Ideas for Treating Parasites on Organic Cattle Farms

By Hubert J. Karreman, V.M.D.

How do we treat internal parasite infestations on certified organic farms?


Ivermectin, moxidectin and fenbendazole are allowed to be used but only for an emergency after methods acceptable to organic have not succeeded in restoring an animal to health. A 90-day milk withhold is required if lactating cows are treated. There is some discus­sion to reduce the 90 days to seven or 10 days. Typically in the past I have recommended a synthetic wormer as a one-time treatment— essentially to reset the individual animals infested—and then get the management in place to keep things in prevention mode rather than reaction (treatment) mode.

Fortunately, there are also many plant-based medicines being used around the world against internal parasites. In the chapter I wrote called “Phytotherapy for Dairy Cows” in the book Veterinary Herbal Medicine, (Susan G. Wynne and Barbara Fougère, Veterinary Herbal Medicine (St. Louis, MO: Mosby, 2007) I reported on a study that showed birdsfoot trefoil or chicory interplanted into pasture decreased the stomach worm larva burden significantly compared to a straight white clover and rye pas­ture. This is because of tannins contained in the birdsfoot trefoil and chicory.

What should we treat with later in the grazing season if our young stock looks crummy? Treatments can range from materials that are high in tannins, like black walnut hulls; dewormer mixes that are added to the feed; to Ferro, which has extremely high levels of hu­mates, iron and minerals. One treatment is to give 10cc of Ferro once daily for five days in a row. This course of treatment is highly effective but requires dosing individual animals, which most farmers understandably do not like to do when it comes to a group of heifers outside. Any herbal formulas with ginger, garlic and neem would be helpful to battle internal parasites in the digestive tract. Another op­tion to try would be Neema-Tox or Vermi-Tox from Agri-Dynamics. Vermi-Tox was shown to have positive benefits in clinical trials at Chico State University. In that study, Vermi-Tox and ivermectin gave equally good reduction of fecal egg counts whereas the no-treatment group became much worse. Weaned cattle are dosed at one ounce per three hundred to four hundred pounds for three days in a row. Re­member, you can use a synthetic wormer if your animals are in really bad shape, and you probably should at that point. Bear in mind, how­ever, that ivermectin is totally poisonous to the dung beetle popula­tion, those friendly beetles that decompose manure paddies quickly in healthy biological systems.

Organic Guernsey cattle
Organic Guernsey cattle graze in a paddock.

If a farm is found using a synthetic wormer on a certain age class of animals every year, most certifiers would rightly ask to see what the farm is doing to prevent parasite pressures from developing. (By using rotational pasture management so animals get new paddocks every twelve hours and by giving the grazed paddocks a rest in order to re­grow.) Just as important, dragging pastures to spread out manure will allow quicker drying out of manure to kill the fragile microscopic larva crawling about. The ideal time to drag out manure pies is three days from when the cows are on the paddock, which will not hinder pasture regrowth and more importantly will allow the dung beetles to do their incredibly important work, drilling manure into channels they create in the soil. This timing also allows time for horn flies and face flies to lay their eggs, so eggs will be hatched and the fragile young larva can also be killed by spreading out the manure pies and quickly drying out the living areas of internal parasites and developing flies.

Conventional farms can put an ear tag into an animal that gives a slow release insecticide to the animal’s system to kill flies when they bite the animal. The manure from such an animal will also kill flies or fly larvae that feed on the manure (both good and bad bugs are killed). Insecticide ear tags as well as regular fly sprays and the blue “sprinkles” are prohibited for use on organic farms. In most years, a combination, multi-prong approach to fly control on organic farms can be fairly effective. The following are usual methods of controlling flies—and remember that it is a combination of these approaches that works best. You are fooling yourself if you think that using only one or two approaches will work. The list includes: sticky paper in the barns, pheromone fly traps, wasp predators routinely placed in strategic areas, botanical fly sprays applied daily, hanging barrel feeders with salt in the pasture with solar-powered sprayers, electric zappers that animals walk through and of course clean, dry cows (since flies are attracted to moisture) and tunnel ventilation.

When farmers apply concepts of biology, chronic problems like flies can be managed better. Take for instance that flies like warm, humid conditions and flies don’t like wind. How many times are you bothered by flies on a windy day? Applying this basic concept to farms would indicate that air flow in the barn would mean dramatically less fly problems. Lo and behold, go into a barn that has tunnel ventilation and you will experience few if any flies. It certainly need not be tun­nel ventilation, but something about tunnel ventilation simply works extremely well against flies.

You have probably heard by now of the Spalding Cow-Vac, a ma­chine that generates high-velocity wind in a walk-through chamber. It also has a vacuum aspect that sucks the flies that have been blown off the cows into a large jar. Without a doubt this is the best way to reduce the amount of flies tormenting your cows as well as eliminating them from the breeding population, thereby lowering fly numbers through­out the fly season. The Spalding Cow-Vac is now commercially avail­able (see your trade magazines). It was developed at North Carolina State University.

While I will always promote a multipronged approach to solving problems, if there was ever a “one-stop shopping” method of dealing with flies, the wind/vacuum chamber is it. While other methods like sticky tape catch random flies and parasitic wasps will help reduce the number of flies that become adults, the fly-vac basically wipes out large numbers quickly—right off the cows—which will make your cows more comfortable, allowing them to graze better. The fly-vac may well be the single best invention yet for non-chemical fly control.

As the seasons change, young animals carrying parasite burdens are especially susceptible to damp, chilly air, especially if brought indoors once the pasture season is over. Never, ever bring young stock back inside to a building that shares air with older animals. A rule of thumb is that once an animal leaves the main barn where it was housed as a youngster, always raise it outdoors (with proper shelter) and bring it back into the main adult barn only when it is ready to join the milking string. Too many times I have been called to see sick and coughing parasitized animals that were brought back into the barn in October or November when the weather got bad. Major mistake. By feeding animals well and keeping them outdoors in managed pastures and shelters, your young stock will grow up to become healthy, productive members of your dairy herd.

In summary, make sure you clip your pastures to splatter out ma­nure patties to expose the worm larvae to the drying effects of sun and wind. This will also give uniform regrowth. Also keep animals off a paddock three weeks before putting them back on, as worm larvae need to be ingested by then to complete their life cycle inside the animal. And never have young stock follow adults through paddocks, as adults can live in balance with the worms they shed but will infect young stock. Immunity to worms usually starts becoming effective at about 12 months of age.

Source: Four-Seasons Cattle Care