Abstract: Abstract Analysis of salivary cortisol is increasingly used to assess stress responses in horses. Since spontaneous or experimentally induced increases in cortisol concentrations are often relatively small for stress studies proper controls are needed. This requires an understanding of factors affecting salivary cortisol over longer times. In this study, we have analysed salivary cortisol concentration over 6 mo in horses (n = 94) differing in age, sex, reproductive state and housing. Salivary cortisol followed a diurnal rhythm with highest concentrations in the morning and a decrease throughout the day (P < 0.001). This rhythm was disrupted in individual groups on individual days; however, alterations remained within the range of diurnal changes. Comparison between months showed highest cortisol concentrations in December (P < 0.001). Cortisol concentrations increased in breeding stallions during the breeding season (P < 0.001). No differences in salivary cortisol concentrations between non-pregnant mares with and without a corpus luteum existed. In stallions, mean daily salivary cortisol and plasma testosterone concentration were weakly correlated (r = 0.251, P < 0.01). No differences in salivary cortisol between female and male young horses and no consistent differences between horses of different age existed. Group housing and individual stabling did not affect salivary cortisol. In conclusion, salivary cortisol concentrations in horses follow a diurnal rhythm and are increased in active breeding sires. Time of the day and reproductive state of the horses are thus important for experiments that include analysis of cortisol in saliva.

Abstract: Initial equestrian training and especially first mounting of a rider are stressful challenges for young horses (1). Most young horses are raised in groups but, in association with equestrian training, they are commonly transferred to individual stabling in loose boxes. Although, in most stables, visual contact with horses in adjacent boxes is possible, separation from the herd might be an additional stressor. We have studied physiological stress parameters, in 3-year-old sport horse mares (n=8), transferred from a group stable with access to a paddock to individual boxes without paddock. Once stabled in the individual boxes, mares underwent a standard training for young horses. Horses had been accustomed to lunging and tolerating a rider on their back several weeks before the study. Mares were studied from 5 days before to 5 days after changing the stable. Cortisol concentration in saliva, locomotion activity (ALT pedometers), heart rate (HR) and HR variability (RMSSD: root mean square of successive beat-to-beat intervals) were determined. We hypothesized that the change of the stable increases cortisol release and is associated with changes in HR and RMSSD and reduced locomotion. Before mares were moved to individual boxes, cortisol concentration showed a pronounced diurnal rhythm with values around 0.6 ng/ ml in the morning and a continuous decrease throughout the day. When the mares were moved to individual boxes, cortisol concentration increased to 1.8±0.2 ng/ml and did not return to baseline values within 6 h (p<0.05 over time). On subsequent days, a diurnal rhythm was re-established but shifted to a higher level than before. Locomotion activity determined by ALT pedometers was increased for some minutes only after mares has been placed in individual boxes but was only slightly higher than during the time mares spent with the group in a paddock. On days 2-5 in individual boxes, locomotion activity was reduced compared to the group stable. HR increased and the HRV variable RMSSD decreased when mares were separated. In conclusion, separating horses during initial training from their group is an additional stressor, although the stress is less pronounced than induced by other social challenges, e.g. weaning of foals (2). When stabled in individual boxes, mares move less than when kept as a group. Horses kept in a group thus appear to exercise themselves freely, such an effect is absent when the animals are kept individually.

Abstract: Identification of horses with hot iron branding is one of the most controversial issues in German horse breeding and also discussed in other countries. Traditionally horses have been identified by hot iron branding with breed-specific symbols and additional numbers. Since 2009, European Union legislation requires that all horses born after that year must have a microchip implanted for identification, although some exceptions are possible. So far it has not been tested using scientific criteria to what extent branding and microchips reliably allow identification of individual horses. In this study, the readability of branding symbols and numbers was analyzed by 3 independent investigators in 248 horses participating in an equestrian competition. Microchip transponders implanted into the neck were read in another 182 horses on different breeding farms. Microchip readings were made on both sides of the neck and 3 different commercially available ISO 11785/11785 scanners were compared (A: Minimax II, B: I-MaxPlus, C: Isomax V, all by Virbac, Germany). Correct reading of the branding breed symbol in horses at an equestrian championship by the individual investigators was close to 90% and differed only marginally between the investigators. Correct identification of the breed-specific symbol by all 3 investigators occurred in 84% of cases. The double-digit number branded together with the breed symbol was identified correctly by all 3 investigators in 39% of cases with correct readings by individual investigators ranging from 47 to 54%. Correct identification of the branding signs did not differ significantly between horses of different coat color and age group. Readability of microchips differed between scanners. Best results were obtained with scanner C which allowed microchip reading on the implantation side in 100% and on the contralateral side of the neck in 95% of 182 horses. Time for location of the microchip on the implanted side ranged from 1 to 4 sec (1.1±0.4). Scanner A identified 92 and 25% of microchips on the implanted and contralateral side, respectively while corresponding values for scanner B were 86 and 20%. Readability of microchip transponders on the side contralateral to implantation was influenced by size and thus caliber of the horse. In conclusion, hot iron branding does not allow unique identification of horses and individual branding numbers can be read in less than 40% of the horses. Readability of microchip transponders is more reliable compared to hot iron branding but depends on the type of scanner used. Scanner C allowed identification of all horses tested and gave good results also when used on the contralateral side of the horses` neck. KW -