Altrenogest treatment reduces the stress response of three-year-old warmblood mares during their initial equestrian training

Stress response of 18-, 24- and 30-month-old sport horse stallions to a pretraining programme

Warmblood sires traditionally have been presented for stallion licencing at 2 years of age, but the age at which horses are mentally fit for training is a point of controversy. We have therefore investigated the stress response of young stallions to pretraining for licencing. Salivary cortisol concentration, heart rate and heart rate variability (HRV) were determined repeatedly over 12 weeks. Stallions were 24 and 30 months old and either housed in groups or individual boxes (Group 24, n = 9; Box 24, n = 10; Box 30, n = 10). Pretraining included free movement in an indoor arena, training in a horse walker, lunging and jumping of obstacles without rider. In addition, group-housed 18-month-old stallions (Group 18, n = 10) underwent an abbreviated programme with only free movement and horse walker exercise. We hypothesised that the stress response to pretraining is reduced by group housing but not affected by age. In stallions of all groups, cortisol concentration increased in response to pretraining events (P < 0.001). Cortisol release differed among events (P < 0.001) was most pronounced after free movement in weeks 1 and 2 and became less pronounced with event repetition (P < 0.001). When horses were in the horse walker for the first time, cortisol release was increased in group-housed in comparison to individually housed stallions (time × stable P < 0.001). An increase (P < 0.001) in heart rate differed among events (P < 0.001) and became smaller with repetition (P < 0.001). The HRV decreased transiently in response to pretraining events (P < 0.001) indicating sympathoadrenal activation. In conclusion, pretraining of young stallions is both a physical and a mental demand and induces a stress response. With the repetition of events, even stallions as young as 18 months adapted rapidly to these demands. Group housing had no stress-reducing effects. Our study does not provide evidence that the systematic pretraining of young Warmblood stallions raises animal welfare concerns.

Suppression of reproductive behaviour and gonadal function in female horses-An update

The behaviour of mares is often detrimental to their performance resulting in frequent demand for methods to suppress gonadal function. In addition, prevention of unintended reproduction especially in feral horse populations may require methods for suppression of gonadal function. Surgical ovariectomy is a safe method but not an acceptable approach in feral mares and undesired in mares where future breeding is considered. There are different approaches for artificial prolongation of the luteal phase resulting in transient inhibition of oestrus and ovulation. Among those, treatment with natural or synthetic progestogens is considered the most common and successful method. Whereas application of intrauterine devices may result in prolongation of luteal function in non-pregnant mares, intrauterine insertion of glass balls is no longer recommended because of complications in individual mares. There are several safer alternatives that may be of interest, especially for population control in free-roaming horses. Treatment with long-acting deslorelin implants inhibited ovulation and oestrus behaviour in mares for limited and variable time intervals in a dose-dependent manner. The effect of GnRH vaccines varies considerably among individual mares, is age dependent, and oestrus-like behaviour may still occur. Contraception via immunization against native porcine or recombinant zona pellucida antigen is successful, but immunocontraception is as much a result of ovarian inactivity as an antibody-based block to sperm-oocyte binding. In conclusion, several treatments for suppression of gonadal function in mares are available, but there are advantages and disadvantages associated that have to be considered. The treatment of choice will thus differ with regard to the demands.