This paper analyzes the structure of “overproduction” in light-breed horses in Japan. By analyzing both aspects of the breeding structure from the aspect of supply and the stable of situation from the aspect of demand, it is the intention of this paper to clarify the charac teristics “overproduction” in light-breed horses in the 1990's. As the 1st horse racing boom before and after 1970 brought on the 1st overproduction in the latter part of the 1970's, the 2nd horse racing boom in the latter part of the 1980's brought about the 2nd overproduction into the 1990's. However, “overproduction” in the 1990's fundamentally differed from that of the 1970's on the following points. First, the bubble economy in the latter part of the 1980's caused an abnormal expansion of purchasing power where the number of foals purchased greatly exceeded the demand. In other words, this brought about a breakdown of coordination in supply. As the bubble economy was of such an extensive scale, the rebound was likewise devastating in which the increase of the number bred was far greater than the previous “overproduction period.” Second, into the 1980's, as the foals and yearlings were dispersed and kept at the stud farms, the yearling training farms in the breeding area, the yearling training farms in and around the training centers, it gave the impression that a certain degree of the “overproduction” had been absorbed. But, the “overproduction” this time was so grave that even this absorbing function would no longer work. Third, the “overproduction” this time was an “overproduction” of only Thoroughbreds. There was a difference in scope with the previous overproduction in that there was an “over production” of both Thoroughbreds and Anglo-Arabs. This was because during this period, light-breed horse breeding continued to specialize on Thoroughbreds. At the present, there is no “overproduction” of Anglo-Arabs. However, depending on the subscription Anglo-Arab horse problem in National Racing and the degree of recession in Regional Public Racing, it isbelieved that eventually the recession in Anglo-Arabs will become a problem. At such a time, if Anglo-Arab horse management was forced to convert, even in a partial way, to Thoroughbred horse management, the “overproduction” of Thoroughbreds will probably become more serious. Fourth, during this period, the light-breed horse management as a principal occupation and specialization have further increased creating a Thoroughbred-inclined structure. For this reason, conversion to other forms of agriculture industry is difficult and countermeasures against “overproduction” become more difficult, both in management and regionally. For these reasons, demands may be forthcoming for drastic “countermeasures against overproduction.”

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Today, as we greet the 2nd year of the founding of the Japanese Society of Equine Science, upon looking back again over the history of how the animal, the horse, came to live together with humans as a domestic animal, the horse presents an objective aspect different from that of other domestic animals and domestic fowls. As the cognition of the Japanese toward domestic animals possessing such diversity differs remarkably from other countries, the existing conditions point out that a change in conception was in order. And, in reviewing the past of the horse as an animal, there are many factors which have not been clarified even concerning biological characteristics and it was pointed out that the horse has the potential of becoming an invaluable object of humane research not only because of its high possibilities as research material but also as a domestic animal from the point of its relation with mankind. In Japan, we are unaccustomed to hearing the words Equine Science but it was pointed out that, in the field of scientific research into the 21st Century, there is the necessity that a diversified approach be made to any particular phenomenon and my personal views are offered here regarding how Equine Science should be as a specialized science.

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Experiment was carried out to measure digestibility and voluntary intake in horses and digestible nutrients of timothy hays harvested at different times in Hidaka district of Hokkaido. First cutting hays harvested on different swards from Tune 8 to July 28 were used. In horses, the dry matter digestibility of hay decreased as the harvest time was delayed; the digestibility of hay harvested on June 8 was 57%, whereas that harvested during late July was about 30%. Similarly, digestibility of crude protein, acid detergent fiber and energy of hays decreased with maturity advancement. Significant relationships were found between the digestibilities in dry matter, in energy and the growing period. As the harvest time was delayed these digestibilities decreased to 0.5% unit per day. Digestible energy of hays also decreased considerably, ranging from 2.52 to 1.41 kcal/g, with advancing maturity. There was no relation ship between the dry matter intake and dry matter digestibility of hays. In sheep, digestibilities of dry matter and nutrients and digestible energy of hays decreased with maturity advancement as well . However, the rate of decrease in digestibility with maturity advancement was less than that of digestibilities in horses .

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The present study was to describe the relationships between stride frequency, stride length, step length and velocity in the upper submaximal velocity range in Thoroughbreds. Three Thoroughbred horses, aged two-year-old, in race training were used. Each horse performed six trials at six different velocities including near maximum velocity for each individual horse. Stride length and step length were measured from the hoof prints on the ground and stride frequency was measured from the acceleration curve upon hoof impact on the recording paper. As the mean variation coefficients for stride length and stride frequency were 2.1% and 1.6% respectively, it was considered that the gait characteristics of stride length and stride frequency exhibited good stability at canter and gallop in each individual horse. Both stride length and stride frequency almost linearly increased with increasing velocity. However, at higher velocities, stride length tended to show a decreased rate of increase, whereas stride frequency tended to indicate an increased rate of increase. Airborne and mid step lengths showed a greater increase with increasing velocity than hind and fore step lengths. Airborne step length showed a leveling off, whereas mid step length showed an increased rate of increase at higher velocities. It was considered that the leveling off in airborne step length resulted from the braking force to the forelimb growing bigger and the increased rate of increase in mid step length resulted from the propelling force to the hind limb growing bigger at higher velocities.

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We determined the weight, volume and center of gravity (CG) of 20 frozen body segments using three Thoroughbred horses. Segment weight and volume to whole body weight and volume were 4.4 and 4.1 (%) for the head, 7.0 and 6.5 neck, 59.5 and 63.0 torso, 9.2 and 8.6 scapulabrachia, 1.8 and 1.6 antebrachia, 0.5 and 0.4 metacarpi, 0.5 and 0.4 digiti, 13.8 and 12.7 thigh, 2.0 and 1.6 crura, 0.8 and 0.6 metatarsi, 0.6 and 0.4 digiti, and 0.1 and 0.1 for the tail. Segmental body density was more than 1 g/m³ except 0.90 g/cm³ for the torso. Total body density calculated from total weight and volume was 0.95 g/cm³. The location of CG for each body segment was presented on the reference line by percentage of distance from location of segment CG to proximal end which was divided by the segment length.

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For research on hemolysis with exercise, changes of plasma amino acids and inorganic ions concentrations with maximum exercise (913±6.5 m/min) in 2 years old thoroughbred horses were investigated. Sixteen experimental horses were classified into two types by variation of free amino acid concentrations in red cells, namely basic amino acid-positive (BA⁺) type (3 females and 2 males) and -negative (BA^-) type (5 females and 6 males). Blood samples were collected at 30 minutes before and 5 minutes after exercise. The results obtained are as follows; 1) MCHC slightly decreased after exercise. In contrast, osmotic fragility of red cell membrane and hemoglobin concentration in plasma significantly increased after exercise. 2) Concen trations of alanine, serine, threonine and lysine in plasma of BA⁺ type were similar to those of BA^- type before exercise. However, the concentration of those amino acids in plasma of BA⁺ type significantly increased after exercise. 3) K⁺ concentration in plasma significantly increased after exercise in both BA types. The increase rate by exercise of K⁺ of BA⁺ type was significantly lower than that of BA^- type. These results suggested that several substances are released from red cells to plasma be caused by hemolysis with maximum exercise.

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Diurnal pattern of cribbing in three horses, whose cribbing became habitual and persistent, were observed in stalls for 24 hours using video recorders. The frequency of cribbing varied in a day, with three major cribbing periods in early morning, evening and midnight. There was a strong association between the frequency of cribbing and feeding. Before and after the roughage meal delivery, the level of cribbing frequency was low, and around the concentrated meal delivery, the level of cribbing frequency became high. These results suggest that cribbing may be caused not only by boredom, but also by frustration in ingestive behavior related to the physical quality of the meal which horses are fed.

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