Andrological and cytogenetic investigations of an infertile Przewalski's stallion.

The case of an 8-year-old, sexually active but infertile Przewalski's stallion (Equus ferus przewalskii) was studied. Besides the infertility, the stallion also showed permanent problems with its body condition, being obviously weaker than all the other group members. The horse was kept in a separate place for two years with 12 mares in its harem group (six mares had foals earlier); however, none of the mares covered got pregnant.

Seasonal Variations in Heart Rate Variability as an Indicator of Stress in Free-Ranging Pregnant Przewalski's Horses () within the Hortobágy National Park in Hungary.

Ecosystems with seasonal fluctuations in climate and food availability present physiological challenges to resident mammals and may cause "stress." The two predominant physiological responses to stressors are (1) the activation of the hypothalamic-pituitary-adrenal axis and (2) the modulation of the autonomic nervous system. To date, the primary indicator for "stress" in wildlife- and zoo animal research are glucocorticoid levels.

A comparison of fecal steroid metabolite concentrations between harem and bachelor stallions in a free-Ranging population of przewalski's horses (Equus ferus przewalskii).

The aim of this study was to determine whether concentrations of reproductive steroid hormone metabolites significantly differed between harem stallions and bachelor stallions in the free ranging group of Przewalski's horses (Equus ferus przewalskii) at the Hortobágy National Park in Hungary. Throughout the study, fecal samples were collected from 21 harem stallions and 15 bachelor stallions and analyzed for immunoreactive estrogen and androgen metabolites. Harem stallions demonstrated significantly higher concentrations of estrogen (P < 0.