Previously the authors reported that favorable results had been obtained from a collecting test of horse flies by using a trap remodeled partially from Kitaoka's and Shinohara's traps in 1968. In 1969, a newly improved trap, or the Equine Health Laboratory (EHL) trap was made by referring to the results obtained in the previous year (Figs. 1 and 2). Then, collecting tests of horse flies were performed by the EHL trap in the Niigata Race Course and the Joban Branch of the Equine Health Laboratory. The results obtained are as follows. 1) Over a period from July 24 to August 21, 5, 276 horse flies were col lected by 10 EHL traps in the Niigata Race Course. Over a period from August 1 to 28, 6, 445 horse flies were caught by 7 EHL traps in the Joban Branch. Although the numbers of collected horse flies were related to the growth of horse flies in the habitat, it was recognized that the EHL trap had a very excellent effect on the collection of horse flies, taking the results mentioned above and Hayakawa's report2) into consideration. 2) Traps were installed at the following three sites. Site A was in a very wide place without obstacles near stable, race track, or wet low zone. Site B was in a relatively narrow place near the same place as site A. Site C was in a very narrow place among trees and houses. Then, a trap installed at A was found to have a more excellent effect than one at B or C. A trap at C gave a worse effect than any other. 3) It is considered from the results of the present test that at least one trap should be installed in two hectares of the controling area of horse flies.

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Bolts and nuts (Wilson type, 100 mm in length and 2.5 mm in diameter) were used in reducing fractures of the third metatarsal bone in two cases. Case 1 : A 3-year-old Thoroughbred colt. Fracture of the right third me tatarsal bone induced during training exercise on the race track. Two days later, the colt was sent to the Equine Health Laboratory with a temporary plaster cast applied. A radiograph (Fig. 1) showed that the third-metatarsal fracture line reached the joint surface on the fetlock joint. Anesthesia was induced with a mixture of 5 ro guaiacol glycerin ether and 0.25% thiopenton sodium, and then maintained with halothane-oxygen. A skin incision was made on the medial aspect of the fracture fragment. A drill only slightly smaller than the bolt was used to serve as a guide hole for the bolt. One year after the surgery, the bolts were tried to be removed. As it was very difficult to loose a screw, one of the bolts remained in the bone, but the colt had a normal gait and a normally appearing limb. Case 2 : A 3-year-old Thoroughbred colt. Fracture of the right third me tatarsal bone produced at racing on the Nakayama Race Course. The colt was presented to the Veterinary Clinic immediately after, the racing. Radio graphs were taken by the official race veterinarian. A radiograph (Fig. 2) showed the same fracture as in Case 1. Seven days later, the operation was carried out at the Veterinary Clinic in the Nakayama Race Course, Anesthe sia and surgical procedures were the same as in Case 1. The bolts and nuts were removed easily, since they were removed 80 days after the surgery. Four months after the operation (one month after the removal of the bolts), the colt went back to training for racing. During the training exercise, the colt accidentally hit against the fence and died of fracture of the thoracic verte bra. Postmortem examination revealed that the fracture line had been completely healed in the metatarsal bone, including the fetlock joint surface, in the colt.

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Normal values of plasma alkaline phosphatase of Thoroughbred horses were determined in relation to age and sex. The horses employed were those stood in the Utsunomiya Rearing Farm and in the Tokyo Race Course, and ages ranged 2 to 3 years in the Farm and 3 to 5 years or more in the Race Course. The enzyme activity decreased with the increase of age. However, no signifi cant difference between both sexes could be observed. Furthermore, it was found that, when the values of the horses of the same age of 3 years were compared, there was a significant difference between the values in the Farm and in the Race Course. It was presumed that the different environment or degree or manner of training might have caused such dif ference.

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A complete pelletized ration for racing horses was designed, so that it might be developed in place of conventional feeds. Then suggestions were made on the feeding standard of this ration at each stage of growth, based on literatures. Except for the stage of weanling, the growing stage of horses yearling or more was divided into three periods on the basis of the development of bone and muscle, as well as the burden of exercise assigned. The requirements of digestible crude protein (DCP), total digestible nutrients (TDN), and crude fiber at each stage of growth were suggested. The protein requirements, for example, were set up for three stages of growth as 12, 10, and 8%, respectively. Due to these feeding standards, three formulae of complete pelletized ration were established for racing horses. Of course, the vitamins and minerals essen tial for racing horses were included as premixes. When the feed consumption was estitmated to be 2 % of body weight, the required energy was also pro duced from the ration.

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The authors had experience of raising race horses of the Arabian breed on complete pelletized rations in each stage of growth. These rations were produced originally in Japan for the first time. Observation was made in detail on the effect of feeding, growth, and characteristics of blood. The results obtained are summarized as follows. Feeding : 1) The palatability of the complete pelletized rations was so good that horses were accustomed to the replacement of conventional feeds with pellets for two or three days. Horses could be raised completely on pelleted feeds for a week. 2) In horses fed the complete pelletized rations, droppings were well-formed, but soft and moist. 3) There were no horses chewing wood in the course of the experiment. 4) The feeding standard of pellets at two percent of body weight was suitable for feeding horses daily. Growth : 1) The growth of race horses raised on the complete pelletized rations was satisfactory as a whole. So good was the balance of bone development. 2) Although the contents and rates of feeds were changed by the stage of growth and the feed consumption was limited in proportion to body weight, race horses appeared to grow, adapting themselves to suggested conditions of nutrition. 3) Exercises were carried out in the process of growth, but no growth inhibition accompanying them was recognized. Blood : 1) Hemoglobin and packed cell volume tended to increase, and MCHC remained almost constant, or above the normal level, during the wholeexperimental period. These results suggest that the pelletized rations may be rather favorable for growing horses. 2) Alkaline phosphatase activity in blood decreased gradually. The epiphyseal fusion of the tuber calcis was proved radiographically to proceed normally. These findings suggest that the bone may be growing normally with the pelletized ration.

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In a 3-year-old Thoroughbred colt, a worm was detected from the right ventricle and identified as Dirofilaria immitis. The worm was found to measure 156 mm in length and 675 p in width. The morphological findings and measure ments of the worm were similar to those of 3 female worms of Dirofilaria immitis which had been detected from an infected dog 150 days after artificial infection. Histologically, a nodule consisting of plasma cells and lymphocytes, small hemorrhages, edema, and separation of muscle fibers were shown in the cardiac papillary muscle around which the worm had twisted. It was speculated that such histological lesions might have been caused by the parasite of Dirofilaria immitis.

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The case studied was a Thoroughbred colt 3 years and 1 month old. In the posterior portion of the left diaphragmatic lobe of this animal, there was a lesion caused by Dirofilaria immitis. A worm was collected and found to measure 113 mm in length and 600 p in width. It seemed to be immature and female. Microscopical examination of the worm and pulmonary lesion revealed that transverse striations had appeared evidently on the cuticular surface of the worm, but no longitudinal ridges. The findings of the body wall of the worm, including the cuticula membrane, agree with those of Dirofilaria immitis, so far as the cross section of the worm is concerned. Consequently, the size and structure of the worm that could be recognized were consistent in diagnosis with those of Dirofilaria immitis. The changes of pulmonary embolism shown in the present case were similar to those of pulmonary dirofilariasis in the canine case.

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Atrial return extrasystole associated with SA block, AV block, premature beat, and wandering and/or shifting pacemaker was observed in a 3-year-old Thoroughbred colt. A diagnosis of atrial return extrasystole was made on the basis of the following findings : (a) Bizarre curves were observed on the ST segment (BST). (b) In spite of slight variation in PP intervals, bizarre curves had a fixed coupling time with preceding QRS complexes. (c) The amplitudes of BST in chest lead EGG were great in those areas where the sinus P waves were also great. (d) The polarities of BST were inverted, as compared with those of the preceding sinus P wave. (e) BST appeared only when the preceding PQ intervals had been prolonged. (f) BST disappeared in association with exercise. The PP intervals, including atrial return extrasystole, were longer than those without arrhythmia. It was probable that the retrograde P wave might have reached the sinus node, which, in turn, cancelling the excitation of the node, might have reset the sinus rhythm. Some beats which were probably induced by an atrio-ventriculo-atrio-ventriculo-atrial conduction and an atrio-ventriculo-atrio-ventricular conduction were observed.

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Intermittent ventricular parasystole was observed in a racing Thoroughbred filly. Electrocardiograms showed a marked variation in the coupling of ectopic beats and the regular appearance of ectopic beats . The electrocardio graphic tracings recorded during exercise, revealed that ectopic beats appeared at walking, and trotting, except for canter . The etiology of arrhythmia was briefly discussed.

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