Deworming Strategies for Livestock

General Remarks

Deworming strategies have evolved over the years to accomplish three main goals:

-Reduce the chance of developing resistant parasites.

-Reduce operational expenses for livestock producers

-Reduce the use of drugs in food animals.

In most herds, 20% of the animals shed 80% of the parasite load. Therefore, in small herds it is more economical to treat only the most infected animals, this practice is used in equine and small ruminant operations. In larger production herds such as cattle, animals should be treated as management categories and each category be treated according to their risk. In large small ruminant production systems, a percentage of animals should be tested to determine if the herd needs to be treated.

Deworming protocols for every operation should be developed with a veterinary consult. Protocols will vary based on the type, location, herd, and individual animals of an operation. The southeast United States is the ideal breeding ground for parasites year round so it is important to manage parasites all year.


Equine deworming has moved away from the use of a rotational deworming strategy every 4-8 weeks to a much more targeted, individual treatment protocol. The use of targeted deworming significantly reduces the chance of developing drug resistant parasites and reduces the chance of confusion on which dewormer to use and when.

Florida peak season for equine parasite infections are spring, fall, and winter, treatments should be focused during these time frames. Operations should be utilizing fecal egg counts to determine which horses have a high enough parasite load to justify treating and which horses will not need a treatment. Fecal egg counts are often a small cost through your veterinarian and often do not require a farm visit. Horses with a fecal egg count higher than 500 should be treated based on the species of eggs present, a veterinarian should give the recommendation on which dewormer to use to provide the most effective treatment.

It is important to note that fecal egg counts can not identify tape worms, therefore horses should be treated with praziquantel biannually or annually.

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Equine deworming should focus on prevention and control through the use of management techniques:

  • Clean and dispose of manure in the pasture at least twice weekly.
  • Mow and harrow pastures regularly to break up manure and expose parasite eggs to the sun.
  • If possible, rotate pastures by allowing other livestock to graze them.
  • Group horses in a pasture by age to reduce exposure to certain parasites, and maximize the deworming program geared to that group.
  • Prevent overgrazing and reduce fecal contamination by keeping the number of horses per acre to a minimum.
  • Feed horses in a feeder for hay and grain rather than on the ground.
  • Remove bot eggs from the hair routinely to prevent ingestion.

Small Ruminants (Sheep/Goat)

Sheep & Goat deworming treatments should be made using FAMACHA or fecal egg count (FEC) scoring. FAMACHA scoring is a practice that determines a small ruminants anemia level, and therefore its level of parasite infection. FEC scoring, like in other livestock species, is the practice of counting parasite eggs in a fecal sample. FEC scoring can give a more specific recommendation since species of parasite can be determined, this leads to a more targeted deworming protocol.

Livestock producers can benefit from the use of mixed species grazing. Grazing small ruminants after horses or cattle can help break parasite life cycles since the same parasites do not inflict small ruminants and other livestock. Utilizing this grazing strategy can increase forage utilization while still allowing longer periods between when a particular livestock species is re-introduced to a pasture, reducing the parasite load over time.

Learn more about Sheep & Goat parasite control here:


Cattle standing in line

Deworming strategies for cattle are unlike other livestock species since they are treated by management category and not by individual animal. Cattle parasite control methods focus on stomach and intestinal worms, lung worms are often controlled with a proper intestinal worm control program and liver flukes are not a problem on every Florida cattle operation.

Parasitism in cattle is a herd wide issue. Focusing treatments methods on the most susceptible animals and separating treatments by management category can reduce production costs while accomplishing three goals:

-Saving clinically affected animals

-Improving overall production of the herd

-Reduce pasture contamination levels and thus reinfection rates/need for re-treatments.

Nursing calves, stockers, and replacement heifers (any cattle pre-weaning to a year after weaning) are the groups of cattle most affected by parasites. These management categories are most susceptible to clinical affects of parasites such as poor performance or death, they also are the heaviest shedders of eggs and the reason for most re-infection. Mature cattle have a strong enough immunity to resist ill effects of parasites but poor body condition associated with heavy loads of parasites can affect reproductive efficiency. Control of parasites in younger cattle will reduce needs of treatment of mature cattle.

James E. Miller of Louisiana State University states, “strategically timed treatments with appropriate products will increase the return for each dollar invested.”

Although long pasture rotation times (in excess of 6 months) can break parasite life cycles and reduce the need for dewormers, this is not generally a feasible production style for Florida ranchers, therefore strategic deworming is necessary. Strategic programs should be developed with these four core production aspects in mind:

-Time of year grazing begins. Since cattle are infected with parasite eggs through grazing, grazing seasons will determine potential parasite loads and timing of treatment.

-Age/Category of animals. Management categories of animals will determine whether it is economically feasible to work animals in order to deworm and can allow for appropriate timing of deworming protocols.

-Type of operations grazing system. Grazing systems, such as rotational strategies, use of cool season forages, etc. can influence deworming protocol timing.

-Grazing history of pastures. Pastures that have not had cattle grazing in the last 6 months or more likely have reduce parasite contamination when compared to pastures that have had recent (<6 months) cattle grazing.

The two parasites of most economic importance in the southeast US are brown stomach worms (active November through February) and barber pole worms (active June through September).

All approved cattle dewormers are effective against all species of adult parasites, selection of specific dewormers is important when trying to control larvae or liver flukes. There are products that can effectively dose dewormers without having to work cattle, such as blocks, salt/mineral mix, top dress, cubes, and others. These products can be beneficial if working cattle at the time dewormer is needed is not ideal or does not fit into other production practices (calving season, working calves, etc.)

All Florida pastures that currently, or have had cattle on them in the last 6 months, have parasites present. However, every Florida pasture does not have liver flukes. Before selecting liver fluke specific parasite products it is important to test for fluke eggs in manure or check for fluke damage in a cull cows liver.

Adult cattle have a strong immunity to parasites and generally anthelminitic (parasite control) treatments do not provide a return on investment unless cattle are showing clinical signs of infection (severe weight loss/anemia). Immunity to worms forms about one year after weaning. Therefore, treatment of calves and weanlings is the most critical and will provide the most return on investment.

Treatment Plans for Florida Cattle Ranches

Make sure to have a bio-security plan in place. Separate and treat any new herd animals before co-mingling with established herd, this helps to reduce parasite loads and ensures your deworming plan of action is most effective.

Summer treatments, especially those with larvae inhibitors, are highly effective in reducing overall pasture contamination and fall re-infection rates. Summer treatments should use products such as Panacur at double dose (fenbendazole), Ivomec (ivermectin), Valbazen (albendazole), or Synanthic (oxfendazole) as these are the approved cattle dewormers that inhibit larvae development.

Animals treated with fenbendazole or oxfendazole can return to grazing pastures 8-12 hours after treatment. Animals treated with ivermectin should not be returned to grazing pastures for at least 48 hours after treatment. If animals treated with ivermectin are returned to grazing pastures before 48 hours have passed viable eggs will still be shed in manure and will lead to re-infection/pasture contamination.

Weaned calves should be treated when they are first placed on pasture.

Deworming weanlings
  • Their first grazing season
  • Deworm at weaning and anytime they are moved to a new pasture
  • If over-winterd on un-grazed pastures (pasture has not had cattle in at least 6 months). then 1 treatment is sufficient. If pasture has been grazed by other cattle in the last 6 months, then retreat in 30 days to ensure effective blocking of the parasite life cycle.
  • Overstocked pastures will require more treatments as cattle are more likely to come in contact with parasite larvae.
Liverfluke treatments

Treatment for Liverflukes should focus in Spring (March/April) with Curatrem (clorsulon) as it is effective against both mature and immature bots, and fall (October-December) with Valbazen or Ivomec F as these are effective only against mature bots. Treatment in late summer/early fall is helpful to reduce fall infection of snails with the fluke larvae.

In general, deworming strategies should be matched with other production goals and timelines to ease stress on cattle and provide the greatest return on investment.

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Posted: November 12, 2019

Category: Agriculture, Farm Management, Livestock, Pests & Disease, UF/IFAS, UF/IFAS Extension
Tags: Animals, Farm, FL, Livestock, NFLAG

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