Common Parasite Control Methods in Feedlots

Parasite control is a critical aspect of managing animal health and productivity in feedlots. Parasites, both internal and external, can cause significant economic losses by reducing weight gain, feed efficiency, and overall animal well-being. Effective parasite management ensures healthier livestock, improved performance, and greater profitability. This article explores the most common parasite control methods used in feedlots, focusing on strategies to combat internal parasites such as worms and external parasites like lice and flies.

Importance of Parasite Control in Feedlots

Feedlots are high-density environments where cattle are confined in relatively small spaces for finishing before slaughter. This setting creates ideal conditions for the spread of parasites due to close contact between animals, accumulation of manure, and stress that may weaken immunity.

Internal parasites such as gastrointestinal nematodes (roundworms), liver flukes, and coccidia can impair digestion and nutrient absorption. External parasites including lice, mites, ticks, and various fly species cause irritation, blood loss, and can transmit diseases.

Without proper control measures, parasite infestations can lead to:

• Reduced weight gain and feed conversion efficiency
• Lowered immunity and increased susceptibility to other diseases
• Stress and discomfort, impacting welfare
• Economic losses through veterinary costs and decreased performance

Therefore, implementing effective parasite control methods is essential for maintaining healthy stock and maximizing feedlot productivity.

Internal Parasite Control Methods

1. Anthelmintic Treatments (Dewormers)

Deworming is the cornerstone of controlling internal parasites in feedlot cattle. Anthelmintics are drugs specifically designed to kill or expel parasitic worms. Several classes of anthelmintics are available:

• Benzimidazoles (e.g., fenbendazole)
• Macrocyclic lactones (e.g., ivermectin, doramectin)
• Imidazothiazoles (e.g., levamisole)
• Amino-acetonitrile derivatives (e.g., monepantel)

Application Strategies

• Pre-entry treatment: Administering dewormers before cattle enter the feedlot reduces parasite load introduced into the facility.
• Strategic treatment: Scheduled treatments at key times during the feeding period help control parasite populations.
• Targeted selective treatment: Treating only animals showing clinical signs or high parasite burdens minimizes drug use and delays resistance.

2. Pasture Management and Hygiene

Although feedlot cattle are often kept on dry lots rather than pasture, hygiene practices still affect parasite control by minimizing fecal contamination.

• Manure removal: Regular cleaning reduces egg and larval stages of parasites.
• Pen rotation: Moving cattle between pens allows contaminated areas to rest and reduces parasite loads.
• Drainage improvement: Preventing muddy or wet conditions inhibits survival of many parasite larvae.

3. Nutritional Management

Good nutrition supports the immune system’s ability to fight off parasitic infections.

• Balanced diets with adequate protein, vitamins (especially vitamin A), and minerals (such as zinc) help maintain resistance.
• Nutritional supplements may be used during periods of high parasite risk or stress.

4. Biological Control Agents

Some emerging control methods explore biological agents that reduce parasites naturally:

• Nematophagous fungi: These fungi trap and consume nematode larvae in the environment.
• While still experimental in feedlots, these agents offer potential as alternatives or supplements to chemical anthelmintics.

External Parasite Control Methods

External parasites cause considerable discomfort to cattle and can lead to secondary infections or disease transmission.

1. Insecticides and Acaricides

Chemical treatments remain the primary method for controlling external parasites such as lice, mites, ticks, horn flies, face flies, stable flies, and mosquitoes.

Common Application Methods:

• Pour-ons: Liquid insecticides applied along the animal’s back provide systemic protection.
• Sprays: Directly sprayed onto animals for rapid knockdown.
• Dust bags: Animals pass through dust boxes containing insecticide powder.
• Back rubbers/rollers: Devices coated with insecticide placed in feeding areas encourage animals to self-treat as they rub against them.
• Ear tags: Contain slow-release insecticides effective against certain pests like ticks.

Classes of Chemicals Used

• Pyrethroids (permethrin, cypermethrin)
• Organophosphates
• Carbamates
• Macrocyclic lactones (also effective internally)

2. Integrated Pest Management (IPM)

IPM combines multiple approaches to reduce reliance on chemicals and delay resistance development.

Key IPM strategies include:

• Monitoring pest populations regularly to determine treatment thresholds
• Environmental modifications such as fly traps or sticky tapes
• Biological controls like parasitic wasps that attack fly larvae
• Proper sanitation to eliminate breeding sites (manure piles, wet areas)

3. Physical Barriers and Environmental Controls

Though less commonly used in large feedlots due to scale limitations:

• Fans can reduce fly populations by disrupting their flight
• Screens or netting around feeding areas protect vulnerable animals
• Managing moisture by improving drainage lowers habitat suitability for many flies

4. Vaccination and Immunological Approaches

Research is ongoing into vaccines targeting specific external parasites like ticks. Although not yet widely available commercially for feedlot use, immunological methods represent a promising future avenue for sustainable control.

Resistance Management

A major challenge in parasite control is the development of resistance to chemical treatments by both internal worms and external pests.

To mitigate resistance:

• Rotate chemical classes regularly rather than relying on a single product
• Use correct dosages based on accurate animal weights
• Avoid unnecessary treatments; treat only when needed based on monitoring data
• Combine chemical treatments with non-chemical measures such as hygiene and biological controls

Proper management prolongs the efficacy of available products ensuring continued control success.

Conclusion

Parasite control in feedlots involves a multifaceted approach combining chemical treatments with management practices aimed at breaking parasite life cycles while supporting animal health. Dewormers remain essential for controlling internal parasites while insecticides effectively reduce external pest burdens. Integrating monitoring, sanitation, nutrition, environmental management, and new technologies enhances overall effectiveness.

Sustainable parasite control protects animal welfare, optimizes weight gain and feed efficiency, reduces disease risks, and ultimately improves economic returns for feedlot operators. Remaining vigilant about resistance development through appropriate use practices will ensure these tools remain effective components of successful parasite management programs into the future.