For example osteoporosis in the elderly is usually only diagnosed following a fracture which seems strange when the detrimental impact that bone fractures can have on quality of life is concerned. We are also told that certain population groups are ‘at risk’ of bone conditions, but even then, supplements are usually only used ‘once the horse has bolted’ if you excuse the pun.
It would appear prudent then, that reducing the risk of developing such conditions would be in the interest of both the horse owner and the horse alike and using a scientifically researched, natural and safe complementary animal feed supplement should be considered to help achieve this.
Bone conditions in horses can arise for many reasons but the interaction and activity of osteoblasts (bone forming cells) and osteoclasts (bone destroying cells) appears to be a root cause. The maintenance of bone mineral density (BMD) and bone quality is directly related to the balance of activity between these two cells and maintaining this balance is becoming the focus of scientists looking into the reasons why vitamin and mineral supplementation is limited in its effectiveness.
MBP (milk basic protein) has been researched for over 10 years relating to bone conditions in both human and animals and appears to show that the bone health properties of milk stretches way beyond its calcium content.
Fig.1 Illustration of healthy bone remodelling
Bone is in a constant state of remodelling with the balance between the activity of osteoblasts (bone forming cells) and osteoclasts (bone resorbing cells) determining the condition of the bone. Osteoblasts are more active early in life and osteoclasts are more active later in life causing an imbalance and an increased fracture risk with age. Various hormonal influences are thought to be one of the causes of this imbalance along with decreased osteoblast proliferation coupled with increased apoptosis (controlled cell death). The activity and balance between these two cells is referred to as bone remodelling.
The remodelling cycle consists of three consecutive phases (ARF):
Activation - Pre-osteoclasts attach to bone surface in response to activation.
Resorption - Digestion of old bone by osteoclasts.
Formation - Osteoblasts lay down new bone until the resorbed bone is replaced.
Remodelling has an important role in prolonging the fatigue life of a given volume of bone by replacing bone that has accumulated microdamage and to adjust bone architecture to meet changing mechanical needs as well as playing an important role in monitoring plasma calcium homeostasis. Remodelling inhibition may occur as the result of extreme training causing bone damage accumulation1. Microdamage initiates at molecular level as de-bonding between the mineral and collagen phases and breakage of collagen fibres.
However, bone remodelling rates are reduced during conditions of sustained high-magnitude cyclic loading (as occur in young equine athletes), when microdamage is accumulating as the result of remodelling inhibition and de-coupling of the ARF-sequence with new activation and resorption occurring before formation has been completed2. Frost (1986) explained how one or more of the following processes may cause fatigue breakdown of intact bone from normal mechanical usage in the absence of osteopenia:
a) Suppression of the activation of new BMU' (Basic Multicellular Units)
b) Retarding of the progress of already active BMU's
c) Sufficient delay of the onset of the bone forming phase of a BMU relative to the completion of its resorption phase ("de-coupling")
d) An increase in the production of the new microdamage so much that it surpasses the ability of the remodelling system.
However, even well-adapted bone accumulates microdamage and therefore working with and encouraging the remodelling process is also important.
Bone Health: Concerns
Fig.2 Density of collagen matrix in healthy and osteoporotic bone
Effective measures to maintain bone strength and integrity have never been more important in an ageing animal but it is also vital that the bones of younger animals are given the optimum conditions to increase in size and strength. Fractures usually refer to failure of bone as an organ, but bone is composed of microscopic sheets of subunits and if these collectively fail to develop maximally, the overall quality and strength of the bone as an organ reduces. While this may not necessarily result in a fracture, it may result in damaged bone which no longer can support the joints effectively.
Developmental Orthopedic Disease (DOD) is an umbrella term used to describe a number of growth disturbances of growing horses. The primary issue relating to these disturbances is the failure of cartilage to mature and develop into quality bone.
DOD can include the following:
Angular limb deviations (ALD)
Osteochondrosis (OC) which may develop into osteochondritis dissecans (OCD)
Subchondral bone cysts
Physitis or epiphysitis
Contracted tendons: Flexural limb deformities
Wobbler’s: Cervical vertebral malformation
Osteochondrosis dissecans (OCD) is a common condition in all domesticated animals such as broiler chickens, pigs, beef calves and foals and all animals where the growth rate and weight gain for commercial reasons have been selectively and genetically altered for faster physical development ahead of their natural timescale compared to their “native” forefathers. 11-24% of Thoroughbred and 20-25% of Warmblood foals will develop OCD3. OCD is rare in humans occurring in only 15 to 30 people per 100,000 in the general population each year4 but may occur in adolescents following impact injuries.
Fig.3 An illustration of the process of bone remodelling
Calcium constitutes 99% of the mineral content in bone and is therefore an essential nutrient for the maintenance of strong, healthy bones. The study of the composition of healthy bone compared to osteoporotic bone has lead to bone health advice being focussed on calcium and osteoporosis being described as a calcium deficiency which can be corrected by increased calcium consumption.
The supplement industry for both humans and animals regarding bone health has been promoting calcium supplements for many years. However, the research regarding the effectiveness of calcium supplementation for bone health is inconclusive at best.
A meta-analysis of prospective cohort studies and randomised controlled trials showed no association with hip fracture risk and no significant reduction in hip fracture risk with calcium supplementation5. Likewise, a study investigating bone mineral density (BMD) in the femur and spine found no benefit following calcium supplementation6. It is now proposed that dietary calcium cannot be incorporated into the bone matrix if the collagen structure has degraded which may explain why calcium supplementation alone is ineffective.
When considering bone formation and maintenance in relation to age it is evident that osteoblast activity and bone mineral density are closely related. BMD peaks at around 30 years of age in humans and 6 years of age in horses7. At this point the activity between osteoblasts and osteoclasts is equal. Following this point osteoclast activity begins to dominate and BMD decreases which raises the risk of fracture. In women experiencing the menopause, a lack of oestrogen production accelerates osteoclast activity and furthers the risk of fracture compared to men.
Warmblood horses can continue to compete in show jumping or dressage far beyond peak bone mass is reached and so regulating the balance between osteoblasts and osteoclasts would be advantageous to help delay the onset of BMD decline in the ageing horse.
Other nutrients important for bone health include magnesium, phosphorus, vitamin K and vitamin D. While magnesium and phosphorous play a similar role to calcium, the function of vitamin K is to allow the incorporation of such minerals into the bone.
Vitamin K is responsible for the carboxylation of osteocalcin which enables this protein (produced by osteoblasts) to bind minerals and maintain bone mineral density.
The synthesis of osteocalcin by osteoblasts is regulated by Vitamin D3.
Milk Basic Protein (MBP): Introduction
Fig.4 Illustrating the specific fraction of milk protein which consists of MBP
MBP is the alkaline fraction of whey protein found in all types of milk and consists of a group of specific proteins. Due to the biochemical processes by which osteoblasts and osteoclasts exert their effects, certain proteins have been found to either stimulate or inhibit these processes.
As the activity and proliferation of osteoblasts is directly related to bone mineral density and therefore bone quality, it would seem logical to consider therapies that will stimulate this.
MBP: Mechanism of Action
The mechanism of action of MBP is unique. The specific proteins within this alkaline fraction of whey protein, have been shown to:
Inhibit cathepsin K produced by osteoclasts which is the enzyme responsible for the breakdown of collagen within the bone matrix8.
Stimulate osteoblast proliferation measured by significant increases in blood osteocalcin concentrations after only 16 days of supplementation9.
Screenshot 1In this study measurement of pit numbers at different MBP concentrations over a period of 17 weeks demonstrated its ability to significantly reduce bone resorption by monitoring pit numbers10.
Screenshot 2The bone health promoting fraction of milk was successfully identified in this study as MBP. Osteoblast proliferation and collagen production increased while osteoclast activity was inhibited in a dose dependant manner11.
In this respect, the inclusion of concentrated MBP into the diet of humans and animals will directly and indirectly influence bone health by ensuring sufficient numbers and activity of osteoblasts along with the prevention of excessive osteoclast activity thus enabling essential nutrients such as calcium and vitamin K to work effectively.
MBP: Clinical Data
Fig 6. The effect of supplementation with MBP on RBAE in Thoroughbred racehorses. *Significant differences (p<0.05) between groups Bone health is a major concern for horse owners as conditions are often debilitating and can arise at any time of the life of a horse. For young racehorses in particular, lameness due to Developmental Orthopaedic Disease (DOD) is one of the primary causes of loss of training days.
DOD is an umbrella term for a variety of bone health conditions including osteochondrosis dissecans and sore shins which have a high incidence in young race and sports horses. OCD affects 11-24% of Thoroughbred and 20-25% of Warmblood horses3. Sore shins can affect around 70% of young race horses in training and is a condition caused by micro-fractures in the cannon bone12.
Musculoskeletal Injury (MSI) in general occurs in around 40% of young Thoroughbred racehorses in training and fractures of the tibia (20.7%) and phalanx were most common (14.5%)13.
Forced exercise has also been associated with bone conditions and it appears the period between 3 and 9 months of age is the most precarious for the foal in terms of DOD. The skeletal development of the foal during this period should be monitored closely as complications can seriously impact on the athletic ability of the horse14.
A study published in the Equine Veterinary Journal showed that young Thoroughbred racehorses (n=10) supplemented with MBP over a period of 3 months showed an increase in bone mineral density measured by radiographic bone aluminium equivalence (RBAE) analysis along with increased osteocalcin production indicating greater osteoblast activity compared to the control group (n=10)15. (See figure 6)
Two unpublished preliminary studies have shown similar results. One study using horses with a mean age of 7.9 years found that the blood biomarker for osteoclast activity (ICTP) decreased and osteocalcin concentrations increased in the MBP group (n=16) compared with control (n=15). Another study showed that OCD type pathologies were reduced in the MBP group following 7.5 months of supplementation.
It is evident that bone health is a major concern for horse owners and that current nutraceutical intervention remedies are limited in their effectiveness as they rely on the efficient activity of osteoblasts. It is known that osteoblast numbers decrease with age partly due to a reduced production of osteoblasts from mesenchymal cells coupled with increased apoptosis16. Along with this, osteoclastic activity increases17 causing an imbalance between the two cells and accelerating bone loss.
Therefore, it is logical that the focus of nutraceutical intervention should revolve around maintaining the balance between these two types of cells and not by supplementing with nutrients such as calcium and vitamin K alone.
MBP has been shown to exert these effects and has been studied extensively in both horses and humans in relation to bone health with positive results. By simultaneously increasing the proliferation of osteoblasts and inhibiting the action of osteoclasts while indirectly increasing bone mineral density, MBP could be the missing link in equine bone health. The consistent balance of these two cells is not only vital for horses post BMD peak, but also for younger horses with lifestyles which may lead to a de-coupling of the ARF sequence (bone remodelling) due to repetitive trauma or stresses from training.
While it is clear that more equine research is needed, there are very interesting preliminary studies which show the potential of MBP to help protect against bone disease in horses. Many feed supplements in the equine industry have evolved from human health supplements following strong research and a history of positive and safe use. MBP is no exception to this and we expect the research data to increase significantly in the coming years due to the growing excitement around this fascinating ingredient.
The research collated to date appears to shed light on the reasons why calcium supplements have not been effective in reducing fracture risk following decades of use and the interest should now be in nutraceutical ingredients which promote osteoblast activity and maintain the efficiency of the bone remodelling process.
MBP is a natural, safe ingredient with a promising future and should be considered seriously if equine bone health is a concern to the veterinarian or horse owner.
Insert Figs 7&8 - where
1. Bone fatigue and its implications for injuries in racehorses. Martig et al. (2014): Equine Veterinary Journal,46 (2014) 408-415
2. Frost H.M (1986): Intermediary organisation of the Skeleton, Vol.1 & 2, CRC Press Inc., Boca Raton, Florida.
3. Incidence of osteochondrosis (dissecans) in Dutch warmblood horses presented for pre-purchase examination. Ir Vet J. 2008 Jan 1;61(1):33-7. doi: 10.1186/2046-0481-61-1-33. Vos NJ,
4. Osteochondritis dissecans of the distal femur and patella. Clinical Journal of Sports Medicine 16 (1): 157–74
5. Calcium intake and hip fracture risk in men and women: a meta-analysis of prospective cohort studies and randomized controlled trials1,2,3. Am J Clin Nutr December 2007 vol.86 no.6 1780-1790.
6. Calcium intakes and femoral and lumbar bone density of elderly U.S. men and women: National Health and Nutrition Examination Survey 2005-2006 analysis. J Clin Endocrinol Metab. 2012 Dec;97(12):4531-9. doi: 10.1210/jc.2012-1407. Epub 2012 Oct 15.
7. Principles of Bone Development in Horses. Larry A. Lawrence, Kentucky Equine Research, Versailles, Kentucky USA.
8. Cystatin C in milk protein and its inhibitory effect on bone resorption in vitro. Biosci. Biotechnol. Biochem., 66 (12), 2531-2536, 2002Y Matsuoko et al;
9. Milk basic protein promotes bone formation and suppresses bone resorption in healthy adult men. Biosci. Biotechnol. Biochem. 2001 Jun;65(6):1353-7.
10. Identification of angiogenin as the osteoclastic bone resorption inhibitory factor in bovine milk. Bone 42 (2008) 380-387
11. Biological significance of MBP for bone health, Food Sci. Technol. Res., 11 (1), 1-8.(2005) Kawakami;
12. Wastage in the Australian thoroughbred racing industry. RIRDC Research Paper No. 98/52. Bailey, C.J. 1998. Rural Industries Research and Development Corporation, Canberra, Australia pp. 16–17.
13. Musculoskeletal injuries in Thoroughbred racehorses: A study of three large training yards in Newmarket, UK (2005–2007) Peter H.L. Ramzan, , Lorraine Palmer The Veterinary Journal Volume 187, Issue 3, March 2011, Pages 325–329
14. Daniel J. Burba, DVM, Diplomate ACVS Professor, Equine Surgery, Equine Health Studies Program, LSU School of Veterinary Medicine
15. The effect of milk basic protein supplementation on bone metabolism during training of young thoroughbred racehorses. Equine Vet J Suppl. 2006 Aug;(36):654-8.
16. Osteoblast progenitor fate and age-related bone loss. J Musculoskelet Neuronal Interact. 2002 Dec;2(6):581-3.
17. Osteoclastogenic potential of bone marrow cells increases with age in elderly women with fracture. Mech Ageing Dev. 2002 Jul;123(10):1321-31.