Abstract: Based on plasma cortisol concentrations it is widely accepted that transport is stressful to horses. So far, cortisol release during transport has not been evaluated in depth by non-invasive techniques such as analysis of salivary cortisol and faecal cortisol metabolites. Transport also causes changes in heart rate and heart rate variability (HRV). In this study, salivary cortisol, faecal cortisol metabolites, heart rate and HRV in horses transported by road for short (one and 3.5 h) and medium duration (8 h) were determined. With the onset of transport, salivary cortisol increased immediately but highest concentrations were measured towards the end of transport (4.1 ± 1.6, 4.5 ± 2.6, 6.5 ± 1.8 ng/ml in horses transported for one, 3.5 and 8 h, respectively). Faecal cortisol metabolite concentrations did not change during transport, but 1 day after transport for 3.5 and 8 h had increased significantly (p < 0.01), reflecting intestinal passage time. Compared to salivary cortisol, changes in faecal cortisol metabolites were less pronounced. Heart rate increased and beat-to-beat (RR) interval decreased (p < 0.05) with the onset of transport. Standard deviation of heart rate increased while root mean square of successive RR differences (RMSSD) decreased in horses transported for 3.5 (from 74 ± 5 to 45 ± 6 ms) and 8 h (from 89.7 ± 7 to 59 ± 7 ms), indicating a reduction in vagal tone. In conclusion, transport of horses over short and medium distances leads to increased cortisol release and changes in heart rate and HRV indicative of stress. The degree of these changes is related to the duration of transport. Salivary cortisol is a sensitive parameter to detect transient changes in cortisol release.

Abstract: The influence of steroids of adrenal cortical origin on estrous behavior in the ovariectomized mare was evaluated by adrenal suppression via dexamethasone (DEX) administration in two experiments. In Experiment I, 12 mares (six DEX, six control) were tested for sexual behavior in harem groups (two DEX and two control mares plus one stallion per group) for 9 consecutive days. In Experiment II, estradiol (E2) was given to a group of DEX-treated mares as an additional control. Twelve mares (four DEX, four DEX + E2, and four control) were tested in harem groups (one DEX, one DEX + E2, and one control mare plus one stallion per group) for 10 days. All DEX mares showed a clear suppression of sexual response compared to control or DEX + E2 mares, indicating that the estrous behavior seen in ovariectomized mares may be due to steroids from the adrenal cortex. The control and DEX + E2 mares were similar in all measures of proceptivity. Despite being more receptive, as indicated by fewer negative responses, the DEX + E2 mares received fewer intromissions and ejaculations than did the control animals. The ability of estradiol to induce estrous behavior in the dexamethasone-suppressed mare notwithstanding, other adrenal steroids, e.g., androgens, may be involved in estrous behavior in the untreated, ovariectomized mare.

Abstract: Ten ovariectomized (OVEX) and ten intact, but seasonally anovulatory (ANOV), pony mares were observed for sexual activity with five stallions, using a “harem group” social testing paradigm (two OVEX and two ANOV mares plus one stallion per group) for 15 consecutive daily tests lasting 20 min each. All mares in both conditions showed proceptive behavior in at least one test, all mares but one were mounted, and 14 of 20 mares received ejaculations. No statistical differences were found between the two conditions for any measure of proceptivity, copulatory activity, or days in estrus. The quality of estrus was judged to be equivalent to that displayed by periovulatory mares during their initial and terminal days of estrus, but less intense than that seen near ovulation. Mares in both groups were in estrus during approximately 60-70% of the tests and only 3 of the 20 mares were sexually refractory for more than five consecutive tests. Thus, the typical 2-week phase of sexual refractoriness seen in intact diestrous mares was absent in OVEX and ANOV mares, suggesting that the ovary plays a major role in actively suppressing estrous responses during the luteal phase of the cycle.

Abstract: In small animals like mice, the monitoring of endocrine functions over time is constrained seriously by the adverse effects of blood sampling. Therefore, noninvasive techniques to monitor, for example, stress hormones in these animals are highly demanded in laboratory as well as in field research. The aim of our study was to evaluate the biological relevance of a recently developed technique to monitor stress hormone metabolites in fecal samples of laboratory mice. In total, six experiments were performed using six male and six female mice each. Two adrenocorticotropic hormone (ACTH) challenge tests, two dexamethasone (Dex) suppression tests and two control experiments [investigating effects of the injection procedure itself and the diurnal variation (DV) of glucocorticoids (GCs), respectively] were conducted. The experiments clearly demonstrated that pharmacological stimulation and suppression of adrenocortical activity was reflected accurately by means of corticosterone metabolite (CM) measurements in the feces of males and females. Furthermore, the technique proved sensitive enough to detect dosage-dependent effects of the ACTH/Dex treatment and facilitated to reveal profound effects of the injection procedure itself. Even the naturally occurring DV of GCs could be monitored reliably. Thus, our results confirm that measurement of fecal CM with the recently established 5alpha-pregnane-3beta,11beta,21-triol-20-one enzyme immunoassay is a very powerful tool to monitor adrenocortical activity in laboratory mice. Since mice represent the vast majority of all rodents used for research worldwide and the number of transgenic and knockout mice utilized as animal models is still increasing, this noninvasive technique can open new perspectives in biomedical and behavioral science.