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Organic farming strategies useful for controlling parasites

Parasite control in our livestock is an evolving process. When we started farming, we had clean land and a handful of animals — we couldn’t understand what all the excitement was about. Now, we’ve come to realize that parasite control is an economic reality and one that has many facets. Just pouring chemicals repeatedly on our livestock is not a total solution.

The more research that’s done it becomes more obvious that conventional livestock producers need to pay attention to how organic producers control parasites on their farms.

That’s because for several years now there has been absolutely no testing to develop new products. And studies are showing that certain common parasites have developed resistance to such deworming products such as benzimidazole, levamisole and even ivermectin, due to too-frequent use. Hot humid weather is ideal for parasite numbers to explode and this wet year so far has been ideal.

Starts at the pasture

Pasture management is a major focus of natural parasite control. The first rule is not to overstock livestock numbers on pasture, which increases the concentration of parasites. When trying to use chemical wormers less often it is recommended to worm the flock at least 10 days before releasing animals to pasture.

This will kill off the new season’s hatch and hopefully assist in not populating the pasture. It is generally estimated that parasite infections increase with the square of the animal load per surface unit. Therefore, for a given parcel of land, parasite infestations are four times greater where animal density is doubled. Density varies depending on whether grazing is intensive or extensive. Extensive grazing for sheep, for example, is fewer than 10 lambs to 2.5 acres.

Pasture rotation, or intensive grazing, consists of dividing pastures into parcels of varying sizes called paddocks and frequently moving the animals from one paddock to another to optimize grass use.

For optimum parasite control, the objective is to not put the animals back onto the same field until the risk of infection has diminished. Theoretically this means that parasitism will decrease if the number of parcels of land is increased or the rotation rest period is increased. Unfortunately, in practice, it appears difficult to diminish the parasitic load with intensive grazing.

  • From the Canadian Cattlemen: Grazing habits of cattle

It is helpful to have fecal samples tested so producers know what type of parasites are on their farm and thereby can learn their specific life cycle. The lifespan of some parasites is in fact always greater than the time required between grazing periods for maximum grass use. Therefore, by waiting six weeks before returning animals to a paddock, the quality of the grass decreases as well as the quantity of grass ingested by the animals, whereas the level of parasites only diminishes slightly.

Use the sun

When animals are put onto new uninfected pastures experts say they should be allowed to graze grass very close to the ground. This allows the sun to dry the manure quickly and lowers the survival rates of shedded parasites. Studies in New Zealand and Ireland also show the use of chemical wormers slow the decomposition of manure, thereby not allowing this natural process the same efficiency. There is also a marked decrease in dung beetles on manure that has chemicals in it, again decreasing the efficiency of a natural cleaning system.

A new pasture is considered a field where animals have not been grazing for a number of years or was last visited before extreme winter temperatures, which killed the existing parasites. On subsequent trips through this “new” pasture, it is important to remember that about 80 per cent of parasites live in the first five centimetres of pasture growth. Parasite infection and multiplication are prevented by allowing animals to graze only to 10 cm (about four inches) from the ground in a field where there are parasites.

We like to keep our sheep and goats in a night pen with hay. This practice can also limit exposure to parasites. The drier the grass, the more parasites will stay at the base of the plants. It is estimated in wet grass, larvae can be found over 30 cm (about 12 inches) above the manure piles, whereas they venture only a few centimetres away when the grass is dry.

The risk of infection is greatly reduced by waiting until the dew has lifted or until the grass has dried after rain before putting animals out to pasture. The larvae of most parasites move to the tops of plants when light levels are low, that is, when the sky is overcast or at sunrise and sunset. They avoid strong light however. Limiting grazing time to when the sun is strong also diminishes the risk of infection.

Different species

When it is not economically sound to leave a long rest period between pasture or paddock grazing, farmers might consider grazing a different animal species. Generally parasites are species specific. This does not apply to sheep and goats though. Apparently their parasites find each other perfectly acceptable hosts but they will not infest cattle. Therefore if the sheep/goats go through first and then the cattle are put through on regrowth this could be a better use of resources. Another option is to utilize poultry on pasture.

Virginian grass farmer Joel Salatin recommends moving the cattle daily onto fresh pastures and following them with poultry. The poultry will scratch through the manure, picking out the parasites, allowing the manure to decompose. A bonus is that unlike chemical wormers, that could cost producers thousands of dollars, the poultry produce meat and eggs for your family for the winter while doing parasite control work.

Properly timed, mechanically harrowing pastures is also an option for reducing parasite loads. This should only be done after the last fall rotation and only if freezing temperatures are imminent. If not this practice will just broadcast parasites over the pasture rather than keeping them in the manure clumps.

During pasture season make notes on which animals have no resistance to parasite loads and require repeated treatments. We have stopped keeping replacement females from dams that are constantly in need of treatment as it is proven to be a genetic trait. There is more to natural parasite control than just pasture management, but without this nothing is going to work. Recurring infestation, which points to the contaminated pastures is the major problem on most sheep and goat farms so this is where we need to start. The next steps will involve utilizing nutrition and perhaps herbal treatments, in the control program.

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