96 Your Sport November 2016
Popular bit types and their effects on horse
welfare. Part 2
By Randi Wilson, Senior at Oregon State University and
Claudia Ingham, Senior Instructor in the Department of Animal and Rangeland Sciences Oregon State University
ost of us are familiar with three main types of bits: snaes, curbs,
and combinations. Snae action uses direct pressure, curbs rely
on leverage, and combinations, as the name describes, use both
of these actions.
e curb bit is typically paired with a curb strap that ts snugly under the
horse’s jaw and is attached to the top of the shank. When the rider pulls on the
reins, pressure is applied at the poll and chin. e amount of pressure on the poll
is determined by how snug the curb strap is on the horse’s chin and the length
of the shanks which act as levers. is encourages the horse to lower its head
and ex at the poll. For this reason, curbs are often considered more severe than
snaes and their severity increases with the length of the shank (Duberstein
and Johnson, 2014.) However, longer shanks can increase communication with
the mouth and allow quicker alleviation from pressure if used precisely (Mata et
al., 2015). Many curbs have a port which puts more pressure along the horse’s
bars and soft palate and allows for more tongue release encouraging the horse
to ex more at the poll and lower its head (Duberstein and Johnson, 2014).
Undesired behavior, like mouth opening, can result from excessive pulling on
a bit with a port (Scoggins, 1989). Ports can have disastrous consequences if
used improperly or harshly as seen in a study on Icelandic competition horses
performed by Björnsdóttir and colleagues (2014), a veterinarian and ocer of
horse health and welfare in Iceland. To obtain the ve special gaits of Icelandic
competition horses, the horse needs to maintain high levels of exion at the poll
which has led to increased use of ported bits. ese were not part of traditional
Icelandic curbs. Björnsdóttir and colleagues (2014) examined 45 Icelandic
horses prior to an event and after showed a 23.4% increase in lesions on the bar
region of the mouth due to a ported curb. Horses in the traditional Icelandic
bit showed no sign of bit-induced lesions. Since the tongue is thought to act
as a cushion between the bars and the bit, these researchers hypothesized that
the port takes away that ability and allows the bit to apply more direct pressure
on the bars, thus producing more lesions.
e snae bit is one of the most widely used bits in Europe (Engelke and
Gasse, 2003) and the most commonly accepted bit in competition (Manfredi
et al., 2005). e snae can have a myriad of mouth pieces, though they were
originally single jointed. Today, they can be xed, jointed, double jointed, or
have a solid mouthpiece (Duberstein and Johnson, 2014). Single-jointed snae
bits are said to have a “nut-cracker” eect if much force is applied. Some claim
this can be avoided in double-jointed snaes by adding a separating link.
However, a radiographic study by Manfredi and colleagues (2005) showed
that the tongue absorbs the single-jointed snae bit, cushioning it as the
angle decreases and preventing it from rising into the palate. In some cases, bit
manufacturers have added twists or chains to their mouthpieces (Duberstein
and Johnson, 2014), which arguably increases severity and risk of injury to the
horse’s mouth (Scoggins, 1989).
Some riders will combine the snae with a running martingale, which
increases the amount of leverage the rider has on the reins, but also increases
the chance of bruising if misused (Scoggins, 1989). Björnsdóttir and colleagues
(2014), examined 26 Icelandic horses in snae bits and found the amount
of lesion increased by 4% over the course of the competition. However, the
overall frequency of lesions in the buccal region of the mouth was 62%. In
comparison, only 13% of the horses in the ported curb bit had mouth lesions.
Considering these results, is it correct to assume the snae is the more ethical
and safe choice of bit?
Other types of bits are usually combinations of a curb and a snae. Gag bits
are snaes, usually with a jointed mouthpiece and shanks attached to the snae
ring. is allows for the gag bit to add up to three times the pressure and leverage
of the traditional snae bit (Mata and colleagues, 2015). ese types of bits can
possibly break the lower jaw if enough force is applied (Scoggins, 1989). Gag
bits are commonly used in polo ponies because polo players are required by the
game’s rules to have their horses suitably under control. However, the gag bit
shues the pressure points from the bars to the tongue and the corner of the
mouth, resulting in increased damage to the tongue in the form of lacerations
and sometimes completely severing the tongue (Mata et al., 2015).
e double bridle is the combination of two bits: a curb and a bradoon,
which is a type of snae bit with smaller rings and a thinner mouthpiece.
is is a characteristic tool of high level dressage competition where enhanced
communication with the horse is required for achieving the complex movements.
Double bridles were required by USEF regulations in fourth level dressage
competitions and above but now other options are allowed, like a bridle with a
simple snae (Schoer, 2016). ough some believe the double bridle increases
stress response (McGreevy et al., 2012), many dressage riders nd it an invaluable
tool. Sarah Martin, a United States Dressage Federation (USDF) gold medalist
and certied trainer claims the double bridle is appropriate at high levels when
the tiniest slip of a complicated maneuver could cost the rider points. She also
says the double bridle is great for enhancing communication and catching the
horse before it can become unbalanced (Schoer, 2016).
Recently, new bits have been developed to help relieve stress on the horse and
protect the horse’s welfare. Myler Bits® has broken away from the traditional
snae bits with a myriad of mouthpieces and cheek pieces available. Most of the
mouthpieces have replaced the central link with a roller barrel and the majority
have ports of varying heights and incorporated with forward-curved cannons
(Manfredi and colleagues, 2005). Myler Bits® designs their mouthpieces based
on discipline and training level of the horse. A 2013 study trained dressage
horses using both a traditional snae and a level ⅔ Myler bit with a tongue port
and barrel. When ridden in the Myler, which provided more tongue freedom
and was thinner in diameter, the horses exhibited lower heart rates and less
uctuations in head posture than when ridden in the traditional snae bit.
Tongue color was also visibly dierent between the two treatments, with the
Myler allowing better circulation (Vanderhorst et al., 2013). In Manfredi and
colleagues’ (2005) radiographic study, the Myler bits were best able to remain
in place when rein tension was applied. ey also sank more deeply into the
tongue than the traditional bits, which could indicate relaxation of the oral tissue
and thus comfort in the horse. When tted correctly, they also t closer to the
cheek teeth, which is thought to be the reason the horses had much quieter
mouths when ridden in this bit. e port also allowed more relief for the bars
by pressing against the tongue.
In next issue, learn about the bitless bridle and whether or not the bit is the
root cause of suering.
References for this section:
Björnsdóttir, S., R. Frey, T. Kristjansson, and T. Lundström. 2014. Bit-related lesions in Icelandic
Duberstein, K. J., and E. L. Johnson. 2013. Bits 101. University of Georgia Extension. http://
Engelke, E. and H. Gasse. 2003. An anatomical study of the rostral part of the equine oral cavity
Manfredi, J., H.M. Clayton, and D. Rosenstein. 2005. Radiographic study of bit position within
Mata, F., C. Johnson, and C. Bishop. 2015. A Cross-Sectional Epidemiological Study of Prevalence
and Severity of Bit-Induced Oral Trauma in Polo Ponies and Race Horses. J. Appl. Anim. Welf.
McGreevy, P., A. Warren-Smith, and Y. Guisard. 2012. The effect of double bridles and jaw-clamping
crank nosebands on temperature of eyes and facial skin of horses. J. Vet. Behav. 7: 142-148.
Scoggins, R.D. 1989. Bits and Mouth Injuries. J. Equine Vet. Sci. 9:101-102.
The effect of type of bit on welfare and performance of horses. J. Vet. Behav. 8:e22.