Natural infection with Dictyocaulus arnfieldi in pony and donkey foals

From June to October 1978 four pony mares and foals and two donkey mares and foals grazed a paddock contaminated with Dictyocaulus arnfieldi larvae. No signs of respiratory disease were seen in the foals but within 11 weeks of exposure to the paddock all six developed patent lungworm infections. In October 1978 one donkey and two pony foals were killed. At post mortem examination parasites in various stages of development and measuring up to 8 cm in length were found in the lungs. At this time the three surviving foals were stabled for the remainder of the experiment. Two of these ceased passing D arnfieldi larvae during the winter months but in one pony foal patency persisted until the study ended in August 1979. Patent lungworm infections were not seen in the pony mares, although two started to cough four to six weeks after starting to graze the infected paddock. One of the affected mares was killed in October 1978 when seven small (less than 7 mm) D arnfieldi were recovered. The other continued to cough until the end of the study over a year later.     

Effects of excess caloric fat feeding on the lipid metabolism in Shetland ponies

To investigate the influence of overweight and dietary fat supplementation on lipid and insulin glucose metabolism of Shetland ponies, eight Shetland pony geldings were fed a hypercaloric (30 MJ DE/150 kg bwt. and day) fat diet (10% fat as soybean oil) or a carbohydrate control diet for nine months until ponies gained an overweight of 15%. Afterwards oral glucose tolerance tests (oGTT; 5, 6 mmol/kg bwt.) were performed after a 12 hour fast and after a fast which led to an increase of plasma triglyceride concentrations to a threshold of 3 mmol/l (36-65 hrs.). Plasma concentrations of glucose, insulin, triglycerides and non esterified fatty acids (NEFA) were determined for 480 minutes after the glucose load. Ponys having had received the control diet tended to a higher insulin secretion in case of both oGTTs, whereas the glucose tolerance was similar in both groups but lower than in ponies of normal weight. During the oGTTs after fasting leading to the plasma triglyceride threshold, triglyceride concentrations decreased significantly (p < 0.05) faster and stronger in fat fed ponies. Additionally, fat fed pony showed significantly (p < 0.05) lower NEFA levels. The results of this study demonstrate a positive effect of fat feeding on the triglyceride clearance of overweight Shetland ponies.     

Influence of time of food administration on daily rhythm of total locomotor activity in ponies

The activity rhythm can be entrained by nonphotic cues, especially food availability. Daily feeding schedules can act as “Zeitgeber” to synchronize the circadian system. In this study, the authors evaluated the influence of different feeding schedules on the daily rhythm of total locomotor activity in ponies. Six clinically healthy Shetland ponies were kept under natural 12/12-h light/dark cycle and monitored during 4 different feeding schedules: fed twice (at 8 am and 8 pm), fasted, fed at 8 pm, fed at 8 am, and fed twice a day again. Water was available ad libitum. To record total activity, we equipped the animals with actigraphy-based data loggers (Actiwatch-Mini). Two-way analysis of variance revealed a significant main effect of the time of day and no effect of feeding schedules on the amount of total locomotor activity. Locomotor activity showed daily rhythmicity in all experimental conditions, with diurnal acrophase. The amplitude of the rhythms and their robustness statistically changed across all experimental conditions. Our findings support the theory that when given essentially free choice hay, the time of feeding did not entrain activity, and suggest that feeding behavior can influence the distribution of locomotor activity during a 24-hour period in ponies, with changes in the amplitude and robustness of the rhythm.     

Length of gestation periods of horses and ponies belonging to different breedsDurée de gestation des juments de différentes races de chevaux et de poneysTragezeiten von stuten verschiedener pferde- und ponyrassen

The mean gestation periods of mares belonging to different horse and pony breeds common in The Netherlands have been calculated using data from the birth registers of five stud-book societies. The following mean values have been determined: Fjord pony: 342.2; Haflinger pony: 341.3; Draught horse: 343.3; Shetland pony: 337.2; and Frisian horse: 337.7 days. The variation in the mean gestation period is greater in horses than in cows, sheep or pigs. Colts are carried a little longer than fillies. Differences between years are not significant, but differences between the various breeds have been determined. Shetland foals born before 1 June are carried longer than those born after 1 June. The gestation period for mares of this breed mated at 2 years, is significantly longer than for those mated at more than 2 years.The length of the gestation period in horses is possibly affected by physiological factors other than those influencing the gestation period in some other farm animals.     

Experimental Coxofemoral Replacement Hemiarthroplasty in the Pony

For the in vivo evaluation of hip joint prostheses that are developed for man, the suitability of the pony as an animal model has been studied. Human and custom made prostheses were implanted into 1 femur in each of 7 ponies to replace the femoral head. The surgical approach was through a caudolateral incision. The prosthesis was fixed in the femur with bone cement. Because of errors in the implantation technique and resulting lack of sufficient fixation 2 ponies as well as 1 control animal with an excision arthroplasty were unwilling or unable to stand. Rigid fixation of the implant was achieved in 3 ponies. They were returned to pasture after 8 days. A full return to a normal gait did not occur within an observation period of up to 3 months. All 3 ponies developed a dorsolateral coxofemoral luxation and pseudarthrosis within the first 10 days. A mismatch between the equine anatomy and human prosthesis geometry was thought to be the cause. We, therefore, believe that the pony does not provide a suitable model for the testing of human femoral joint implants. The results, however, indicate that coxofemoral surgery can be performed in the adult pony. For clinical reconstruction of joint function, a custom made total artificial hip joint might provide better results.     

Suppression of the pathogenic effects of Strongylus edentatus larvae with thiabendazole.

Four pony foals were inoculated with Strongylus edentatus infective larvae and on days 3 and 4 postinfection two of the ponies were treated with thiabendazole, each at the rate of 440 mg/kg of body weight. Total circulating eosinophil counts in untreated ponies increased to over 1700 per cu mm after the second week postinfection. In the treated ponies as well as in an uninfected untreated pony eosinophil counts did not increase beyond 100 per cu mm. At necropsy on day 35 postinfection the cecum, colon and omentum of treated ponies were normal and few tracks were present on the surface of the liver. In untreated ponies nodules were observed on the serosal surface of the cecum and right ventral colon and white foci and tracks were numerous on the surface of the liver. A total of 53 fourth stage larvac was recovered from the livers of the thiabendazole treated ponies and 1194 from the untreated ones.     

Long-term outcome of treatment of a squamous cell carcinoma of the foot by amputation of the distal limb in a pony

This report describes a rare case of squamous cell carcinoma (SCC) in a 10-year-old Shetland pony. The pony was presented for evaluation of a chronic, ulcerating mass of the foot associated with a nonweightbearing lameness of the right forelimb. Foot radiographs revealed an aggressive bone lesion with severe osteolysis of the distal phalanx. Amputation of the digit was performed under general anaesthesia at the level of the metacarpophalangeal joint using a palmar flap technique and a transfixation cast for protection of the stump. Avascular necrosis, infection and dehiscence of the stump occurred 3 weeks later and a second amputation was performed at the level of the proximal third of the third metacarpal bone. Histopathology revealed a squamous cell carcinoma. After healing of the stump, a prosthesis was fitted to the limb for improved ambulation of the pony. Two years after the amputation, telephone follow-up with the referring veterinarian and the owner, revealed that the pony was healthy and able to go out daily in a paddock with its prosthesis. SCC represents an unusual indication for limb amputation. Successful outcome is rarely reported in horses.     

Pathogenicity of equine herpesvirus 1 subtype 2 for foals and adult pony mares

Three pony mares and 4 pony foals were inoculated with a subtype 2 strain of equine herpesvirus 1. Foals had periods of fever 12 h and 2.5 days after inoculation and leukopenia, involving both neutrophils and lymphocytes, followed by leukocytosis. Mares had transient fever and leukopenia 24 hours after inoculation that were less severe than in foals. An increase in circulating virus-neutralizing antibody was seen in 2 of 3 inoculated mares, but not in foals. Attempts to isolate virus from blood were unsuccessful. These studies show that equine herpesvirus 1 subtype 2 is a mild pathogen for ponies and infection may result in inapparent clinical disease.     

Sequential mesenteric arteriography in pony foals during repeated inoculations of Strongylus vulgaris and treatments with ivermectin

Semiselective mesenteric arteriography was performed at regular intervals (inoculation weeks [IW] 0, 11, 18, and 24) in 9 of 10 pony foals raised to be free of parasites. Fifty infective larvae (L3) of Strongylus vulgaris were administered weekly for 4 weeks, then every 2 weeks through the 20th week. Three ponies were given ivermectin (oral paste, 0.2 mg/kg of body weight) treatment at IW 8, 16 and 24. Four ponies were inoculated, but did not receive ivermectin, and a third group of 2 ponies acted as uninoculated controls. Control ponies did not have gross or arteriographic lesions, whereas the inoculated untreated ponies had gross and progressive arteriographic lesions typical of verminous arteritis. Arteriographic lesions in the ivermectin-treated inoculated ponies were not as severe those in the untreated inoculated group, and there was either a partial resolution or a lack of progression of arteriographic lesions in all treated ponies. One untreated inoculated pony did not have progressive arterial lesions as did the 3 others in the group, and may develop resistance to the parasite.     

Use of DNA fingerprinting in paternity analysis of closely-related Exmoor ponies

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.     

A description of the motion of the navicular bone during in vitro vertical loading of the equine forelimb

Motion of the navicular bone might play a role in the development of navicular disease in horses but is difficult to asses. In the present study, 3-dimensional motion of this bone was determined using roentgen stereophotogrammetric analysis. Tantalum pellets were inserted, in vitro, in the bones of 6 forelimbs of mature Shetland ponies and kinematics were measured during vertical loading up to 2 kN. The motions of the navicular bone and coffin joint were limited to flexion/extension, there were no substantial out-of-plane motions. There was only little flexion between the navicular bone and the coffin bone, which was correlated (r = 0.66) with coffin joint flexion. There was substantial flexion between the navicular bone and the short pastern, which was highly correlated with coffin joint flexion (r = 0.97). We conclude that the navicular bone, generally, follows the coffin bone during coffin joint flexion, although there are small but consistent motions between the navicular bone and the coffin bone. These motions might play a role in the development of navicular disease in horses.     

Study of arterial blood pressure in newborn foals using an electronic sphygmomanometer

An electronic sphygmomanometer which functions on oscillometric principles, was used to measure arterial blood pressure in foals. Its accuracy was assessed by comparison with results obtained by direct measurement in anaesthetised pony foals, aged 34 to 64 days. Correlations between data obtained by the two methods were highly significant but the sphygmomanometric readings were consistently lower than those obtained by direct measurement. An equation was derived from the pooled values for mean, systolic and diastolic pressure measurements. This was used as a correction factor when the oscillometric method was employed in the field on Thoroughbred foals, during the first three days post partum, and on pony foals during the first day only. There were no significant differences between systolic, diastolic and mean values in Thoroughbreds on Days 1, 2 or 3 after birth. Measurements recorded on the first day after foaling were significantly lower (P less than 0.025) in ponies than in Thoroughbreds. Blood pressure measurements in Thoroughbreds and ponies were substantially higher than those reported previously using the ultrasonic Doppler technique.     

An anatomical study of the dorsal and ventral nasal conchal bullae and middle nasal conchae in normal Shetland ponies: Computed tomographic anatomical and morphometric findings

Equine paranasal sinuses are susceptible to inflammation. Insufficient drainage through the nasal passages and meatus may lead to the accumulation of inspissated purulent discharge. Particularly in ponies, these anatomical structures are suspected to be relatively small. To date, there are no reports considering the morphology of nasal conchal bullae in small horse breeds such as Shetland ponies. The aim of the present study was to evaluate the size of the conchal bullae and the medial nasal conchae of Shetland ponies and their relation to the skull dimension using computed tomography. Reconstructed images of healthy adult heads of Shetland ponies were used. Linear skull measurements as well as two cranial indices of the head dimensions were taken. Length, width and height of the dorsal and ventral conchal bullae and the medial nasal conchae were measured in relation to the skull and compared with the data of skulls of large breed horses. The anatomical proportions of pony heads were characterized by a smaller cranial index and a greater nasal index than those of large breed horses. Shetland ponies showed a longer cranial length compared with the nasal length. Heads are consistently smaller, and the relationship of the bullae to the head length was also smaller than those measured in large breed horses. A negative correlation between the head and bullae size was found. In conclusion, this study suggests that Shetland ponies have distinguishing proportions of the head. These findings are relevant for clinical examination and surgical treatment of equine sinus disease in those breeds.     

Studies on fenbendazole for treating lung and intestinal parasites in horses and donkeys

The efficacy of orally administered fenbendazole on lung and intestinal parasitism in equids was investigated in a mixed herd of pony mares, jenny donkeys and foals. A single dose of 7.5 mg fenbendazole/kg body weight effectively removed intestinal parasites from the ponies, donkeys and foals, but higher doses and repeated treatments failed to eliminate lungworm infections in donkeys. The finding of eosinophilia proved useful in detecting lungworm infections in donkeys.     

Immunoglobulin and peripheral B-lymphocyte concentrations in Fell pony foal syndrome

REASONS FOR PERFORMING STUDY: Fell pony foals are affected by a congenital fatal disease that leads to profound anaemia and immunodeficiency. Previous studies comparing healthy and affected foals have shown normal T-cell populations, but a severe B-lymphopenia. OBJECTIVES: To measure the levels of individual immunoglobulin subisotypes in normal and affected Fell ponies and correlate these levels with the number of peripheral B-lymphocytes. METHODS: Serum levels of individual immunoglobulin subisotypes were measured by ELISA and correlated with the number of peripheral B-lymphocytes (measured by flow cytometry). RESULTS: Affected foals had significantly reduced serum levels of IgM, IgGa, IgGb and IgG(T) that coincided with the normal reduction in maternally derived immunoglobulin in foals and, with the exception of IgGb, correlated strongly with the B-lymphopenia. CONCLUSIONS: These data suggest that affected foals are unable to produce their own immunoglobulins. Therefore, once maternal immunity has waned, it may be the lack of specific foal-derived immunoglobulin that gives rise to the clinical signs of immunodeficiency. POTENTIAL RELEVANCE: Measurement of IgM after age 4 weeks may provide a more accessible means of confirming the status of future affected Fell pony foals than the measurement of B-lymphocytes (a technique limited to a few specialist laboratories).     

Comparison of two control systems for cyathostome infections in the horse and further aspects of the epidemiology of these infections

The small strongylid infections of two groups of three yearling female Shetland ponies and one yearling Shetland tracer pony were studied. One group was set stocked from April to November and was treated monthly with 5 mg kg-1 albendazole from two days before turnout until July. The other group grazed similar pasture until July, was treated with 5 mg kg-1 albendazole and subsequently removed to pasture grazed by sheep from April to July. The tracer ponies were added to both groups in September. The efficacy of both methods was not completely satisfactory probably because of low efficacy of anthelmintic treatment. There were no significant differences between the cyathostome burdens of the two groups. A high proportion of the cyathostome populations of all ponies consisted of inhibited early third stage larvae (L3). The finding of low numbers of immature fifth-stage worms in the tracer ponies indicated that the considerable adult burdens in the permanent ponies originated from infection picked up before the tracer ponies were added. In the group which was removed to sheep pasture after treatment in July it was likely that the majority of the adult worm burden had been ingested as infective larvae before treatment.     

Cardiovascular, acid-base, electrolyte, and plasma volume changes in ponies developing alimentary laminitis.

Twelve Shetland ponies were fed a high-starch ration. Seven ponies which had a transitory metabolic acidosis developed laminitis 56 hours (+/- 3.5, SEM) after overfeeding. These ponies also developed persistent hypokalemia, hyperthermia, and increased heart rate 24 hours before the onset of lameness. Serum sodium, serum chloride, hematocrit, plasma volume, and blood volume were unchanged. At the onset of clinical signs of laminitis, cardiac output and blood pressure increased, but total peripheral resistance was unchanged. None of the measured or calculated values predicted the onset of laminitis. Hypertension appeared to be a response to, rather than a cause of, lameness. Three of the remaining ponies apparently died of shock 29.3 +/- 2.7 hours after overfeeding. All 3 had severe metabolic acidosis; decreased cardiac output, systemic arterial pressure, and plasma volume; and increased hematocrit, total peripheral resistance, and pulmonary vascular resistance. The 11th pony was unaffected and the 12th pony was euthanatized.     

Intra-osseous pressure of the equine third metatarsal bone

Intra-osseous pressure was measured in the third metatarsal bone of 8 pony foals at the age of 1, 3, 6 and 26 weeks of age, and on one occasion in the third metatarsal bone of 5 ponies aged 1-5 years; the animals were under general anesthesia and in lateral recumbency. Saphenous venous pressure and lateral superficial plantar metatarsal arterial pressure were also monitored throughout the procedure. There were no statistically significant changes in the epiphyseal, diaphyseal, venous or arterial pressures with increasing age of the foals. There was no statistically significant difference between the mean epiphyseal and mean diaphyseal pressures in the foals. Individually however, the diaphyseal pressure exceeded the epiphyseal pressure in 32 of the 36 measurements made in the foals. Saphenous vein occlusion and intravenous adrenalin administration showed that both venous and arterial pressures influence intra-osseous pressure. Intra-osseous injection of heparinized saline on one side of the growth plate produced an immediate massive increase in intra-osseous pressure on that side of the growth plate, but in almost all cases a concomitant rise in intraosseous pressure on the other side of the physis did not occur. Simulated effusion of the metatarsophalangeal joint was associated with an increase in intraosseous pressure in the adjacent metatarsal epiphysis, and flexion of the joint with an increase in intraosseous pressure in both the epiphysis and the metaphysis.     

Determination of the minimum alveolar concentration of isoflurane in Shetland ponies using constant current or constant voltage electrical stimulation

Objective To determine the minimum alveolar concentration (MAC) of isoflurane in Shetland ponies using a sequence of three different supramaximal noxious stimulations at each tested concentration of isoflurane rather than a single stimulation. Study design Prospective, experimental trial. Animals Seven 4‐year‐old, gelding Shetland ponies. Methods The MAC of isoflurane was determined for each pony. Three different modes of electrical stimulation were applied consecutively (2 minute intervals): two using constant voltage (90 V) on the gingiva via needle‐ (CVneedle) or surface‐electrodes (CVsurface) and one using constant current (CC; 40 mA) via surface electrodes applied to the skin over the digital nerve. The ability to clearly interpret the responses as positive, the latency of the evoked responses and the inter‐electrode resistance were recorded for each stimulus. Results Individual isoflurane MAC (%) values ranged from 0.60 to 1.17 with a mean (±SD) of 0.97 (±0.17). The responses were more clearly interpreted with CC, but did not reach statistical significance. The CVsurface mode produced responses with a longer delay. The CVneedle mode was accompanied by variable inter‐electrode resistances resulting in uncontrolled stimulus intensity. At 0.9 MAC, the third stimulation induced more positive responses than the first stimulation, independent of the mode of stimulation used. Conclusions The MAC of isoflurane in the Shetland ponies was lower than expected with considerable variability among individuals. Constant current surface electrode stimulations were the most repeatable. A summation over the sequence of three supramaximal stimulations was observed around 0.9 MAC. Clinical relevance The possibility that Shetland ponies require less isoflurane than horses needs further investigation. Constant current surface‐electrode stimulations were the most repeatable. Repetitive supramaximal stimuli may have evoked movements at isoflurane concentrations that provide immobility when single supramaximal stimulation was applied.     

Scapulohumeral arthrodesis in four Shetland ponies

Four Shetland ponies were presented with severe osteoarthritis of the scapulohumeral joint to the Faculty of Veterinary Medicine of Ghent University over a period of 4 years. Ponies were treated with internal fixation using locking compression plates (LCPs) applied cranially across the scapulohumeral joint. Although two ponies developed mild complications, all ponies were more comfortable in the limb within a few hours following arthrodesis.