Abstract: REASONS FOR PERFORMING STUDY: Horses housed in conventional stable environments are exposed to high dust loads. Long-term exposure to inhaled dust may lead to subclinical airway disease. HYPOTHESES: Airway inflammation and mucus accumulation are 1) common in asymptomatic well-performing sport horses, 2) increased in older compared to younger individuals and 3) correlated. METHODS: Mucus quantity and quality (endoscopic scoring) and BALF differential cytology were assessed in 13 younger horses (mean age 5 years) and 13 older horses (mean age 15 years), which had no historical or clinical evidence of lower airway disease, were performing well and were housed permanently in a conventional stable environment. RESULTS: 1) Airway inflammation and/or mucus accumulation were very common. All sport horses showed evidence of subclinical inflammatory airway disease (IAD). 2) Older horses, having been exposed for 10 more years to a conventional stable environment, did not show increased subclinical airway inflammation or mucus accumulation. The only differences between the age groups were increased BALF total and lymphocyte cell counts in the younger horses. 3) Mucus quantity and quality scores were not significantly correlated with each other or with BALF neutrophil percentages and absolute numbers. CONCLUSIONS: Although clinically healthy and performing well, all of the examined horses housed in a conventional stable environment showed evidence of IAD. The degree of IAD was not increased in older horses that had not developed clinical signs. POTENTIAL RELEVANCE: The effect of subclinical degrees of IAD on performance in dressage and show jumping should be investigated further to better understand the clinical significance of IAD in sport horses.

Abstract: Faecal samples were collected at weekly intervals from pregnant Lipizzan mares during Weeks 7-16 following mating and from Lipizzan, Trotter and Thoroughbred mares during the last 3 months of gestation. After parturition, samples were taken daily from the Thoroughbred mares for another 6 days. Non-pregnant mares served as controls. The concentrations of unconjugated oestrogens (Eg), 20 alpha-OH-progestagens (20 alpha-G) and 20 beta-OH-progestagens (20 beta-G) were measured by enzyme immunoassay. In the faeces of Lipizzan mares, immunoreactive progestagens were significantly (P less than 0.01) elevated above the levels in non-pregnant mares by Week 11, and Eg by Week 13 of pregnancy onwards. During the last 3 months of gestation, concentrations of Eg were significantly higher in Trotter mares than in Lipizzan and Thoroughbred mares. Concentrations of 20 alpha-G and 20 beta-G increased to maximal values in the last month of gestation. There was no significant difference among the 3 breeds with respect to 20 alpha-G but, during the 10 weeks before parturition, concentrations of 20 beta-G in the Lipizzan mares were significantly lower (P less than 0.05) than those in the Thoroughbred mares. They were also significantly lower than those of the Trotter mares during the last 4 weeks of gestation. After parturition, the concentrations of Eg and progestagens had declined to baseline values by Days 3 and 4 respectively. From these results we conclude that high concentrations of progestagens with 20 alpha- and 20 beta-hydroxyl groups are present in the faeces of pregnant mares, especially during the last month of gestation.

Abstract: Lateralization of emotions has received great attention in the last decades, both in humans and animals, but little interest has been given to side bias in perceptual processing. Here, we investigated the influence of the emotional valence of stimuli on visual and olfactory explorations by horses, a large mammalian species with two large monocular visual fields and almost complete decussation of optic fibres. We confronted 38 Arab mares to three objects with either a positive, negative or neutral emotional valence (novel object). The results revealed a gradient of exploration of the 3 objects according to their emotional value and a clear asymmetry in visual exploration. When exploring the novel object, mares used preferentially their right eyes, while they showed a slight tendency to use their left eyes for the negative object. No asymmetry was evidenced for the object with the positive valence. A trend for an asymmetry in olfactory investigation was also observed. Our data confirm the role of the left hemisphere in assessing novelty in horses like in many vertebrate species and the possible role of the right hemisphere in processing negative emotional responses. Our findings also suggest the importance of both hemispheres in the processing positive emotions. This study is, to our knowledge, the first to demonstrate clearly that the emotional valence of a stimulus induces a specific visual lateralization pattern.

Abstract: In various species, sex, hormonal treatments and oestrous-cycle stage have been shown to affect the animal's response in behavioural tests. Few such studies have been performed in the horse. The main aim of the present study was to investigate whether oestrous-cycle stage affects mares' response to a novel object test and isolation test and, in part, to study whether mares, assumed to suffer from oestrous-related behavioural problems, respond differently in these tests when compared with controls. Twelve mares were tested twice, in oestrus and dioestrus, in a crossover design. Seven behavioural and two heart rate variables were measured for the novel object test and two heart rate variables for the isolation test. Oestrous-cycle stage and whether a mare was classified as a 'problem' mare did not affect the mare's response. However, test order, i.e. the cycle stage a mare was tested in first, affected its reaction. This effect could partly be explained by significant differences between test occasions 1 and 2 in three behavioural variables and one heart rate variable (p < 0.05) in the novel object test. The mares explored the novel object more and had a higher mean heart rate in the first test. Exploring the novel object more could largely be attributed to those mares tested in dioestrus first, perhaps indicating that the mares in oestrus were less receptive to the novel object. The reason for the differences between test occasions could be an effect of learning or habituation.

Abstract: Chicks learned to find food hidden under sawdust by ground-scratching in the central position of the floor of a closed arena. When tested inan arena of identical shape but a larger area, chicks searched at 2 different locations, one corresponding to the correct distance (i.e., center) in the smaller (training) arena and the other to the actual center of the test arena. When tested in an arena of the same shape but a smaller area, chicks searched in the center of it. These results suggest that chicks are able to encode information on the absolute and relative distance of the food from the walls of the arena. After training in the presence of a landmark located at the center of the arena, animals searched at the center even after the removal of the landmark. Marked changes in the height of the walls of the arena produced some displacement in searching behavior, suggesting that chicks used the angular size of the walls to estimate distances.