Calcium: How Important Is It for Hoof Health?

Calcium is required in the diets of all horses for optimal health and well-being. Considered a macromineral, it is needed in a relatively large amount, especially when compared to trace minerals. Though calcium is aligned most often with musculoskeletal strength and soundness as well as nerve conductivity, its importance in hoof health is unquestionable. A severe calcium deficiency in the diet is, however, likely to have deleterious effects on other body systems before a significant collapse in hoof health occurs.

The provision of a well-balanced diet will ensure that calcium levels are appropriate for the type of horse being fed. A qualified equine nutritionist can determine if a horse is being offered a suitable diet for its age and use. Most horses given a balanced diet will not have hoof problems, and this is particularly true of young horses and those not engaged in demanding work.

In the hoof, calcium is present in minuscule amounts, approximately 300-350 mg/kg (ppm) of hoof wall. One of calcium’s primary roles is assisting in the creation of sulfur cross-links between hoof proteins that allow for cohesion among cells. The stronger the cohesion, the more healthy and impenetrable the hoof.

The amount of calcium in the hoof is dependent on numerous factors, according to a study conducted in Virginia.^* In one trial, 30 mature Thoroughbred mares were fed one of three diets, with 10 mares relegated to each diet. The three diets were significantly different: (1) all-forage, in which the mares had access to pasture; (2) drylot, in which the mares had free-choice access to barn-stored, one-year-old cured hay; and (3) forage and concentrate, in which pasture feeding was supplemented with vitamins and minerals to meet National Research Council recommendations for mature horses. Mares were allowed access to a mineralized salt block at all times and were fed their respective diets for at least one year before the study began.

After hoof tissue collection and testing, researchers concluded that hoof wall characteristics, including calcium content, were influenced by season and nutritional management. The average amount of calcium found in hooves ranged from 906 ppm (October, 1993) for mares on the drylot diet to 1404 ppm (October, 1993) for mares on the all-forage diet. This study confirmed the notion that different nutritional and management regimes influence hoof composition, and changes in composition are commonplace between seasons and years.

Other observations, recorded in the mid-1980s by Kempson, illustrate the importance of adequate calcium in the diet for hoof health.^** Researchers gathered 33 hoof samples from horses with brittle hooves. To qualify for review, horses had to be diagnosed with loss of tubular structure in the stratum medium and the stratum internum, as determined by scanning electron microscopy.  The hoof wall is composed of three layers: stratum externum, stratum medium, and stratum internum. The stratum externum is the outermost layer, and its primary functions involve moisture equilibrium and structural support. The intermediate layer is the stratum medium, and it is involved in shock dispersion and circulation. The innermost layer is the stratum internum, and it provides the anatomical features, specifically the laminae, by which the coffin bone is anchored to the hoof capsule. Of the 33 samples, 31 showed the requisite compromise between the stratum medium and stratum internum layers. Extreme cases also showed a loss of integrity to the stratum externum.

Twenty of the horses from which clippings were taken failed to show an improvement when biotin was added to the basal diet of oats or bran and chaff or grass hay; however, when diets were upgraded through the addition of alfalfa, and protein and calcium levels increased, the majority of horses responded with enhanced hoof health. Certain horses were also diagnosed with a bacterial infection of their hooves, which was cleared through the use of topical metronidazole. Was the improvement caused by a boost in protein and amino acid intake or because of a swell in calcium consumption? Or through eradication of the bacterial infection? The exact reason for improvement cannot be determined from this study. If calcium levels in the diet are too low for optimal health, then supplying extra calcium may positively impact overall well-being and specifically hoof and bone quality.

This study reinforces the notion that properly nourished horses rarely have hoof problems. Yes, there are exceptions, but most horses can maintain reasonably healthy hooves with appropriate diet and regular hoof care.

A similar study with two horses showed parallel results.^** The horses, a Thoroughbred mare and a Thoroughbred-Connemara gelding, had myriad hoof problems, culminating in a propensity to lose shoes. The mare’s hooves improved with biotin supplementation, but the gelding’s hooves did not, even after six months of biotin supplementation at 20 mg/day. Hoof clippings from the gelding were examined microscopically at that time, and there was a complete loss of cohesion between the stratum medium and stratum internum. Calcium supplementation was then commenced in the form of 7.5 g/day of limestone. After nine months of biotin and calcium supplementation, the stratum medium had regained its structural rigidity. The horse showed a reduction in the tenderness of his hooves and lost fewer shoes. Upon evaluation of the entire diet, hoof health hastened further with an increase in protein levels.

Looking at research performed in other species often provides insight about horses. A German study set out to investigate the relationship of single structures during keratinization of bovine hoof epidermis to specific nutritional factors such as lipids, minerals, and vitamins.⁺ Keratinization is the conversion of squamous epithelial cells into keratin, the predominant protein in hooves. According to the researchers, calcium was essential for the activation of certain enzymes that are required for normal keratinization. Under normal circumstances, keratinization creates resilient connections between the three layers of the wall. Abnormal or incomplete keratinization leaves hooves susceptible to damage.

Changes in the plasma level of calcium influence the differentiation of epidermal cells in hooves, which in turn impacts keratinization.The researchers noted that peripartum heifers and cows experience a decrease in plasma calcium level, especially at the onset of lactation, which impacts differentiating epidermal cells. This may account for the distinctive horn rings that are oftentimes associated with pregnancy in cattle. Though this work was done on cattle hooves, the importance of calcium could be extrapolated for equine hooves.

Without calcium, horses are incapable of achieving optimal growth, performance, or health. A sustained lack of calcium would almost assuredly affect hoof health. Therefore, providing a well-balanced diet to horses, with a keen eye on macromineral and micromineral balance, is the first step in the maintenance of healthy hooves.

^*Ley, W.B., R.S. Pleasant, and E.A. Dunnington. 1998. Effects of season and diet on tensile strength and mineral content of the equine hoof wall. Equine Veterinary Journal, Suppl. 26:46-50.

^**Kempson, S.A. 1987. Scanning electron microscope observations of hoof horn from horses with brittle feet. Veterinary Record 120:568-570.

⁺Mülling, K.W., H.H. Bragulla, S. Reese, K.D. Budras, and W. Steinberg. 1999. How structures in bovine hoof epidermis are influenced by nutritional factors. Anatomia, Histologia, Embryologia 28:103-108.