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Kronfeld, D. S., Custalow, S. E., Ferrante, P. L., Taylor, L. E., Wilson, J. A., & Tiegs, W. (1998). Acid-base responses of fat-adapted horses: relevance to hard work in the heat. Appl. Anim. Behav. Sci., 59(1-3), 61–72.
Abstract: Feeding and training may affect acid-base responses to strenuous exercise. Acidosis usually correlates with higher blood lactate concentrations during intense exercise, but alkalosis has been found in several studies of horses, and higher lactate responses during sprints have been found in fat adapted horses. To elucidate these unexpected findings, we applied a comprehensive physicochemical approach to evaluate acid-base responses during exercise in fat adapted horses. In incremental tests and repeated sprints, changes in blood [H+] were dependent upon corresponding changes in pCO2 but not strong ion difference (SID, the algebraic sum of ions of sodium, potassium, chloride and lactate). The influence of changes in [Lac-] were largely offset by changes in [Na+], [K+] and [Cl-], so that SID was unchanged and did not contribute to the exercise induced acidemia, so it may be inaccurate to term this a lacticacidosis. During repeated sprints, central venous [H+] increased (acidosis) but arterial [H+] decreased (alkalosis). These changes were consistent with concurrent changes in venous and arterial pCO2 but not SID. Fat adaptation decreased mixed venous pCO2 during repeated sprints, which is consistent with the lower respiratory quotient associated with fat oxidation. Less pulmonary work to eliminate CO2 could benefit horses under hot and humid conditions, especially those with mildly reduced pulmonary function. The blood lactate response was decreased during aerobic tests but increased during anaerobic tests on fat adapted horses. Fat adaptation appears to facilitate the metabolic regulation of glycolysis, by sparing glucose and glycogen at work of low intensity, but by promoting glycolysis when power is needed for high intensity exercise. The blood lactate response to repeated sprints was increased more by the combination of fat adaptation and oral supplementation of sodium bicarbonate than by the sum of the responses to fat alone or bicarbonate alone. This synergism suggests that need for further studies of the interaction of fat adaptation with dietary cation-anion balance, especially under hot conditions. These results integrate harmoniously with previous findings of lower feed intake and fecal output, lower loads of heat and CO2, lower water losses in the feces and by evaporation, and less spontaneous activity and reactivity in fat adapted horses. Thus fat adaptation confers several advantages on horses and presumably other equids used for hard work, especially in the heat.
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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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Muller, C. E., & Uden, P. (2007). Preference of horses for grass conserved as hay, haylage or silage. Animal Feed Science and Technology, 132(1-2), 66–78.
Abstract: The purpose of this experiment was to determine if different methods of forage conservation influenced horse preference for conserved forages. Silage, haylage with two different dry matter (DM) levels and hay was produced from the same grass crop at the same botanical maturity stage. Four horses were simultaneously offered the four forages (1 kg DM of each forage) once daily for four consecutive experimental periods, each period consisting of 5 days. On each experimental day, the horses were observed for 2 h and their first choice, eating time and forage consumption was registered for every forage. The number of times each horse depleted individual forages and the number of times each horse tasted or smelled a forage, but left it in favour of another forage, was also recorded. Silage had the highest rate of consumption (0.90 kg DM/day, S.D. 0.14) and longest eating time (28.4 min/day, S.D. 5.16). Hay had the lowest rate of consumption (0.23 kg DM/day, S.D. 0.14) and shortest eating time (6.8 min/day, S.D. 4.08), while the haylages were intermediate. Silage was the first choice 72 of 84 times (85%). Hay was never completely consumed and silage was never left in favour of another forage after smelling or tasting it. We conclude that the forage conservation methods had an impact on horse preference in favour of silage, even if the reason for silage preference remains to be explained.
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Slater, C., & Dymond, S. (2011). Using differential reinforcement to improve equine welfare: Shaping appropriate truck loading and feet handling. Behav. Process., 86(3), 329–339.
Abstract: Inappropriate behavior during common handling procedures with horses is often subject to aversive treatment. The present study replicated and extended previous findings using differential reinforcement to shape appropriate equine handling behavior. In Study 1, a multiple baseline across subjects design was used with four horses to determine first the effects of shaping target-touch responses and then successive approximations of full truck loading under continuous and intermittent schedules of reinforcement. Full loading responses were shaped and maintained in all four horses and occurrences of inappropriate behaviors reduced to zero. Generalization of the loading response was also observed to both a novel trainer and trailer. In Study 2, a changing criterion design was used to increase the duration of feet handling with one horse. The horse's responding reached the terminal duration criterion of 1 min and showed consistent generalization and one-week maintenance. Overall, the results of both studies support the use of applied equine training systems based on positive reinforcement for increasing appropriate behavior during common handling procedures.
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Cozzi, A., Sighieri, C., Gazzano, A., Nicol, C. J., & Baragli, P. (2010). Post-conflict friendly reunion in a permanent group of horses (Equus caballus). Behav. Process., 85(2), 185–190.
Abstract: Gregarious animals living in permanent social groups experience intra-group competition. Conflicts over resources can escalate into costly aggression and, in some conditions, non-dispersive forms of conflict resolution may be favoured. Post-conflict friendly reunions, hence reconciliation, have been described in a variety of species. The aim of this study was to explore, for the first time, the occurrence of reconciliation in a group of domestic horses (Equus caballus) and learn more about strategies used to maintain group cohesion. The behaviour of seven horses living as permanent group in an enclosure for at least 2 years was observed by video for 108 h from June to August 2007. We used a Post-Conflict/Matched Control method to assess the existence of reconciliation and third-party affiliation. Behaviours recorded Post-Conflict, or during Matched Control periods, were classified as affiliative based on previous descriptions of visual communication patterns in horses. The proportion of attracted pairs over total post-conflict situations was significantly greater than the proportion of dispersed pairs, both during dyadic interactions (p < 0.001) and during triadic interactions (p = 0.002). The results of the present study show that both dyadic reconciliation and third-party post-conflict affiliative interactions form important social mechanisms for managing post-conflict situations in horses.
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Blackmore, T. L., Foster, T. M., Sumpter, C. E., & Temple, W. (2008). An investigation of colour discrimination with horses (Equus caballus). Behav. Process., 78(3), 387–396.
Abstract: 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.
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Feh, C., & Munkhtuya, B. (2008). Male infanticide and paternity analyses in a socially natural herd of Przewalski`s horses: Sexual selection? Behav. Process., 78(3), 335–339.
Abstract: The sexual selection hypothesis explains infanticide by males in many mammals. In our 11-year study, we investigated this hypothesis in a herd of Przewalski's horses where we had witnessed infanticidal attacks. Infanticide was highly conditional and not simply linked to takeovers. Attacks occurred in only five of 39 cases following a takeover, and DNA paternity revealed that, although infanticidal stallions were not the genetic fathers in four cases out of five, stallions present at birth did not significantly attempt to kill unrelated foals. Infanticide did not reduce birth intervals; only in one case out of five was the infanticidal stallion, the father of the next foal; mothers whose foals were attacked subsequently avoided associating with infanticidal stallions. Therefore, evidence for the sexual selection hypothesis was weak. The “human disturbance” hypothesis received some support, as only zoo bred stallions which grew up in unnatural social groups attacked foals of mares which were pregnant during takeovers.
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Murphy, J., & Arkins, S. (2007). Equine learning behaviour. Behav. Process., 76(1), 1–13.
Abstract: Scientists and equestrians continually seek to achieve a clearer understanding of equine learning behaviour and its implications for training. Behavioural and learning processes in the horse are likely to influence not only equine athletic success but also the usefulness of the horse as a domesticated species. However given the status and commercial importance of the animal, equine learning behaviour has received only limited investigation. Indeed most experimental studies on equine cognitive function to date have addressed behaviour, learning and conceptualisation processes at a moderately basic cognitive level compared to studies in other species. It is however, likely that the horses with the greatest ability to learn and form/understand concepts are those, which are better equipped to succeed in terms of the human-horse relationship and the contemporary training environment. Within equitation generally, interpretation of the behavioural processes and training of the desired responses in the horse are normally attempted using negative reinforcement strategies. On the other hand, experimental designs to actually induce and/or measure equine learning rely almost exclusively on primary positive reinforcement regimes. Employing two such different approaches may complicate interpretation and lead to difficulties in identifying problematic or undesirable behaviours in the horse. The visual system provides the horse with direct access to immediate environmental stimuli that affect behaviour but vision in the horse is of yet not fully investigated or understood. Further investigations of the equine visual system will benefit our understanding of equine perception, cognitive function and the subsequent link with learning and training. More detailed comparative investigations of feral or free-ranging and domestic horses may provide useful evidence of attention, stress and motivational issues affecting behavioural and learning processes in the horse. The challenge for scientists is, as always, to design and commission experiments that will investigate and provide insight into these processes in a manner that withstands scientific scrutiny.
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Heitor, F., do Mar Oom, M., & Vicente, L. (2006). Social relationships in a herd of Sorraia horses: Part II. Factors affecting affiliative relationships and sexual behaviours. Behav. Process., 73(3), 231–239.
Abstract: The influence of age, dominance rank, kinship and aggressiveness over affiliative relationships and sexual behaviours were analysed in a herd of Sorraia horses, Equus caballus, kept under extensive management. Subjects were 10 adult mares 5-18 years old that had known each other since birth, and a stallion introduced into the group for breeding for the first time. Kinship coefficient and dominance rank were the most important factors affecting affiliative relationships. Bonds were reciprocal and stronger among mares with higher kinship. Mares spent more time in proximity to close-ranking and lower-ranking females. Mares with stronger affiliative relationships or higher relatedness were not less aggressive towards each other. Affiliative relationships between the stallion and the mares were not reciprocal: lower-ranking mares formed stronger bonds with the stallion but he preferred the less genetically related mares for proximity. However, the stallion was involved in sexual behaviours more frequently with the mares that were more genetically related to him. These results suggest that kinship beyond close relatives may affect affiliative relationships both among familiar and among unfamiliar horses. However, the influence of kinship does not imply that horses possess a kin recognition system and alternative explanations are discussed.
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Wolff, A., Hausberger, M., & Le Scolan, N. (1997). Experimental tests to assess emotionality in horses. Behav. Process., 40(3), 209–221.
Abstract: Different tests were used to assess different aspects of the emotionality of 1-3 year-old horses: arena test; a [`]novel object' test; and a handling test. In reaction to the test situations no important differences were observed according to age or sex in the behaviour patterns, but clear individual differences were observed within these classes. The arena test seemed to reveal the degree of gregariousness of the animals whereas the results in the two other tests were correlated and seemed to reflect an inherent degree of fearfulness in the horse. Indices were developed that enabled to rank the animals, by taking into account all behaviour patterns shown. Such individual characteristics might have some genetic basis: half-siblings tended to behave the same way in most cases.
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