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Sufit, E., Houpt, K. A., & Sweeting, M. (1985). Physiological stimuli of thirst and drinking patterns in ponies. Equine Vet J, 17(1), 12–16.
Abstract: The stimuli that elicit thirst were studied in four ponies. Nineteen hours of water deprivation produced an increase in plasma protein from 67 +/- 0.1 g/litre to 72 +/- 2 g/litre, a mean (+/- se) increase in plasma sodium from 139 +/- 3 to 145 +/- 2 mmol/litre and an increase in plasma osmolality from 297 +/- 1 to 306 +/- 2 mosmol/litre. Undeprived ponies drank 1.5 +/- 0.9 kg/30 mins; 19 h deprived ponies drank 10.2 +/- 2.5 kg/30 mins and corrected the deficits in plasma protein, plasma sodium and plasma osmolality as well as compensating for the water they would have drunk during the deprivation period. In order to determine if an increase in plasma osmolality would stimulate thirst, 250 ml of 15 per cent sodium chloride was infused intravenously. The ponies drank when osmolality increased 3 per cent and when plasma sodium rose from 136 +/- 3 mmol/litre to 143 +/- 3 mmol/litre. Ponies infused with 15 per cent sodium chloride drank 2.9 +/- 0.7 kg; those infused with 0.9 per cent sodium chloride drank 0.7 +/- 0.5 kg. In order to determine if a decrease in plasma volume would stimulate thirst, ponies were injected with 1 or 2 mg/kg bodyweight (bwt) frusemide. Plasma protein rose from 68 +/- 2 g/litre pre-injection to 75 +/- 2 g/litre 1 h after 1 mg/kg bwt frusemide and to 81 +/- 1 g/litre 1 h after 2 mg/kg bwt frusemide.(ABSTRACT TRUNCATED AT 250 WORDS)
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Sullivan, K. A., Hill, A. E., & Haussler, K. K. (2008). The effects of chiropractic, massage and phenylbutazone on spinal mechanical nociceptive thresholds in horses without clinical signs. Equine Vet J, 40(1), 14–20.
Abstract: REASON FOR PERFORMING STUDY: Common methods used to treat back problems in horses need to be assessed objectively. OBJECTIVES: To measure spinal mechanical nociceptive thresholds (MNTs) and evaluate the effects of chiropractic, massage and phenylbutazone, compared with active and inactive control groups. METHODS: Baseline MNTs at 7 sites within the thoracolumbar and sacral regions were measured in 38 healthy mature horses exhibiting no clinical signs of lumbar pain. Horses were assigned to one of 3 treatment groups: instrument-assisted chiropractic treatment, therapeutic massage and phenylbutazone; or 2 control groups: ridden exercise (active control) or routine paddock turnout with no ridden exercise (inactive control). MNT measurements were repeated at 1, 3 and 7 days post treatment. The percentage change from baseline MNT values was calculated within groups. RESULTS: On Day 7, the median MNT had increased by 27, 12 and 8% in the chiropractic, massage and phenylbutazone groups, respectively. MNT changes of <1% were seen within the active and inactive control groups. CONCLUSIONS: Chiropractic treatment and massage therapy increased spinal MNTs within horses not exhibiting signs of lumbar pain. POTENTIAL RELEVANCE: Pressure algometry provides an objective tool to evaluate the effects of commonly used, but currently unproven treatment modalities on spinal MNTs. Future studies need to evaluate combined treatment effects and longer-term MNT changes in horses with documented back pain.
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Summerley, H. L., Thomason, J. J., & Bignell, W. W. (1998). Effect of rider and riding style on deformation of the front hoof wall in warmblood horses. Equine Vet J Suppl, (26), 81–85.
Abstract: A rider modifies the weight distribution and dynamic balance of the horse. But what effect does a rider have on the mechanical behaviour of the hoof during each stance phase? Does riding style have any effect on this behaviour? We attempted to answer these questions using strains recorded from 5 rosette strain gauges glued to the surface of the front hooves of 4 Warmblood horses. Comparisons were made between strains with and without a rider, and when the rider was sitting, rising at a trot, or in a forward seated position. The change in strains from trot to lead or nonlead at a canter, and the effect of turning were also studied. Changing lead at a canter had as least as much effect on strain magnitudes as did turning; strains were up to 43% higher for the nonlead foot, but with little redistribution. Perhaps surprisingly, strains were significantly lower on the quarters by up to 30% with a rider than without, with a 10% increase or decrease at the toe, depending on the individual. Riding style changed strain magnitudes by up to 20% and also caused strain redistribution: strains were higher medially for sitting, and laterally for forward seat, with strains for a rising trot being more evenly distributed and intermediate in magnitude. Studying the range of, and causes of variation in hoof wall strain gives baseline data aimed, in the long term, at providing a biomechanical definition of hoof balance.
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Takahashi, T., Kasashima, Y., Eto, D., Mukai, K., & Hiraga, A. (2006). Effect of uphill exercise on equine superficial digital flexor tendon forces at trot and canter. Equine Vet J Suppl, (36), 435–439.
Abstract: REASONS FOR PERFORMING STUDY: One cause of overstrain injury to the superficial digital flexor tendon (SDFT) in horses is the force loaded on the SDFT during repeated running. Therefore, decreasing this force may reduce SDFT injury. It has been reported that strain on the SDFT decreases with a toe-wedge shoe. Uphill courses are used for training of racehorses, and the angle of hoof-sole to the horizon during uphill running is similar to that of the toe-wedge shoe. OBJECTIVES: To determine the effects of uphill exercise on the force on the SDFT during trotting and cantering. METHODS: Arthroscopically implantable force probes (AIFP) were implanted into the SDFT of the left or right forelimb of 7 Thoroughbred horses and AIFP output recorded during trotting and cantering on a treadmill inclined at slopes of 0, 3 or 8%, and then 0% again. Superficial digital flexor tendon force was calculated as a relative value, with the amplitude of AIFP output voltage at initial 0% slope equal to 100. RESULTS: Out of 14 sets of experiments, AIFP data were analysed successfully in 9 at the trot, in 3 at the canter in the trailing forelimb on a slope of 3 and 8%, and in 2 at the canter in the leading forelimb on a slope of 3%. Increasing the incline from 0-8% tended to decrease peak force in the SDFT at the trot, and in the trailing forelimb at the canter. However, force in the SDFT was unchanged in the leading forelimb at the canter on the 3% incline. CONCLUSIONS: The force in the SDFT trotting or cantering uphill is unchanged or lower than that loaded at the same speed on a flat surface. Because at similar speeds the workload for uphill exercise is greater than on the flat, uphill running increases exercise intensity without increasing force in the SDFT. POTENTIAL RELEVANCE: Uphill exercise may reduce the risk of SDFT injury as both running speed and SDFT force are decreased on an incline as compared to the flat, even when exercise intensity is the same. Further study is needed to confirm these findings at canter in a larger population of horses.
Keywords: Animals; Biomechanics; Exercise Test/veterinary; Female; Forelimb/physiology; Hoof and Claw/physiology; Horses/*physiology; Male; Physical Conditioning, Animal/*methods/*physiology; Tarsal Joints/*physiology; Tarsus, Animal; Tendon Injuries/etiology/prevention & control/veterinary; Time Factors
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Trim, C. M., Moore, J. N., & Clark, E. S. (1989). Renal effects of dopamine infusion in conscious horses. Equine Vet J Suppl, (7), 124–128.
Abstract: An ultrasonic flow probe was implanted around a branch of the left renal artery in five horses. The effects of dopamine were studied in the unsedated horses 10 days after surgery. Three experiments, separated by at least two days, were performed in random order on each horse. In two experiments, dopamine was infused intravenously for 60 mins at either 2.5 and 5.0 micrograms/kg bodyweight (bwt)/min. Saline was infused for 60 mins before and after each infusion, and for 180 mins in the third experiment as a control. Renal blood flow increased during administration of dopamine at both dose rates (P = 0.0001). Urine volume increased (P = 0.055), and osmolality decreased (P < 0.05), with infusion of dopamine at 5.0 micrograms/kg bwt/min. Arterial blood pressure and heart rate were not significantly affected. Fractional excretions of sodium and potassium were not significantly changed with dopamine infusion. The higher dopamine dose rate was accompanied by dysrhythmias in some horses.
Keywords: Animals; Blood Pressure/drug effects/physiology; Consciousness/*physiology; Creatinine/blood; Dopamine/administration & dosage/*pharmacology; Dose-Response Relationship, Drug; Female; Heart Rate/drug effects/physiology; Horses/*physiology; Infusions, Intravenous/veterinary; Kidney/blood supply/*drug effects/physiology; Osmolar Concentration; Potassium/blood; Random Allocation; Regional Blood Flow/drug effects/physiology; Renal Artery/drug effects/physiology/ultrasonography; Sodium/blood; Time Factors; Ultrasonography/methods/veterinary; Urination/physiology
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Tutt Jb,. (1944). Vet J, 100, 69–80.
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van der Kolk, J. H., Nachreiner, R. F., Schott, H. C., Refsal, K. R., & Zanella, A. J. (2001). Salivary and plasma concentration of cortisol in normal horses and horses with Cushing's disease. Equine Vet J, 33(2), 211–213.
Keywords: Adrenal Cortex Function Tests/standards/veterinary; Animals; Cushing Syndrome/diagnosis/metabolism/*veterinary; Female; Horse Diseases/blood/*diagnosis/metabolism; Horses/blood/*metabolism; Hydrocortisone/blood/*metabolism; Male; Predictive Value of Tests; Reference Values; Saliva/*metabolism
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Verheyen, K. L., Price, J. S., & Wood, J. L. (2006). Fracture rate in Thoroughbred racehorses is affected by dam age and parity. Vet J, .
Abstract: This study's aim was to determine the effects of dam age and parity on the rate of fracture in offspring in Thoroughbred racehorses in training for flat racing. It was hypothesised that first foals and those from older mares would have a higher fracture rate than subsequent foals and those from younger mares. A two-year observational cohort study collected data from eight trainers on 335 horses that were monitored since the start of their training as yearlings. Multivariable Poisson regression analyses showed that first foals had a significantly lower fracture rate than subsequent ones (RR=0.33; 95% CI=0.12, 0.89; P=0.02) and rate of fracture decreased with increasing dam age (RR=0.91 per year increase in dam age; 95% CI=0.83, 0.99; P=0.03). This study shows for the first time that the rate of equine injury may be influenced by factors that affect skeletal development. Further research on intra-uterine and peri-natal determinants of injury risk in later life in horses is needed.
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Vermeulen, A. D., & Evans, D. L. (2006). Measurements of fitness in thoroughbred racehorses using field studies of heart rate and velocity with a global positioning system. Equine Vet J Suppl, (36), 113–117.
Abstract: REASONS FOR PERFORMING STUDY: Field based studies of changes in fitness are difficult to conduct in galloping Thoroughbreds. Measurements of heart rate (HR) and real time velocity with a global positioning system (GPS) could provide a method for routine field studies of fitness. OBJECTIVE: To investigate measurements of fitness in the field without using multiple, standardised steps of increasing velocity in the exercise test. METHODS: Twelve healthy 3- to 5-year-old Thoroughbreds were used in the study of reliability, and twelve 2-year-old Thoroughbreds in the investigation of the effect of training. Five second averages of velocity and HR were recorded during a typical fast exercise training session, using a GPS and Polar HR monitor. A standardised exercise test protocol was not used. Regression analyses using trot and gallop data were used to calculate velocities at HR of 200 beats/min (V200), and at maximal HR (VHRmax). Data were collected on consecutive 'fast' day training sessions to assess the reliability of measurements. The effect of training was investigated with fitness tests in weeks 2 and 6 of 'fast' training. Absolute and relative differences were calculated to evaluate reliability, and paired t tests were used to detect an effect of training. RESULTS: VHRmax, V200 and HRmax were reliable measurements of fitness, with mean differences of 2% or less. Reliability of VHRmax was not dependent on VHRmax. VHRmax and V200 both increased significantly with training (P<0.01), but there was no effect of training on HRmax. There were no significant changes in the slope or intercept of the regression equations after training. CONCLUSIONS: Velocity and HR measurements during field gallop exercise provided reliable measures of fitness which enabled a measurement of the response to training. POTENTIAL RELEVANCE: This approach offers a simple, noninvasive method for monitoring adaptations to training in the field.
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Virga, V., & Houpt, K. A. (2001). Prevalence of placentophagia in horses. Equine Vet J, 33(2), 208–210.
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