Equine Science Update
Reports from the world of  equine research.
Join our FREE Email Newsletter List
Traditionally, bitted bridles have provided the main means of controlling ridden horses. The metal bit applies focused pressure on  areas of sensitive tissue within the horse's mouth.

Although bitted bridles are widely used and accepted, the need for a bit has been questioned. Indeed, it has been suggested that the bit, far from being essential, may actually cause behavior problems and disease.

According to Dr Robert Cook, Surgery Professor Emeritus at Tuft's University in Massachusetts, the bit is to blame for numerous problems in the horse, including headshaking and upper respiratory obstruction.

For the past ten years Dr Cook has been researching the adverse effects of the bit and the advantages of communicating without using a bit. He developed a new type of bitless bridle that differs from hackamores and other traditional bitless bridles in being painless and incorporating a crossunder principle.
The bridle (marketed as the "BitlessBridle") works by applying mild pressure across the bridge of the nose, less under the chin, even less  along the cheek, and least of all at the poll. "Its action can best be described as a benevolent headlock or whole head hug" he explains.

Is the bitless bridle as effective as Dr Cook would have us believe?  Two small-scale studies have looked at how horses behave and perform in bitless or bitted bridles.

Jessica Quick and Dr Amanda Warren-Smith compared the response of four 2-year old horses to foundation training. The work was performed at the Orange Campus Equine Centre of Charles Sturt University in New South Wales, Australia. Results of the study were presented at the International Society for Equitation Science Conference in Dublin and published in the Journal of Veterinary Behavior.

The researchers looked at whether two horses wearing a crossunder bitless bridle responded differently to two horses wearing a bridle with standard full-sized Fulmer (full-cheek) snaffle when undergoing foundation training (i.e., first-time bridling, long-reining and riding). The study was done under field conditions over a period of some weeks, as part of an educational course.

They found that the two horses wearing the bitted bridle showed more chewing and mouth opening than did those wearing the bitless bridle. This was present throughout the training process, but became less frequent as training progressed.

Horses wearing the bitted bridle did more headshaking during bridling and long reining. However, when ridden, the horses wearing the bitless bridle showed more headshaking.

During long-reining, horses wearing the bitted bridle had a higher  heart rate and heart rate variability. They also took more steps before stopping after being given the stimulus to halt.

The bitted horses showed less head lowering during long reining than the bitless horses.

The researchers caution against drawing firm conclusions from the work, as the low number of animals may have affected the outcome. However, they say that “horses wearing bitless bridles performed at least as well as, if not better than, those in bitted bridles.”  They suggest that the use of bitless bridles could be beneficial and warrants further investigation with more horses in a range of disciplines.

Dr Cook set up the second controlled study at the Certified Horsemanship Association’s International Conference in October 2008 at the Kentucky Horse Park in Lexington Kentucky, USA. The results, co-authored by Professor Daniel Mills at Lincoln University,  have been reported in the Equine Veterinary Journal. Video recordings of the 32 minute experiment are available at

Four Certified Horsemanship Association riding instructors were each allocated a mature riding school horse, previously unknown to them, which they rode twice through a four minute, 27- phase exercise test. The first time they used a bitted (jointed snaffle) bridle. They then repeated the test using a crossunder bitless bridle. Each phase was judged using a 10-point scale. None of the horses had been ridden in a bitless bridle before and only two of the riders had had previous experience of the bitless bridle.

An experienced and independent dressage judge marked the tests.

All four horses accepted the bitless bridle without hesitation. The mean score when bitted was 3.7. In the first four minutes of using the bitless bridle, rider's improved their scores by an average of 75% to a mean of 6.4.

Could the improved performance have been due to the horses being better warmed up for the second test? Unlikely, says Dr Cook, as all horses had been in regular work throughout a long day. Maybe the horses were more familiar with the test the second time around. Again, the authors consider this unlikely as the extent of the improvement was too marked.  They also point out that the video shows the horses were more alert & happier when wearing the bitless bridle.  A statistical analysis of the results provided " strong evidence to suggest that the results are not random.”

Drs Cook & Mills believe that the bit can be a welfare and safety problem for both horse and rider. They urge equestrian organizations that currently mandate use of a bit for competitions to review their rules.

For more details see:

"Preliminary investigations of horses (Equus caballus) responses to different bridles during foundation training."
JS Quick, AK Warren-Smith
Journal of Veterinary Behavior (2009) 4, 169 - 176

"Preliminary study of jointed snaffle vs crossunder bitless bridles: Quantified comparison of behaviour in four horses."
WR Cook, DS Mills.
Equine Vet Journal (2009) 41,
doi 10.2746/042516409X472150
Written by Mark Andrews. Published online 25.10.09.
© Copyright Equine Science Update  2009
Assessing bitless bridles
Sign up for our FREE e-mail newsletter.