Hoof wall (or horn) problems, such as thin, brittle walls, flakiness, cracks, or soft and crumbly white line inevitably mean lost shoes, hoof tenderness affecting gait, performance issues and susceptibility to infections. Owners often turn to biotin supplements to improve hoof problems, but is there evidence of its effect? Karen Richardson reviews the research...
Biotin, of the vitamin B family, is sourced by the horse from food and from microbial activity in the digestive tract. The biotin requirement for a normal horse is thought to be low and is estimated to be around 1-2mg per day. This small amount is believed to be met by feeding concentrates, commercial vitamin and mineral premixes, or by intestinal synthesis1, and this may be true as, to date, no occurrence of biotin deficiency in the horse has been reported2. However, there is a substantial amount of research on the effects of biotin on equine hooves that show supplementation with biotin above the minimum requirement can lead to positive changes in the hoof wall.
Biotin was initially used in pigs to improve hoof health and its use subsequently followed in sheep, cattle and horses. Its mechanism of action in the hoof is largely unknown, but it is known to have important roles in the chemical processes essential to life, including amino acid (protein) metabolism, metabolism of cholesterol, and fatty acid synthesis and metabolism2,3. The hoof wall is made up of keratin (protein) and fat (including cholesterol sulphate), and the intercellular cementing substance in hoof walls is dependent upon fatty acid synthesis, so any alterations to these processes via a biotin deficiency or limitation could affect the integrity of the hoof wall3.
The following information provides a summary of the scientific literature which examined the effect of biotin on the condition of the equine hoof. In particular, it explores markers of hoof condition, including growth rate, tensile strength, histological (cell and tissue) changes and hoof quality.
Hoof growth rate
Buffa, Van den Berg, Verstraete and Swart (1992)4 examined hoof growth rate in 32 randomly selected riding horses (Thoroughbreds and Thoroughbred crosses) without obvious hoof problems. Eight horses served as a control group (they received no treatment) and 24 horses were separated into three biotin treatment groups receiving either 15mg biotin per day, 7.5mg biotin per day or 15mg biotin per day every second month. The trial lasted for a period of 10 months.
Growth rate was shown to be statistically greater for horses receiving biotin in all treatment groups (irrespective of dose) compared to the control group, with a greater effect observed for the groups receiving 15mg biotin per day and 7.5 mg biotin per day. Furthermore, there was a trend towards higher growth rate with higher dosage of biotin.
These findings are in agreement with Reilly, Cottrell, Martin and Cuddeford (1998)5 who conducted a study on eight match-paired ponies (of Welsh type and Shetlands), all without obvious hoof problems. Four ponies were allocated to treatment with 0.12mg biotin per kilo of bodyweight, equating to 20-30mg biotin per day, and four ponies served as controls. The trial period lasted five months. The average hoof growth after five months was statistically greater for the biotin group than for the control group (3.5cm and 3cm respectively), as was the average rate of hoof growth.
In contrast to the findings of the above two studies, are the results of a long-term experiment by Josseck, Zenker and Geyer (1995)6. Their study was conducted using 42 Lipizzaner stallions with hoof wall defects. 26 received treatment with 20mg biotin per day for 38 months and 16 served as controls. After 19 months of treatment, no significant difference was found for hoof growth rate between the groups.
Thus, these studies suggest that biotin may stimulate hoof growth rate in horses and ponies with 'healthy' hooves, but not in horses with problem hooves, where the biotin may be diverted for other purposes (as explained later). Supplementing biotin for increased hoof growth rate may be useful for barefoot horses, or in equine disciplines where shoes need to be replaced regularly, such as for racehorses whose shoes are often changed every four weeks, or horses ridden regularly on hard and rocky ground causing premature wearing.
Despite the findings regarding growth rate, biotin supplementation did appear to have other beneficial effects that may not be obvious on the surface.
Histological (cell and tissue) changes
Zenker, Josseck and Geyer (1995)7 examined histological changes in 26 Lipizzaner stallions receiving 20mg biotin per day for a period of 38 months. Hoof wall specimens were retrieved from the load bearing border of the hoof. They assessed abnormalities, such as micro-cracks in the coronary horn, damaged connections between horn leaflets and detachment of the terminal horn from the horn leaflets in the white zone. Histological improvements were visible after 19 months of biotin supplementation, when compared to baseline values and the control group.
Tensile strength
Zenker, et al. (1995)7 also looked at the effect of biotin on tensile strength in specimens taken from the load bearing border. Baseline values for the biotin treated group and control group were 39.4 N/mm2 and 38.8 N/mm2 respectively. After 33 months of receiving biotin (20mg/d), the biotin treatment group mean tensile strength had increased to 44.1 N/mm2, which was significantly stronger than the control group, 34.8 N/mm2.
Hoof quality
Josseck, et al. (1995)6 visually assessed hoof quality using a classification system that evaluated different areas of the hooves looking at characteristics, such as hardness, consistency, compactness, smell, elasticity, the presence of white line separation, and horn cracks and chips. A significant improvement in hoof quality following nine months of biotin supplementation (20mg per day) was reported. The quality continued to improve up to 14 months, after which the hoof quality remained static, whilst remaining on treatment. Following 12 months of biotin treatment consistent hoof quality was evident from the coronary band to the weight bearing border.
Zenker, et al. (1995)7 concluded that hoof quality is compromised by poor cell and tissue structure and function, and reduced tensile strength. Improvements in the underlying cell structure and intercellular cement need to occur before optimal strength and quality can be achieved.
There’s more to hooves than biotin
Whilst long-term supplementation with biotin certainly improved hoof wall histology, strength and quality, the horses with problem hooves mentioned above did not end up with ‘top quality’ hooves. The outcome may have been different had the diet in the study by Josseck, et al. (1995)6 not been deficient in zinc.
Indeed, in a subsequent experiment following a two year washout period where the hoof quality regressed significantly, the horses received a daily supplement containing 20mg biotin, 40mg zinc proteinate and 1g methionine (Munzinger, 2005). After receiving the combined supplement for 18 months, the condition of the hoof horn had once again improved and the tensile strength was found to be significantly greater than when treated with 20mg biotin/day alone.
Interestingly, Higami (1999)8 showed that white line disease in horses at a local stable yard was due to diets deficient in zinc and copper. The incidence of white line disease decreased dramatically after including sufficient zinc and copper in the horses feed. Both zinc and copper are involved with keratin production.
Additionally, Kempson (1987)9 identified two types of hoof defect in horses with brittle hooves. Type 1 responded to treatment with biotin, whereas Type 2 responded to increased protein and calcium in the diet, and not biotin.
Finally, Ley, Scott Pleasant and Dunnington (1998)10 reported a strong correlation between tensile strength and hoof wall sulphur concentration. Hence, the presence of methionine in hoof supplements as it is a sulphur containing amino acid. Care should be taken, however, as excessive methionine can cause degeneration of the hoof horn11.
Conclusion
The research discussed above suggests that for horses with problem hoof walls long-term daily supplementation (greater than 12 months) with biotin at a dose of 15-20mg per day may induce positive changes in hoof wall histology, strength and quality. Additionally, it may hasten hoof growth rate in healthy hooves. However, optimal hoof wall quality can only be attained by also taking into account other dietary factors, along with quality farriery and/or trimming and environmental factors.
Prior to purchasing a biotin supplement be sure to read the label and calculate how much biotin is provided per dose. Many 'biotin' supplements do not contain high quantities of biotin and large quantities need to be administered. Try to find a highly concentrated source of biotin. Always consult your veterinarian or equine nutritionist when formulating a balanced diet for your horse.
References
- [1] Huntington, P. and Pollitt, C. (2005) Nutrition and the Equine Foot [online]. Available at: www.ker.com/library/advances/303.pdf [Accessed 9 October 2011].
- [2] National Research Council (2007) Nutrient Requirements of Horses. 6th Ed. Washington: The National Academies Press.
- [3] Mulling, C.K.W., Bragulla, H.H., Reese, S., Budras. K.-D., and Steinberg, W. (1999) How Structures in Bovine Hoof Epidermis are Influenced by Nutritional Factors. Anat. Histol. Embryol. 28: pp.103-108.
- [4] Buffa, E.A., van den Berg, S.S., Verstraete, F.J.M. and Swart, N.G.N. (1992) Effect of dietary biotin supplement on equine hoof horn growth rate and hardness. Equine Vet. J. 24(6): pp.472-474.
- [5] Reilly, J.D., Cottrell, D.F., Martin, R.J., and Cuddeford, D.J. (1998) Effect of supplementary dietary biotin on hoof growth and hoof growth rate in ponies: a controlled trial. Equine Vet. J., Suppl. 30(S26): pp.51-57.
- [6] Josseck, H., Zenker, W., and Geyer, H. (1995) Hoof horn abnormalities in Lipizzaner horses and the effect of dietary biotin on macroscopic aspects of hoof horn quality. Equine Vet. J. 27(3): pp.175-182.
- [7] Zenker, W., Josseck, H., and Geyer, H. (1995) Histological and physical assessment of poor horn quality in Lipizzaner horses and a therapeutic trial with biotin and a placebo. Equine Vet. J. 27(3): pp.183-191.
- [8] Higami, A. (1999) Occurrence of white line disease in performance horses fed low-zinc and low-copper diets. J. Equine Sci. 10: pp.1-5.
- [9] Kempson, S.A. (1987) Scanning electron microscope observations of hoof horn from horses with brittle feet. Vet. Rec. 120: pp.568-570.
- [10] Ley, W.B., Pleasant, R.S. and Dunnington, E.A. (1998), Effects of season and diet on tensile strength and mineral content of the equine hoof wall. Equine Vet J. 30: pp.46–50.
- [11] Kempson, S.A. (2005) Nutritional management of horses with hoof diseases. In: Applied Equine Nutrition. Equine Nutrition Conference 2005.