3.5 Minimize Exposure to Parasites
Katie Steneroden
It’s impossible to eliminate parasites in livestock completely. Preventing and controlling them relies heavily on a strong immune system and low exposure. Parasites come in many shapes and forms. Conventional producers often use a one-step pour-on to take care of parasites. Organic and alternative farmers/ranchers don’t have that option. O/A farmers and ranchers must use and will be most successful using a combination of methods for parasite prevention and control—integrated pest management—mentioned below and throughout this chapter.
Parasites were considered an important problem for O/A farmers and ranchers in an ISU survey conducted in 2021 (Steneroden, 2021). It’s no wonder, as external and internal parasites can cause blood loss, decreased appetite, poor weight gain, and losses due to irritation—for external parasites, diarrhea, decreased milk production, reduced reproductive performance, anemia, weakness, and, in some cases, death.
The Code of Federal Regulations Part 205(G) guides USDA-certified organic operations. More detailed and specific information can be found in the chapters of the Rules and Regulations and Modalities and treatments.
Parasite prevention, control, and monitoring are opportunities for veterinarians to assist O/A farmers and ranchers. Taking samples—or having producers bring samples to the veterinary clinic—and analyzing them at regular intervals would go a long way in helping farmers know if their parasite prevention and control plan is working.
- A healthy immune system is critical—good nutrition, exercise, and low stress (all key elements from the Focus on Health section of this chapter) also help prevent parasites.
- Use a multi-prong approach—multiple interventions affecting animals and the environment are necessary.
- Focus on pasture conditions, housing, and sanitation that help minimize diseases/parasites.
- In wet years, parasites can maintain themselves for very long periods. Also, in the South, mild winters don’t allow for the die-off of common GI parasites of ruminants. Some parasites can persist over winter in fields. For these reasons and more, managed rotational grazing is the most important thing farmers can do to manage parasites.
Have diverse pastures with a variety of plants and provide browse.
- Susceptibility to parasites varies between cows, sheep, and goats. Multispecies grazing can help break parasite cycles. Cattle do not share parasites with sheep or goats—but sheep and goats do share parasites.
- A crucial consideration in pesticide use is avoiding environmental damage to natural controls such as dung beetles and manure recyclers. For an interesting research article that discusses dung beetles, fly control, organic crop production, and improved food safety, see Jones 2019.
Some specific considerations:
- Keep new animal additions separate from the home herd for at least three weeks to identify and prevent all disease introduction, including parasites. This is often a difficult practice for all types of farmers and ranchers, and its benefits should be stressed and reiterated often.
- Graze younger, more vulnerable animals on a fresh pasture before allowing other, older animals.
- Even if parasitized, animals can stay ahead of actual pathology if fed well, even if it might mean greater feed costs.
- Because larvae are concentrated near the ground, don’t allow grazing lower than 4–6 inches.
- Before allowing animals back on a pasture to graze with a different livestock species, cut it for hay or rest the pasture for 45–60 days to let parasites die off.
- High tannin forages have been shown to reduce fecal egg counts in sheep and goats (ATTRA Tools for Managing internal parasites in Sheep and Goats, 2015).
- Calves “sent out back” to the same place year after year are likely to experience parasitism—especially if “forgotten” because of more important animal classes to care for (milking herd and neonatal animals).
