The Science Behind Equine Joint Supplements - Part 1
Osteoarthritis is one of the leading causes of lameness in horses, and is dreaded by horse owners and veterinarians alike. The market is flooded with joint supplements which claim to treat, prevent and relieve symptoms of arthritis in horses, and are hugely profitable for manufacturers as horse owners spend hundreds of dollars a year in supplements for their horses. But what does the research say about the ingredients used in these supplements? Is there any evidence to justify their use? And can they really do what the companies say?
Read on for part one of this two-part series investigating the science behind common ingredients in joint supplements and whether you might be wasting your $$$
Green Lipped Mussel
Green lipped mussel (Perma caniculus) is a mussel sourced from the coast of New Zealand, and is a common ingredient used in joint supplements for humans and animals. It contains a high proportion of long chain Omega-3’s within the lipid portion of the mussel, and glucosamine and chondroitin within the carbohydrate portion of the mussel.1
Studies specific to Green Lipped Mussel supplementation in horses are rare – with only 2 studies published to date. Cayzer et al (2011) dosed horses with fetlock osteoarthritis with either a placebo or 25mg/kg bwt per day of powdered green lipped mussel product for 56 days, with horses in the treatment group showing a reduction in lameness and responsiveness to joint flexion compared with the horses in the placebo group.1 Pearson et al (2009) studied the effects of feeding a supplement with shark cartilage, green lipped mussel and Biota Orientalis extract to horses at 15mg/kg bwt per day, which showed no increase in anti-inflammatory joint mediators within the joint fluid, or any increases in glycosaminoglycans within the joint compared to non-treated horses.2
Green-lipped mussel is likely to provide some benefit as a disease-modifying osteoarthritis nutraceutical due to the high concentration of Omega-3’s and glucosamine/chondroitin within its lipid and carbohydrate contents, respectively.
To feed green-lipped mussel at 25mg/kg bwt/day (studied dose), a 500kg horse would require 12.5g daily. Green-lipped mussel powder usually retails at about 15-16c per gram, so a daily feeding rate of 12.5g would cost about $2 per day.
Hyaluronic Acid
Hyaluronic acid is a natural component of joint fluid which contributes to its thickness and lubrication properties within the joint. While hyaluronic acid is most effectively administered intra-articularly, some studies have investigated its use orally in horses.
Carmona et al (2009) studied the effects of 250mg HA given daily over a period of 60 days to horses with osteochondrosis lesions of the tarsocrural joint, compared to a placebo group. Horses which received HA supplementation had no difference in the amount of inflammatory mediators or hyaluronic acid within their joint fluid at the end of the treatment period.4 Bergin et al (2006) supplemented horses with 100mg HA daily for 30 days following arthroscopic surgery, compared to a placebo group. Horses receiving the HA were subjectively found to have less effusion (swelling) in the operated joints 30 days post-operatively than those horses receiving the placebo.5 A recent study in dogs with stifle osteoarthritis showed that oral administration of 27mg HA or 54mg of HA (dose depending on dog size) improved subjective lameness scores by owners and veterinarians, and increased the amount of HA obtained from the fluid of affected joints after 10 weeks of treatment compared to dogs given a placebo.6
If you compare the dose rates between these studies, in mg HA/kg bwt, the horse studies used ½ to ¼ of the dose rates used in the canine study. This may explain the lack of clinical efficacy of HA supplementation in horses.
To use similar dosages as in canine studies, horses would require 500mg HA daily in feed, which for retailed products would cost around $9 - $11 per day. Studies at lower dosages (100mg – 250mg daily given orally) tend to show minimal to no effect.
Above: Green-lipped mussels (Perna canaliculus), or kūkū (also known as kūtai and kūkūtai) to the Māori people, are indigenous to the inshore coastlines of Aotearoa/New Zealand.
Vitamin E
Vitamin-E is high in tocopherols, with a-tocopherol being particularly relevant within human literature in its role in prevention of deficiency disease in humans. Tocopherols function within the body to decrease the production of free-radicals (or “oxidants”), therefore functioning as an antioxidant. Vitamin E deficiency contributes to Equine Degenerative Myeloencephalopathy, in horses with restricted dietary intake of Vitamin E.7 As Vitamin E is naturally found within green pasture, horses with access to grazing usually do not suffer from Vitamin E deficiency.
A study done in 2020 by Fagan et al, showed that horses receiving natural Vitamin E supplementation, as opposed to synthetic Vitamin E, had higher circulating a-tocopherol levels than horses given low-dose or high-dose synthetic Vitamin E.8 It is hypothesised that Vitamin E may help to reduce cartilage degeneration due to reducing oxidative damage, however there are no studies in horses which demonstrate any efficacy of Vitamin E on improving joint health.
The benefit of supplementing horses with free access to grazing (and therefore likely to have high circulating Vitamin E levels) is unknown, however the NRC has set the upper limit for dietary concentration of Vitamin E at 20 IU/kg bw, above which level issues with clotting and bone mineralisation have been reported.9
Vitamin C & Rosehips
Vitamin C functions as a strong antioxidant within the body, helping to rid the body of free radicals and preventing cell damage. Vitamin C is also essential for the synthesis of collagen, which is a major component of connective tissues within the body including tendons, ligaments, cartilage and bone.
A study in 1987 investigated the effect of oral supplementation of horses with Vitamin C on plasma Vitamin C levels, which showed that oral supplementation with both 4.5g and 20g daily increased plasma Vitamin C levels in six horses supplemented with Vitamin C.10
Supplementation of horses with Rosehips (Rosa canina) has been shown to increase plasma Vitamin C levels. A study by Winther et al (2010) showed that supplementation of horses with 210g of a Rosehip-based product increased circulating plasma Vitamin C levels, but showed no other benefits initially proposed by the study authors.11 A subsequent study by the same group showed that 50g of Rosehip powder (equivalent to 250mg natural Vitamin C) significantly increased the serum Vitamin C levels in horses as opposed to horses fed 25g Rosehip powder.12 The same study showed a significant reduction in the release of oxidative anions in horses receiving 50g of Rosehip powder, demonstrating the antioxidant effects of Vitamin C.12
There are NO studies demonstrating any effect of supplementation of horses with Rosehips on arthritis treatment, joint health or improvement in lameness or performance!
Unless you are interested in the potential antioxidant effects of supplementing your horse with Vitamin C or Rosehips, there are other ingredients that have demonstrated efficacy in joint health that are much more worthy of an investment!
Above: Rosehips (Rosa canina) are a potent source of Vitamin C
References
1. Miller MR, Abshirini M, Wolber FM, Tuterangiwhiu TR, Kruger MC. Greenshell Mussel Products: A Comprehensive Review of Sustainability, Traditional Use, and Efficacy. Sustainability. 2023; 15(5):3912. https://doi.org/10.3390/su15053912
2. Cayzer J, Hedderley D, Gray S. A randomised, double-blinded, placebo-controlled study on the efficacy of a unique extract of green-lipped mussel (Perna canaliculus) in horses with chronic fetlock lameness attributed to osteoarthritis. Equine Vet J. 2012;44(4):393-398. doi:10.1111/j.2042-3306.2011.00455.x
3. Pearson W, Orth MW, Lindinger MI. Evaluation of inflammatory responses induced via intra-articular injection of interleukin-1 in horses receiving a dietary nutraceutical and assessment of the clinical effects of long-term nutraceutical administration. Am J Vet Res. 2009;70(7):848-861. doi:10.2460/ajvr.70.7.848
4. Carmona JU, Argüelles D, Deulofeu R, Martínez-Puig D, Prades M. Effect of the administration of an oral hyaluronan formulation on clinical and biochemical parameters in young horses with osteochondrosis. Vet Comp Orthop Traumatol. 2009;22(6):455-459. doi:10.3415/VCOT-09-01-0001
5. Bergin BJ, Pierce SW, Bramlage LR, Stromberg A. Oral hyaluronan gel reduces post operative tarsocrural effusion in the yearling Thoroughbred. Equine Vet J. 2006;38(4):375-378. doi:10.2746/042516406777749218
6. Serra Aguado CI, Ramos-Plá JJ, Soler C, Segarra S, Moratalla V, Redondo JI. Effects of Oral Hyaluronic Acid Administration in Dogs Following Tibial Tuberosity Advancement Surgery for Cranial Cruciate Ligament Injury. Animals (Basel). 2021;11(5):1264. Published 2021 Apr 27. doi:10.3390/ani11051264
7. Young AE, Finno CJ. Current insights into equine neuroaxonal dystrophy/equine degenerative myeloencephalopathy. Vet J. 2024;305:106129. doi:10.1016/j.tvjl.2024.106129. Available at: https://www.sciencedirect.com/science/article/pii/S1090023324000686.
8. Fagan MM, Harris P, Adams A, et al. Form of Vitamin E Supplementation Affects Oxidative and Inflammatory Response in Exercising Horses. J Equine Vet Sci. 2020;91:103103. doi:10.1016/j.jevs.2020.103103
9. University of California Davis - School of Veterinary Medicine. Vitamin E in horses. Available at: https://www.vetmed.ucdavis.edu/labs/finno-laboratory/vitamin-e-horses. Accessed July 11, 2024.
10. Snow DH, Gash SP, Cornelius J. Oral administration of ascorbic acid to horses. Equine Vet J. 1987;19:520-523. doi:10.1111/j.2042-3306.1987.tb02664.x.
11. Winther K, Kharazmi A, Hansen ASV, Falk-Rønne J. A randomized placebo-controlled double-blind study on the effect of subspecies of rose hip (Rosa canina) on the immune system, working capacity, and behaviour of horses. In: The Impact of Nutrition on the Health and Welfare of Horses. In press. doi:10.3920/978-90-8686-711-0_052.
12. Winther K, Kharazmi A, Hansen ASV, Falk-Rønne J. The absorption of natural vitamin C in horses and antioxidative capacity: a randomized, controlled study on trotters during a three-month intervention period. Comp Exerc Physiol. 2012;8(3-4):195-201. doi:10.3920/CEP12006.