Evaluation of serum concentrations of biochemical markers of bone metabolism and insulin-like growth factor I associated with treadmill exercise in young horses

Concurrent measurement of serum and radiomic biomarkers in the clinical investigation of equine musculoskeletal injuries: A prospective pilot study

The prevention of musculoskeletal injuries and their related welfare and economic impacts represent an immediate priority for the horse racing industry. This prospective pilot study aimed to evaluate a method to quantitatively analyze scintigraphic features of specific anatomical regions of the horse's appendicular skeleton in combination with secondary measures of musculoskeletal metabolism in blood. Twelve horses referred for scintigraphic assessment of lameness were enrolled. Blood samples were collected immediately prior to the administration of radiotracer. Serum concentrations associated with bone turnover were determined for the following biomarkers: C-terminal telopeptides of type I collagen, proteoglycans and sulfated glycosaminoglycans, collagen type II, osteocalcin, and procollagen II C-terminal propeptide. Scintigraphic images underwent radiomic analysis of discrete regions of the distal limbs and these data were correlated to bone turnover markers. Three lame horses demonstrated asymmetrical radiomic abnormalities. The concentration of osteocalcin in the lame horses was significantly higher when compared to the control group, while no significant changes were observed for the other screened serum biomarkers. Findings from the current study provided evidence that radiomic analysis of equine scintigraphy is feasible. This method has the potential to interrogate which serum markers are associated with musculoskeletal injuries.

Novel computed tomographic analysis demonstrates differences in patterns of bone mineral content between fracture configurations in distal condylar fractures of the third metacarpal/metatarsal bones in 97 Thoroughbred racehorses

OBJECTIVE

To evaluate bone mineral content patterns between fracture configurations using novel CT image analysis.

ANIMALS

CT images from 97 Thoroughbred racehorses with third metacarpal/tarsal condyle fractures provide the case population for analysis.

PROCEDURES

Fractures were grouped by radiographic appearance. Image analysis objectively measured area of highly attenuating pixels (aHAP), areal density of highly attenuating pixels (dHAP) utilizing novel convex hull analysis, and subjective assessment of apparent attenuation intensity ranking (AAIR) for each fracture. Differences between fracture configuration groups were evaluated.

RESULTS

Analysis of dHAP identified lower-density regions of highly attenuating pixels in propagating fractures and higher-density regions of highly attenuating pixels in unicortical fractures (P = .028). Complete and incomplete configurations were almost indistinguishable in dHAP (P = 1.000). The ratio of dHAP between fractured and nonfractured condyles revealed higher density gradients between condyles in unicortical (P = .040) and incomplete (P = .031) fractures than propagating fractures.

CLINICAL RELEVANCE

Differences in patterns of bone mineral content were identified between propagating, bicortical (incomplete and complete), and unicortical fractures of third metacarpal/tarsal bone condyles. Computer-assisted geometric measurement of dHAP identified on CT images could help to assess fracture risk in equine athletes. This application may have greater relevance as standing CT screening becomes more available.

Reduced high-intensity training distance in growing horses had no effect on IGF-1 concentrations, but training onset interrupted time-dependent IGF-1 decline

This study investigated plasma insulin like growth factor (IGF)-1 concentrations in 16 young Standardbred horses introduced to systematic high-intensity training at two different levels of intensity. Growth and locomotion asymmetry and correlations between these and plasma IGF-1 concentrations were also examined. From September as 1-year olds to March as 2-year olds (Period 1), all horses were subjected to the same submaximal training program. In March (start of Period 2), the horses were divided into two groups (n=8) and one group was introduced to regular high-intensity training. The other group was introduced to a program where the high-intensity exercise distances were reduced by 30%. These two training programs were maintained for the remaining 21 months of the study (Periods 2, 3, and 4). There was no effect of training group on plasma IGF-1 concentrations. A continuous decline in IGF-1 levels was observed throughout the study (P<0.0001), with one notable interruption in Period 2 when the IGF-1 concentration remained at the level seen at the start of Period 1. Growth rate of body length was equally high in Periods 1 and 2 (P>0.05). Front and hind limb asymmetry was elevated in Period 2 compared with Period 1. There were positive correlations between IGF-1 concentrations and changes in body condition score, and a negative correlation between IGF-1 concentration and weight. These results indicate that introduction to high-intensity training induces IGF-1 release in horses, but that a 30% difference in the distances used in high-intensity training does not affect IGF-1 levels. The temporary interruption in decline in IGF-1 release with the onset of high-intensity training may influence growth pattern and locomotion asymmetry, but further studies are needed to assess causality.

The Effect of a Moderate Exercise Program on Serum Markers of Bone Metabolism in Dogs

Simple Summary

In this article, we investigate the long-term (four months) effects of a 25 min moderate-intensity treadmill exercise, three times per week, on serum markers of bone metabolism (bone alkaline phosphatase and osteocalcin as bone formation markers and C-terminal telopeptide as bone resorption marker) in dogs. Twenty healthy dogs (Labrador and Golden Retrievers), median age 16.2 (11.7–24.4) months underwent the exercise program. Blood samples were collected as a baseline, mid-term (after two months) and at the end of the study. The values of bone formation markers significantly decreased following two months of exercise program; after which, bone alkaline phosphatase increased while osteocalcin concentration continued to decrease towards the end of the study. Bone resorption marker did not significantly change through the exercise duration. In overall, moderate exercise resulted in no change in bone resorption, and a mild bone formation in young developing dogs.

Abstract

The beneficial effect of physical activity on the musculoskeletal health in dogs is well recognized, but the level of intensity, duration, and frequency of exercise is not fully described. Measurement of serum markers of bone metabolism (bone alkaline phosphatase and osteocalcin as bone formation markers and C-terminal telopeptide as bone resorption marker) during four months of organized moderate-intensity physical training in Labrador retriever and Golden retriever dogs aged between 11.7–24.4 months, showed variations of bone metabolism. Dogs were included in treadmill running sessions for 25 min, three times per week. Blood samples were taken at the beginning of the program (baseline), after two months (mid-term) and at the end of the study after four months. The values of bone alkaline phosphatase and osteocalcin significantly decreased following two months of exercise program. Bone alkaline phosphatase increased by the end of four-month training cycle, but did not reach baseline value. Osteocalcin levels continued to decrease towards the end of the study. C-terminal telopeptide concentrations did not significantly change throughout the study duration. The results of this study show that aerobic exercise of moderate-intensity caused an initial decrease in bone formation followed by an increase of bone alkaline phosphatase and a further decrease of osteocalcin concentration. The response of two formation markers can be explained by the different stage of osteoblast activity that they express. In summary, moderate exercise resulted in no change in bone resorption, and a mild bone formation in young developing dogs.

Growth patterns, metabolic indicators and osteoarticular status in the Lusitano horse: A longitudinal study

Development of a healthy musculoskeletal system is of high concern for horse breeders and users. A longitudinal field study was performed in order to: (i) evaluate growth patterns and long-term changes on bone quality, bone metabolism, growth factors and metabolic variables in the Lusitano horse; and (ii) retrospectively assess whether these changes were related with radiographic findings regarding osteochondrosis-like lesions (OC) at the onset of training. Thirty-four Lusitano foals born and raised at four stud-farms, were periodically weighed (BW), and measured (withers height-WH) from birth to 36 months of age. On the same days, blood samples were collected for determination of osteocalcin, bone alkaline phosphatase, insulin-like growth factor I (IGF-I), leptin, insulin, glucose, parathyroid hormone (PTH), calcium, phosphorus and magnesium plasma concentrations, and quantitative ultrasound measurements were performed on the right third metacarpal bone (McIII). At the end of the study horses underwent radiographic examination of the four fetlocks, hocks and stifles. According to their radiographic status (OC negative vs. OC positive), Richards growth function was adjusted to BW and WH data. Instantaneous BW and WH growth rates (BW IADG and WH IADG) were calculated for each foal, from the resolution of the first derivative of growth models for seven age-classes. The presence of radiographic findings compatible with OC at the onset of training was associated with changes in BW and WH growth rates. Positive horses presented higher BW IADG from six to 18 months of age and lower WH IADG before 45 days of age (P<0.001). Speed of sound measurements (SOS), bone markers, growth factors and other metabolic variables change markedly with age (P<0.01). OC positive horses tended to have lower SOS values at the lateral region of McIII, lower IGF-I, and higher insulin and PTH concentrations (P<0.1). This study provides indirect evidence that monitoring foals’ growth during the first year of life may be of assistance in managing the occurrence of OC. Further studies with a higher number of animals and a controlled feed intake should be pursued.

Experimental investigation of bone mineral density in Thoroughbreds using quantitative computed tomography

Bone mineral density (BMD) is one of the indications of the strength and health. BMD measured by quantitative computed tomography (QCT) was compared with that measured by dual energy X-ray absorptiometry (DXA) and radiographic bone aluminum equivalence (RBAE). Limbs were removed from horses that had been euthanized for reasons not associated with this study. Sixteen limbs (left and right metacarpals and metatarsals) from 4 horses were used to compare BMD as measured by QCT with those measured by DXA and RBAE. There was a strong correlation between BMD values measured by QCT and those measured by DXA (R(2)=0.85); correlation was also observed between values obtained by QCT and those obtained by RBAE (R(2)=0.61). To investigate changes in BMD with age, 37 right metacarpal bones, including 7 from horses euthanized because of fracture were examined by QCT. The BMD value of samples from horses dramatically increased until 2 years of age and then plateaued, a pattern similar to the growth curve. The BMD values of bone samples from horses euthanized because of fracture were within the population range, and samples of morbid fracture were not included. The relationship between BMD and age provides a reference for further quantitative studies of bone development and remodeling. Quantitative measurement of BMD using QCT may have great potential for the evaluation of bone biology for breeding and rearing management.

Thoroughbred horses in race training have lower levels of subchondral bone remodelling in highly loaded regions of the distal metacarpus compared to horses resting from training

Bone is repaired by remodelling, a process influenced by its loading environment. The aim of this study was to investigate the effect of a change in loading environment on bone remodelling by quantifying bone resorption and formation activity in the metacarpal subchondral bone in Thoroughbred racehorses. Sections of the palmar metacarpal condyles of horses in race training (n = 24) or resting from training (n = 24) were examined with light microscopy and back scattered scanning electron microscopy (BSEM). Bone area fraction, osteoid perimeter and eroded bone surface were measured within two regions of interest: (1) the lateral parasagittal groove (PS); (2) the lateral condylar subchondral bone (LC). BSEM variables were analysed for the effect of group, region and interaction with time since change in work status. The means ± SE are reported. For both regions of interest in the training compared to the resting group, eroded bone surface was lower (PS: 0.39 ± 0.06 vs. 0.65 ± 0.07 per mm, P = 0.010; LC: 0.24 ± 0.04 vs. 0.85 ± 0.10 per mm, P < 0.001) and in the parasagittal groove osteoid perimeter was higher (0.23 ± 0.04% vs. 0.12 ± 0.02%). Lower porosity was observed in the subchondral bone, reflected by a higher bone area fraction in the LC of the training group (90.8 ± 0.6%) compared to the resting group (85.3 ± 1.4%, P = 0.0010). Race training was associated with less bone resorption and more bone formation in the subchondral bone of highly loaded areas of the distal metacarpus limiting the replacement of fatigued bone. Periods of reduced intensity loading are important for facilitating subchondral bone repair in Thoroughbred racehorses.

Influence of racing on the serum concentrations of acute-phase proteins and bone metabolism biomarkers in racing greyhounds

This study was designed to evaluate the influence of racing on the serum concentrations of the acute-phase proteins (APPs) C-reactive protein (CRP), haptoglobin (Hp) and serum amyloid A (SAA) in 32 endurance-racing greyhounds. The study also aimed to investigate the effect of a 7 km race on the bone biomarkers osteocalcin (OC), bone-specific alkaline phosphatase (b-ALP) and pyridinoline cross-links (PYD). Total white blood cell (WBC) count, and the serum concentrations of cortisol, tumour necrosis factor-α (TNF-α), vitamin D and testosterone were also determined. Blood samples were collected 24 h prior to (T0) and within 2 h of completion of the race (T1). Compared to baseline values, WBC count did not change significantly (P = 0.2300), serum cortisol, Hp and SAA increased, while TNF-α and CRP decreased (P <0.0001 for each). There were no significant differences between the pre- and post-race serum concentrations of OC and PYD (P = 0.9500 and P = 0.2600, respectively), but serum b-ALP increased significantly (P = 0.0004). Serum concentrations of vitamin D and testosterone increased after racing (P = 0.0100 and P <0.0001, respectively). In this study, a 7 km race stimulated an acute-phase response, demonstrated by significant increases in the serum concentrations Hp and SAA in racing greyhounds. Increased serum b-ALP post-race probably indicates a change in bone metabolism and deserves further study.

Exercise-induced inhibition of remodelling is focally offset with fatigue fracture in racehorses

Bone remodelling is inhibited by high repetitive loading. However, in subchondral bone of racehorses in training, eroded surface doubled in association with fatigue fracture and there was greater surrounding trabecular bone volume suggesting trabecular modelling unloads the bone focally, allowing damage repair by remodelling.

INTRODUCTION

Remodelling replaces damaged bone with new bone but is suppressed during high magnitude repetitive loading when damage is most likely. However, in cortical bone of racehorses, at sites of fatigue fracture, focal porosity, consistent with remodelling, is observed in proportion to the extent of surrounding callus. Focal areas of porosity are also observed at sites of fatigue damage in subchondral bone. We hypothesised that fatigued subchondral bone, like damaged cortical bone, is remodelled focally in proportion to the modelling of surrounding trabecular bone.

METHODS

Eroded and mineralizing surfaces and bone area were measured using backscattered scanning electron microscopy of post-mortem specimens of the distal third metacarpal bone in 11 racehorses with condylar fractures (cases) and eight racehorses in training without fractures (controls).

RESULTS

Cases had a two-fold greater eroded surface per unit area at the fracture site than controls (0.81 ± 0.10 vs. 0.40 ± 0.12 mm(-1), P = 0.021) but not at an adjacent site (0.22 ± 0.09 vs. 0.30 ± 0.11 mm(-1), P = 0.59). Area fraction of surrounding trabecular bone was higher in cases than controls (81 ± 2 vs. 72 ± 2 %, P = 0.0020) and the eroded surface at the fracture site correlated with the surrounding trabecular area (adjusted R (2) = 0.63, P = 0.0010).

CONCLUSION

In conclusion, exercise-induced inhibition of remodelling is offset at sites of fatigue fracture. Modelling of trabecular bone may contribute to unloading these regions, allowing repair by remodelling.

Effects of extracorporeal shock wave therapy and polysulfated glycosaminoglycan treatment on subchondral bone, serum biomarkers, and synovial fluid biomarkers in horses with induced osteoarthritis

OBJECTIVE

To evaluate effects of extracorporeal shock wave therapy (ESWT) and polysulfated glycosaminoglycan treatment (PSGAGT) on subchondral bone (SCB), serum biomarkers, and synovial fluid biomarkers in horses with induced osteoarthritis.

ANIMALS

24 healthy 2- to 3-year-old horses.

PROCEDURES

An osteochondral fragment was created on the distal aspect of the radial carpal bone in 1 middle carpal joint of each horse. Horses were randomly allocated to receive local application of ESWT (days 14 and 28; n = 8), PSGAGT (IM, q 4 d for 28 days; 8), or a sham ESWT probe (placebo; days 14 and 28; 8). Serum biomarkers were measured every 7 days, and synovial fluid biomarkers were measured every 14 days. Bone density was measured by use of computed tomography on days 0 and 70, and microdamage and bone formation variables were compared among groups at the end of the study (day 70).

RESULTS

There was no significant effect of ESWT or PSGAGT on any bone variable. Serum osteocalcin concentration was significantly greater in horses that received ESWT, compared with placebo-treated horses, and serum concentration of the C-terminal telopeptide of type I collagen was significantly higher in horses that received ESWT, compared with placebo- and PSGAG-treated horses. Concentrations of the synovial fluid epitope CS846 were significantly higher in joints with osteoarthritis treated with ESWT CONCLUSIONS AND CLINICAL RELEVANCE: Treatment of osteoarthritis with ESWT had no effect on SCB but did induce increases in serum biomarkers indicative of bone remodeling. Treatment of osteoarthritis with PSGAG had no effect on SCB or biomarkers.

Serum biomarker levels for musculoskeletal disease in two- and three-year-old racing Thoroughbred horses: A prospective study of 130 horses

REASON FOR PERFORMING STUDY

Biomarkers have shown some in vivo promise for the detection of musculoskeletal injuries, but further study to assess biomarker levels in clinical orthopaedic disease is required.

OBJECTIVE

To assess 7 serum biomarkers for the detection of musculoskeletal injuries.

METHODS

Two- and 3-year-old racehorses were entered into the study (n = 238). Exit criteria were lack of training for >30 days, or completion of 10 study months. Data from horses with solitary musculoskeletal injuries and completion of >2 months were analysed. Musculoskeletal injury was considered intra-articular fragmentation (IAF), tendon or ligamentous injury (TL), stress fractures (SF) and dorsal metacarpal disease (DMD). Monthly lameness examination and serum collection were performed. Serum was analysed for glycosaminoglycan (GAG), type I and II collagen degradation (C1, 2C), type II collagen synthesis (CPII), type II collagen degradation (Col CEQ), aggrecan synthesis (CS846), osteocalcin (OC) as a marker of bone formation and (C-terminal telopeptide of type I collagen) CTX as a marker of bone degradation.

RESULTS

Of the 238 horses 59 injured and 71 uninjured control horses met the analysis criteria. Based on injury no significant differences in the proportions were observed for age, gender or lesion type, although a higher proportion of injuries occurred at the beginning of the study. Of injured horses, 16 (27%) sustained an IAF, 17 (29%) a TL injury, 7 (12%) SF and 19 (32%) were diagnosed with DMD. There were significant changes seen in biomarkers based on the injury incurred when longitudinal samples were assessed. Furthermore, based on the serum biomarkers collected prior to injury, horses could be correctly classified as injured or uninjured 73.8% of the time.

CONCLUSIONS

A unique biomarker pattern occurred before each injury and this was beneficial in classifying horses as injured or uninjured.

POTENTIAL RELEVANCE

Biomarkers have the potential to be used as a screening aid prior to musculoskeletal injury.

Third metacarpal condylar fatigue fractures in equine athletes occur within previously modelled subchondral bone

Bone modelling and remodelling reduce the risk of fatigue fractures; the former by adapting bone to its loading circumstances, the latter by replacing fatigued bone. Remodelling transiently increases porosity because of the normal delay in onset of the formation phase of the remodelling sequence. Protracted intense loading suppresses remodelling leaving modelling as the only means of maintaining bone strength. We therefore hypothesized that race horses with fatigue fractures of the distal third metacarpal bone (MC3) will have reduced porosity associated with suppressed remodelling while continued adaptive modelling will result in higher volume fraction (BV/TV) at this site. Using high resolution peripheral quantitative computed tomography (HR-pQCT), we measured the distal aspect of the MC3 obtained at postmortem from 13 thoroughbred race horses with condylar fractures of the MC3 (cases), 8 horses without fractures (training controls), 14 horses with a fracture at another site (fractured controls) and 9 horses resting from training (resting controls). Porosity of the subchondral bone of MC3 was lower in cases than resting controls (12±1.4% vs. 18±1.6%, P=0.017) although areas of focal porosity were observed adjacent to fractures in 6/13 horses. BV/TV of the distal metacarpal epiphysis tended to be higher in horses with condylar fractures (0.79±0.015) than training controls (0.74±0.019, P=0.070), but also higher in controls with a fracture elsewhere (0.79±0.014) than the training controls (0.74±0.019, P=0.040). BV/TV was higher in horses over three years of age than those aged two or three years (0.79±0.01 vs. 0.74±0.01, P=0.016). All metacarpal condylar fractures occurred within focal areas of high BV/TV. We infer that intense training in equine athletes suppresses remodelling of third metacarpal subchondral bone limiting damage repair while modelling increases regional bone volume in an attempt to minimise local stresses but may fail to offset bone fragility.

Biochemical markers of bone metabolism and risk of dorsal metacarpal disease in 2-year-old Thoroughbreds

REASONS FOR PERFORMING STUDY

Dorsal metacarpal disease (DMD) is a common problem in 2-year-old racehorses and results in loss of a significant number of days from training. Biochemical markers of bone cell activity measured early in the training season could have value for identifying 2-year-old Thoroughbred racehorses that develop DMD.

OBJECTIVES

To determine the association between serum concentrations of osteocalcin, the carboxyterminal propeptide of type I collagen (PICP) and the carboxyterminal cross-linked telopeptide of type I collagen (ICTP) measured early in the training season and the risk of DMD.

METHODS

Blood samples were collected from 165 two-year-old Thoroughbreds during late November/early December. Osteocalcin and PICP were measured as markers of bone formation, and ICTP as a marker of bone resorption. Training and veterinary records for each horse were monitored over the following training/racing season (10 months). Cases were defined as an episode where signs of DMD were sufficiently severe for a horse to miss at least 5 consecutive days of training. Classification tree and logistic regression analysis were used to identify the most important factors suitable for prediction of DMD risk.

RESULTS

There were 24 cases of DMD during the season (14.6% cumulative incidence), with an average time to recognition of approximately 6 months (May). The earliest recognised case was in February and the latest in September. Osteocalcin and ICTP concentrations in the early stages of the training season were significantly higher in horses that subsequently developed DMD (P = 0.017 and 0.019, respectively). DMD cases were also significantly older compared to noncases (21.04 vs. 20.44 months, P = 0.023). Using a multivariable logistic regression model, it was possible to postulate a set of diagnostic rules to predict the likelihood of DMD injury during the season. This suggested that horses with ICTP concentrations above 12365 ug/l and older than 20.5 months are 2.6 times more likely to develop DMD.

CONCLUSIONS

The measurement of the bone resorption marker ICTP could be useful for identification of 2-year-olds at increased risk of developing DMD.

POTENTIAL RELEVANCE

These findings, together with other strategies such as modification of training regimens, e.g. early introduction of short distances of high-speed exercise into the training programme, could help reduce the days lost to training as a result of DMD.

Age-related changes in serum insulin-like growth factor-I, insulin-like growth factor-I binding protein-3 and articular cartilage structure in Thoroughbred horses

REASONS FOR PERFORMING STUDY

Structural changes in articular cartilage associated with the ageing process require definition for investigators performing developmental and age-related studies, for which information is lacking.

OBJECTIVES

To 1) determine the onset and end of puberty as defined by serum insulin like growth factor (IGF-I) and IGF-binding protein-3 (IGFBP-3) concentrations and 2) correlate articular-epiphyseal cartilage complex structural changes with the onset and end of puberty.

METHODS

IGF-I and IGFBP-3 were measured in serum samples from normal female and male horses age 9-715 days to determine peak and steady-state values for horses transitioning through puberty. Osteochondral tissue sections were obtained from horses age 120-840 days (4-28 months) and examined histologically for cartilage canals and tidemark formation.

RESULTS

In male and female horses, serum IGF-I/IGFBP-3 concentrations peaked at approximately 225 days, defining the onset of puberty. Cartilage canals were absent from articular cartilage just prior to this time point. IGF-I/IGFBP-3 concentrations declined to steady-state levels at approximately age 450 days, signalling exit from puberty and therefore the beginning of ageing. This time point correlated to initial formation of a tidemark in the osteochondral tissue sections.

CONCLUSIONS

Horses may be considered pubescent at age 225-450 days, and post pubescent and ageing after age 450 days.

POTENTIAL RELEVANCE

Defining the normal post natal to post pubescent concentrations for serum IGF-I and serum IGFBP-3 establishes subsets of animals for age-related studies and may be used to monitor horses for abnormally high IGF-I concentrations due to natural disease or subsequent to systemic growth hormone administration.

Bone biomarkers and risk of fracture in two- and three-year-old Thoroughbreds

The aim of this study was to determine whether bone biomarkers (osteocalcin, PICP, ICTP and CTX-I) could be used to identify 2- and 3-year-olds at increased risk of fracture in the subsequent flat racing season. It was concluded that these bone biomarkers cannot be used to identify 2- and 3-year-olds that sustain a fracture. Whether bone biomarkers have better predictive value in older horses or when measured serially in the same animal remains to be determined.

Descriptive epidemiology of fracture, tendon and suspensory ligament injuries in National Hunt racehorses in training

REASONS FOR PERFORMING STUDY

While fractures and tendon injuries are known to be important diseases in National Hunt (NH) racehorses during racing, there are no accurate estimates of their incidence in NH training yards.

OBJECTIVES

To estimate the incidence of fractures and tendon and suspensory ligament injuries (TLIs) in NH racehorses in training; to describe the injuries incurred and to compare injury incidence rates by horse age, trainer, gender and background (ex-flat vs. ex-store horses).

METHODS

Cohort data were collected from 14 UK NH training yards for 2 racing seasons. Daily exercise regimens and details of fractures and TLIs occurring in study horses were recorded.

RESULTS

Data were gathered from 1223 horses that spent 9466 months at risk of injury. The fracture incidence rate was 1.1/100 horse months and varied significantly by trainer (P<0.001) but not by gender, age or background. The pelvis and third metacarpal bone (MCIII) were the most common fracture sites, although this varied between racing and training. The TLI incidence rate was 1.9/100 horse months and varied significantly by trainer (P = 0.05) and age (P<0.001) but not by gender or background. However, ex-store horses were significantly more likely to have a TLI on the racecourse than ex-flat horses (P = 0.01). Superficial digital flexor injuries accounted for 89% of all TLIs, the remainder being suspensory ligament injuries.

CONCLUSIONS AND POTENTIAL RELEVANCE

Fractures and TLIs are important causes of morbidity and mortality in NH racehorses in training in England. This study provides accurate estimates of their incidence in this population and provides a baseline against which to monitor the effect of future interventions.

Relationship between biochemical markers and radiographic scores in the evaluation of the osteoarticular status of Warmblood stallions

Establishing the osteoarticular status of the horse is often performed by means of radiological screening of the animals. Widespread blood sampling could reveal to be an interesting alternative to this procedure which is time consuming and sometimes technically difficult. The aim of this study was to investigate the relationship between the radiological status of the horses and the levels of biochemical markers of cartilage degradation and synovial inflammation. A specific radiological scoring and classification system was therefore developed and applied on 63 stallions presented for studbook admission. Additionally, groups of horses were established according to the occurrence of osteochondrosis, degenerative joint disease and distal interphalangeal joint effusion. Insulin growth factor-I, myeloperoxidases, Coll2-1 and Coll2-1NO(2) were used as blood markers. The combination of the blood parameters did not seem to correlate with the used scoring system. Coll2-1NO(2) levels however tended to increase with poorer radiological class and this could therefore potentially be a useful predictor of the osteoarticular status in the horse. Coll2-1 levels were significantly higher in the degenerative joint disease group. A high percentage of horses with distal interphalangeal joint effusion was present in this study and was associated with decreased IGF-I and increased Coll2-1 levels.

Response of biochemical markers of bone metabolism to exercise intensity in thoroughbred horses

We studied the response of biochemical markers of bone metabolism to exercise intensity in horses. Four horses were walked on a mechanical walker for one week (pre-exercise). Then they performed low-speed exercise on a high-speed treadmill in the first week and medium-speed exercise in the second week and high-speed exercise in the third week of training. We measured two indices of bone resorption, serum hydroxyproline concentration and the urinary deoxypyridinoline/creatinine ratio, and serum osteocalcin (OC) concentration as an index of bone formation. Both indices of bone resorption gradually decreased during the experiment. Serum OC concentration did not change in the first week but was significantly lower in the second and the third weeks compared to in the pre-exercise period and in the first week. These results suggest that the low-speed exercise decreased bone resorption but did not affect bone formation, which possibly results in increasing bone mineral content and strengthening of bones. The high-speed exercise decreased bone formation and bone resorption, i.e., bone turnover was suppressed. The low-speed exercise may be preferable for increasing bone mineral content.

Analysis of biochemical markers of bone metabolism in Asian elephants (Elephas maximus)

Two human enzyme immunoassays (EIA) and one radioimmunoassay (RIA) were validated and used to measure osteocalcin (OC), bone alkaline phosphatase (BAP), and the cross-linked telopeptide domain of type I collagen (ICTP), in serum from Asian elephants (Elephas maximus). Sera from four adult females sampled on 7 consecutive days were also analyzed to assess the existence and magnitude of intraindividual day-to-day variability of the serum concentration of these markers. Sample dilution curves were parallel with assay standard curves, which demonstrated that excellent cross reactivity existed between assay antibodies and elephants marker antigens. Statistically significant inverse correlations were found between age and concentrations of all three markers: BAP, r = -0.862 (P < 0.01); OC, r = -0.788 (P < 0.002); and ICTP, r = -0.848 (P < 0.01). Strong positive correlations were found between BAP and OC (r = 0.797, P < 0.01), OC and ICTP (r = 0.860, P < 0.01), and between BAP and ICTP (r = 0.958, P < 0.01). No statistically significant intraindividual variability was found over 7 days in the four adult females for any of the markers assessed (OC: P = 0.089; ICTP: P = 0.642; BAP: P = 0.146; n=4 in each case). The overall coefficient of variability observed in this group of animals was 10.3%, 7.4%, and 5.5% for OC, BAP, and ICTP, respectively. These results suggest a potential role for biochemical markers of bone turnover in monitoring skeletal health and bone disease in Asian elephants.

Changes in synovial fluid and serum biomarkers with exercise and early osteoarthritis in horses

OBJECTIVE

To discriminate between changes in biomarkers with exercise compared to changes in biomarkers with osteoarthritis (OA) in exercising horses.

METHOD

Sixteen, 2-year-old horses were randomly assigned either to an exercise-alone (n=8) or OA-affected (also exercised) (n=8) group. All horses had both mid-carpal joints arthroscoped and OA induced in one mid-carpal joint in the OA-affected joints of OA-affected horses. Two weeks after surgery all horses commenced a strenuous exercise program on a high-speed treadmill. Clinical outcomes and synovial fluid and serum biomarkers, were evaluated weekly. Synovial and serum biomarkers evaluated were epitope CS846 (CS846), epitope CPII (CPII), glycosaminoglycans (GAGs), epitope Col CEQ (Col CEQ) (a marker of type II collagen degradation), type I and II collagen degradation fragments (C1,2C), osteocalcin, C-terminal of bone type I collagen (CTX1), type I collagen (Col I) and (synovial fluid only of cartilage) prostaglandin E2 (PGE2) levels. Horses were euthanized at day 91 and their joints assessed grossly, histopathologically, and histochemically.

RESULTS

Exercise induced a significant increase in synovial fluid CS846, CPII, GAG, Col CEQ, C1,2C, osteocalcin and Col I concentrations. There was a significant increase in synovial fluid CS846, CPII, Col CEQ, C1,2C, osteocalcin, Col I and PGE2 concentrations in OA-affected joints compared to exercise-alone joints. The concentration of serum CS846, CPII, GAG, osteocalcin, C1,2C and Col I increased with exercise. For each of these biomarkers there was also a statistically significant increase in serum biomarker levels in OA-affected horses compared to exercise-alone horses.

CONCLUSIONS

Six synovial fluid and serum biomarkers were useful in separating early experimental OA from exercise alone but synovial fluid CTX1 and serum Col CEQ and CTX1 were not.

Joint dependent concentrations of bone alkaline phosphatase in serum and synovial fluids of horses with osteochondral injury: an analytical and clinical validation

OBJECTIVES

Validate use of a commercially available immunoassay for measurement of bone alkaline phosphatase (BAP) in equine serum and synovial fluid (SF), and investigate the effects of osteochondral (OC) injury in horses on BAP concentrations in serum and SF.

METHODS

SF was collected from 37 joints of 34 Thoroughbred (TB) racehorses undergoing arthroscopic surgery for the removal of OC fragments from either the carpal joints (n=18) or the metacarpo-/metatarsophalangeal (MP) joints (n=19). SF was also obtained from 52 joints of 16 normal TB horses, collected bilaterally from carpal joints of 10 horses (n=40), and MP joints of six horses (n=12). Blood was obtained from all 50 horses. A commercially available immunoassay was validated and subsequently used to determine equine serum and SF BAP concentrations. Correlations to radiographic and arthroscopic scores were assessed.

RESULTS

BAP concentrations were significantly lower in serum from horses with OC injury in their carpal or MP joints than in serum from normal horses. SF BAP concentrations in normal and OC injured carpal joints were significantly higher than MP joints. BAP concentrations were significantly higher in SF from OC injured carpal joints than normal. BAP concentrations were affected by joint sampled, with age having a significant interaction. Concentrations of BAP in the serum (<30U/L), SF (>22U/L) and a ratio of SF to serum > or = 0.5 were predictive of OC injury. Radiographic and arthroscopic scores significantly correlated with serum BAP concentrations, and SF:serum BAP correlated with arthroscopic scores.

CONCLUSIONS

Determination of serum and SF BAP concentrations may be beneficial in the investigation of early joint injury. Joint and injury dependent differences in BAP concentrations allowed the estimation of predictive value for identifying OC injury.

Pharmacological effects of tiludronate in horses after long-term immobilization

INTRODUCTION

Tiludronate, a bisphosphonate, has recently been introduced in veterinary medicine to treat orthopedic conditions in the horse. This study was designed to evaluate its effects on biochemical biomarkers of bone metabolism and on bone density and structure in an experimental model of disuse osteoporosis induced by cast application in horses.

METHODS

Two groups of eight horses were immobilized during 8 weeks. The first group (P-group) received a placebo, and the second group (T-group) received tiludronate 1 mg/kg by slow IV infusion. Both treatments were administered twice, 28 days apart. Immobilization consisted of stall rest with the left forelimb packed in a fiberglass cast. It was followed by a 4-week remobilization period and an 8-week standardized training protocol. One biomarker of bone resorption, the C-telopeptides of type I collagen cross-links (CTX-1) and one biomarker of bone formation, the bone isoenzyme of alkaline phosphatase (bone ALP), were assessed. Metacarpus III (MCIII) bone mineral density (BMD) and speed of sound (SOS) were evaluated respectively by dual energy X-ray absorptiometry (DEXA) and quantitative ultrasonography (QUS). Lameness was regularly assessed during the remobilization and training periods. Group- and time-related effects were tested by analysis of variance on repeated measurements.

RESULTS

A rapid, transient and significant decrease in CTX-1 concentration was seen after each treatment in the T-group only. No significant differences between groups were seen in the evolution of bone ALP activity. At the end of the experiment, the loss of MCIII BMD measured by DEXA in the immobilized limb was significantly less in the T-group than in the P-group. The MCIII SOS measured by QUS did not significantly vary within or between groups throughout the study.

DISCUSSION AND CONCLUSIONS

Tiludronate was found to significantly reduce bone resorption during immobilization, as well as to prevent long-term osteopenia in the immobilized limb. Disuse osteopenia did not affect the lateral superficial cortex of MCIII.

Plasma concentration of insulin-like growth factor I (IGF-I) in growing Ardenner horses suffering from juvenile digital degenerative osteoarthropathy

Degenerative osteoarthropathy resulting in a reduced active lifespan was observed in Ardenner horses. In the context of joint biology, insulin-like growth factor I (IGF-I) is a potential candidate to affect the anabolism of cartilage matrix molecules. A group of 30 Ardenner horses reared under standardized conditions from weaning were evaluated periodically from 15 to 28 months of age to detect the early manifestations of the disease. At the end of this period, horses were classified in two pathological groups related to the degree of interphalangeal degenerative osteoarthropathy based on clinical and radiographic evaluations: healthy (46.7%) and pathological (53.3%) horses. Seven sequential blood samples were taken from each horse (during the evaluation period) to study the variation of IGF-I plasma concentration. We tested the variations of the IGF-I plasma concentration during growth, and the effect of sex and of pathological classes. Significant variations were observed during the research period, with a maximum value corresponding to spring and a minimum in autumn. A significant reduction of the IGF-I plasma concentration was also observed in the pathological horses (433.5 +/- 19.5 ng/ml) compared to the healthy horses (493.9 +/- 18.2 ng/ml). An alteration in the level of this growth factor could induce a disregulation of the mechanisms involved in the local control of joint and bone tissue development.

Relationship between stages of the estrous cycle and bone cell activity in Thoroughbreds

OBJECTIVE

To investigate the relationship between stage of estrous cycle and bone cell activity in Thoroughbreds.

SAMPLE POPULATION

Blood samples collected from forty-seven 2-year-old Thoroughbred mares in training for racing.

PROCEDURES

Blood samples were collected monthly (in April through September) from the mares. Stage of estrus was determined by assessing serum progesterone concentration. Bone cell activity was determined by measuring concentrations of 2 markers of bone formation (osteocalcin and the carboxy-terminal propeptide of type I collagen [PICP]) and a marker of bone resorption (the cross-linked carboxy-terminal telopeptide of type I collagen [ICTP]) in sera.

RESULTS

When the relationship between stage of the estrous cycle and markers of bone cell activity was examined, serum concentrations of both osteocalcin and ICTP were significantly higher in mares that were in the luteal phase, compared with mares that were at other stages of the estrous cycle. Stage of estrus did not affect serum PICP concentration.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicate that bone cell activity in Thoroughbred mares fluctuates during the estrous cycle; serum concentrations of markers of bone formation and bone resorption are increased during the luteal phase. Further studies are required to determine whether these changes are of clinical importance and increase the risk of injury for mares in training during the breeding season. As in humans, stage of estrus must be considered as a source of uncontrollable variability in serum bone marker concentrations in horses.

Future Directions in Treatment of Joint Disease in Horses

Osteoarthritis is one of the most economically important diseases facing equine practitioners. The loss of use associated with joint disease is a leading problem in the equine industry. Although osteoarthritis in all species is believed to be a multifactorial disease that is not well understood, significant advances are being made. This article presents areas of research that are relatively well developed but have not made it to commercialization or routine clinical practice and looks at new applications being investigated for peo-ple that may have an equine application.