Cortisol and heart rate response of mares during the in-hand breeding procedure with and without restraint

Background: In-hand breeding involving restraint methods is likely the most common practice in the horse breeding industry worldwide. However, welfare issues that arise from such management have not been investigated in detail.

Objectives: (1) To investigate whether the mares show increased stress responses during in-hand breeding using (a) a lip twitch and (b) hobbles. (2) To evaluate if the use of restraint methods influences the mare's expression of oestrous behaviour.

Study design: Intra-individual cross-over design.

Methods: Six Franches-Montagnes stallions and 10 warmblood mares were used in these experiments. Each mare underwent standardised teasing and breeding sessions with and without one of the two restraint methods (morning and afternoon) on the day before ovulation. Salivary cortisol concentrations, continuous heart rate (HR) and heart rate variability (HRV) before, during and after the teasing and breeding sessions were measured as objective stress indicators. An ethogram was established to evaluate the behaviour during breeding.

Results: Using the lip twitch increased cortisol concentrations (with twitch from 0.77 ± 0.07 to 1.20 ± 0.07 ng/mL vs. without twitch from 0.73 ± 0.07 ng/mL to 0.99 ± 0.07 ng/mL; p = 0.04), and the hobbles could not be applied to 2 out of the 10 mares in our study, as they did not tolerate this restraint method.

Main limitations: The sample contained a small number of mares.

Conclusions: Using a lip twitch in mares during in-hand breeding is accompanied by a slight degree of stress, while hobbles are tolerated very well or not at all by the mares.