Does bridle type influence frequency of occurrence of conflict behaviours in high-level dressage horses?

Background: It is not known whether bridle type influences the frequency of occurrence of conflict behaviours in high-level dressage horses.

Objectives: To compare the type and frequency of conflict behaviours in high-level dressage horses wearing a snaffle bridle (SB) and double bridle (DB).

Study design: Experimental.

Methods: Twelve high-level dressage horses (Intermediare II/Grand-Prix) were ridden by their regular riders in their own SB and DB in random order. A veterinary assessment was performed before the study. The noseband was adjusted to the horses’ usual setting of two finger-equivalents using an ISES taper gauge. A standardised exercise test was performed at a collected walk, trot and canter. Trials were recorded to video (iPhone). A trained researcher used a pre-determined ethogram to retrospectively analyse the frequency of (1) head nodding; (2) ear movements; (3) nasal planum >10° ahead of vertical; (4) nasal planum >10° behind the vertical; (5) visibility of the sclera; (6) tail swishing; (7) teeth grinding; (8) separation of the teeth; (9) protrusion of the tongue; and (10) salivation intensity. The frequency of observations was summed for each gait separately and across all gaits combined (TOTAL). Data were analysed using a Wilcoxon signed rank test (Adjusted alpha: p ≤ 0.02).

Results: TOTAL values differed significantly between bridle types for the following variables, all of which occurred more frequently in the SB: mouth opening (DB: 104; SB: 186, p ≤ 0.001), sclera visible (DB: 2; SB: 7, p ≤ 0.02) and tongue visible (DB: 1; SB: 13, p = 0.01). In walk, the frequency of mouth opening was greater for the SB (93) than the DB (49) (p = 0.008). No differences were found for the remaining observations in trot (p > 0.07) or canter (p ≥ 0.06).

Main limitations: Only high-level horses and riders were studied.

Conclusion: The majority of measured conflict behaviours showed no differences between bridle types in this group of high-level horses but, when differences occurred, conflict behaviours occurred more frequently with the SB than DB.