What is rain scald or mycotic dermatitis in horses
Rain scald, also known as rain rot, mud fever or mycotic dermatitis, is a microbial skin infection that causes sores and scabbing along a horse's body, usually concentrated on the back, rump and legs. These organisms grow under anaerobic conditions, ie in the lack of oxygen. They form lesions and scabs that cause irritation. This generally occurs under wet and humid conditions and high temperatures, where the skin does not effectively dry. The rain washes the protective oils from the coat, leaving it unprotected against these organisms.
Rain scald is usually a relatively minor problem, provided that it receives immediate treatment, and the infectious organisms are stopped from spreading. The infection is spread by either rolling in mud, direct contact between horses, or transmission by stable and house flies carrying the organism from the skin lesions of infected horses.
How do I know my horse has rain scald
- Itchy skin
- Bald patches
- Hair falling out
- Scabbing of coat
What causes rain scald in horses
Rain scald is a condition caused by the actinomycetes organism called Dermatophilus congolensis. Actinomycetes is not a bacteria, nor a fungus, however behaves like both a bacteria and a fungus. This condition occurs mainly when the skin is continually wet, hence the name.
The organism that causes rain scald grows best under anaerobic conditions, ie in the absence of oxygen, as will occur when the skin is continually wet, or under the dry scabs caused by the condition. Successful treatments involve elimination of the organism by hygiene, cleaning the infected areas, and maintaining good skin condition.
How diet helps rain scald in horses
While diet alone cannot cure rain scald, proper nutrition strengthens the immune system, supports skin health, and enhances the horse’s ability to resist and recover from infections.
Rain scald thrives in wet, humid conditions and often affects horses with compromised skin barriers or weakened immunity. A balanced diet addresses underlying factors that make horses susceptible, supports healing, and prevents recurrence. Here’s how:
1. Strengthen the Immune System
A robust immune system helps horses fight Dermatophilus congolensis and prevent secondary infections (e.g., Staphylococcus). Key nutrients include:
- Zinc: Essential for immune function and skin repair. Zinc deficiency can lead to poor wound healing and increased susceptibility to infections.
Sources: High-quality forage, commercial feeds fortified with zinc, or supplements (e.g., zinc sulfate or zinc methionine, typically 100-200 mg/day for a 500 kg horse).
Consideration: Ensure proper zinc-to-copper ratios (4:1) to avoid imbalances.
- Vitamin A: Supports skin and mucous membrane integrity, acting as a barrier against infections.
Sources: Green pasture, fresh hay, or supplements (e.g., beta-carotene or retinyl palmitate, 20,000-40,000 IU/day for a 500 kg horse).
Consideration: Avoid over-supplementation, as excess vitamin A can be toxic.
- Vitamin E: An antioxidant that supports immune function and reduces inflammation.
Sources: Fresh pasture, fortified feeds, or supplements (1,000-2,000 IU/day for a 500 kg horse).
Consideration: Vitamin E levels drop in stored hay, so supplementation may be necessary.
2. Promote Skin and Coat Health
A healthy skin barrier reduces the risk of Dermatophilus congolensis penetrating the skin, especially in wet conditions. Key nutrients include:
- Omega-3 Fatty Acids: Reduce inflammation and maintain skin elasticity, helping prevent cracking or dryness that allows bacterial entry.
Sources: Flaxseed (ground or oil, 1-2 cups/day), chia seeds, or fish oil (though less palatable for horses).
Consideration: Introduce oils gradually to avoid digestive upset.
- Biotin (Vitamin B7): Supports hoof and skin health, improving coat resilience.
Sources: Found in small amounts in forage; supplements provide 15-20 mg/day for a 500 kg horse.
Consideration: Benefits may take weeks to show, so consistency is key.
- Protein (Amino Acids): Essential for tissue repair and skin regeneration. Methionine and cysteine are particularly important for keratin production in the coat.
Sources: High-quality hay, alfalfa, or protein-rich feeds like soybean meal (10-12% protein in total diet).
Consideration: Avoid excessive protein, as it can strain the kidneys.
- Oils. Oil supports healthy skin conditions.
3. Address Potential Deficiencies
Deficiencies in certain nutrients can exacerbate rain scald, especially in horses on poor-quality forage or high-grain diets.
- Vitamin B1 (Thiamine): Supports nerve function and may reduce stress-related susceptibility to infections.
Sources: Whole grains, brewer’s yeast, or supplements (500-1,000 mg/day for a 500 kg horse).
Consideration: High-grain diets can deplete thiamine, so supplementation may be necessary.
- Copper: Works with zinc to support skin health and immune function.
Sources: Fortified feeds or supplements (25-50 mg/day for a 500 kg horse).
Consideration: Ensure proper zinc-to-copper balance to avoid toxicity.
- Magnesium: Supports overall health and may reduce stress, indirectly aiding skin recovery.
Sources: Forage, fortified feeds, or supplements (5-10 g/day for a 500 kg horse).
Consideration: Choose bioavailable forms like magnesium citrate.
4. Support Gut Health
A healthy gut microbiome enhances nutrient absorption and immune function, indirectly supporting skin health.
- Probiotics and Prebiotics: Promote beneficial gut bacteria, improving digestion and immunity.
Sources: Probiotic supplements (e.g., Lactobacillus or Saccharomyces cerevisiae), prebiotic fibers like psyllium, or fermented feeds.
Consideration: Useful for horses on antibiotics for secondary infections, as antibiotics can disrupt gut flora. Clean Culture can be used strategically to restore gut health Promune supports the immune system
- High-Fiber Diet: Forage-based diets (hay or pasture) support gut health and provide steady energy, reducing stress.
Sources: Grass hay, pasture, or low-starch feeds (at least 1.5-2% of body weight in forage daily).
Consideration: Avoid sudden feed changes to prevent colic. CoolStance copra meal is low NSC and contains oil for skin support.
5. Feeding Strategies to Prevent and Manage Rain Scald
- Provide High-Quality Forage: Fresh pasture or good-quality hay ensures baseline nutrient intake. Avoid moldy or dusty hay, which can weaken immunity.
- Balance the Diet: Use a ration balancer or fortified feed to address nutrient gaps without overloading calories. Consult an equine nutritionist for tailored plans.
- Limit High-Grain Diets: Excessive grains can disrupt gut health and thiamine levels, increasing susceptibility to infections.
- Supplement Wisely: Only add supplements after testing for deficiencies (e.g., via bloodwork or forage analysis). Over-supplementation can cause imbalances.
Ensure Clean Water: Adequate hydration supports skin health and overall wellness.
- Provide clean, fresh water daily (10-15 gallons/day for a 500 kg horse).
6. Combine Diet with Management Practices
Diet works best alongside environmental and hygiene measures:
- Keep the Horse Dry: Shelter from rain, use waterproof rugs, and avoid muddy pastures to prevent skin saturation, which encourages Dermatophilus congolensis.
- Clean Affected Areas: Gently wash with disinfectant shampoo (e.g., 10% betadine or chlorhexidine) and dry thoroughly to support healing.
- Disinfect Equipment: Clean tack, blankets, and grooming tools to prevent spreading the infection.
- Monitor Stress: Stress weakens immunity, so maintain a consistent routine and consider calming supplements (e.g., magnesium or ashwagandha) if needed.
- Individual Variation: Older horses, young horses, or those with compromised immunity may need more aggressive nutritional support.
Stance Equitec products to support normal skin conditions
Final Thoughts
Diet supports rain scald management by boosting immunity, enhancing skin health, and addressing deficiencies that increase susceptibility. Focus on zinc, omega-3s, Vitamin A, Vitamin E, and biotin, while ensuring a balanced, forage-based diet. Combine nutrition with proper hygiene, dry conditions, and veterinary care for the best outcomes. Regular monitoring and tailored feeding plans can prevent recurrence and keep your horse’s skin healthy.
