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Managing Parasites in Livestock

By Jerry Brunetti

Internal parasites are part and parcel of the animal’s ecosystem, or its “body ecology.” Wild ungulates are continually moving, leaving their parasite loads behind where they desiccate in the sun or just plain run out of nourishment before the animals return to the pasture. However, animals that are subjected to pasture or loafing areas without adequate rest will build up parasite loads, especially on humid landscapes, where moisture and temperature are conducive to their growth and reproductive cycles.

Young animals and those with weakened immune systems are most vulnerable, and this includes pregnant and lactating animals. Never allow your stock with parasite challenges to become underweight.

Parasites: Landscape Management

The first and most important component in parasite management is landscape management by employing sound rotation practices. This includes not only the adequate amount of time for the rest period between rotational grazing, but also grazing height management.

Most worm larvae crawl up the plant only 1 to 2 inches from the ground. Thus, allowing livestock to graze pastures too short increases the numbers of parasite larvae they ingest. The wetter the weather, the higher the larvae will climb.


Larvae also seldom migrate more than 12 inches from a manure pat. If one is mob grazing it’s important to recognize that more manure pats are deposited in a given area, thus the proper plant height and adequate animal movement over time is essential to minimize parasitical larvae ingestion.

Biodiverse Pastures

Biodiverse pastures populated with plants rich in plant secondary metabolites (PSMs) are a must. Tannins are a group of PSMs that acts as a natural wormer found in many species. Plants like chicory, birdsfoot trefoil, plantain, lespedeza, willow, burdock, curly dock and miscellaneous shrubs, vines and trees are rich in tannins and perform not only as an anthelmintic but also a scavenger of rumen ammonia that can produce toxic blood urea nitrogen (BUN) or milk urea nitrogen (MUN).

Livestock Species Diversity

If you run small ruminants like sheep and goats along with cattle you can benefit from the species-specific nature of these livestock, as cattle do not share the same species of parasites as sheep and goats. Therefore cattle can “clean” pastures for sheep and goats and vice versa by ingesting their larvae prior to small ruminants ending up on that paddock.

Allowing poultry, like chickens and Muscovy ducks, to follow ruminants three to four days later can also clean pastures. They tear apart manure pats searching for both fly and worm larvae which exposes the pat to sunlight, drying it out and desiccating the eggs and larvae.

Encourage Decomposers

It’s ecologically vital for a community of decomposers to be in the pasture in adequate numbers. Earthworms and dung beetles consume dung and also incorporate it into soil where it is further decomposed by soil and further decomposed by soil microorganisms.

If there has been a routine use of wormers, larvicides for flies, insecticide pour-ons, etc. these “decomposer” organisms will be damaged to the extent that manure will not readily rapidly decompose, thus inviting more pests to plague your stock in the future.

Infective larvae can survive long periods in undisturbed dung pats. If your pasture ecology has been compromised you may want to harrow the pats to break them up until your dung beetle and earthworm populations increase, or bring in pigs and poultry to work the pats over.

Wormers becoming Obsolete

Wormers are becoming obsolete! There is a high degree of resistance now with the benzimidazoles such as Safeguard and Valbazen. The avermectins like Ivomec are apparently the least effective of all drugs, especially in small ruminants.

It’s just a matter of time before the same resistance gets transferred to the imidazothiazoles such as Tramisol, Strongid and Rumatel, which are becoming increasingly less effective.

Several practices accelerate the resistance issue: 1) frequent de-worming (more than three times per year); 2) under-dosing by miscalculating body weight; 3) treating affected animals and moving them to clean pastures; and 4) treating all animals in the flock or herd.

These practices have decreased the numbers of worms susceptible to the parasiticides.

Worms that are not treated cannot become resistant. This creates what is known as a refugia, which insures that a surviving population of untreated worms actually dilutes the number of worms with resistant genes to the drugs.


If doing a fecal egg count (FEC) to determine parasite loads, keep in mind that the worm egg count is a picture of the parasite load on the pasture three weeks ago. The highest pressure for internal parasites is in the autumn. The most susceptible animals besides young stock are ewes and does in late pregnancy/early lactation because they experience a drop in their immunity and consequently pass more worm eggs in their manure.

Calves born in the spring become infected once they nibble contaminated pastures from larvae that have over-wintered.

This results in a heavier load that can reinfect calves in the late summer and autumn when the weather cools off.

The “favorite” temperature for the larvae in the pasture is about 68-78°F. Thus, they can survive eight to 12 months at this temperature, whereas in the hot summer months they can only survive two to three months.

Small ruminant operators can readily utilize an effective earlier detection method called the Famacha card, a color-coded hand card that measures the level of anemia in the animal by holding the card up to the eye to see how pink or white it is. It allows the producer to only treat animals in need and to select animals to keep in the flock that are more resistant, since parasite resistance can be a genetic trait.

Some breeds of sheep and goats show increased resistance to parasites, but there is resistance with all breeds, thus no matter what breed you are working with, you can continue to genetically select for such strengths. Research shows that 20-30 percent of your animals carry 70-80 percent of the worms. The good news is that adult cattle, sheep and goats develop immunity to worms between 18-20 months of age (except at calving, lambing and lactating times).

Remedies to the Rescue

Fortunately, there are practices and products that can contribute to the systems approach needed to keep the farm or ranch parasite-free (at least clinically):

  • Apple Cider Vinegar (ACV) or acetic acid is a great tonifyer because a healthy rumen which ferments fiber produces adequate amounts of it to provide fast acting energy and healthy pH in the G.I. tract and lymphatic fluids. One cup of 50-60 grain (5-6 percent acidity) to 20 gallons of drinking water, put out a 50/50 mix of 50-60 grain ACV with water as a free choice supplement (organically acceptable).
  • Aqua-Nox Stock Saver. As a prevention, a mere 1 ounce per 100 gallons of water can really help, not only with parasites, but G.I. tract integrity as a whole. If livestock are compromised, 2 to 4 ounces per 100 gallons of water is in order. To treat individual animals, add one teaspoon to 60 cc (2oz) per 150 pounds of body weight of water in a large syringe and drench daily for several days (organically acceptable).
  • PC Pre-Mix is a high copper, sulfur and herbal mix that can be put out free choice for livestock. However, always ensure that livestock have other complete pre-mixes in their diet included as a free choice option. Additionally, if supplying as a free choice to sheep, cut PC Premix 50/50 with salt while insuring they have loose salt by itself and free choice minerals (organically acceptable).
  • Grazier’s Essentials are comprehensive pre-mix formulas that can be provided free choice or force fed as per nutritional recommendations. Balanced macro elements (Ca, P, Mg, S, Si) and trace elements (B, Zn, Cu, Co, Mn, Se, I, Cr, Vn Ni) are rounded out with Dyna-Min, kelp, pre-biotics, probiotics, enzymes and fat and water soluble vitamins (organically acceptable).
  • Native Lick and K-N-S (Kelp-Native Lick-Salt). Native Lick is a blend of five prehistoric sea bed minerals (including Dyna-Min) and some producers found that blending one-third salt, one-third Native Lick and one-third kelp does wonders for both worms and protozoic parasites like coccidiosis and crytptosporidia (organically acceptable).
  • Vermi-Tox and Neema-Tox are both drenches to treat afflicted animals with a) worm infestations; b) cocci/crypto and c) bacterial scours. Vermin-Tox can be used in all three challenges. Neema-Tox is used for cocci/crypto and bacterial challenges (organically acceptable).
  • Hydrogen Peroxide (35 percent H2O2 technical/Food Grade). This has been utilized for overall herd health in Pennsylvania at least since the 1980s. Apparently 8 ounces per 1,000 gallons of drinking water can help prevent outbreaks. Higher doses are needed for treating afflicted animals (organically acceptable).
  • Dyna-Min consists of mined colloidal clay minerals and is typically fed at 4 ounces per head per day (1,000 pounds of body weight) as well as free choice. Note: if animals are new to it, for some it may be a novel feed supplement-mix 50/50 with salt to introduce it to picky eaters (organically acceptable).
  • Nematode-Trapping Fungus (Duddingtonia flagrans). This fungal spore is fed to livestock and the fungus germinates in the dung, killing the critical Stage 3 larvae. Not yet commercially available. Stay tuned.
  • Copper wire particles are little boluses that can be effective for lambs, but apparently not sheep. High doses may increase risk of copper toxicity.
  • Basic H is a non-ionic surfactant (not organically approved) that is added to the sole source of drinking water at 1 cup of Basic H to 100 gallons of water. Animals need to be confined to the water source for two days. Treatment is repeated six times yearly.
  • Diatomaceous Earth is an 89 percent silica compound from the diatom skeletons from fresh water deposits. It acts via dehydration of the parasites and should probably be force fed 2-4 ounces per head per day (1,000 pounds of body weight) as well as free choice.

Note: When implementing worming (drenching and supplemental) strategies, is it traditionally recognized to dose when the moon is waxing, i.e. three to five days before the full moon.


The short note on these critters is that lice and mange tend to show up when:

  • Nutrition is inadequate leading to immunosuppression, especially trace elements and fat-soluble vitamins.
  • Animals are crowded and/or too confined.
  • Inadequate sunlight.
  • Poor genetics equals more susceptibility.

Follow the same back-to-basics ground rules written above and try some of the same remedies.

Editor’s Note: This article appeared in the February 2014 issue of Acres U.S.A. Brunetti’s The Farm as Ecosystem, The Keys to Herd Health and Holistic Veterinary Care are available from Acres U.S.A. For more assistance, call 800-355-5313.

Visit Agri-Dynamics for more information on some of the remedies listed in the article. Also, visit Primo Pet Products.