Clodronate improves lameness in horses without changing bone turnover markers.

BACKGROUND: Clodronate is prescribed to performance horses with lameness. Despite its clinical popularity, little research has been done to understand the effects of clodronate in the horse. OBJECTIVES: Our objective was to determine if a single treatment with clodronate at the clinically approved dose altered bone remodelling, bone cell recruitment or lameness in the horse. STUDY DESIGN: Twelve university-owned equestrian team competition horses with a history of forelimb lameness due to navicular syndrome were randomised to receive either 1.4 mg/kg clodronate (CLOD n = 6) or an equivalent volume of LRS (CONT; n = 6) in a blinded manner. METHODS: Blood was evaluated weekly for 8 weeks before and after drug administration (clodronate or placebo) for bone turnover markers CTX-I and osteocalcin. Lameness evaluations were performed to assess for change in lameness 1 week before and 1, 2, 3 and 8 weeks after drug administration. Coach questionnaires were performed to assess for change in ridden performance 1, 2, 3 and 8 weeks after drug administration. Bone cell recruitment was evaluated in vitro 2 weeks before and after drug administration. RESULTS: There were no differences in in vitro bone cell recruitment from whole bone marrow or in bone turnover markers CTX-I or osteocalcin. A small but significant decrease in forelimb lameness was detected in CLOD treated horses 1 week after treatment (P = 0.005). There were no significant differences in hindlimb lameness. Coaches identified an improvement in performance significantly more often in CLOD vs. CONT (P = 0.01) at week 8. MAIN LIMITATIONS: Two CONT horses received intra-articular anti-inflammatory medication after treatment, which may have altered lameness results. CONCLUSIONS: A single dose of clodronate appears to reduce lameness without producing detectable effects on bone turnover markers. Due to the long half-life of a bisphosphonate drug, the effect of multiple doses on bone remodelling and lameness should be investigated. The Summary is available in Portuguese - see Supporting Information.

The equine cervical spine: comparing MRI and contrast-enhanced CT images with anatomic slices in the sagittal, dorsal, and transverse plane.

BACKGROUND: The impact of cervical pathology on performance is of great importance to the horse industry. Accurate diagnosis of cervical disease with imaging modalities, including computed tomography (CT) and magnetic resonance imaging (MRI), requires thorough appreciation of normal cervical anatomy. OBJECTIVES: (1) To describe in detail the anatomy of the equine cervical spine by comparing anatomical sections with corresponding MR and contrast-enhanced CT images in the sagittal, dorsal, and transverse plane. (2) To discuss the ability of MR and contrast-enhanced CT imaging to visualize anatomical structures in the cervical spine. ANIMALS AND METHODS: Three cervical spines of young adults (3-8 years), collected immediately after humane euthanasia, were used. The spine was stabilized on a frame in a natural flexed position with an angle of 20°. MR and contrast-enhanced CT imaging was performed within six hours after euthanasia. Anatomical sections of 1 cm were made in the sagittal, dorsal, and transverse plane and compared with corresponding CT and MR images. The intervertebral disk thickness, facet joint angle, sagittal dural space diameter and ventromedial facet joint projection were quantified. RESULTS: The anatomic location of clinically important structures including the facet joints, spinal cord, cervical nerve roots and intervertebral disks were reliably identified in the anatomical sections and their corresponding MR images. Contrast-enhanced CT images depicted all osseous borders, whereas MR images were superior for soft tissue structures. CONCLUSION AND CLINICAL IMPORTANCE: This study enhances our understanding of normal cervical spine anatomy and the diagnostic usefulness of cervical MRI and contrast-enhanced CT in the horse.

The effect of supramaximal exercise on equine platelet function.

When blood is collected into sodium citrate in the proportion of 9 parts blood:1 part sodium citrate, the concentration of plasma sodium citrate in the sample will depend on the packed cell volume (PCV) of the blood sample. This difference in plasma sodium citrate concentration secondary to alterations in PCV significantly affects human platelet aggregation responses. Since horses attain a high PCV in response to high-intensity exercise we investigated the effect of differences in sample plasma sodium citrate concentration on equine platelet aggregability. In addition, low molecular weight heparin (LMWH) was evaluated as an alternative anticoagulant for assessment of platelet aggregability during strenuous exercise in horses. Blood samples were collected pre-exercise and at fatigue after supramaximal treadmill exercise into either 3.8% sodium citrate (9 parts blood:1 part sodium citrate) or 20 u LMWH/ml of blood. Platelet aggregation responses to 1.25 mumol/l adenosine diphosphate (ADP) were measured via optical aggregometry. For samples collected into sodium citrate, aggregability was significantly less than pre-exercise values in samples collected at fatigue and in pre-exercise samples in which sodium citrate concentrations were adjusted to equal those in fatigue samples. However, samples collected into LMWH showed significantly increased platelet aggregability in samples collected at fatigue when compared to pre-exercise samples. In conclusion, higher plasma sodium citrate concentration had a marked inhibitory effect on equine platelet aggregation responses. Low molecular weight heparin was a good alternative anticoagulant for assessment of equine platelet function and results indicate that equine platelet aggregability was enhanced in response to supramaximal exercise.

Relationship between VO2max, heart score and echocardiographic measurements obtained at rest and immediately following maximal exercise in thoroughbred horses.

We evaluated the relationships of heart score (HS) and echocardiographic measures to maximal oxygen consumption (VO2max), maximal cardiac output (Qmax), and maximal stroke volume (SVmax). Six fit, mature Thoroughbred horses weighing (mean +/- s.e.) 487 +/- 11 kg were run 4 times on an inclined (10%) treadmill. Each run consisted of a 3 min warm-up at 4 m/s followed by completion of an incremental exercise test in which each horse ran until VO2max was reached. Arterial and mixed venous blood was collected to determine arteriovenous oxygen content difference C(a-v)O2[ in the last 15 s of exercise. An ATL HDI 3000 ultrasound system and a 3.5 MHz phased array transducer were used to make echocardiographic measurements before and within 2 min of run completion. Guided M-mode echocardiographic measurements of left ventricular diameter (LVD), interventricular septal thickness (IVS) and left ventricular free wall thickness (LVFW) during diastole (D) and systole (S) were made from the right parasternal short axis view at the level of the chordae, and VO2 and C(a-v)O2 were measured as the appropriate M-mode view was recorded. Maximum heart rate (HRmax) was determined using a cardiotachometer, and HS was calculated on nonexercise days using the established technique. Maximum cardiac output and SVmax were calculated from the Fick equation and HRmax. Backward stepwise regression analysis was used to relate pre- and post exercise echocardiographic measurements and HS to VO2, Q, and SV at the time of measurement, and to VO2max, Qmax, and SVmax. Pre- and post exercise LVDD appeared to be the most important variable in these equations. Mean pre-exercise HR at the time of measurement was 54.7 +/- 1.9 beats/min, while the mean post exercise rate was 111.7 +/- 2.6 beats/min. The mean +/- s.e. VO2max was 150.4 +/- 13.2 ml/(kg.min). Heart score was not correlated with VO2max, Qmax, or SVmax. There was no significant difference between pre- and post exercise measurements of LVD, IVSS, and LVFWS.

Equine plasma beta-endorphin concentrations are affected by exercise intensity and time of day.

Eight mature mares were exercised for 20 min at 60% VO2max and to fatigue at 95% VO2max. Plasma beta-endorphin (EN) concentrations were determined before exercise, after a 10 min warm-up, and at the end of each exercise test. Mean +/- s.e. beta-endorphin concentrations were significantly (P < 0.05) higher following work at 95% VO2max when compared to that at 60% VO2max (420.0 +/- 102.7 vs. 269.9 +/- 30.69 pg/ml). Pre-exercise samples were collected between 1000 and 1500 h. In order to evaluate whether any cyclic changes in EN secretion effects may have influenced results, a subsequent study was completed using 12 horses to assess diurnal fluctuations in EN concentrations, by measuring EN concentration every 2 h for a 24 h period. There was no statistical difference in mean values at any time between 0800 and 2000 h. Whether individual differences in EN concentrations reflected varying degrees of stress associated with the exercise could not be determined. Any possible link between EN concentration and exercise stress in exercising horses awaits clarification.