Preliminary study: snaffle vs. bitless bridles

Preliminary study of jointed snaffle vs. crossunder bitless bridles: Quantified comparison of behaviour in four horses.
W. R. Cook and D. S. Mills, Equine Veterinary Journal (2009) 41(1)

The study tested the null hypothesis that if a horse is ridden in a snaffle bridle and then a crossunder bitless bridle, there will be no change in its behaviour. It was predicted that there would be change and that behaviour would improve when bitless. Four horses, none of which had ever been ridden in a crossunder bitless bridle, were ridden through two 4-min, exercise tests, first bitted then bitless. An independent judge marked the 27 phases of each test on a 10-point scale and comments and scores were recorded on a video soundtrack. The results refuted the null hypothesis and upheld the predictions. Mean score, when bitted, was 37%; and through the first 4 min of being bitless, 64%. A binomial probability distribution suggested that the results were significantly different from random effects. All 4 horses accepted the crossunder bitless bridle without hesitation. Further studies are warranted and it is hoped that others will build on this new field of investigation. The authors are of the opinion that the bit can be a welfare and safety problem for both horse and horseman. Equestrian organisations that currently mandate use of the bit for competitions are urged to review their rules. 

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Exerpt: Discussion

While the binomial probability distribution provides strong evidence to suggest that the results are not random, this calculation assumes that the tests are independent and that performance in the second test is not affected by performance in the first test. It is not known for certain that this assumption holds, though, for reasons given below, the authors believe this is unlikely. The strength of the finding provides sufficient evidence to warrant further investigation in a larger sample size, accommodating for potential experimental limitations and allowing for a more robust statistical analysis. The possibility of an order effect (due to all horses receiving the bitless bridle second) deserves consideration. That improved behaviour could be attributed to the horses being better warmed-up for the second test can be refuted on the grounds that these horses had been in work throughout the day and were fully warmed-up at the time of the first test. That improved behaviour could be attributed to the greater familiarity of the horses with the test on the second occasion and not to the change of bridle is considered unlikely, given both the short latency and the magnitude of the improvement. In addition, such an explanation is not consistent with the sustained improvement that occurs with long-term usage of the crossunder bitless bridle observed by the authors in other contexts. Fatigue as an explanation for improved behaviour might also be considered but, in man, fatigue increases the frequency of error in sport performance and it seems unlikely that horses are any different. The videotape showed that, when bitless, all 4 horses were more willing and alert than when bitted, so this too is inconsistent with a fatigue factor. While there are some weaknesses in the objectivity of the methodology, for example the absence of ‘blinding’ by judge and rider, these are balanced to some extent by the presence of witnesses and the availability of a videotape recording. It is hoped that other researchers will build on this preliminary study, improve its design and conduct some of its many permutations. A recent review of tack-induced riding accidents lists over 200 negative behavioural responses and 40 different diseases caused by the bit (Cook 2009). Yet current competition rules for dressage, show hunter, hunter jumper classes and racing mandate the use of a bit. Applying the precautionary principle, there is strong evidence to suggest that an amendment of these rules is necessary. For the sake of both equine and human welfare a crossunder bitless option is recommended.