TL;DR
- Horses may need vitamin D supplements in summer despite long hours of sunlight since they produce little to no vitamin D3 in their skin.
- Signs of deficiency include weak bones, muscle weakness, stiff joints, slow wound healing, behavioral changes, and impaired immunity.
- Stabled horses, young/growing horses, and those in northern regions are most at risk.
- Over-supplementation can cause toxicity, including soft tissue calcification, weight loss, lameness, kidney and heart issues.
- Ensure vitamin D through fresh forage first, supplement strategically, and consult a veterinarian for personalized guidance.
Why Do Horses Need Vitamin D Supplements During Summer?
During summer, as warm sunshine pours over fields and paddocks, most horse owners assume their horses get enough vitamin D from natural sunlight. But with new research, a startling reality has been brought to the attention of the equine world.
Unlike humans and other animals, horses produce little to no vitamin D3 in their skin through sunlight exposure. This makes them reliant on foods and supplements for vitamin D, even under strong summer sun.
This article explains how to recognize when your horse might benefit from vitamin D supplements in summer.
7 Signs of Vitamin D Deficiency in Horses
Research shows that horses grazing in full summer sunlight may still be vitamin D deficient if their forage lacks adequate vitamin D for horses. According to the latest findings and veterinary expertise, the following are the major signs that indicate your horse may be vitamin D-deficient even during summer:
1. Reduced Bone Density and Strength
Imperfect or weak bone formation in horses usually arises from a deficiency or imbalance of calcium, phosphorus, and vitamin D. Even with proper exercise and a seemingly adequate diet, affected horses may show mild lameness or an increased susceptibility to fractures.
2. Muscle Weakness or Poor Growth
Muscles rely on adequate vitamin D for proper function. A deficiency can cause general weakness, fatigue, or poor muscle development, which may affect performance, especially in active or athletic horses.
3. Stiff or Swollen Joints
Vitamin D deficiency affects calcium absorption, which can lead to joint stiffness, swelling, or discomfort during movement. You may notice your horse walking more slowly or hesitantly in addition to the topical symptoms.
4. Slowed Wound Healing
Slow healing of wounds following surgery or injury can be an indicator that your horse’s vitamin D level is too low.
5. Behavioral Changes and Decreased Performance
Some horses may show irritability, lower work enthusiasm, temperament change, or decreased athletic performance.
6. Impaired Immune Function
Vitamin D reinforces the immune system. Deficient horses could have higher illness rates or reduced recovery from infection.
7. Dental Problems
Vitamin D deficiency can impair calcium and phosphorus balance, affecting tooth development and condition.
Which Horses Are Most at Risk of Vitamin D Deficiency?
Some horses require higher concentrations of vitamin D supplements in summer:
- Stabled Horses: The management of stabled, non-grazing racehorses qualifies as a risk factor for low vitamin D status. Horses with restricted pasture access need appropriate supplementation under the guidance of a vet.
- Young, Growing Horses: For immature horses in early development, the recommended level is 800 -1,000 IU of vitamin D3 per kg of dry matter intake.
- Horses in Northern Regions: Horses living north of 51°N latitude or in areas with prolonged winters may need supplementation year-round due to insufficient UVB exposure.
Are There Any Risks of Over-Supplementing Vitamin D?
Though deficiency is risky, over-supplementation with the vitamin D supplement for horses also poses certain dangers. The maximum tolerable intake of vitamin D is 44 IU/kg body weight, which is equal to 22,000 IU/day for a 500 kg (1100 lb) horse.
Vitamin D Toxicity Symptoms
A surplus of Vitamin D supplements in summer can activate the deposition of excess calcium in the soft tissues. Symptoms of vitamin D toxicity in horses are:
- Soft tissue calcification
- Weight loss and poor feeding
- Stiffness and lameness
- Kidney impairment
- Cardiovascular disorders
How to Balance Supplement Intake?
Developing an efficient vitamin D supplement for horses plan involves weighing several factors:
1. Dietary Sources First
Vitamin D is plentiful in fresh forages and sun-cured hay, but levels drop with extended storage time. Fresh pasture and good-quality cured hay should form the base of the diet.
2. Strategic Supplementation
When forage alone is insufficient, consider researching and adding the best vitamin D supplement for horses to meet their nutritional needs. For mature horses, a vitamin D3 concentration of around 500 IU/kg of dry matter is recommended.
3. Professional Guidance
Research shows there are still significant gaps in understanding vitamin D requirements in horses. Always consult a veterinarian to determine the right supplementation plan for your horse’s specific needs and environment.
Final Thoughts
The issue of whether horses require vitamin D supplements in summer is not a straightforward one that can be reduced to assumptions about sunlight exposure.
The unique way horses process vitamin D, along with evolving management practices, makes a vitamin D supplement a great idea for keeping your horse healthy and happy.
At Med-Vet Pharmaceuticals, we specialize in high-quality horse supplements designed to support healthy living for your horses. From vitamin D formulas to other types of horse supplements, we have it all.
Take a moment to browse our carefully formulated supplements, and if you’re unsure what your horse needs, our team is always happy to help. Reach out online or call us at 833-809-4848.
FAQs
Q1. Can horses be vitamin D-deficient even in sunny months?
Ans. Indeed, horses may become vitamin D-deficient in summer if they do not have access to fresh pasture or eat stored hay with lowered vitamin D levels. Stabled horses with restricted grazing are more prone to low vitamin D status.
Q2. What are the signs of vitamin D deficiency in horses?
Ans. Signs of deficiency are reduced bone density, muscle weakness, impaired wound healing, aggravated respiratory problems, mineral imbalance, changes in behavior, and weakened immune status.
Q3. Is it okay to administer vitamin D supplements to horses during the summer?
Ans. Yes, when well-dosed with professional veterinary advice. The ideal concentration is 500 IU per kg of dry matter in mature horses, and the safe maximum is 44 IU per kg body weight. Supra-supplementation leads to toxicity.
Q4. Which horses are most at risk of vitamin D deficiency?
Ans. High-risk horses include those stabled with restricted grazing, performance horses, growing horses, and those primarily fed stored hay instead of fresh forage.
