Abstract: The equilibrium unfolding and the kinetics of unfolding and refolding of equine lysozyme, a Ca2+-binding protein, were studied by means of circular dichroism spectra in the far and near-ultraviolet regions. The transition curves of the guanidine hydrochloride-induced unfolding measured at 230 nm and 292.5 nm, and for the apo and holo forms of the protein have shown that the unfolding is well represented by a three-state mechanism in which the molten globule state is populated as a stable intermediate. The molten globule state of this protein is more stable and more native-like than that of α-lactalbumin, a homologous protein of equine lysozyme. The kinetic unfolding and refolding of the protein were induced by concentration jumps of the denaturant and measured by stopped-flow circular dichroism. The observed unfolding and refolding curves both agreed well with a single-exponential function. However, in the kinetic refolding reactions below 3 M guanidine hydrochloride, a burst-phase change in the circular dichroism was present, and the burst-phase intermediate in the kinetic refolding is shown to be identical with the molten globule state observed in the equilibrium unfolding. Under a strongly native condition, virtually all the molecules of equine lysozyme transform the structure from the unfolded state into the molten globule, and the subsequent refolding takes place from the molten globule state. The transition state of folding, which may exist between the molten globule and the native states, was characterized by investigating the guanidine hydrochloride concentration-dependence of the rate constants of refolding and unfolding. More than 80% of the hydrophobic surface of the protein is buried in the transition state, so that it is much closer to the native state than to the molten globule in which only 36% of the surface is buried in the interior of the molecule. It is concluded that all the present results are best explained by a sequential model of protein folding, in which the molten globule state is an obligatory folding intermediate on the pathway of folding.

Abstract: This article reviews the effects of diet on equine feeding behavior and feeding patterns, before considering the evidence that diet affects reactivity in horses. A growing body of work suggests that fat- and fiber-based diets may result in calmer patterns of behavior, and possible mechanisms that may underpin these effects are discussed. In contrast, there is little evidence that herbal- or tryptophan-containing supplements influence equine behavior in any measurable way. The role of diet in the development of abnormal oral behaviors, particularly the oral stereotypy crib-biting, is also reviewed, and suggestions for future work are presented.

Abstract: Recent studies have suggested that crib-biting in horses is associated with diminished capacity of learning or coping with stress. Such findings raise the question whether trainability, which is fundamentally important in practice, could also be affected by stereotypic behaviour. Trainability of a horse is difficult to assess in simple tests, however, it is reliably estimated by experienced riders. To assess trainability and other characteristics related to that, a questionnaire survey was conducted with the owners of 50 crib-biting and 50 control horses. Where possible, control horses were selected from the same establishment as crib-biters. Groups did not differ significantly regarding age, breed, gender, training level or usage. Principal component analysis revealed three main factors which can be labelled as [`]Anxiety', [`]Affability' and [`]Trainability'. The [`]Anxiety' factor consisted of the items [`]Nervousness', [`]Excitability', [`]Panic', [`]Inconsistent emotionality', [`]Vigilance', [`]Skittishness', and [`]Timidity'. [`]Affability' consisted of [`]Friendliness toward people', [`]Cooperation', [`]Docility' and [`]Friendliness toward horses'. [`]Trainability' involved [`]Concentration', [`]Trainability', [`]Memory', and [`]Perseverance'. Temperament traits were not affected by age, gender, breed or training level, but the usage of the horse and the presence of crib-biting behaviour had significant effects. Competition horses had lower level of [`]Anxiety' (p = 0.032) and higher level of [`]Trainability' (p = 0.068) than leisure horses. Crib-biting horses had significantly lower level of [`]Anxiety' than control horses (p < 0.001), while [`]Trainability' and [`]Affability' did not differ between groups (p = 0.823 and p = 0.543, respectively). Competition horses are more often exposed to novel environment and to frightening stimuli (e.g. colourful obstacles) than leisure horses and therefore might have also become more habituated to these types of stimuli. Coping with novel situation may be enhanced by defusing nervous behaviour by the more experienced riders of competition. Previous studies indicated crib-biting horses to be less reactive when challenged as compared to control horses. We suggest that the virtual calmness and lower nervousness of the crib-biting horses might be due to the passive coping style of these animals. [`]Affability' of horses might be more related to housing and management conditions than to crib-biting. Contrary to expectations, scores on [`]Trainability' had not coincided with the impaired learning of crib-biting horses reported in laboratory tests. However, previous behavioural tests on equine learning rarely had a direct relevance to the training abilities of the horses. Our results do not support crib-biting stereotypy to affect performance in training, which is a complex learning process involving cooperation and docility in the social environment.

Abstract: Removing a horse from its social group may be considered risky, both for the handler and the horse, because other horses can interfere in the catching process. The main aim of this study was to identify where and when these risk situations occur while removing a horse from its group. A potential risk situation was defined by the closeness of loose horses in the group or by any physical contact with them. Whether the number of horses following would be influenced by the social rank of the horse being led out, and whether more horses would follow to the gate when a larger proportion of the group was removed compared to when a single horse was taken out were also investigated. Thirty-two mares (1–2 years) were kept in groups of four. All horses were taken out of their home paddock twice alone (64 tests) and twice with a companion (32 tests). One handler (or two handlers when two horses were removed) was asked to approach (phase 1) and catch the target horse (phase 2), walk it to the centre of the paddock and remain stationary at a post for 30 s (phase 3), walk to the paddock entrance (phase 4) and through the gate (phase 5). The number of horses following, and the number of loose horses in proximity (<2 m, 2–5 m) to the target horse and handler was estimated, and horse–horse and horse–human interactions were recorded continuously for the five scoring phases. Significantly more loose horses were within 2 m of a single target horse during the phases approach (mean ± SD: 1.5 ± 0.8), catch (1.6 ± 0.9) and post (1.7 ± 0.7) than during walk (1.0 ± 0.5) and gate (1.1 ± 0.6). Rank did not influence the number of horses following to the gate (high rank: 2.4 ± 0.7; lower rank: 2.0 ± 1.0; P = 0.396) and interactions between horses were rare. A greater proportion of the loose horses followed when two horses (0.9 ± 0.2) were removed compared to when a single horse (0.7 ± 0.3) was taken out (P = 0.011). In conclusion, maintaining a distance to other horses in the group by reducing the time being relatively stationary, so giving loose horses fewer chances to approach, is likely to contribute to improved handler's safety. Removing a small proportion of the group may also decrease the probability of the other horses following.

Abstract: Objective The goal of this work is to study the dark adaptation curve of the normal horse electroretinogram (ERG). Procedures The electroretinographic responses were recorded from six healthy female ponies using a contact lens electrode and a mini-Ganzfeld electroretinographic unit. The horses were sedated intravenously with detomidine, an auriculopalpebral nerve block was then performed, and the pupil was fully dilated. The ERG was recorded in response to a low intensity light stimulus (30 mcd.s/m2) that was given at times (T) T = 5, 10, 15, 20, 25, 30, 40, 50, and 60 min of dark adaptation. Off-line analysis of the ERG was then performed. Results Mean b-wave amplitude of the full-field ERG increased continuously from 5 to 25 min of dark adaptation. The b-wave amplitude peaked at T = 25, however, there was no statistical significance between T = 20 and T = 25. The b-wave amplitude then remained elevated with no significant changes until the end of the study at T = 60 (P > 0.49). The b-wave implicit time increased continuously between T = 5 and T = 20, then gradually decreased until T = 60. No distinct a-wave was observed during the testing time. Conclusions Evaluation of horse rod function or combined rod/cone function by means of full-field ERG should be performed after a minimum 20 min of dark adaptation.