bluuebunny/crossref_metadata_2025 huggingface dataset:
Clinical use of epidural xylazine in the horse
Authors: LeBLANC P. H. , CARON J. P.
Published: April 2010

Xylazine was administered into the epidural space of nine horses to facilitate various perineal manipulations (ie rectovaginal laceration repair, replacement of prolapsed rectum and urethral extension). The resulting caudal analgesia was sufficient for all procedures. The duration of analgesia from a single injection of epidural xylazine (0.17 to 0.22 mg/kg bodyweight) was at least 3.5 h. No horses were ataxic during or after the treatment. This trial demonstrates that xylazine given into the epidural space of horses provides prolonged regional analgesia which is sufficient for clinical use.
Observer variation in equine abdominal auscultation
Authors: EHRHARDT E. E. , LOWE J. E.
Published: April 2010

The reliability of abdominal auscultation was investigated via an observer variation study. Clinicians listened to a variety of minute‐long equine gut sound recordings. They evaluated the amount of gut sounds as ‘absent’, ‘decreased’, ‘normal’, or ‘increased’. They subsequently evaluated the same recordings replayed in a different order. Intra‐ and inter‐observer agreement was measured by the statistic kappa. There was significant intra‐observer (kappa 0.57) agreement, but less agreement between observers (kappa 0.37). The best agreement was on the classification of sound tracks as ‘absent’ (intra‐observer kappa 0.72 and inter‐observer kappa 0.55). There was significant correlation between the clinicians’ average assessment of the recordings and their acoustic energy levels. In this study abdominal noise was reliably assessed by auscultation. Standardised techniques and definitions would probably enhance the reliability of abdominal auscultation for the evaluation of gastrointestinal disease.
Longitudinal growth analysis of horses following limited andad libitumfeeding
Authors: CYMBALUK NADIA F. , CHRISTISON G. I. , LEACH D. H.
Published: April 2010

Eighteen colts were assigned to one of two groups: limit orad libitumfeeding. Three periods were evaluated: 1) six to 12 months, 2) 12 to 18 months and 3) 18 to 24 months of age. At 24 months of age,ad libitumfed horses weighed 13 per cent (51 kg) more and were 3.6 per cent (5.2 cm) taller than those fed limited amounts. Total, fore and hind body mass increased quadratically irrespective of dietary treatment. Fore body mass comprised 57 per cent of total body mass for both groups and this did not change with age or dietary treatment. Heart girth was directly related (R2= 0.96) to total body mass. Average daily gains in total body mass ofad libitumfed horses were 13 and 71 per cent more rapid (P<0.05) than for limit fed horses in Periods 1 and 3, respectively.Ad libitumfed horses gained hind body mass 25 per cent more rapidly (P<0.05) than limit fed horses only in Period 1. Growth curves of wither and croup heights were quadratic in form.Ad libitumfed horses gained 12 and 13 per cent more rapidly at the wither than limit fed horses in Period 1 and overall, respectively.Ad libitumfed horses grew 33 per cent more rapidly at the croup than limit fed horses but only in Period 2. From six to 12 months of age, the wither and croup grew two‐fold and four‐fold more rapidly than between 12 to 18 months and between 18 to 24 months of age, respectively. Croup height exceeded wither height by 2.5 to 4.4 per cent throughout the study. Clinical assessment indicated thatad libitumfed horses had a higher occurrence of conformational and musculoskeletal abnormalities.
Equine insect hypersensitivity: skin test and biopsy results correlated with clinical data
Authors: FADOK VALERIE A. , GREINER E. C.
Published: April 2010

Forty‐four seasonally pruritic horses and 21 asymptomatic horses in Florida, USA, were tested for insect, grass and mould hypersensitivity by intradermal injection of allergenic extracts. The affected horses ranged in age from 10 months to over 30 years and included a variety of breeds. Affected horses reacted to varying dilutions of extracts made fromCulicoides, mosquitoes, horse flies and black flies. Reactions toCulicoideswere more intense than those caused by injection of antigens from other arthropods. Mild pruritus existed from the end of February until the end of June when the condition worsened and remained severe until November when it improved to an asymptomatic state. Histopathological examination of skin biopsies demonstrated changes compatible with arthropod hypersensitivity. Three clinical syndromes associated with insect hypersensitivity were described as follows: 1) horses with lesions on face, ears, mane, withers, rump and tail; 2) horses with lesions on face, ears, intermandibular space, chest, belly and groin, and 3) those with a combination of dorsal and ventral lesions.
Carbonic anhydrase III in equine tissues and sera determined by a highly sensitive enzyme‐immunoassay
Authors: NISHITA T. , MATSUSHITA H.
Published: April 2010

A sensitive sandwich enzyme immunoassay (EIA) for measuring equine carbonic anhydrase III (CA‐III) was established using a microplate as a solid‐phase and peroxidase as a labelling enzyme. The assay can detect concentrations as low as 5 ng/ml using 20 μl of sample sera. Within‐run coefficients of variation obtained using standard equine CA‐III were less than 5 per cent. CA‐III levels in equine serum ranged from 5 to 50 ng/ml (n=370), and apparently abnormal levels of CA‐III from 100 to 1900 ng/ml (n=27) were observed. The concentrations of immunoreactive CA‐III in the extracts of various equine tissues were also determined; it was present at high concentrations in skeletal muscle and liver and to a much lesser extent in the thymus. Other tissues contained much smaller amounts.
Effects of three anthelmintic schedules on the incidence of colic in horses
Authors: UHLINGER CHRISTINE
Published: April 2010

Four privately owned herds (25 to 49 animals per herd) were used in a five‐year trial designed to evaluate the effect of anthelmintic schedules on the incidence of colic. These herds had been treated bi‐monthly with non‐ivermectin, non‐benzimidazole drugs for two years before the trial. Prior parasitological studies showed that they had substantial pre‐treatment faecal egg counts (900 to 2200 eggs per gramme), and that they were infected with benzimidazole‐resistant cyathostomes. In Years 1 and 2 of the trial, all herds (A, B, C, D) were treated bi‐monthly with non‐ivermectin anthelmintics (Schedule I). In Years 3 to 5, Herd A received monthly non‐ivermectin anthelmintics (Schedule II) and Herd C was treated with bi‐monthly ivermectin (Schedule III). Herd B was treated with Schedule II in Years 3 and 4 and Schedule III in Year 5. Herd D was maintained on Schedule I throughout the study period. In each herd, the incidence of colic, while on Schedule I, was compared to the incidence while on Schedule II or III. The risk of colic for horses on Schedule I was 2.61 to 13.04 times that of the same horses while on Schedule II and 2.27 to 9.64 times that of the same horses while on Schedule III. In Herd D, treated according to Schedule I for five years, the incidence of colic did not vary significantly throughout the study period. More effective anthelmintic treatment schedules decreased the incidence of colic in these herds, supporting the conclusion that bimonthly treatment with non‐ivermectin drugs may not maximise horses' health in all management conditions. Further, the data suggest that a high proportion of colics seen in this study had a parasitic aetiology, and that cyathostomes, rather than large strongyles, were the primary cause of disease.
The effects of phenylbutazone on the intestinal mucosa of the horse: a morphological, ultrastructural and biochemical study
Authors: MESCHTER CAROL L. , GILBERT M. , KROOK L. , MAYLIN G. , CORRADINO ROBERT
Published: April 2010

Phenylbutazone, a non‐steroidal anti‐inflammatory drug known to produce intestinal erosions, was administered intravenously (13.46 mg/kg bodyweight) to 12 horses which were killed after 24, 48, 72 and 96 h. Eight untreated horses served as controls. Annular erosions in the duodenum and mucosal necrosis in the colon were seen after 48 h which progressed in severity. The erosions were characterised by sloughing of the surface epithelium, subepithelial cleft and bleb formation, necrosis of thelamina propria, degeneration of the walls of subsurface capillaries and microthrombosis. Large numbers of neutrophils with abundant fibrin and cellular debris were present at the erosion sites. Ultrastructurally, there was swelling of the endothelium of capillaries and small vessels, and of pericyte and smooth muscle cytoplasm in arterioles. In capillaries and post capillary venules, the endothelium ranged from swollen to lysed and necrotic. Extensive extravasation of erythrocytes and oedema were seen. These lesions were not seen in the control horses. Phenylbutazone produces a microvascular injury associated with the formation of duodenal and colonic erosions in horses. The duodenal and colonic mucosa were assayed at 48 and 96 h for prostacyclin and PGE2. There was no statistically significant difference between prostaglandin levels in the mucosa of control and treated horses. It was concluded that there was no correlation between mucosal prostaglandin levels and intestinal erosions after 48 h.
Haemodynamic effects of small volume hypertonic saline in experimentally induced haemorrhagic shock
Authors: SCHMALL L. M. , MUIR W. W. , ROBERTSON J. T.
Published: April 2010

A comparison of the haemodynamic benefits of small volume hypertonic saline (2,400 mOsm/litre) versus isotonic saline (300 mOsm/litre) was conducted in 12 adult horses using a haemorrhagic shock model. The horses were anaesthetised and intravascular catheters placed for the measurement of haemodynamic data. Mean systemic arterial pressure was then reduced to 50 to 60 mmHg by controlled haemorrhage and maintained at that level for 40 mins. Cardiac output, stroke volume, mean systemic arterial pressure, plasma volume and urine production decreased significantly following blood loss. Hypertonic or isotonic saline was administered randomly by intravenous infusion and haemodynamic data recorded for a 2 h period. Treatment with hypertonic saline produced rapid elevations in cardiac output, stroke volume, mean systemic and pulmonary arterial pressures, cardiac contractility and urine output, and was accompanied by expansion of the plasma volume. The changes in cardiac output and stroke volume were maintained for the duration of the recording period, whereas increases in mean systemic arterial pressure were not as remarkable. Infusion of isotonic saline caused only transient increases in cardiac output and mean systemic and pulmonary arterial pressure, and cardiac output; urine output and plasma volume did not change. This study indicates that hypertonic saline produces haemodynamic improvements in experimentally induced haemorrhagic shock in horses.
Haematological, serum electrolyte and blood gas effects of small volume hypertonic saline in experimentally induced haemorrhagic shock
Authors: SCHMALL L. M. , MUIR W. W. , ROBERTSON J. T.
Published: April 2010

The effects of treatment with small volume hypertonic (2400 mOsm/litre) and isotonic (300 mOsm/litre) saline on serum electrolyte and biochemical concentrations, haemograms and blood gases were evaluated in 12 horses using a haemorrhagic shock model. Intravascular catheters were placed surgically for sample collection prior to anaesthesia. Controlled haemorrhage was initiated and continued until mean systemic pressure reached 50 to 60 mmHg. Hypertonic or isotonic saline (2 litres) was administered by intravenous infusion and data collected for 2 h. Following haemorrhage, packed cell volume (PCV), haemoglobin, blood glucose concentrations and erythrocyte numbers increased whereas plasma total protein and albumin concentrations decreased. Infusion of hypertonic saline resulted in a further decrease in total protein and albumin concentrations. Glucose concentrations and other haematological variables were unaffected. Isotonic saline administration did not affect electrolyte, total protein or albumin concentrations. Concentrations of sodium and chloride were unaffected by hypotension but increased significantly following hypertonic saline treatment, exceeding normal values during the immediate post treatment period. Serum osmolality increased concurrently. No significant changes in arterial and venous blood gas values were observed with haemorrhage or isotonic saline treatment. A transient decrease in arterial and venous blood pH and a sustained decrease in venous bicarbonate and base excess concentrations occurred following hypertonic saline administration. No significant increases in any serum biochemical concentrations occurred during hypotension or following infusion of either isotonic or hypertonic saline. These results demonstrate that small volume hypertonic saline can be administered safely to horses without producing extreme changes in electrolyte concentrations, blood gases or haematological parameters.
Atelectasis causes gas exchange impairment in the anaesthetised horse
Authors: NYMAN G. , FUNKQUIST B. , KVART C. , FROSTELL C. , TOKICS L. , STRANDBERG Å. , LUNDQUIST H. , LUNDH B. , BRISMAR B. , HEDENSTIERNA G.
Published: April 2010

The anatomical basis of gas exchange impairment in the anaesthetised horse was studied by computerised tomography (CT; three Shetland ponies) and morphological analysis (one pony and three horses). By means of CT, densities were seen in dependent lung regions early during anaesthesia, both with spontaneous breathing and with mechanical ventilation. The densities remained for some time where they had initially been created when the animal was turned from dorsal to sternal recumbency. Deep insufflation of the lungs reduced the dense area. Gas exchange was impaired roughly in proportion to the dense area. On histological analysis, the densities were atelectatic and congested with blood. Gravimetry showed no more extravascular water per unit lung tissue in the atelectatic than in the ‘normal’ regions, and the blood content was increased only slightly. It is concluded that the horse develops atelectasis in dependent lung regions early during anaesthesia in dorsal recumbency, and that atelectasis is the most likely explanation for the large shunt and impaired arterial oxygenation regularly seen during anaesthesia.
Doxapram infusion during halothane anaesthesia in ponies
Authors: TAYLOR POLLY M.
Published: April 2010

Doxapram, 0.05 mg/kg bodyweight/min, was infused during the second hour of 2 h halothane anaesthesia in six ponies. Two of the ponies were anaesthetised on a second occasion as controls and given 5 per cent dextrose in place of the doxapram. Respiratory depression typical of halothane anaesthesia in ponies developed in the first hour of anaesthesia and continued during the second hour in the control animals. During doxapram infusion arterial carbon dioxide tension decreased and pH increased. Arterial blood pressure increased but there was no change in pulse rate, the electrocardiogram or arterial oxygen tension. Anaesthesia lightened during doxapram infusion necessitating an increase in the vapouriser setting in order to prevent arousal. Recovery from anaesthesia appeared unaffected by the doxapram infusion.
The influence of photoperiod on gonadotrophin‐releasing hormone stimulated luteinising hormone release in the anoestrous mare
Authors: NEQUIN LYNN G. , KING SHERYL S. , MATT KATHLENE S. , JURAK RITA C.
Published: April 2010

The transition from anoestrus to oestrus in mares is controlled by photoperiod. The present study examined whether additional daylength would accelerate the mares' response to gonadotrophin‐releasing‐hormone (GnRH). Nine anoestrous mares were placed under ambient or artificial long lighting on 7th January. The four month experimental period was divided into a three‐day sequence which was repeated at 21 day intervals. Ovaries were palpated rectally on Day 1; saline was injected (1 ml intravenously [iv]) on Day 2; GnRH was administered (0.59 μg/kg bodyweight iv) on Day 3. Blood was taken at −60, 0, 15, 30, 60 and 120 mins relative to saline or GnRH treatment. Serum luteinising hormone (LH) was determined by a homologous equine radioimmunoassay (RIA). Several criteria were employed to define a positive response to GnRH and the results were analysed by Fisher's exact probability test. Treatment with artificial light allowed a response to GnRH within six weeks whereas the mares in ambient lighting took 12 weeks to respond to GnRH. The advancement in the time of response to GnRH under the long photoperiod could be related to changes in pituitary LH content, accelerated follicular activity or alterations in other brain‐pituitary hormone levels.
Cardiopulmonary effects of epidurally administered xylazine in the horse
Authors: LEBLANC P. H. , EBERHART SUSAN W.
Published: April 2010

This study was designed to determine whether the epidural administration of an alpha2agonist, xylazine, would produce measurable changes in arterial blood pressure, electrocardiographic (ECG) activity and arterial blood gas values in horses. Six horses were given each of four treatments: epidural xylazine, intravenous xylazine, epidural lidocaine and epidural saline. A carotid artery catheter was used to measure arterial blood pressure and to collect samples for blood gas analysis before treatment and at intervals post treatment. Heart rate, arterial pressures, ECG activity and respiratory rate were recorded at the same intervals. No significant changes were recorded between time intervals or between individual treatments. It was concluded that this method of xylazine administration to horses produced potent caudal analgesia without measurable cardiopulmonary effects.
An investigation of the second heart sound in the normal horse
Authors: WELKER F. H. , MUIR W. W.
Published: April 2010

The second heart sound was evaluated in conscious, normal horses using intracardiac and external sound detection devices and echocardiography. The second heart sound (S2) in the normal horse is single or split by a narrow interval, not usually detected by external phonocardiographic evaluation. Splitting of S2 was classified as normal (aortic [A2] preceding pulmonic [P2] components) in 66.7 per cent and reversed (P2 preceding A2) in 33.3 per cent of the horses studied. Normal splitting appears to result from lower impedance of the pulmonary vasculature delaying the onset of P2. Reverse splitting appears to result from a delay in A2 resulting from prolongation of PEP and LVET. There does not appear to be variation in splitting of S2 due to respiration based on the cases in which this was measured.
Effects of time of insemination relative to ovulation on pregnancy rate and embryonic‐loss rate in mares
Authors: WOODS JEANINE , BERGFELT D. R. , GINTHER O. J.
Published: April 2010

The effects of pre‐ovulatory and post ovulatory insemination on pregnancy rate and embryonic‐loss rate were studied in 268 mares in two experiments. Within each experiment mares were randomised within replicates as follows: to be inseminated on the day the pre‐ovulatory follicle reached 35 mm (pre‐ovulatory group), to be inseminated on the day of ovulation (Day 0 group), and to be inseminated on the day after ovulation (Day 1 group). Ultrasonic pregnancy diagnoses were performed on Days 11, 12, 13 and 14 (Experiment 1) and Days 11, 12, 13, 14, 15, 20 and 40 (Experiment 2). Combined for the two experiments, pregnancy rates were different (P<0.01) among the three groups. For Experiment 2, pregnancy rate within the pre‐ovulatory group was lower (P<0.05) for insemination 4 days or more before ovulation than for up to 3 days before ovulation. Pregnancy rate was lower (P<0.05) for the Day 0 group than for the pre‐ovulatory group inseminated up to 3 days before ovulation. In Experiment 2, ovulation was detected by examinations every 6 h; pregnancy rate was greater (P<0.05) for mares inseminated 0 to 6 h after ovulation than for mares inseminated at 18 to 24 h. No pregnancies occurred when mares were inseminated 30 h or more after ovulation. The mean day of first detection of the embryonic vesicle was different (P<0.0001) among the three groups. Diameter of embryonic vesicle averaged over Days 11 to 15 also differed (P<0.0001) among groups. The rate of embryonic loss (Experiment 2) between day of first detection of the conceptus and Day 40 was greater (P<0.05) for the Day 0 group than for the pre‐ovulatory group. Insemination up to 12 h post ovulation resulted in pregnancy rates equivalent to those for pre‐ovulatory insemination. Thereafter, the pregnancy rates diminished with no pregnancies occurring after 30 h. Embryonic vesicles were smaller and embryonic‐loss rate was greater for mares inseminated after ovulation.
Inflammatory components in uterine fluid from mares with experimentally induced bacterial endometritis
Authors: PYCOCK J. F. , ALLEN W. E.
Published: April 2010

Exudate and uterine flushings were collected at either 30, 60, 120 or 240 mins after intrauterine infusions ofStreptococcus zooepidemicusin genitally normal mares during oestrus. Uteri were also flushed without prior induction of endometritis. Protein concentrations in exudate and flushings increased with time and exudate pH decreased with time; the pH of flushings did not alter. Lysozyme and lactate dehydrogenase were present in flushings from non‐infected uteri, but concentrations increased with time after infection. Immunoreactive prostaglandin E2 was undetectable before infection, but concentrations rose after infection. No neutrophils were present in non‐infected flushings but, by 30 mins, there were significant (P<0.01) neutrophil numbers in exudate and flushings; thereafter numbers increased, particularly in exudate. Acute endometritis resembled acute inflammation at other sites in the horse and a significant response had occurred by 30 mins after experimental infection.
The effects of copper supplementation on the prevalence of cartilage lesions in foals
Authors: KNIGHT DEBRA A. , WEISBRODE S. E. , SCHMALL L. M. , REED S. M. , GABEL A. A. , BRAMLAGE L. R. , TYZNIK W. I.
Published: April 2010

The potential role of dietary copper in the development of cartilage defects in foals was investigated. Twenty‐one mares were fed rations containing 13 ppm copper (CuC, control) or 32 ppm copper (CuS, supplemented) during the last three to six months of gestation and first three months of lactation. Their foals were fed pelleted concentrate containing 15 or 55 ppm Cu and were destroyed at 90 (5 CuC and 5 CuS foals) or 180 (6 CuC and 5 CuS foals) days. Focal cartilage lesions were found at multiple sites on necropsy. In foals killed at 90 days, there were over twice (9 versus 4) as many lesions of osteochondrosis and more than four times (9 versus 2) as many articular lesions of osteophyte formation or thinning in CuC foals compared with CuS foals. These differences were due predominantly to a higher number of lesions in one CuC foal. Two 90‐day CuC foals had osteochondrosis of articular‐epiphyseal (A‐E) complex, one with thickenings and separation from subchondral bone and one with subchondral fibrosis. One 90‐day CuS foal had a cartilage thickening of the A‐E complex in the tibiotarsal joint with separation from subchondral bone. In foals killed at 180 days, there were seven times more articular lesions (21 versus 3) of osteophyte formation or thinning, nearly twice as many lesions of osteochondrosis (13 versus 7) in the physis and over five times as many involving the A‐E complex (11 versus 2) in six CuC foals compared with five CuS foals. Thirteen lesions of osteochondrosis in the A‐E complex had separation of the thickened cartilage from the subchondral bone, with nine exhibiting subchondral fibrosis. These were observed in 180‐day CuC foals only. Lesions of osteochondrosis with separation of cartilage from subchondral bone were not observed in CuS foals. Supplementation of dietary copper to mares during late stage pregnancy and to their foals from 90 to 180 days of age appears to reduce the prevalence and severity of osteochondrosis and other developmental cartilage lesions in the foals, compared with foals and their dams fed slightly above National Research Council recommended levels.
Hordenine: pharmacology, pharmacokinetics and behavioural effects in the horse
Authors: FRANK M. , WECKMAN T. J. , WOOD T. , WOODS W. E. , TAI CHEN L. , CHANG SHIH‐LING , EWING A. , BLAKE J. W. , TOBIN T.
Published: April 2010

Hordenine is an alkaloid occurring naturally in grains, sprouting barley, and certain grasses. It is occasionally found in post race urine samples, and therefore we investigated its pharmacological actions in the horse. Hordenine (2.0 mg/kg bodyweight [bwt]) was administered by rapid intravenous (iv) injection to 10 horses. Typically, dosed horses showed a flehmen response and defecated within 60 secs. All horses showed substantial respiratory distress. Respiratory rates increased about 250 per cent and heart rates were approximately double that of resting values. All animals broke out in a sweat shortly after iv injection, but basal body temperature was not affected. These effects were transient, and the animals appeared normal within 30 mins of dosing. Treated horses were tested in a variable interval responding apparatus 30 mins after dosing and no residual stimulation or depressant effects of hordenine were apparent. Animals dosed orally with 2.0 mg/kg bwt of hordenine showed no changes in heart rate, respiratory rate, basal body temperature or behaviour. After iv injection of hordenine, (2.0 mg/kg bwt) plasma reached a maximum value of about 1.0 μg/ml, and declined thereafter in a biexponential fashion. Kinetics of plasma concentration satisfied the concept of a two compartment open system, with an α‐phase half‐life of about 3 mins, and a ß‐phase half‐life of about 35 mins. Total urinary concentrations of hordenine (free and conjugated) peaked at about 400 μg/ml, and then declined exponentially to background levels by 24 h after dosing. Oral administration of hordenine (2.0 mg/kg bwt) showed peak plasma levels of about 0.15 μg/ml 1 h after dosing, followed by a slow multi‐exponential decline in blood levels of the drug. Total urinary concentrations of hordenine (free and conjugated) peaked at about 200 μg/ml, remained at this level for about 8 h, and then declined to background levels. Plasma levels of hordenine were reflected by a kinetic model which assumed very slow absorption of hordenine from the gastrointestinal tract and no effect on behaviour, heart rate or respiratory rate were noted after oral administration. Because of the low plasma levels, it would appear to be particularly difficult to obtain a pharmacological effect of hordenine after oral administration.
The distribution of ventilation‐perfusion ratios in the lungs of a dysmature foal
Authors: STEWART JENNIFER H. , ROSE R. J. , YOUNG I. H. , COSTAS L.
Published: April 2010

The distribution of ventilation‐perfusion (VA/Q) ratios, before and after 100 per cent oxygen, was studied in an induced‐premature foal at 4 h and again at eleven days of age, using the multiple inert gas elimination technique. The major finding was an absence of low VA/Q ratios when breathing air, indicating that low PaO2, in the neonatal period was totally attributable to the right‐to‐left shunt. At 4 h of age the PaO2 was 5.48 kPa and the right‐to‐left shunt represented 33.4 per cent of the cardiac output. At eleven days of age the PaO2 was 9.76 kPa and right‐to‐left shunt was 10.1 per cent of cardiac output. At both ages there was a separate high mode where ventilation was greatly in excess of blood flow but at neither age were units with low VA/Q ratios present. Oxygen breathing for 40 mins did not increase the right‐to‐left shunt, but at eleven days right‐to‐left shunt decreased when 100 per cent oxygen was administered.
Prolongation of xylazine/ketamine induced recumbency time with temazepam in horses
Authors: MATTHEWS NORA S. , DOLLARS N. S. , YOUNG D. B. , SHAWLEY R. V.
Published: April 2010

Short term anaesthesia induced with xylazine and ketamine was compared to a combination of xylazine, ketamine and temazepam (a benzodiazepine) in six adult horses. Duration of recumbency was significantly prolonged when temazepam was administered with xylazine and ketamine. No significant differences in heart rate, respiratory rate, blood pressure or arterial pH, pCO2and pO2were seen between the xylazine and ketamine combination plus temazepam, and xylazine and ketamine combination only treated horses.
The action of low dose endotoxin on equine bowel motility
Authors: KING J. N. , GERRING E. L.
Published: April 2010

Post operative ileus (POI) is a common and serious complication of colic surgery in the horse. There is a high correlation between the incidence of POI and the presence of ischaemic bowel, suggesting a role for endotoxin. 0.1μg/kg endotoxin was administered intravenously to six ponies with chronically implanted gastrointestinal electromechanical recording devices. It produced profound disruption of normal fasting bowel motility patterns, with an inhibition of gastric contraction amplitude and rate, left dorsal colon contraction product and small colon spike rate. In the small intestine an increase in abnormally arranged regular activity and a decrease in irregular activity was observed. There was no significant prolongation in stomach to anus transit time as assessed by the passage of plastic spheres. The bowel motility patterns induced by endotoxin could be mimicked by the intravenous infusion of PGE2and less potently by PGI2(prostacyclin), but not by PGF2α. This study provides evidence that systematic endotoxin present in clinical cases of colic may play a role in the pathogenesis of equine ileus. The acute effects of endotoxin on bowel motility appear to be mediated indirectly by prostaglandins, and the inhibitory effects may be mediated mainly by PGE2.
Effects of slow infusion of a low dosage of endotoxin on systemic haemodynamics in conscious horses
Authors: CLARK E. SUSAN , GANTLEY B. , MOORE J. N.
Published: April 2010

The effects of intravenous (iv) infusion of endotoxin for 60 mins at a cumulative dosage of 0.03 μg/kg bodyweight on systemic arterial, right atrial and pulmonary arterial pressures, heart rate, cardiac output, and derived pulmonary vascular resistance and total peripheral vascular resistance were compared to the effects of iv infusion of saline solution in four healthy horses. Heart rate was increased significantly after endotoxin infusion, although diastolic arterial pressure, systolic arterial pressure, electronically averaged arterial pressure, cardiac output, total peripheral resistance, and right atrial pressure did not change significantly. Average pulmonary arterial pressure was increased significantly by endotoxin infusion. This was accompanied by a trend toward increased diastolic pulmonary arterial pressure (P=0.1), systolic pulmonary arterial pressure (P=0.08) and pulmonary vascular resistance (P=0.07). These results suggest that low dosages of endotoxin produce pulmonary hypertension without causing hypotensive, hypodynamic shock.
Proximal suspensory desmitis: clinical, ultrasonographic and radiographic features
Authors: DYSON SUE
Published: April 2010

Clinical, ultrasonographic and radiographic features of proximal suspensory desmitis in the forelimb and the hindlimb are described. Acute cases may present with slight, localised, oedematous swelling, heat, distension of the medial palmar (plantar) vein and/or pain, whereas chronic cases or those rested immediately after onset of lameness usually have no detectable clinical signs suggestive of the source of pain. In these cases local analgesia is required to identify pain in the proximal metacarpal (metatarsal) region. Transverse ultrasonographic images of the suspensory ligament usually yield the most information and a variety of abnormalities of the proximal suspensory ligament have been identified including i) enlargement ii) poor definition of one or more of the margins of the suspensory ligament, especially dorsally iii) a well circumscribed, central hypoechoic area iv) one or more poorly defined hypoechoic areas, central or more peripheral v) a larger area of diffuse decrease in echogenicity (such lesions were seen most commonly in the hindlimb and appeared to warrant a more guarded prognosis than focal lesions). Radiographic abnormalities were identified in hindlimbs more often than in forelimbs and were usually seen in a dorsopalmar (dorsoplantar) view, and/or a lateromedial projection. Radiographic abnormalities included sclerosis of the trabeculae, a change in orientation of the trabeculae and entheseophyte formation. The most extensive radiographic abnormalities were seen together with an ultrasonographic type v lesion. The prognosis for return to full athletic function and sustained future soundness was better for forelimbs than hindlimbs, especially if the lesion, identified ultrasonographically, resolved.
Low dose calcium heparin in horses: plasma heparin concentrations, effects on red blood cell mass and on coagulation variables
Authors: GERHARDS H.
Published: April 2010

Low dose calcium heparin was administered subcutaneously at 12 hourly intervals to six healthy horses at an initial dose of 150 iu of heparin/kg bodyweight (bwt) and at a maintenance dose of 120 iu/kg bwt. All injections were given at 0900 and 2100 h. Blood samples for monitoring plasma heparin concentrations were obtained prior to, at 2 hourly intervals for 84 h (treatment period), and at Hours 24, 32, 48 and 96 of the control period. Blood samples for monitoring red blood cell (RBC) mass, plasma antithrombin III activity (AT III), activated partial thromboplastin time (APTT), and thrombin time (TT) were taken at 8 hourly intervals during the treatment period and at all of the Control Period Hours. Mean plasma heparin concentrations increased significantly (P<0.01) from 2 h after the first to 32 h after the last (seventh) injection. Mean values corresponding to the desired range of heparin in plasma (0.05 to 0.20 iu/ml) were achieved at 21 h after initiation of heparin treatment and were maintained during the following 81 h. Great individual variations in the sensitivity to heparin among horses, cumulation of heparin in plasma with prolonged administration and a marked circadian periodicity in the disposition of heparin affected actually measured plasma heparin values. A chronodiagram revealed peak values around 1300 h, trough values around 0500 h. The peak‐trough difference amounted to about 50 per cent. Increasing plasma heparin concentrations were associated with erratic prolongations of mean APTT and TT values. The AT III curve was not affected significantly. Low dose heparin treatment induced significant RBC mass depletion by about 30 to 35 per cent and agglutination of erythrocytesin vitroin healthy horses. In a splenectomised, otherwise healthy pony, given large doses of heparin, only a minor decrease in the RBC mass was evident. The RBC indices of the horses and the pony were not significantly altered. Four days after cessation of heparin administrations all values were within the baseline range. The agglutination could be reversed by adding trypsin to the sample, but not by neutralising heparin in the sample or by incubation of washed, agglutinated cells with plasma from an untreated horse. Incubation of washed erythrocytes from an untreated horse with plasma from a heparinised horse did not produce RBC agglutination. Other than some degree of pale mucous membranes no clinically detectable signs were attributable to the heparin‐induced agglutination‐anaemia phenomenon. The outlined heparin regimen may be useful for efficacious low‐dose heparin treatment in horses.
Assessment of an immunoturbidimetric method for measuring equine serum haptoglobin concentrations
Authors: KENT JOYCE E. , GOODALL JANE
Published: April 2010

Serum haptoglobin was measured by immunoturbidity in Thoroughbreds stabled in three Newmarket yards for nine months. The mean serum haptoglobin value for horses housed in Stable 1 was 1.43 ± 0.68 g/litre, similar to values in grazing adult ponies. The mean monthly haptoglobin values remained constant. For horses in Stable 2 there was an increase in serum haptoglobin values in June and July whereas, in Stable 3, the increases early in the training season were associated with an increase in serum viral titres. In equine serum, haptoglobin values estimated in g/litre by immunoturbidimetry were twice the haemoglobin binding capacity (HbBC). The correlation coefficient, between the methods, exceeded 0.96. Surgical interference caused a 2‐ to 3‐fold increase in serum haptoglobin, with levels peaking between three and five days post surgery. The concomitant presence of haematomata following surgical interference (castration) resulted in the disappearance of haptoglobin from the circulation. There was no significant increase in serum haptoglobin levels following vaccination of Thoroughbreds against influenza and tetanus. However inhalation of influenza virus by vaccinated and non‐vaccinated ponies resulted in a 2‐ to 3‐ fold increase in both groups of ponies, peaking seven to 10 days post infection. Serum haptoglobin proved to be a useful indicator of infection/ inflammation and haemolytic disease in the horse and could be used to monitor the health status of stabled Thoroughbreds.
Antithrombotic actions of aspirin in the horse
Authors: CAMBRIDGE H. , LEES P. , HOOKE R. E. , RUSSELL C. S.
Published: April 2010

The antithrombotic effects of aspirin at two dose rates (4 mg/kg and 12 mg/kg bodyweight [bwt]) were evaluated in normal, healthy ponies by measuring template bleeding time. Inhibition of platelet aggregation in response to adenosine diphosphate (ADP) and collagen was evaluated and cyclo‐oxygenase activity was monitored by radioimmunoassay of thromboxane B2(TXB2), the stable metabolite of thromboxane A2(TXA2). TXB2was measured in serum and platelet rich plasma. Bleeding time was prolonged significantly until 48 h after treatment at 12 mg/kg bwt and until 4 h at the lower dose rate. Synthesis of TXB2and collagen induced aggregation were diminished for much greater periods with similar results at each of the dose rates. The prolonged effects of aspirin on platelet function occurred in spite of a very short plasma half‐life of aspirin, because of its irreversible action on platelet cyclo‐oxygenase. The results show that low dose aspirin has a potential role in antithrombotic therapy in horses although the relationship between skin bleeding time in normal horses and improvement of clinical conditions requires further research and evaluation in clinical trials. TXB2measurement appears to overestimate the duration of antithrombotic effects of aspirinin vivo.
Clinical evaluation of poor performance in the racehorse: the results of 275 evaluations
Authors: MORRIS ELISABETH A. , SEEHERMAN H. J.
Published: April 2010

A clinical sports medicine evaluation was applied to 275 racehorses with a history of poor racing performance. The poor performance evaluation included a) general physical examination and basic laboratory screening; b) respiratory examination including auscultation, thoracic radiographs, ventilation‐perfusion lung scintigraphy and upper airway endoscopy at rest and during maximal treadmill exercise c) examination of the musculoskeletal system including lameness examination, video gait analysis at high speed, post exercise serum chemistry to identify obvious as well as sub‐clinical myopathies, high detail radiography and nuclear scintigraphy; d) cardiac examination including auscultation, electrocardiographic analysis during strenuous exercise and, when indicated, echocardiography; and e) a standardised exercise stress test entailing the measurement of oxygen consumption, carbon dioxide production, venous blood lactate concentration and heart rate during sequentially increasing running speeds on the high speed treadmill. The choice of diagnostic methodologies utilised were tailored to each individual in order to determine most efficiently the abnormalities contributing to inadequate racing performance. The results of this clinical evaluation showed that 1) many of the diagnoses were subtle requiring the use of sophisticated diagnostic equipment including scintigraphy and dynamic evaluation of the horse exercising on the high speed treadmill and 2) 84 per cent of the horses were diagnosed as suffering from more than one problem leading to the supposition that inadequate athletic performance is often caused by a constellation of abnormalities requiring a comprehensive approach to diagnosing decreased athletic capability.
Characterisation and distribution of epidermal growth factor receptors in equine hoof wall laminar tissue: comparison of normal horses and horses affected with chronic laminitis
Authors: GROSENBAUGH D. A. , HOOD D. M. , AMOSS M. S. , WILLIAMS J. D.
Published: April 2010

Epidermal growth factor (EGF) receptors were detected in plasma membrane preparations of equine hoof wall laminar tissue at concentrations comparable to that of equine liver. Scatchard analysis of the equilibrium binding data suggested the presence of two classes of EGF binding sites in most of the controls (plasma membranes from clinically normal horses); a high‐affinity class and a more numerous low‐affinity class. The dissociation constant of the low‐affinity class of EGF‐specific receptors (KD=1 × 10−9M) is in reasonable agreement with other values established for the EGF receptor. The variability between individual estimates for the KDof the high‐affinity receptor class precluded an accurate estimate for those sites. A possible explanation is discussed. The high‐affinity binding sites were uniformly absent in plasma membranes prepared from horses affected by chronic laminitis. Autoradiographic analysis localised the EGF receptors primarily to the secondary epidermal laminae, with an apparent greater density over the proliferative basal keratinocytes. Little label was associated with the dermal or the keratinised primary epidermal laminae. Tissue from horses with chronic laminitis had EGF receptors located uniformly over the hyperplastic epidermal keratinocytes. These data suggest that an EGF‐mediated response may be involved in the hyperproliferative response that is characteristic of chronic laminitis.
Exercise induced hormonal and metabolic changes in Thoroughbred horses: effects of conditioning and acepromazine
Authors: FREESTONE J. F. , WOLFSHEIMER K. J. , KAMERLING S. G. , CHURCH G. , HAMRA J. , BAGWELL C.
Published: April 2010

Nine Thoroughbred horses were assessed to determine the normal response of insulin, glucose, Cortisol, plasma potassium (K) and erythrocyte K through conditioning and to exercise over 400 and 1,000 m. In addition, adrenaline, noradrenaline, Cortisol, plasma K, erythrocyte K and L‐lactate concentrations were evaluated in response to maximal exercise with and without the administration of acepromazine. Conditioning caused no obvious trends in plasma K, erythrocyte K, insulin or glucose concentration. Serum Cortisol increased (P < 0.05) from the initial sample at Week 1 to Weeks 4 and 5 (attributed to a response to training), and then decreased. During conditioning, three horses had low erythrocyte K concentrations (< 89.3 mmol/litre). Further work is needed to define the significance of low erythrocyte K concentrations in the performance horse. In all tests maximal exercise increased plasma K, glucose and Cortisol concentrations, whereas insulin and erythrocyte K concentrations decreased. Thirty minutes following exercise, plasma K and erythrocyte K concentrations returned to resting values, whereas glucose and Cortisol concentrations continued to increase and the insulin concentration also was increased. The magnitude of the changes varied for pre‐conditioned vs post‐conditioned exercise tests and the duration of exercise. The administration of acepromazine prior to exercise over 1,000 m failed to alter the circulating noradrenaline and adrenaline concentrations in anticipation of exercise or 2 mins following exercise. Acepromazine administration, however, did cause lower L‐lactate concentration 2 mins (P < 0.03) and 30 mins (P ≤ 0.005) following exercise. Also, erythrocyte K showed a delayed return to baseline levels at 30 mins post exercise. Further evaluation of these trends may help explain the beneficial role acepromazine plays in limiting signs of exertional rhabdomyolysis when administered prior to exercise.
A comparison of two techniques for arthrocentesis of the equine metacarpophalangeal joint
Authors: MISHEFF MARTHA M. , STOVER SUSAN M.
Published: April 2010

Because arthrocentesis of the metacarpophalangeal joint through the proximal palmar pouch may induce synovial haemorrhage, this study evaluated arthrocentesis through the lateral collateral sesamoidean ligament. The proximal palmar pouch and collateral sesamoidean ligament approaches were used in contralateral forelimbs to obtain paired initial synovial fluid samples from 16 horses 12 to 15 h before being killed. Synovial fluid samples also were collected from the same joints at necropsy and the subcutis, synovium and articular cartilage were evaluated. Metacarpophalangeal joint arthrocentesis through the collateral sesamoidean ligament yielded fewer haemorrhagic synovial fluid samples with less subcutaneous and synovial inflammation, and also yielded 2 ml of synovial fluid more often than arthrocentesis through the proximal palmar pouch.
Use of DNA fingerprinting in paternity analysis of closely‐related Exmoor ponies
Authors: HOPKINS B. , O'CONNELL F. M. , HOPKINS J.
Published: April 2010

DNA fingerprinting techniques were used to try to resolve the parentage of an Exmoor pony foal. Three young Exmoor ponies, one female and two males, shared a paddock and the female subsequently became pregnant. The two possible sires were three‐quarter siblings and were also half‐siblings to the dam. Southern hybridisation of Exmoor pony DNA with human mini‐satellite probes resolved the disputed parentage in spite of the fact that there was a 70 per cent band share between the individuals involved. Colt M6 was 2.06 times more likely to be the father than an uncle, and Colt M3 was 477 times more likely to be an uncle than the father.
Fusion of the distal intertarsal and tarsometatarsal joints in the horse using intraarticular sodium monoiodoacetate
Authors: BOHANON T. C. , SCHNEIDER R. K. , WEISBRODE S. E.
Published: April 2010

Six normal horses received 3 intra‐articular injections of sodium monoiodoacetate (MIA) in the distal intertarsal (DIT) and tarsometatarsal (TMT) joints of one hindlimb. Injections were at three week intervals, and post injection pain was controlled with routine administration of phenylbutazone for five days following each injection. All horses underwent a gradually increasing exercise programme consisting of walking and trotting beginning one week after the first injection and continuing for 24 weeks. All treated joints showed increasingly severe radiographic evidence of degenerative joint disease with time. Clinical signs were mild or absent during exercise. All treated joints showed radiographic and histological evidence of fusion 24 weeks after the first injection. Amount of radiographic fusion ranged from 54.49 per cent to 88.64 per cent of the joint space. Histologically, the joint space that appeared radiographically fused was filled mainly with woven and lamellar bone. Fibrocartilage and fibrous tissue was seen frequently in the transition between fused and unfused areas. Articular cartilage in unfused areas was thin, fibrillated, hypocellular and histochemically showed diminished proteoglycan content. Existing joint space was filled with fibrin and necrotic, acellular chondroid matrix. We conclude that MIA will produce fusion of the DIT and TMT joints of normal horses in 24 weeks, and may offer a relatively easy, inexpensive and non‐invasive treatment for distal tarsal osteoarthritis in the horse.