Ryo Kusunose

Association between equine temperament and polymorphisms in dopamine D4 receptor gene.

The variable number of tandem repeats (VNTR) polymorphism of the dopamine D4 receptor (DRD4) gene has been reported to be associated with the personality trait of novelty-seeking in humans. In the genus Equus, this region includes an 18-bp repeat unit and there are inter- and intraspecies differences in the number of repetitions. Because horses are unique among livestock species in that their temperament is considered important, we investigated the possible role of this region on equine temperament in thoroughbred horses. We simultaneously determined the sequences of this polymorphic region and administered a questionnaire survey to horse caretakers with questions about 20 different traits of their horses’ temperament. Although there was no difference in the number of repeats among the 136 thoroughbred horses studied, two single nucleotide polymorphisms (SNPs), one of which might cause an amino acid change (A-G substitution), existed. By analyzing the association between these SNPs and temperament scores, a significant association was revealed between two temperament traits (Curiosity and Vigilance) and the A-G substitution. Horses without the A allele had significantly higher Curiosity and lower Vigilance scores than those with the A allele at the A-G substitution. In addition, similar associations between both temperament scores and each genotype of the A-G substitution were observed in two subgroups divided according to the time of their introduction to the farm. These results suggested that the SNP in the VNTR region of the equine DRD4 gene might be related to individual differences in equine temperament.

A horse identification system using biometrics

This paper introduces an application of iris recognition technology, using the iris pattern for horse identification. There are several problems to be solved in horse iris recognition: (1) It is very difficult for horses to remain motionless, which leads to mislocation and loss of focus during image acquisition, so that the images often have poor quality. (2) Pupil size varies significantly between the conditions of dilation (mydriasis) and contraction (miosis). (3) Horse iris patterns are not clear. As a solution for issue (1), we used the reflection of the illumination sources employed for image acquisition and chose adequate images suitable for recognition. For issues (2) and (3), we propose region extraction appropriate to the equine eye structure, a stable coordinate model for pupil variation, and recognition using orthogonal wrinkles in the iris pattern. Recognition experiments based on 100 sets of horse iris data show that highly accurate horse identification is possible.

Effects of bedding material on the lying behavior in stabled horses.

The objective of this study was to investigate the effect of straw, sawdust, coconut husk (husk), and coconut fiber (fiber) on the welfare of stable horses by observing their resting behavior. Twenty horses with ages ranging from 3 to 21 years were used at the Equine Research Institute of the Japan Racing Association, Utsunomiya, Japan. Five horses were allocated to each bedding condition. The behavior of each horse was recorded by video camera for 3 days and was continuously sampled from 17:00 to 05:00. The total duration, the number of bouts, and the mean and the maximum duration of bouts in standing rest, sternal lying, and lateral lying were calculated and analysed by the Kruskal-Wallis test and post hoc Steel-Dwass test. There was no difference in the standing rest and the sternal lying among beddings. Significant differences were observed in these values in the lateral lying among the different beddings (P<0.05). The values of the means of the total duration, the number of bouts, and the mean and the maximum duration of bout in the lateral lying were greater when husk was used as the bedding material than when sawdust were used (P<0.05). The results of the observations show that the new bedding materials would be as usable as straw. However, lateral lying was observed less frequently when sawdust were used as bedding; this indicates that use of sawdust as bedding material will decrease the welfare of stabled horses.

Characteristic of inflammatory airway disease in Japanese thoroughbred racehorses.

Inflammatory airway disease (IAD) is a common cause of poor performance, interruption of training and premature retirement in racehorses. It is also reported that up to 80% of horses are affected at some point in the first years of training in UK and Australia. However, no studies with regard to the information on occurrence of IAD in Japanese Thoroughbred racehorses have been reported. To investigate the occurrence and the characteristics of IAD, epidemic research including endoscopic examination of the airway tract and trachea wash was conducted for Thoroughbred racehorses presenting coughs or poor performance which airway tract disease was suspected stalled in training facility managed by Japan Racing Association. Fifty-six out of 76 Thoroughbred racehorses (73.7%) presenting coughing or poor performance were diagnosed as IAD. Mean incidence rate of IAD was 0.3% and it has been confirmed that constant number of IAD exists in Japan. Up to 35.7% of IAD horses showed upper airway abnormalities in some extent. There was a trend for IAD horses to use wood shavings for bedding and fed hay from the ground compared with the control group. Therefore, improvement of stabling environment may aid in preventing IAD. This study demonstrated that Japanese Thoroughbred racehorses are affected by IAD likewise other countries as well as demonstrated the characteristics of IAD which may contribute to the clarification of the pathogenesis of IAD.

Changes in the heart rate and plasma epinephrine and norepinephrine concentrations of the stallion during copulation

AimThe physiological indexes of the copulatory behavior of the stallion have not been investigated in detail and may differ from those of other species, such as humans and rats.MethodsIn order to understand the breeding capability of various stallions, their behavior during copulation was observed, and heart rate (HR) and the plasma concentrations of norepinephrine (NA) and epinephrine (Ad) were measured sequentially for a total of 13 copulations carried out during 2 days.ResultsThe mean HR at rest was 35.3 ±0.9 beats per minute (b.p.m.) and it peaked during mounting (162.1 ±5.4 b.p.m.). The HR at ejaculation was 145.7 ±5.1 b.p.m, which was less than the peak. The plasma concentrations of NA and Ad showed similar changes to the HR; immediately after ejaculation they were, respectively, 4.7-fold and 1.9-fold higher than the resting values and there was a difference in the degree of increase of each catecholamine.ConclusionsThe present results show that in the stallion the HR peaks at mounting and there is a greater change in the activity of the sympathetic nervous system because of the shortterm, highly intense exercise performed during copulation. It is considered that this, combined with the particular mental stress placed on the stallion during copulation, has the potential to cause sudden cardiac death.

Continuous measurements of eyeball area and their spectrum analyses. Toward the quantification of rest rhythm of horses by image processing

The motion of eyelids and eyeballs in domestic animals has been recognized as agreeing well with the sleep depth estimated by spectrum analyses of an electroencephalogram for half-closed eye and fully closed eye. This study aimed at quantitative estimation of the rest rhythm of horses by analysis of eyeball movement. The mask attached with a miniature CCD camera was newly developed. The continuous images of the horse eye for about 24 hours were transmitted by a telemetry system and were recorded to a time-lapse video recorder. The continuous images were captured on hard disc (rate 1 frame / 2 sec), the time information was obtained by OCR technology, the eyeball area was smoothed to average gray values, and threshold obtained for segmentation. The eyeball area was obtained via image processing and the spectrum analyzed. The temporal trend, the histogram and the spectrum of the eyeball area were calculated. As for the results, the fluctuating status of the eyeball area was analyzed quantitatively, and the rest rhythm of horses was clearly observed. It is possible to apply this technology to other animals.