PARASITE PREVENTION STRATEGIES

Internal parasites of sheep, goats and young dairy cattle can be a challenge for both organic and non-organic farms. In the absence of chemical controls, keeping organic animals healthy and productive during the grazing season requires a good understanding of parasite-host interactions, grazing management strategies and animal selection. Worms and coccidia and other organisms are developing resistance to multiple chemicals so even if you are not organic it is advised that you start looking at alternatives to routine de-worming. Dr. Ann Wells presented some very useful and practical information on parasite control and prevention systems in April at two days of NOFA VT workshops. You can get a copy of one of her recent articles from the NOFA Dairy and livestock technical assistance website, and you can contact Sarah if you’d like a copy of the notes taken at Dr Wells workshops.

Dr Wells has not found any alternative treatment which works as well as the pharmaceutical treatments, so management and prevention is essential. Currently Ivermectin is the only pharmaceutical dewormer that is allowed in organic production. It can NOT be used in slaughter stock and it requires a 90 day milk withholding for diary animals. It is also damaging to the dung beetle populations on farms where it is used.

Here are just a few key points to consider in developing a parasite prevention plan for your goats, sheep or cattle:

Selection: Keep replacement animals from dams and sires that don’t have parasite problems or/and who don’t shed as many eggs in their manure.
Nutrition: Provide good nutrition including a mineral mix to animals. This is particularly important for animals which are most susceptible (young stock and small ruminants).
Grazing management is an essential part of prevention.
Since most of the infective larvae are in the bottom 2 inches of the pasture, manage to leave a 2 to 4 inch residual behind to minimize parasite infection.
Rotate pastures: this improves the nutrition going into the animals, it improves the pastures, it can prevent them from grazing too short if done correctly
Stock density is important. Lower density = fewer problems
Grazing with multiple species can be helpful. Goats will graze around cattle manure and cows will graze around goat manure and they are a dead-end host for each others parasites. For sheep they have found that never grazing sheep after sheep in a pasture makes a big improvement. Dr Wells grazes cattle after the sheep in the rotation.
Diversity of plant species in the pasture can be a useful part of parasite management system. This will provide more minerals as well as some medicinal components to the animals.
Consider planting some high tannin forages. These include plants such as birdsfoot trefoil, yellow dock, curly dock, and chicory. Dr Wells is doing some research on grazing chicory as part of the parasite prevention strategy for sheep and is seeing some preliminary success.

A few other points to consider:

Weather has an effect on how long the parasites live in the pastures. High humidity allows parasites to live much longer in the pastures. Hot and dry weather will reduce the number of infective parasites in the pasture.
Unhealthy soils have fewer of the beneficial organisms which can kill parasites and reduce infection rates in the pasture. Soil organisms such as dung beetles and nematophagous fungi kill the parasites.
Treatment needs to be the last resort: this includes alternative and pharmaceutical treatment materials.
The alternative treatments can be a useful method when added onto good animal selection and grazing prevention but are not going to treat serious problems on farms that don’t have a prevention plan including selection, nutrition and grazing.

Some of the research which Dr Wells has done on alternative treatment materials includes:

Dr Wells has done 3 years of Garlic Barrier research on sheep and goats. This is a crop protection product which is being used experimentally as a drench for parasites. It is showing some clinical improvement but may be just working as a tonic to improve gut health and prevent secondary infection.
Some research on African marigold in alcohol will be started this year.
Trials of a commercial product called “Molly’s finest” research did not show promising results with dairy and meat goats.
Some preliminary results from the use of Papaya seeds showed that it may have some deworming effect but more research is needed to determine dose size and method.
DE (Diatomaceous Earth) research in IA, MN, VA, TX all show that it has no impact on internal parasites but many producers still use it and claim it is working. It DOES work on external parasites. Wear a mask so you don’t breath in the dust