The Impact of Bits on Equine Welfare, Part 1
The Danish government has announced that it plans to ban double bridles, curb bits and hyperflexion from equestrian sport. This has become a hot topic for many equestrians. After horse and hound posted about it on FB, the comments (of course from what I could see) were a resounding no to this change. According to these comments, double bridles shouldn't be banned, it is a safe piece of equipment, it doesn't affect horse welfare and riders should have better education on how to use it correctly.
“Bits are only as harsh as the hands using them”
Is often the argument I hear in favor of keeping double bridles, so let's explore the literature around horse bits, their action and rein tension.
Oral behaviour and Lesions in horses
One welfare issue is the prevalence of bit-related oral lesions in competition horses across a variety of equestrian disciplines. Ill-fitting tack and inappropriate training techniques are often seen as the cause of oral lesions. In a study titled oral behaviour during riding is associated with oral lesions in dressage horses (Christensen and Uldahl, 2024) found that 5 out of 11 randomly selected horses from an Intermediate 1 national Danish dressage competition, had oral lesions.
These horses were then eliminated from the competition under the federation rules. When looking to behaviour, a blinded observer to the outcome of the oral inspections, found that horses with oral lesions showed more mouth opening behaviours than horses without lesions, during the dressage test. The conflict behaviour of mouth opening during dressage has been found in other studies. 68% of 123 top level dressage horses showed their mouth open during tests for more than 10 seconds (Dyson & Pollard, 2021).
It was said by the researchers that the effect of the double bridle on mouth opening needs further investigation, as 44% of sport horses (Dyson & Pollard, 2021) and 45% of three day event dressage horses (Dyson & Ellis, 2020) showed mouth opening, but these horses had snaffle bits and the top level dressage horses had a higher occurrence of mouth opening. Unusual oral behaviour was also found in 100% of horses at the warm up of Grand Prix special (CDIO5*) of the CHIO in Aachen (Kienapfel et al., 2021).
In a study looking into oral lesions in ridden and unridden horses (Tell et al., 2008) found that the presence of oral ulcers was significantly higher in ridden horses than unridden. This shows that riding horses with a bit and bridle is a high risk factor for the development of oral ulceration in horses.
It was found in a study evaluating 3143 horse/rider combinations competing in Danish Equestrian Federation that the presence of lesions at the commissures of the lips differed between disciplines and increased with level of competition, but it did not differ between bit types including bitless bridles. What did have a significant effect on the likeliness of the presence of ulcers was noseband tightness. Lesions at the commissures of the lips were related to tightness of the upper strap of the noseband (cavesson, Mexican or Micklem). Loosening the upper noseband from <2 to 2–3 cm or from 2–3 to >3 cm decreased the prevalence of commissural lesions by 34% (Uldahl and Clayton, 2018).
This is also said by a LANTRA qualified bit fitter that a main reason for blood in the mouth is that tight nosebands squeeze the tissue between the upper teeth and the noseband, causing sores and blood. Interestingly, when searching for blood in the mouth eliminations in dressage competition, 14 instances can be found online (there could be more) ranging from 2010 to 2024, with all horses wearing double bridles.
Even though bit type wasn’t a factor in the risk of oral lesions in the previous study, it was found that Icelandic ponies ridden with curb bits which had a port had 75 times higher odds for lesions on the bars compared to ponies ridden with snaffle bits and Icelandic curb bits (Björnsdóttir et al., 2014). They also noted in that study that snaffle bits had a higher risk of buccal lesions (on the inside cheeks of the horse) compared to curb bits. Not only this, but it has been found that eventing horses wearing thin (10-13mm) or thick (18-22mm) bits had a higher risk of moderate/severe oral lesion status than horses wearing middle-sized bits (14-17mm). However, bit thickness was associated with bit type so that double-jointed bits were mostly middle-sized and unjointed bits were mostly thick (Tuomola et al., 2021).
These studies show us that conflict behaviours such as opening of the mouth is more likely seen in horses with oral lesions and with double bridles. Ridden horses have a significant risk of oral lesions and increasing that risk has been shown to be associated with tight nosebands, curb bits and bits that are too thick or too thin.
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