The kinematic data which based on stepping sequence, contact duration, airborne duration, step length, stride length and stride frequency were measured on 7 Thoroughbred racing horses for the purpose of clarifying characteristics of quadrupedal walking and running. Horses on walking and running at specified velocities were filmed using four 16mm high speed cameras. There were 6 velocities of running from 400m/min to 900m/min. The results were obtained as follows.
1) All horses changed irregularly their stepping sequences with running velocity. The proportion of left lead to right lead was 6:1 at 396m/min, 5:2 at 527m/min, 2:5 at 593m/min, 5:2 at 713m/min, 2:5 at 831m/min and 3:4 at 950m/min.
2) Contact duration decreased with velocity in all horses. No change could be detected in airborne duration.
3) Both of airborne step length and mid step length, which was the distance from the fore trailing limb to the hind lead limb, increased with running velocity. As a result, the stride length increased.
4) The stride length at the highest velocity increased as much as 183.5% of that at the lowest and the stride frequency at the highest velocity increased to 130.9%. It was evident that increase of the stride length contributed much to increasing running velocity more than the stride frequency.

View full abstract

To clarify lipid component and lipoprotein in blood plasma of Thoroughbred horses, investigation was performed by density gradient ultracentrifugation on blood plasma taken from horses of 16 stallions aged 6 to 20, 16 mares aged 5 to 12, and each 6 male or female horses aged 2-years-old. As a result, lipoproteins was separated into 3 main fractions in order of the density named high density lipoprotein (HDL), low density lipoprotein (LDL) and very low density lipoprotein (VLDL) plus chylomicron (CM). The composition of these components in horses was as followed.
1) Among plasma lipids, total cholesterol (TC) values in the female were significantly higher than those of the male.
2) The lipid composition of HDL was observed nearly at the certain level appoximately 65% in phospholipids (PL), and 30% in TC among the male and female.
3) The values of TC, PL and total lipids (TL) in the LDL of the female were significantly higher than those of the male despite of showing a significant low PL/TC ratios (p<0.01) in the LDL and high percentage (p<0.01) in the male.
4) The concentration of PL and TC in the VLDL was maintained at certain level approximately 10% and VLDL was composed of triacylgylcerol (TG) rich component.
These results suggested that the high value of plasma TC in the female comparing with that in the male was resulted in increase of LDL and TC component. In addition, the high ratio of TC and low ratio of PL/TC despite of low value of TC in LDL in the male suggested that there were some factors affected on the composition of LDL in the male.

View full abstract

The separation and the optimal conditions for an electrophoretic assay of serum alkaline phosphatase (ALP) isozymes of horses were studied using “Separateur” (Helena Lab., France), a reagent commercially available for medical use. The results of its clinical application were discussed. The equine serum ALP isozyme was separated distinctly to two bands (type I and II) by electrophoresis with “Separateur” 1: serum 6, under optimal conditions of 180 v, 40 min at 4°C. By serum protein electrophoresis, types I and II of equine serum ALP isozyme appeared at the positions of α₂-globulin and β₁-globulin, respectively. In addition, it was found that types I and II were associated with liver ALP and bone ALP, respectively. In 97 horses ranging in age from 1-day to 22-year-old, isozyme activities of types I and II decreased gradually with age. The activity of type I, however, changed less in horses 3-year-old or more and it was detected as before in 20 out of 27 horses aged 14 to 22 years old. In the ratio of the serum ALP isozyme, type I activity increased in aging and was almost equal with that of type II in horses 3 to 7 years old.
Furthermore, high values of total serum ALP activities were observed in clinical cases followed by dysfunction of the liver (1), liver cirrhosis (1), hemorrhagic colitis (3) and rupture of the caecum (1), in which type 1 activity significantly increased except for a case of ruptured caecum. The results of the present study demonstrated that assay using “Separateur” was sufficient for separating the equine serum ALP isozyme (type I and II), and with respect to sensitivity and precision. In addition, it was found that the assay was useful for determination of the prognosis or extention of clinical cases such as the severe hepatobiliary and intestinal diseases.

View full abstract

In order to determine if training efficacy or racing performance of Thoroughbred horses could be assessed by measurements of left ventricular function, echocardiographic examinations were conducted on 45 horses aged 2 to 6 years old, which belonged to the Ritto Training Center, Japan Racing Association. The following results were obtained.
1) The morphological and functional findings of the left ventricle were determined by a probe, the approarch of which was made a restricted area in the left third intercostal space, the cardiac-window. This approarch was simple and sufficiently acculate for examination of left ventricular function.
2) Correlation coefficiency (r=0.956) based on the stroke volume of 15 Thoroughbred horses (3 to 5 years old) was obtained by echocardiography and dye-dilution method. So that stroke volume as measured by echocardiography was considered reasonable.
3) Stroke index as shown by the stroke volume per kg increased with age and or progress of training. Relatively stable values were obtained ranging from 2.42ml/kg to 3.37ml/kg in horses over 3 years old. Comparing these values for 5 horses (4 years old) with excellent racing performance and 10 horses (4 to 6 years old) of ordinary performance, significantly higher values (p<0.001) were obtained in the former (3.55ml/kg in average) than in the latter (2.85ml/kg).
4) End-systolic internal dimensions in this study did not differ significantly. End-diastolic dimensions did, however, differ significantly in the above two groups of horses. The usefullness of echocardiography assessing left ventricular function of Thoroughbred horses is thus comfirmed. The left ventricular volume at end-diastolic stage in horses with excellent racing performance had much greater than that in horses of ordinary performance.

View full abstract

A continuous-intravenous (iv) drip infusion of ketamine anesthesia was applied on a total nine cases of foals, ranging in age from one day to 19 weeks, undergoing a variety of surgical procedures. They were all premedicated with atropine (1mg/100kg) and xylazine (1mg/kg). Anesthesia was induced by a rapid iv infusion of 0.2 ketamine solution and maintained by a continuous iv drip infusion of the ketamine solution. Mean induction dose of ketamine was 2.3mg/kg, and mean ketamine infusion rate during maintenance anesthesia was 12.1mg/kg/h. Anesthetic induction and recovery from anesthesia were rapid and smooth in all cases. All foals showed good analgesia and muscle relaxation during maintenance anesthesia. Marked changes in body temperature, heart rates and respiration rates were not observed, nor abnormal electrocardiographic alterations were observed during maintenance anesthesia. The changes in arterial blood gases and pH showed slight respiratory acidosis 5min after induction of anesthesia, but no marked respiratory acidosis was observed during anesthesia. Arterial blood pressure remained within normal limits during anesthesia except for a case showing poor risk, which showed hypotention immediately after the ketamine infusion. No other serious side effects were observed. These findings indicate that ketamine anesthesia using iv drip infusion technique under xylazine treatment can be used in foal veterinary practice as a safe and regulatable anesthetic method.

View full abstract

An environmental survey was made based on data from postmortem examinations of 273 cases of perinatal disease in the Hidaka district. The results are summarized as follows.
1. Perinatal diseases occurred throughout the Hidaka district and no causative factor that could be considered a regional specificity was recognized.
2. Most of the infectious diseases were due to indigenous bacteria and occurred more frequently on farms under overcrowded rearing conditions and along rivers.
3. On old farms, the incidence of diseases such as myolysis was high.
These results show that breeding environmental factors have great influence on the occurrence of perinatal diseases.
To prevent perinatal diseases, it is necessary to limit the number of horses according to local conditions and the size of each farm.
It may also be essential to take both health care and improvement of the breeding environment into consideration.

View full abstract

Latex agglutination (LA) with a commercially available drug (Rotalex Orion Diagnostica Corp., Espoo, Finland) was evaluated for the detection of equine rotaviruses in fecal specimens. Six rotavirus strains, four strain of equine rotavirus and each one strain of calf and human rotavirus, were detected as positive by the LA when the virus titers between 10^6.0 and 10^7.0 fluorescent focus-forming units/ml were used. The degree of agglutination accroding to serotype was essentially the same in all case. Eighty five equine rotavirus strains isolated from feces showed positive by LA. Agglutination was positive in feces of 3 foals experimentally infected with equine rotavirus by LA during a period from 4 to 9 days post inoculation. Detection of equine rotavirus from feces of 50 foals with diarrhea was compared with LA and virus isolation. The unanimous rate of the results obtained by the both methods showed 90.0% and only one sample showed non-specific.
Thus LA with Rotalex qualifies as a method for detecting equine rotavirus from feces and is applicable enough as simple and rapid diagnostic method for equine rotavirus infection in field.

View full abstract

From 1980 to 1982, 2407 plasma and 1191 nasal swab samples were collected from 2520 horses with pyrexia for virus isolation at Ritto and Miho Training Center of the Japan Racing Association. A total of 66 agents were isolated, 40 isolates of equine herpesvirus type 1 (EHV-1) from 38 horses, 10 of equine herpesvirus type 2 (EHV-2) from 9 horses and 16 of equine rhinovirus type 1 (ERhV-1) from 14 horses. All isolates were identified as one of these viruses.
Thirty-eight isolates of EHV-1 were recovered from samples collected from winter to early spring, December to March but the remaining two were recovered on May and July. ERhV-1 and EHV-2 were isolated during the year.
EHV-1 was isolated from the plasma of three horses, nasal swabs of 33, and both plasma and nasal swabs of 2. EHV-2 was isolated from the plasma of 1, nasal swabs of 7, and plasma and nasal swab of 1. ERhV-1 was isolated from the plasma of 10, nasal swabs of 2, and plasma and nasal swabs of 2.
EHV-1 was isolated from all Vero cells (African Green Monkey Kidney), RK-13 cells (rabbit kidney) and FHK (fetal horse kidney cells) used, while EHV-2 was found in only FHK cells. Most ERhV-1s were isolated from Vero cells, but a few from FHK or RK-13 cells.
A seroconversion to isolated viruses was also observed in paired sera. Thirty-four out of 35 horses, from which. EHV-1 had been isolated, showed seroconversion to EHV-1. All 11 horses from which ERhV-1 was isolated showed seroconversion to ERhV-1. However, horses from which EHV-2 was isolated and already had high CF antibody titers of 1:8 to 1:32 at acute phase, showed no seroconversion to EHV-2.

View full abstract

A serological survey for Getah virus (GTV) infection was performed on horses raised in 5 regions of Hokkaido during the years 1983-86. A high or relatively high incidence (23-59%) of GTV antibody was detected in the one northern (Soya) and the 3 southern (Hiyama, Shiribeshi and Iburi) districts, whereas a small percentage (4-8%) was seen in the one eastern (Tokachi) district throughout the observation period. In Tokachi district, however, the dissemination of GTV among the horse population was recognized as smal scale during the period of summer to fall of 1984. A few cases in Soya, Hiyama and Iburi also showed increase of antibody titers during the same season in 1983. These results indicate that GTV was prevalent among horse population at sometimes or in some places in Hokkaido.

View full abstract

Magnetic resonance (MR) imaging was used for an in vitro study of the legs of racehorses and it was evaluated for its use on the diagnosis of tendinitis. MR images of normal legs (3 cases) and affected legs with subacute tendinitis of the superficial digital flexor tendon (1 case) and the chronic inflammation of the interosseous muscles (2 cases) were taken. The tendons and interosseous muscles could be clearly observed and their inflammatory lesions were swollen morphologically and increased in signal intensity, giving a cloudy appearance. MR imaging thus appears to qualify for diagnosing tendinitis of racehorses.

View full abstract

To clarify the background factors for the occurrence of failure of passive transfer (FPT) in foals, IgG content of colostrum at postpartum in dams and serum IgG content in foals were determined by the latex agglutination test. A total of 573 out of 1741 colostrum (32.9%) were found to have unqualified IgG content of colostrum at postpartum. Unqualified colostrum also appeared to depend considerably on prelactation in dams when hearing data on lactation at postpartum were obtained from breeders. Serum IgG content in the foals fed unqualified colostrum was significantly less (P<0.05) and the morbidity rate of foals, affected by infectious disease following birth, was relatively higher than those of foals fed qualified colostrum. It would thus appear that unqualified colostrum should be detected as quickly as possible to prevent FPT and infection in foals.

View full abstract

A four-year-old Thoroughbred racehorse suffering from fatal pneumonia was presented to the Veterinary Clinic of Miho Training Center, Japan Racing Association and anesthetized for euthanasia for autopsy. The main gross lesions at postmortem examination were many large and small granulomatous nodules in the lung, small nodules in the liver, cloudy swelling of the kidney, enlargement of the lymph nodes in the whole body and atrophy of the thymus. A large number of acid-fast bacteria, approximately 10¹⁰CFU/g, was isolated in pure form from the nodules of the lung and were bacteriologically identified as Mycobacterium avium complex. This is the first case diagnosed bacteriologically and pathologically as granulomatous pneumonia due to M. avium complex in Japan.

View full abstract