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Khalil, A. M., Murakami, N., & Kaseda, Y. (1998). Relationship between plasma testosterone concentrations and age, breeding season and harem size in Misaki feral horses. J Vet Med Sci, 60(5), 643–645.
Abstract: Jugular vein blood samples were collected from 23 young and sexual mature feral stallions to examine the relationship between plasma testosterone concentration and age, breeding season or harem size. Testosterone concentration increased with the age of the stallions until they formed their own harems, at about 4 to 6 years old. Seasonal variations in testosterone concentrations were observed, and found to be significantly higher (P<0.001) throughout the breeding season than non-breeding season, from 3 years of age. Testosterone levels were correlated with harem size for individual stallions. It can be inferred from these results that there is a relationship between plasma testosterone concentration and age, breeding season and harem size.
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Rapin, V., Poncet, P. A., Burger, D., Mermod, C., & Richard, M. A. (2007). [Measurement of the attention time in the horse]. Schweiz Arch Tierheilkd, 149(2), 77–83.
Abstract: A study carried out on 49 horses showed that it is possible to measure the attention time by operant conditioning. After teaching horses an instrumental task using a signal, we were then able to test their attention time by asking them to prolong it increasingly while setting success and failure criteria. Two tests were performed 3 weeks apart. The 2nd test was feasible without relearning, a proof of memory, and was repeatable, a proof of consistency in the attention time. A significant difference was observed between the 3 age groups. Young horses often performed very well during the 1st test but their attention dropped in the 2nd test while older horses were more stable with respect to attention and even increased it slightly. The study shows that there are individual differences but it was not possible to prove a significant influence of breed, gender and paternal influence. Consequently, learning appears to be one of the most interesting approaches for evaluating the attention of horses and for observing their behaviour.
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Bell, R. J. W., Kingston, J. K., Mogg, T. D., & Perkins, N. R. (2007). The prevalence of gastric ulceration in racehorses in New Zealand. N Z Vet J, 55(1), 13–18.
Abstract: AIM: To establish the prevalence and factors influencing the prevalence and severity of gastric ulceration in racehorses in New Zealand. METHODS: Horses (n=171) in active training for racing by trainers (n=24) located throughout New Zealand were examined using gastroscopy during 2003 and 2004. Images of the examination were recorded and reviewed, and an ordinal grade based on the severity of gastric ulceration present was assigned, using the grading system proposed by the Equine Gastric Ulcer Council (EGUC). Information about the horses such as age, breed, sex, stabling, time at pasture, pasture quality, and presence of clinical signs consistent with equine gastric ulcer syndrome (EGUS) was recorded. RESULTS: Of the 171 horses in the study, 133 (78%) were Thoroughbreds and 38 (22%) were Standardbreds. Evidence of gastric ulceration was present in 151 (88.3%) of these. Prevalence of ulceration was higher at the lesser curvature (LC) and greater curvature (GC) of the stomach than at the saccus caecus (SC; p<0.01), and ulceration was more severe at the LC than at either the GC (p=0.02) or the SC (p<0.001). The prevalence of ulceration did not differ between the two breeds (p=0.51) or between horses of differing ages (p=0.56). Gastric ulceration was evident in 125/141 (89%) horses kept at pasture for at least 4 h/day, in all 13 (100%) horses kept at pasture full time, and in 16/17 (94%) horses stabled full time. Prevalence and severity of ulceration did not differ between horses stabled full time, kept at pasture for part of the day or kept at pasture full time (p=0.33 and 0.13, respectively), and for horses grazed on pasture severity of ulceration did not vary significantly with the quality of the pasture (p=0.12). Neither prevalence (p=0.26) nor severity (p=0.49) of gastric ulceration varied significantly with duration of training. CONCLUSIONS: The prevalence of gastric ulceration in racehorses in New Zealand is similar to that reported elsewhere for horses in active training for racing. Access to pasture for some or all of the day did not appear to be protective.
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Imura, T., & Tomonaga, M. (2003). Perception of depth from shading in infant chimpanzees ( Pan troglodytes). Anim. Cogn., 6(4), 253–258.
Abstract: We investigated the ability to perceive depth from shading, one of the pictorial depth cues, in three chimpanzee infants aged 4-10 months old, using a preferential reaching task commonly used to study pictorial depth perception in human infants. The chimpanzee infants reached significantly more to three-dimensional toys than to pictures thereof and more to the three-dimensional convex than to the concave. Furthermore, two of the three infants reached significantly more to the photographic convex than to the photographic concave. These infants also looked longer at the photographic convex than the concave. Our results suggest that chimpanzees perceive, at least as early as the latter half of the first year of life, pictorial depth defined by shading information. Photographic convexes contain richer information about pictorial depth (e.g., attached shadow, cast shadow, highlighted area, and global difference in brightness) than simple computer-graphic graded patterns. These cues together might facilitate the infants' perception of depth from shading.
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Kaseda, Y., Ogawa, H., & Khalil, A. M. (1997). Causes of natal dispersal and emigration and their effects on harem formation in Misaki feral horses. Equine Vet J, 29(4), 262–266.
Abstract: Misaki feral horses were separated into 2 herds and the difference between dispersal from natal group (natal dispersal) and dispersal from natal area (natal emigration) was studied. The causes of dispersal and emigration and their effects on harem formation were studied 1979-1994. The number of horses ranged from 73 (mature males: 8, mature females: 26, young males: 8, young females: 3, colt foals: 6, filly foals: 10 and geldings: 12) in 1979 and 86 (mature males: 14, mature females: 37, young males: 12, young females: 7, colt foals: 5, filly foals: 7 and geldings: 4) in 1994 when the present study ended. All 29 males which survived to age 4 years and 58 females which survived to age 3 years left their natal or mother groups at age one to 3. Seventeen of 22 dispersing males and 29 of 39 dispersing females left their natal groups around the birth of their siblings and significant correlations were found between natal dispersal and birth of a sibling. The number of emigrating young males correlated negatively and significantly with the total number of young males in another herd and the number of emigrating young females correlated positively and significantly with the total number of young females in the natal herd. All 13 emigrating stallions which survived to age 5 years formed stable harem groups and a significant correlation was found between natal emigration and harem formation. Twenty-three of 35 resident mares formed stable consort relations with harem stallions and a significant correlation was found between residence and formation of stable consort relations.
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Kasashima, Y., Takahashi, T., Smith, R. K. W., Goodship, A. E., Kuwano, A., Ueno, T., et al. (2004). Prevalence of superficial digital flexor tendonitis and suspensory desmitis in Japanese Thoroughbred flat racehorses in 1999. Equine Vet J, 36(4), 346–350.
Abstract: REASONS FOR PERFORMING STUDY: Overstrain injuries to the superficial digital flexor tendon (SDFT) and suspensory ligament (SI) are among the most common musculoskeletal injuries which contribute to the considerable wastage of racing Thoroughbreds. Many epidemiological studies have demonstrated the prevalence of and risk factors for tendon injury when racing but have not included those injuries sustained during training. However, since tendon injury during training is seen commonly in clinical practice, it is appropriate to determine the overall prevalence of tendon injury sustained during both training and racing. OBJECTIVE: To determine the prevalence of overstrain injury to the SDFT and SL during training and racing among Thoroughbred flat racehorses in Japan in 1999. METHODS: A retrospective study was performed using a sample population of 10,262 Thoroughbred racehorses. The medical information database of Thoroughbred racehorses registered by the Japan Racing Association (JRA) in 1999 was analysed for SDFT and SL overstrain injury diagnosed by a veterinarian employed by JRA during training and racing. Jump racehorses were excluded from this study. RESULTS: The prevalence of forelimb SDFT tendonitis and SL desmitis was 11.1% (1130 cases) and 3.61% (370 cases) of the population, respectively. In the hindlimb, there were 0.06% (6 cases) and 0.14% (14 cases), respectively. Risks of SDF tendonitis in the forelimb in 3-year-olds or older horses were significantly higher than in 2-year-olds. In contrast, the risk of SL desmitis in the forelimb at age 3 and 4 years was 2.23 and 2.11 times higher, respectively, than in 2-year-olds, but this increased to 5.07 times in those age > or = 5 years. Entire males were at greater risk in comparison to females and geldings. CONCLUSIONS: The results suggest that the prevalence of SDF tendonitis and SL desmitis in the forelimb was associated with the horse's age and sex. The prevalence of SL desmitis increased further with age compared with SDF tendonitis, possibly reflecting a more rapid accumulation of degeneration in this structure. POTENTIAL RELEVANCE: The age-related risk demonstrated in this study provides further support that overstrain injuries are associated with accumulated degeneration. These data provide a valuable resource for further research into the aetiology of tendon injury in the racehorse.
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Nissani, M. (2006). Do Asian elephants (Elephas maximus) apply causal reasoning to tool-use tasks? J Exp Psychol Anim Behav Process, 32(1), 91–96.
Abstract: Two experiments addressed contradictory claims about causal reasoning in elephants. In Experiment 1, 4 Asian elephants (Elephas maximus) were pretrained to remove a lid from the top of a bucket and retrieve a food reward. Subsequently, in the first 5 critical trials, when the lid was placed alongside the bucket and no longer obstructed access to the reward, each elephant continued to remove the lid before retrieving the reward. Experiment 2, which involved 11 additional elephants and variations of the original design, yielded similarly counterintuitive observations. Although the results are open to alternative interpretations, they appear more consistent with associative learning than with causal reasoning. Future applications of Fabrean methodologies (J. H. Fabre, 1915) to animal cognition are proposed.
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Johnston, C., Holm, K. R., Erichsen, C., Eksell, P., & Drevemo, S. (2004). Kinematic evaluation of the back in fully functioning riding horses. Equine Vet J, 36(6), 495–498.
Abstract: REASONS FOR PERFORMING STUDY: Clinical history and examination are important features in diagnosis of equine back dysfunction. However, interpretation is subjective and therefore may vary substantially. OBJECTIVES: To establish a clinical tool to objectively evaluate the function of the equine back, in the form of a database on the kinematics of the back at the walk and trot in fully functioning riding horses. METHODS: Thirty-three fully functioning riding horses walked and trotted on a treadmill. Morphometrics and kinematics were tested for correlations to age, height, weight and stride length, and differences between gender (geldings and mares) and use (dressage and showjumping). RESULTS: A database for range of movement and symmetry of movement for extension and flexion, lateral bending, lateral excursion and axial rotation was presented. Symmetry values were very high for all variables. Significant differences were observed in use and gender. Age was negatively correlated to extension and flexion of the thoracolumbar junction. CONCLUSIONS: Interrelationships between use, gender and age to conformation and movement were established. POTENTIAL RELEVANCE: The database provides a basis for objective reference for diagnosis, therapy and rehabilitation of clinical cases of back dysfunction.
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Harkins, J. D., Kamerling, S. G., & Church, G. (1992). Effect of competition on performance of thoroughbred racehorses. J Appl Physiol, 72(3), 836–841.
Abstract: The effect of competition and the influence of age and sex on performance were examined in a study of 18 Thoroughbred racehorses. The horses performed two solo and two competitive runs at 1,200 and 1,600 m for a total of eight runs. No group ran faster during competition, which may have been a reflection of the quality of horses used for this study and their susceptibility to stress-induced impairment of performance. Males showed no significant difference between competitive and solo run times, whereas females were consistently slower during competition. Males ran significantly faster than females in all runs. There was no difference in run times due to age, which may have been due to the high mean age (5.9 yr) of the group. The slower competitive run times may have occurred because of an earlier onset of fatigue when compared with solo runs. Plasma lactate was significantly greater for the 1,200-m competitive than for the solo runs.
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Pinchbeck, G. L., Clegg, P. D., Proudman, C. J., Morgan, K. L., & French, N. P. (2004). A prospective cohort study to investigate risk factors for horse falls in UK hurdle and steeplechase racing. Equine Vet J, 36(7), 595–601.
Abstract: REASONS FOR PERFORMING STUDY: Equine fatalities during racing continue to be a major welfare concern and falls at fences are responsible for a proportion of all equine fatalities recorded on racecourses. OBJECTIVES: To identify and quantify risk factors for horse falls in National Hunt (NH) racing and to report the frequency of falling and falling-associated fatalities. METHODS: A prospective cohort study was conducted on 2879 horse starts in hurdle and steeplechase races on 6 UK racecourses. Any horse that suffered a fall at a steeplechase or hurdle fence during the race was defined as a case. Data were obtained by interview and observations in the parade ring and from commercial databases. Multivariable logistic regression models, allowing for clustering at the level of the track, were used to identify the relationship between variables and the risk of falling. RESULTS: There were 124 falling cases (32 in hurdling and 92 in steeplechasing) identified. The injury risk of fallers was 8.9% and fatality risk 6.5%. Duration of journey to the racecourse, behaviour in the parade ring and weather at the time of the race were associated with falling in both hurdle and steeplechase racing. Age, amount of rainfall and going were also associated with falling in steeplechase racing. CONCLUSIONS: Falls at fences are significant contributors to equine fatalities during NH racing. Potentially modifiable risk factors identified were the condition of track surfaces and journey time to the racecourse. POTENTIAL RELEVANCE: It is hoped that information from this study may be used in future interventions to improve horse and jockey safety in racing. The study has also identified areas requiring further research, such as equine behaviour and its effect on racing performance, and the effect of light conditions on jumping ability.
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