A comparison of the mineral composition of milk of domestic and captive wild equids (Equus przewalski, E. zebra, E. burchelli, E. caballus, E. assinus)

Milk samples were obtained in early and/or late lactation from Przewalski horses, Hartmann's zebras, Grant's zebras, domestic horses, ponies and a mule mare made pregnant by embryo transfer. Samples were compared for their content of total solids, ash, calcium, phosphorus, magnesium, sodium, potassium, copper, zinc and iron. Milk from the Przewalski horses, Hartmann's zebra and the domestic horse had similar mineral composition and the content of minerals was higher in early than in late lactation. Milk from the domestic mule contained the lowest concentration of calcium, phosphorus and zinc but the highest concentration of magnesium, sodium and potassium. Milk from the Grant's zebras contained more sodium than potassium, unlike milk from Przewalski horses, Hartmann's zebras or domestic horses in which there was more potassium than sodium.     

Immunocontraception of captive exotic species. I. Przewalski's horses (Equus przewalskii) and banteng (Bos javanicus)

A contraceptive vaccine made of porcine zonae pellucidae (PZP) was tested in three Przewalski's mares and five banteng cows. The vaccine antigen consisted of the complete family of glycoproteins of the porcine zona pellucida, including the sperm receptor ZP3. All mares and three of five banteng were inoculated with 2 or 3 i.m. injections of approximately 65 μg of antigen given over a 6 week period. Two other banteng received inoculations of only 35 μg of antigen on the same schedule. Two of the three mares and three of five banteng cows were pregnant at the time of inoculation. No new pregnancies, as a result of postinoculation breedings, occurred among either the mares 36 months after 65 μg antigen inoculations or among the banteng for 24 months after 65 μg inoculations. One postinoculation pregnancy resulted among the two banteng receiving only 35 μg of antigen. Differences in fertility between treated and control mares and between preinoculation and postinoculation reproductive performance of the banteng were significant (P < 0.05). Urinary ovarian steroid metabolites and behavioral observations indicated follicular development and ovulations were occurring among treated mares during the year following PZP inoculations. PZP immunization produced progressively elevated anti-PZP antibodies in both species, which provided contraceptive protection. PZP immunization appears to be an effective form of contraception in both species. © 1995 Wiley-Liss, Inc.     

FISH analysis comparing genome organization in the domestic horse (Equus caballus) to that of the Mongolian wild horse (E. przewalskii)

Przewalski's wild horse (E. przewalskii, EPR) has a diploid chromosome number of 2n = 66 while the domestic horse (E. caballus, ECA) has a diploid chromosome number of 2n = 64. Discussions about their phylogenetic relationship and taxonomic classification have hinged on comparisons of their skeletal morphology, protein and mitochondrial DNA similarities, their ability to produce fertile hybrid offspring, and on comparison of their chromosome morphology and banding patterns. Previous studies of GTG-banded karyotypes suggested that the chromosomes of both equids were homologous and the difference in chromosome number was due to a Robertsonian event involving two pairs of acrocentric chromosomes in EPR and one pair of metacentric chromosomes in ECA (ECA5). To determine which EPR chromosomes were homologous to ECA5 and to confirm the predicted chromosome homologies based on GTG banding, we constructed a comparative gene map between ECA and EPR by FISH mapping 46 domestic horse-derived BAC clones containing genes previously mapped to ECA chromosomes. The results indicated that all ECA and EPR chromosomes were homologous as predicted by GTG banding, but provide new information in that the EPR acrocentric chromosomes EPR23 and EPR24 were shown to be homologues of the ECA metacentric chromosome ECA5.     

Cross-modal individual recognition in domestic horses (Equus caballus) extends to familiar humans

It has recently been shown that some non-human animals can cross-modally recognize members of their own taxon. What is unclear is just how plastic this recognition system can be. In this study, we investigate whether an animal, the domestic horse, is capable of spontaneous cross-modal recognition of individuals from a morphologically very different species. We also provide the first insights into how cross-modal identity information is processed by examining whether there are hemispheric biases in this important social skill. In our preferential looking paradigm, subjects were presented with two people and playbacks of their voices to determine whether they were able to match the voice with the person. When presented with familiar handlers subjects could match the specific familiar person with the correct familiar voice. Horses were significantly better at performing the matching task when the congruent person was standing on their right, indicating marked hemispheric specialization (left hemisphere bias) in this ability. These results are the first to demonstrate that cross-modal recognition in animals can extend to individuals from phylogenetically very distant species. They also indicate that processes governed by the left hemisphere are central to the cross-modal matching of visual and auditory information from familiar individuals in a naturalistic setting.     

Hemoglobin polymorphism in Equus przewalskii and E. caballus analyzed by isoelectric focusing.

1. Through the use of isoelectric focusing and peptide analysis, the hemoglobins of Przewalski's horse. Equus przewalskii and the domestic horse, E. caballus have been compared. 2. Przewalski's horses have two separate alpha-globin chain polymorphisms similar to domestic horses. Each hemoglobin phenotype could be accurately determined by isoelectric focusing. 3. Confirmation of the electrofocusing hemoglobin determinations was made by comparison to amino acid composition analyses of purified tryptic peptides and by analysis of the rare hemoglobins phenotypes observed in a family of Norwegian trotting horses. 4. Hemoglobin genotypes of fifteen Przewalski's horses were determined and inheritance of hemoglobin haplotypes has been observed.     

Effects of enrichment items on activity and social interactions in domestic horses (Equus caballus)

The aim of this study was to investigate the use of items intended to provide enrichment during turnout, both for individual and group kept horses in an attempt to reduce the amount of passive behaviours. The study was divided into two parts, where study 1 involved eight horses rotated through eight individual paddocks, each containing one of seven enrichment items and one paddock being kept without item, functioning as a control. The horses’ item-directed behaviours; passive behaviours or other non-item related activities were scored using instantaneous sampling, every minute for 1 h at the beginning and the end of the turnout period. Study 2 involved six horse groups (3–6 horses) and the same scoring methods and ethogram as in study 1. The four items that the horses interacted the most with during study 1 (straw STRA, ball filled with concentrates CBALL, branches BRAN and scratching pole POLE) are investigated in study 2. In addition, the amount of social interactions was recorded.Both horses kept individually (P < 0.05) and in groups (P < 0.0001) performed significantly more item-directed behaviours towards edible items like STRA and CBALL than other objects. There was, however, no overall relation between the numbers of item-directed behaviours and the number of passive behaviours observed, indicating that the enrichment items did not alone reduce the amount of passive behaviours during turnout periods. Such a reduction was, however, only apparent when horses spent more time eating green leaves growing on the paddock surface (R = ?0.97 study 1, R = ?0.67 study 2, P < 0.0001). Access to STRA in group kept horses also seemed to reduce the amount of agonistic behaviours (P < 0.0001). In conclusion, if grass is not available in paddocks, the provision of roughage reduces the amount of passive behaviours in singly kept horses and it also reduces the risk of agonistic interactions between horses kept in group.     

Spatial relations between mares and foals of the Welsh pony (Equus caballus)

Welsh pony mares and foals (Equus caballus) were usually found to be within 1 or 5 m of each other during the first week of the foal's life and gradually spent more time at greater distances as the foals became older. There was an overall levelling of the trend during the 9th–15th weeks of life of the foal, followed by a second period of change during weeks 16–24. Through weeks 21–24, mares and foals spent at least half of their time within 5 m of each other. Proximity was primarily due to foal activity except during foal recumbency. During the first 8 weeks of the foal's life, a mare remained close by when it was recumbent, either by grazing in a circle around it or by standing upright beside it. Mares and foals were most likely to be close together when they were resting upright with the other ponies in the herd and most likely to be far apart when the foal was playing. Similarities in patterns of spatial relationship between the foals of a given mare were demonstrated. There was no difference between colts and filies in the development of independence.     

An investigation of colour discrimination with horses (Equus caballus)

The ability of four horses (Equus caballus) to discriminate coloured (three shades of blue, green, red, and yellow) from grey (neutral density) stimuli, produced by back projected lighting filters, was investigated in a two response forced-choice procedure. Pushes of the lever in front of a coloured screen were occasionally reinforced, pushes of the lever in front of a grey screen were never reinforced. Each colour shade was randomly paired with a grey that was brighter, one that was dimmer, and one that approximately matched the colour in terms of brightness. Each horse experienced the colours in a different order, a new colour was started after 85% correct responses over five consecutive sessions or if accuracy showed no trend over sessions. All horses reached the 85% correct with blue versus grey, three horses did so with both yellow and green versus grey. All were above chance with red versus grey but none reached criterion. Further analysis showed the wavelengths of the green stimuli used overlapped with the yellow. The results are consistent with histological and behavioural studies that suggest that horses are dichromatic. They differ from some earlier data in that they indicate horses can discriminate yellow and blue, but that they may have deficiencies in discriminating red and green.     

Urinary androgen concentrations and social status in two species of free ranging zebra (Equus burchelli and E. grevyi)

In both species of zebra, breeding males had higher urinary androgen concentrations (ng androgens/mg Cr) than did non-breeding bachelor males (30.0 +/- 5.0 (N = 9) versus 11.4 +/- 2.8, (N = 7) in the plains zebra; 19.0 +/- 2.2 (N = 17) versus 10.7 +/- 1.2 (N = 14) in the Grevy's zebra). In the more stable family structure of the plains zebra (single male non-territorial groups) variations in androgen concentrations could not be ascribed to any measured variable. In the Grevy's zebra, androgen values were significantly lower in samples taken from territorial (breeding) males which had temporarily abandoned their territories (N = 4) and the urinary androgen concentration for a male on his territory was negatively correlated with the time since females last visited the territory.     

Mitochondrial control region and 12S rRNA variation in Przewalski's horse (Equus przewalskii)

Variation in the control region and the 12S rRNA gene of all surviving mitochondrial lineages of Przewalski's horse was investigated. Variation is low despite the present day population being descended from 13 individuals probably representing animals from three different regions of its range. Phylogenetic comparison of these sequences, with sequences for the domestic horse, does not resolve the ancestral status of either horse.     

Aggression and social spacing in light horse (Equus caballus) mares and foals

Aggression and social spacing were studied in 14 light horse mares and their foals living at pasture. Focal samples were collected on each mare-foal dyad for 6 to 10.5 h from 2 months of foal age until weaning at approximately 4 months of age. Observations on foals continued until approximately 6 months of age for 7.5 to 10.5 h per foal. Every 2 min the identities of all individuals within 5 m were recorded. All occurrences of agonistic behavior, and the participants, were recorded during the focal samples. In addition, during feeding of supplemental grain, all occurrences of agonistic behavior by all subjects were recorded. Significant correlations were found between mare rank and the rank of foals both prior to and after weaning. Before weaning, the rank of the foal was significantly correlated with birth order. No significant correlation between birth order and foal rank was found for the post-weaning hierarchy. An animal's gender had no significant effect on foal rank or the choice of preferred associate. Both prior to and after weaning, foals associated preferentially with the foal of their dam's most preferred associate. In addition, significant positive correlations were found between rank of mares and foals and the rate at which they directed aggression to other herd members.     

Monitoring ovarian function and pregnancy by evaluating excretion of urinary oestrogen conjugates in semi-free-ranging Przewalski's horses (Equus przewalskii).

Immunoreactive urinary oestrogen conjugates were assessed in daily urine samples (approximately 5 samples/week) collected from 8 Przewalski's mares maintained under semi-free-ranging pasture conditions. The relative percentage contributions of immunoreactive urinary oestrogens during different reproductive stages (oestrus, luteal phase, early, mid- and late gestation) were determined using high-pressure liquid chromatography. In general, conjugated forms of oestrone (oestrone sulphate and oestrone glucuronide) were the major excreted immunoreactive oestrogens in nonpregnant and pregnant Przewalski's mares. Variations in urinary oestrogen conjugates indicated that the onset of oestrous cyclicity coincided with increasing daylengths, and the non-conception oestrous cycle was 24.1 +/- 0.7 days (n = 17) in duration. Most copulations (29/35, 82.9%) were observed between Day -4 and Day +1 from the preovulatory oestrogen conjugates peak (Day 0). Based on known copulation dates, the mean gestation length was 48.6 +/- 0.4 weeks (range 47.3-50.3 weeks). During pregnancy, urinary excretion of oestrogen conjugates increased approximately 300-fold over levels in non-pregnant mares, reaching peak concentrations by Week +24 (51% of gestation). These results demonstrate that longitudinal reproductive events, including oestrous cyclicity and pregnancy, can be monitored precisely by evaluating urinary oestrogen conjugates in samples from Przewalski's mares maintained under semi-free-ranging conditions.     

Equine piroplasmoses at the reintroduction site of the Przewalski's horse (Equus ferus przewalskii) in Mongolia

Piroplasmosis has been identified as a possible cause of mortality in reintroduced Przewalski's horses (Equus ferus przewalskii) in the Dsungarian Gobi (Mongolia). A cross-sectional and a longitudinal study were conducted in a representative sample (n = 141) of the resident domestic horse population and in 23 Przewalski's horses to assess the prevalence of Theileria equi and Babesia caballi. Piroplasms were detected in blood by light microscopy in 6.7% (95% confidence interval [CI]: 3.6-12.2%) of the domestic horse samples. Antibody prevalence was 88.6% (95% CI: 82.4-92.9%) for T. equi and 75.2% (95% CI: 67.4-81.6%) for B. caballi. Antibody prevalence did not change over time, but antibody prevalence for both piroplasms were significantly lower in animals less than 1 yr of age. For both piroplasms, the prevalence of presumably maternal antibodies (falling titers) in foals was 100%. Only one of 16 foals seroconverted against T. equi during the study period, despite that piroplasms were found in two other individuals. The incidence density (ID) of T. equi in foals was therefore 0.0012 seroconversions per horse day (95% CI: 0.00029-0.0057). In contrast, yearlings had an ID of 0.0080 (95% CI: 0.0049-0.010) for T. equi and 0.0064 (95% CI: 0.0036-0.0093) for B. caballi, and in seven individuals piroplasms were detected. The seroprevalence of both piroplasms rose from 20% in spring to 100% in autumn. Comparison of domestic and Przewalski's horses resulted in a standardized prevalence ratio (SPR) of 0.98 (95% CI: 0.80-1.24, not significant) for B. caballi; in contrast, the prevalence of T. equi in Przewalski's horses was significantly lower than expected (SPR = 0.51, 95% CI: 0.50-0.64).     

Habitat use and movements of plains zebra (Equus burchelli) in response to predation danger from lions

Prey species must adapt their behavior to avoid predation. Asa key prey item for lions (Panthera leo), plains zebras (Equusburchelli) were expected to respond to immediate threats posedby lions in their area. In addition, zebras were predicted toexhibit behavior tuned to reduce the potential for encounterswith lions, by modifying their movement patterns in the timesof day and habitats of greatest lion danger. We studied a populationof approximately 600 plains zebra living in Ol Pejeta Conservancy,Kenya. We found that zebra abundance on or near a grasslandpatch was lower if lions had also been observed on that patchduring the same day. Predation danger was highest in grasslandhabitat during the night, when lions were more active. Zebrasightings and global positioning system radio collar data indicatedthat zebras also reduced their use of grassland at night, insteadusing more woodland habitat. Zebras moved faster and took sharperturns in grassland at night. It is hypothesized that these moreerratic movements assist zebras in avoiding detection or captureby lions.     

Elastic extension of leg tendons in the locomotion of horses (Equus caballus)

Several of the distal leg muscles of horses have such extremely short muscle fibres that their changes of length in locomotion must be due almost entirely to elastic extension of their tendons. Films of a horse have been analysed to determine these extensions, using data obtained by experiments on dissected legs. The tendons investigated experience peak strains of 3–6% in walking, 3–7% in trotting and 4–9% in galloping. These strains occur while the foot is on the ground.     

Foraging behaviour of wild impala (Aepyceros melampus) and Burchell's zebra (Equus burchelli) in relation to sward height

Foraging behaviour plays a key role in the interaction between herbivores and vegetation, their predominant food source. Understanding this interaction is crucial to providing information that is useful for conservation of herbivores. The objective of this study was to determine how sward height influences functional response and movement patterns of free ranging wild impala and zebra at the Kenya Wildlife Service Training Institute. The study was conducted for 3 months. Sward height is an important parameter that indicates how intensive a sward has been grazed and it influences intake rate through its effect on bite size. Bite size, instantaneous intake rate, specific mass intake rate and feeding station interval for impala and zebra increased with sward height. Sward height in combination with an animal's sex was found to have a profound effect on specific mass intake rate in impala. Zebra had a longer feeding station interval and lower stepping rate in tall swards compared to impala. Despite differences in their specific body mass and digestive strategies, impala and zebra maximized their intake rates in tall swards as a trade‐off among the swards. Tall swards are therefore critical in the study area and should be protected from bush encroachment which is a persistent problem.     

Seasonal thyroid and lipid profiles in Thoroughbred pregnant and nonpregnant mares (Equus caballus)

The purpose of this study was to determine which physiological seasonal thyroid and lipid panel (triglyceride, [TG], total cholesterol, [tCho], high-density lipoprotein cholesterol, [HDL Cho], LDL cholesterol, phospholipids, [PDs]) changes occur in 12 Thoroughbred pregnant and six nonpregnant mares over a period of 12 months, from April to March, by into account the lactation stage. Serum total triiodothyronine (T₃) and thyroxine (T₄) levels were measured using immunoenzymatic assay kits; the serum lipid panel was analyzed using the enzymatic colorimetric method. One-way ANOVA reported a significant effect of time over 12 months for T₃ (F = 5.46; P < 0.001) and T₄ (F = 3.98; P < 0.001), in both pregnant and nonpregnant mares, and for triglyceride (F = 2.57; P < 0.01), tCho (F = 2.32; P < 0.01), HDL Cho (F = 5.60; P < 0.0001), and PDs (F = 7.01; P < 0.0001) in pregnant mares. Two-way ANOVA repoted a significant lactating effect compared with nonlactating stage for T₃ (F = 8.33; P = 0.006), T₄ (F = 6.43; P = 0.003), tCho (F = 10.38; P = 0.0078), HDL Cho (F = 7.64; P = 0.020), and PDs (F = 5.07; P = 0.048). Thus, it appears that under similar environmental condition, nutrition regime, and management system, lactation stage plays a significant role in the seasonal thyroid and lipid profiles in Thoroughbred pregnant mares, with higher T₃, T₄, and PDs values, and lower tCho and HDL Cho in lactating than nonlactating mares. The physiological values obtained in this study may be used as additional resources to evaluate thyroid and lipid profiles in Thoroughbred pregnant and nonpregnant mares, generating a wished numbers of observation, especially when the additional breed and physiological conditions are considered.