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Robert, N., Walzer, C., Ruegg, S. R., Kaczensky, P., Ganbaatar, O., & Stauffer, C. (2005). Pathologic findings in reintroduced Przewalski's horses (Equus caballus przewalskii) in southwestern Mongolia. J Zoo Wildl Med, 36(2), 273–285.
Abstract: The Przewalski's horse (Equus caballus przewalskii) was extinct in the wild by the mid 1960s. The species has survived because of captive breeding only. The Takhin Tal reintroduction project is run by the International Takhi Group; it is one of two projects reintroducing horses to the wild in Mongolia. In 1997 the first harem group was released. The first foals were successfully raised in the wild in 1999. Currently, 63 Przewalski's horses live in Takhin Tal. Little information exists on causes of mortality before the implementation of a disease-monitoring program in 1998. Since 1999, all dead horses recovered (n = 28) have been examined and samples collected and submitted for further investigation. Equine piroplasmosis, a tick-transmitted disease caused by Babesia caballi or Theileria equi, is endemic in Takhin Tal and was identified as the cause of death of four stallions and one stillborn foal. In December 2000, wolf predation was implicated in the loss of several Przewalski's horses. However, thorough clinical, pathologic, and bacteriologic investigations performed on dead and surviving horses of this group revealed lesions compatible with strangles. The extreme Mongolian winter of 2000-2001 is thought to have most probably weakened the horses, making them more susceptible to opportunistic infection and subsequent wolf predation. Other occasional causes of death since 1999 were trauma, exhaustion, wasting, urolithiasis, pneumonia, abortion, and stillbirth. The pathologic examination of the Przewalski's horses did not result in a definitive diagnosis in each case. Several disease factors were found to be important in the initial phase of the reintroduction, which could potentially jeopardize the establishment of a self-sustaining population.
Keywords: Animals; Babesiosis/epidemiology/pathology/*veterinary; Cause of Death; Conservation of Natural Resources; Disease Susceptibility/veterinary; Environment; Female; Food Chain; Horse Diseases/*epidemiology/pathology; Horses; Male; Mongolia/epidemiology; Streptococcal Infections/epidemiology/pathology/*veterinary; *Streptococcus equi; Theileriasis/*epidemiology/pathology; Weather
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Belonje, P. C., & van Niekerk, C. H. (1975). A review of the influence of nutrition upon the oestrous cycle and early pregnancy in the mare. J Reprod Fertil Suppl, (23), 167–169.
Abstract: Attention is drawn to the beneficial effect of improved nutrition during winter and early spring on the ovarian activity of mares. Furthermore, the necessity of an adequate plane of nutrition during early pregnancy to prevent embryonic resorption is stressed.
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Berger, A., Scheibe, K. - M., Eichhorn, K., Scheibe, A., & Streich, J. (1999). Diurnal and ultradian rhythms of behaviour in a mare group of Przewalski horse (Equus ferus przewalskii), measured through one year under semi-reserve conditions. Appl. Anim. Behav. Sci., 64(1), 1–17.
Abstract: Investigations were conducted on four horses from a group of 12 Przewalski mares raised in different zoos and kept in a 44-ha enclosure under semi-natural conditions. Activity and feeding were continuously measured every second and were saved every 15 min by the storage-telemetry system ETHOSYS, from June 1995 to July 1996. Body mass of the horses was regularly recorded. Daily and monthly mean values, power spectra and DFC (as a measure for stability of rhythms synchronised with circadiurnal period) for activity and feeding were calculated. The general pattern of activity and feeding over the year was closely related to sunrise and sunset. Feeding accounted for 40% of total activity in summer and 62% in spring (all-year average being 52%). The level of activity was lowest in winter; whereas feeding was lowest in summer. The time budget for feeding reflected both feeding conditions and the annual pattern of body condition. Greatest activity occurred during daylight hours. Only on hot summer days, activity at night was higher than during daylight hours. Spectral analysis of activity and feeding in Przewalski horse showed a time pattern which was characterised by 24-h rhythmicity, but also by ultradian components with period lengths between 4.8 and 12 h, i.e., an activity pattern of up to five strong bouts per day. Annual variation in the pattern of power spectra was not high during the year. Results are discussed in connection with horse feeding strategy. Analysing the time structure of long-term and continuously measured activity and feeding could be a useful method to follow the general living conditions, especially the nutritional situation and to detect stressful conditions.
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Boyd, L. (1998). The 24-h time budget of a takh harem stallion (Equus ferus przewalskii) pre- and post-reintroduction. Appl. Anim. Behav. Sci., 60(4), 291–299.
Abstract: Focal animal sampling was used to determine the 24-h time budget of a takh harem stallion (Equus ferus przewalskii) during the 2 weeks prior to, and the two weeks following, reintroduction into the Hustain Nuruu Steppe Reserve, Mongolia. Both before and after release, the stallion spent approximately 47% of his time grazing, 6% standing, and 5% in recumbent rest. The biggest changes to the time budget after release were a 4-fold increase in the amount of time spent moving, and a 50% decrease in the amount of time spent resting in a standing position. During the middle of the day when the temperatures were hottest, the stallion exhibited less grazing and more standing resting behaviour than in the morning or evening hours. Recumbent rest invariably occurred in the hours before dawn.
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Breen, M., Downs, P., Irvin, Z., & Bell, K. (1994). Intrageneric amplification of horse microsatellite markers with emphasis on the Przewalski's horse (E. przewalskii). Anim Genet, 25(6), 401–405.
Abstract: Primer sequences flanking 13 microsatellite loci isolated from the domestic horse (E. caballus) were successfully used to amplify homologous loci in the Przewalski's horse (E. przewalskii). The results demonstrate that the level of polymorphism at all 13 loci in the Przewalski's horse was comparable to that in the domestic horse and the overall exclusion probability in the Przewalski's horse was calculated to be 0.9994. The results suggest that it should be possible to use E. caballus-derived microsatellite markers to provide parentage verification and additional valuable information to the captive management of E. przewalskii. The ability to amplify corresponding loci in the remaining five species of the genus was also confirmed, illustrating the general application of markers isolated from the domestic horse to the evaluation of polymorphism in the other six species of the genus.
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Lucas, Z., Raeside, J. I., & Betteridge, K. J. (1991). Non-invasive assessment of the incidences of pregnancy and pregnancy loss in the feral horses of Sable Island. J Reprod Fertil Suppl, 44, 479–488.
Abstract: Field observations of 400 totally unmanaged feral horses on Sable Island, Nova Scotia, were complemented by oestrogen determinations in faecal samples from 154 identified females over a 4-year period (454 mare-years). Of mares that were sampled throughout the year and subsequently produced foals, 92.1% exhibited elevated faecal oestrogens between 15 October and 30 March. The results confirm that faecal oestrogens are a useful indicator of pregnancy after approximately 120 days gestation. Distribution of foaling resembled that seen in other feral populations, with 95% of births occurring from April through July. The foaling rate for mares aged 3 years or older was 62.0%, with 50.7% of mares foaling in 3 or 4 years. Foaling rates were low (4.1%) in mares bred as yearlings and rose with age to 70.8% in those bred as 4-year-olds. Fetal loss after Day 120 was deduced from faecal oestrogens to be 26.0% overall, with marked variation from year to year (9.6-37.3%) and with age (70.0% in those bred as yearlings, decreasing to 5.6% in those bred as 4-year-olds). Of 58 mares aged 2 years or older that were sampled every year, about half (49.6%) the barren years were attributable to fetal loss after 120 days gestation. All mares conceived in at least 2 of the 4 years, suggesting that pregnancy loss, even after Day 120, is as important as failure to conceive in causing barren years.
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Christensen, J. W., Keeling, L. J., & Nielsen, B. L. (2005). Responses of horses to novel visual, olfactory and auditory stimuli. Appl. Anim. Behav. Sci., 93(1-2), 53–65.
Abstract: Responses of horses towards fear-eliciting stimuli can have important consequences for both human and horse safety. This experiment was designed to investigate behavioural and heart rate (HR) responses of horses to novel visual, auditory and olfactory stimuli. Twenty-four 2-year-old, previously unhandled, stallions were habituated to receive a food reward from a container in a test arena. Each horse was exposed to three 2 min tests in a balanced design where in addition to the feed container, either a traffic cone (visual test), white noise (auditory test) or eucalyptus oil applied to the inside of the container (olfactory test) were used as the novel stimuli. Compared to the control, less time was spent eating during all tests. There was no difference in locomotion activity in the different test situations, but presentation of the novel visual and auditory stimuli elicited significantly increased HR responses in the horses, compared to their response to the arena without novel stimuli (control), whereas there was no increase in HR response to the olfactory stimulus. However, during the olfactory test, the horses had an increased number of eating bouts and became more vigilant towards their surroundings, whereas during the visual and auditory tests, more time was spent alert towards the stimulus. The horses also took significantly more steps backwards in response to the auditory test. The heart rate responses correlated between tests and reflect a non-differentiated activation of the sympathetic nervous system, while the behavioural responses were linked to the type of stimulus.
Keywords: Horses; Novelty responses; Fear; Behaviour; Heart rate
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Christensen, J. W., Ladewig, J., Sondergaard, E., & Malmkvist, J. (2002). Effects of individual versus group stabling on social behaviour in domestic stallions. Appl. Anim. Behav. Sci., 75(3), 233–248.
Abstract: Domestic horses (Equus caballus) are typically kept in individual housing systems, in which they are deprived of physical contact. In order to study the effects of social restrictions on behaviour in young horses, nineteen 2-year-old stallions were housed either singly (n=7), or in groups of three (n=12) for 9 months. Subsequently, the stallions were released into two separate 2 ha enclosures according to treatment, and recordings were made on social interactions and nearest neighbours during a 6-week-period, 28 h per week. Previously group stabled stallions frequently had a former group mate as their nearest neighbour (P=0.001), whereas previously singly stabled stallions did not associate more with their former box neighbours, to whom physical contact was limited by bars during the previous treatment. The nearest neighbour was more frequently recorded to be within one horselength of singly stabled than of group stabled stallions (P=0.005). More aggressive behaviour was recorded in the group of previously singly stabled stallions, i.e. bite threats (P=0.032), whereas group stabled stallions tended to make more use of subtle agonistic interactions (displacements, submissive behaviour). Singly stabled stallions also responded to the 9 months of social deprivation by significantly increasing the level of social grooming (P<0.001) and play behaviour (P<0.001), when subsequently interacting freely with other horses. The increased occurrence may relate to a build-up of motivation (a rebound effect), as well as to external factors, such as playful pasture companions and the increased space allowance of the pasture. It is concluded that 2-year-old domestic stallions are sensitive to social deprivation and that stabling has long-term effects, lasting 6 weeks at least, on the social behaviour in stallions.
Keywords: Horse; Individual stabling; Group stabling; Social behaviour
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Barber, J. A., & Crowell-Davis, S. L. (1994). Maternal behavior of Belgian (Equus caballus) mares. Appl. Anim. Behav. Sci., 41(3-4), 161–189.
Abstract: The relationship between ten Belgian mares and their offspring was studied from the first day of foal life to 17 weeks of age. Mares and foals spent more time at greater distances from each other as foals matured. Mares exhibited the recumbency response, being in closer proximity to their foals when foals were recumbent than when they were upright. Foals initiated the majority of nursing bouts. Frequency and duration of nursing bouts and percentage of time resting recumbently declined as foals matured. Foals also terminated the their foals, and they were most likely to do so in the first month of foal life. Maternal initiation of nursing. There was usually no discernible foal response to maternal aggression. Little difference between maternal behavior directed towards colts and fillies was found for all aspects of the study. Maternal behavior in the Belgian draft horse was similar to that reported for other equid breeds.
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Crowell-Davis, S. L. (1994). Daytime rest behavior of the Welsh pony (Equus caballus) mare and foal. Appl. Anim. Behav. Sci., 40(3-4), 197–210.
Abstract: Upright and recumbent rest of 15 Welsh pony foals and their mothers was studied over a 2 year period. During their first week of life, the foals spent 32% of the time in recumbent rest. Subsequently, the percentage of time spent in recumbent rest decreased, but was still greater than for the foal's mother by Week 21, when the foals spent 6.5% of their time in recumbent rest. Adults spent little time in recumbent rest. Foals rested upright only 3.5% of the time during their first week of life. Mares rested upright more than foals did to Week 13, at which time peak values for time spent in upright rest occurred for both mares (32.5%) and foals (23%). Subsequently, mares and foals spent equal, but decreasing, amounts of time resting upright. The total time spent resting by the foals decreased gradually, and was characterized by a transition from recumbent rest to upright rest. Foals were more likely to be resting, either recumbent or upright, if their mother was resting upright. During the late spring, summer, and early autumn, mares and foals were most likely to be resting upright between 09:00 and 17:00 h.
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