Bitting problem or behaviour?

Introduction

A horse that is ridden with a bit and is performing below the expected standard, or is showing signs of oral or head discomfort, should warrant an investigation into the potential role of the bit and its contribution to the problem. However, many horses are presented for poor performance when ridden and these cases can be a particular challenge to owners, trainers and veterinarians. As well as those that are clearly displaying head aversion, head-shaking, and other signs that may suggest a potential bitting problem, many are presented with unusual gaits and abnormalities of head carriage when ridden ‘on the bit’ and these have been shown to be multifactorial [1]. Other factors could also be involved, such as dynamic laryngeal abnormalities only present during exercise, which could potentially be misdiagnosed as a bitting problem.

Horses and bits

Horses are thought to have first been domesticated around five to six thousand years ago by nomadic tribes living on the Steppes of Eurasia [2]. Bit use was first recorded around 1360 BC and since then the design of bridles and bits has changed due to fashion, materials available and partly from research. Modern competitive ridden disciplines invariably demand the use of the bit (e.g. British Dressage 2018), with the bridle and bit being accepted as a method of reliable physical contact between horse and rider, and well-trained communication with this contact being linked to success in dressage [3].

Does the bit cause performance problems?

There is little research documenting the bit directly causing performance problems. Studies have demonstrated the position of the bit in the mouth both ridden and unridden [4,5], identified problems with poorly fitting bits [6] and it has been shown that there is an increased prevalence of mandibular exostosis (‘bone spurs’) and abrasive wear of the 06 teeth [7] and soft tissue ulceration [8] in horses ridden with bridles and bits. Racehorses appear to have a high level of lip and bar injuries [9]. There has been a suggestion that head-shaking from trigeminal neuralgia and other conditions such as dynamic airway disorders are directly attributable to bits [10]. One study comparing behaviour in bitted vs. bitless bridles found that abnormal behaviour was mostly present with the bitless bridle [11] but another showed that with continued training, bitless bridles resulted in lower abnormal behaviours [3]. A recent paper shows many bit-related stereotypies and pain reactions were significantly reduced by bitless bridles [12].

Investigation of a suspected bitting problem

Any performance-related problem where an abnormality of head carriage is present in a bitted horse could potentially be bit-related. A first step is to perform a thorough clinical and musculoskeletal examination including full lameness evaluation, preferably with the patient in a halter or bitless bridle. This should exclude many of the common musculoskeletal problems from being bit-related, leaving those horses only exhibiting signs when ridden under saddle and bridle with a bit. It will be possible to exclude some further by test riding in a bitless bridle; however, some horses will not be accustomed to this and results may not be meaningful, at least initially (e.g. may not work to the same ‘outline’ with the same stresses on either the location of the bit, or other musculoskeletal areas). The age of the horse, [...]