Choosing the most welfare-friendly bridle—bitted or bitless—can be confusing. It might seem kinder to spare horses a jointed metal bar in their mouths. But new study results indicate horses find pressure from most bitless bridles to be just as unpleasant as that from snaffle bridles. And with one of kind of bitless bridle, the researchers found the pressure to be even worse.
“Our study indicates that with different types of headgear, the same rein aid is similarly aversive to horses,” said Anina Vogt, PhD candidate at the University of Giessen, in Germany. Vogt presented the study results on behalf of herself and Uta König von Borstel, PhD, also of the University of Giessen, at the 2017 International Society for Equitation Science conference, held Nov. 22-26 in Wagga Wagga, Australia.
“This indicates that at equal levels of prior training, signals of the same intensity are sufficient to produce a noticeable aid,” Vogt said.
The researchers tested leisure or riding school horses of various ages and breeds that were usually ridden with a snaffle bit bridle. The scientists put four kinds of bitless bridles, one snaffle-bitted bridle, and one rope halter on each horse in random order. They attached the reins to the top of a surcingle (to mimic hand placement) and left them loose enough for the horses to place their heads slightly in front of the vertical. They placed rein tension meters on the reins each time.
The horses then had the opportunity to reach for buckets of feed in front of them. But to get to the feed, they would have to push against the reins, similar to the setup in a Danish study on horses’ rein tension preferences. The researchers tested each horse with each kind of bridle multiple times a day, several days in a row.
They found that the horses all pulled their heads to approximately the same amount of rein tension (an average of about 7 pounds) regardless of the bridle, Vogt said, with one exception: one of the bitless bridles seemed to cause much more discomfort than all other bridles in the tests. Horses stopped pulling the reins at much lower tension levels (only about 6 pounds) with a side-pull bitless bridle.
“Compared to the other bridles, the side pull is equipped with a stiffer and thinner noseband, resulting in equal levels of rein tension in higher pressures on the horse’s nose,” she said. “And that explains the lower threshold of maximally tolerated rein tension for this horse.”
Incidentally, Vogt said they found that overall, ponies and draft-type horses accepted more rein tension than did Warmbloods and Arabian types. For example, ponies and draft-types accepted an average force of about 10 pounds, compared to a little less than 6 ½ pounds for the others. Neither the horse’s age nor the number of times the horses were tested affected the results. In other words, they didn’t “get used” to the tension over the series of trials.
“Our analyses indicate that except for the side pull, the same amount of rein tension results in similar levels of discomfort in the horse,” Vogt said.