocks during these periods will significantly reduce available larvae later on.

Nutrition

Nutrition has a major impact on how well sheep cope with worms. Good nutrition is a vital component of good non-chemical worm management.

Sound pasture management, strategic supplementary feeding and use of fodder crops all contribute to enhancing nutrition.

Fodder crops and crop stubbles

Cropped paddocks normally have extremely low levels of worm contamination. Plowing, fallow, planting and the period until the crop can be grazed reduce worm larvae levels to very low levels.

By the time a fodder crop or stubble is ready to graze, there should be very few surviving larvae available to infest stock and are very useful for susceptible goats such as weanlings.

However, such 'worm free' paddocks can be a very important means of selection for drench resistance. If goats are drenched onto the fodder crop, the only worms that remain are ones resistant to the drench used. Careful thought needs to be given about how to manage the paddock after the crop has been used.

Summer fodder crops, including Lucerne, can also provide excellent nutrition with minimal worm contamination.

Rotational and cell grazing

The use of rotational and/or cell grazing to assist sheep worm control needs careful consideration of the time that non-grazed paddocks are left empty.

Traditional cell grazing systems, with frequent rotations between paddocks, generally do not leave enough time between grazing for significant reductions in pasture worm contamination levels.

During the cooler, wetter months of the year this could require several months stock-free.

It is critical to monitor worm egg counts to detect any increase in worm infestations before production losses and/or animal health occur.

When planning a rotational grazing system, it pays to get professional advice to make sure that the system will deliver the hoped for benefits.

Genetics-breeding worm resistant goats

Resistance to worms in goats is in part due to genes. As a result, improved worm control in goats can be achieved by selecting and breeding with goats that have greater genetic resistance to worms.

Breeding worm resistant goats is possibly the most sustainable worm management tool that can be used.  Combined with other non-chemical management strategies, the need to drench can be very much reduced.

Commercial goat breeders can use bucks from sires that are selecting for worm resistance, and, over time, their goats will become more and more resistant to worms and require less drenching.

Genetic improvement

There is considerable evidence that part of the variation in host resistance to worm infection is under genetic control in goats and sheep. Resistance is most likely based on inheritance of genes which play a primary role in expression of host immunity. Based on survival of the fittest management conditions, several goat and sheep breeds are known to be relatively resistant to infection.

Such breeds include: goat - Small East African,South African Boers,West African Dwarf and Thai Native; sheep - Scottish Blackface, Red Maasai, Romanov, St. Croix, Barbados Blackbelly and the Gulf Coast Native. Katahdin sheep have been considered as being more parasite resistant, but studies to document this are few and not conclusive. Using resistant breeds exclusively or in crossbreeding programs would certainly lead to improved resistance to worm infection, but some level of production might be sacrificed.

 While such a strategy may be acceptable to some, selection for resistant animals within a breed is also a viable option. Selection for resistant lines within breed has been demonstrated with goats (Scottish Cashmere) and sheep (Merino and Romney). Within breed, animals become more resistant to infection with age as their immune system becomes more competent to combat infection.

However, some animals within such a population do not respond very well and remain relatively susceptible to disease. This means that the majority of the worm population resides in a minority of the animal population. It would make sense to encourage culling practices (based on FEC, PCV, FAMACHA©, etc.) where these minority "parasitized" animals were eliminated, thus retaining more resistant stock.

To augment this process, finding sires that throw relatively resistant offspring, would speed up this process. This approach has been used successfully in goats (Scotland) and sheep (New Zealand and Australia), but it may take quite a long time (up to 8-10 years) to achieve satisfactory results. Heritability for FEC, a common measurement for assessing parasite burden, range from 0.17 to 0.40 which is quite good.

Thus, selection for resistance and/or selection against susceptibility using a measurement such as FEC has been moderately successful. The real benefit to this approach is that reliance on dewormer intervention for control can be reduced, thus conserving the activity of such dewormers for when they are needed.

Control with drench

• Drenching is currently an important component of a worm control program.
• Effective drenching means using:
• the right drench (one that a drench resistance test has shown to be effective against the target worms at the time),
• at the right time (given the recommended local worm management program and current worm egg count monitoring results),
• at the right dose rate and
• administered to the animal in the correct way.

When to drench

• A worm egg count (WEC) is the best practical guide currently available to decide on the need for treatment. Worm egg counts tell you whether worm burdens are likely to be affecting production and will highlight potential worm problems, often before any signs such as scouring, anemia or obvious weight loss become visible.
• Regular worm egg counts, coupled with drench resistance testing allows good planning and effective treatment if needed.

A good professional adviser will assist you in interpreting worm egg counts, deciding when to drench and planning management strategies that reduce drenching and increase goat productivity.

Choosing a drench

When choosing a drench you need to know:

• The specific properties and potential uses of all of the different drench groups
• The current drench resistance status of the various drench groups on your property

Drenches are often classified on the basis of their range of activity and/or the class or type of active ingredient's) that they contain. Broad-spectrum drenches provide activity against most of the important worms of goats, provided they are susceptible to the drench.

Narrow-spectrum drenches generally just have activity against one or two species of goat worms. It is preferable to use these against specific worms (e.g. an infestation of barbers pole worm) rather than a broad-spectrum drench. Long acting treatments, such as oral and injectable Moxidectin products, Closantel products and controlled-release capsules, have persistent efficacy against susceptible target worms.

There can be different delivery methods for worm treatments.

The majority of products are administered as oral drenches but injectable products and controlled-release capsules are other delivery methods used for some products. The withholding period and possibly export slaughter interval of the different products should be considered before using any particular drench.

Drench resistance is a major problem Australia-wide. You cannot assume that all drenches will be effective on your property. A fully effective drench is one that has been shown to be more than 95 percent effective (and preferably should be measured as100 percent effective) in a drench resistance test within the last couple of years. Using a drench that is not effective is usually a waste of time and money and can lead to severe problems with worm control and worsening drench resistance.

However, there are some circumstances where using a drench that is, say, 80% - 90% effective can be useful. You should always seek professional advice before using drenches that are not fully effective.

Drenching technique

• With all treatments there are a few simple tips to help to ensure maximum efficacy:
• Always read the label on the container of the product to be used.
• Shake the container to mix the contents thoroughly before use.
• Ensure that goat get the correct dose of the product. Weigh a few of the larger animals in the group to be treated and then calculate the dose of the group on the basis of the heaviest weight.
  When using products with a greater risk of toxicity, such as Levamisole and naphthalophos on groups of goats with a wide range in live weights, divide the animals up into smaller, more uniform groups and treat each with its correct dose to reduce the risk of toxic effects.
• Double check dose calculations and regularly check drench guns to ensure that you are delivering an accurate dose with a medicine glass or similar device.

Holding Goats off feed prior to treatment

• Fasting goats for up to 24 hours before treatment can be used to improve the efficacy of treatments with BZ, ML or Closantel products.
• Fasting slows the flow of digestion through the gut of the goats and therefore keeps the drench in the gut for a longer period of time, allowing greater absorption of the active ingredient.
• This strategy should not be used when treating with Levamisole or naphthalophos as this could increase the risk of toxicity with these products.
• Fasting should not be used in heavily pregnant, stressed or poor goats.
• Goats should have access to water during the fasting period.

Holding Goats off feed after treatment

• Keeping goats off feed for up to six hours after treatment can assist drench efficacy.
• This strategy should not be used on heavily pregnant, stressed or poor goats, or following treatment with Levamisole or naphthalophos as this could increase the risk of toxicity with these products.

Make sure water is available