How Bits Work in a Horse’s Mouth

Understanding the function and effects of bits in a horse’s mouth is essential for effective communication and control when using the reins. Knowledge of the specific ‘action’ of each bit type will enable the rider to select the most suitable bit for their horse.

Bit Action: Function and Purpose

Bit action refers to the unique function and influence of each bit type on the horse’s mouth. Different bit actions can significantly affect the horse’s responsiveness, so understanding their effects is crucial in selecting the most suitable bit.

Notable factors determining the outcome of a bit’s action include:

• The bit’s design and construction
• Shape of the horse’s mouth
• The level of training the horse has received

Bit Families: Snaffles and Curbs

All bits belong to one of two major categories, or ‘families’: snaffles and curbs. These categories represent distinct bit actions and styles.

Snaffle Bits

Snaffle bits are direct-pressure bits, wherein the applied rein pressure is directly transmitted to the horse’s mouth.

Characteristics of snaffle bits include:

• Simple design: usually composed of a mouthpiece and two ring-shaped pieces
• Direct pressure: applies pressure directly to the bars, tongue, and corners of the mouth
• Versatility: suitable for horses of various training levels and disciplines

Curb Bits

Curb bits, also known as leverage bits, magnify the rider’s rein pressure through leverage mechanics.

Characteristics of curb bits include:

• More complex design: composed of a mouthpiece, shanks, and a curb chain or strap
• Leverage action: applies indirect pressure by amplifying the force on the poll, chin groove, and bars of the mouth
• Recommended for more advanced riders: due to its more pronounced action on the horse

Factors to Consider when Choosing a Bit:

1. Horse’s experience and training: Select a bit that aligns with the horse’s current level of education and skill.
2. Rider’s skill and experience: Select a bit that the rider can effectively use while providing clear communication to the horse.
3. Shape of the horse’s mouth: A horse’s mouth shape may impact bit fit and comfort.
4. Type of activity or discipline: Choose a bit that is appropriate for the intended discipline or activity, such as dressage, show jumping, or trail riding.

Operation of Snaffle Bits

The function of a snaffle bit is to apply pressure to the horse’s tongue, the bars (gums), and the corners of the lips, which results from the rider’s pull on the reins.

Straight-Bar Snaffle Bits

Straight-bar snaffle bits apply direct pressure on the horse’s tongue.

Considerations for straight-bar snaffle use include:

• Not ideal for horses or ponies with thick tongues
• Jointed or mullen-mouth snaffles are preferable for thick-tongued horses

The mullen-mouth snaffle exhibits a slight curve, providing additional space for the horse’s tongue.

Single-Jointed Snaffle Bits

When reins attached to rings of a single-joint snaffle are pulled, the pressure lifts off the tongue and is shifted towards the gums and lips, creating a ‘nutcracker action’.

Key points about single-jointed snaffles include:

• The joint pointedly pushes upward towards the roof of the horse’s mouth
• Even gentle bits like the snaffle can inflict discomfort if used by heavy-handed riders
• Care should be taken to avoid crunching the sensitive gums or jabbing upwards

Double-Jointed Snaffle Bits

Double-jointed snaffle bits also apply pressure on the bars and lips, but their ‘squeezing’ action is less pronounced.

Characteristics of double-jointed snaffles include:

• Limited tongue space
• Center links with a straight edge or set at an angle can be severe, as they may potentially dig into the tongue (e.g., Dr Bristol snaffle)

Bit Pressure Response in Horses

When a horse feels bit pressure at the corners of its mouth, its natural response is to raise its head to avoid the sensation. Consequently, snaffle bits are deemed to have a ‘raising’ action as they encourage the horse to gather and raise its body.

The following table provides a comparison of different snaffle bit types.

Operation of Curb Bits

Curb bits exert a powerful impact owing to their ability to apply pressure to the horse’s tongue, bars, lips, poll (behind its ears), and jaw. This makes curb bits, such as Pelham, Kimblewick, or those part of a double bridle, more potent than snaffles, and thus, demand careful handling from the rider.

The Strength of Curb Bits

The strength exhibited by curb bits primarily arises from their unique construction features, such as the cheek pieces and the curb chain.

Contributing Factors of Curb Bits’ Strength:

1. Cheek pieces: When the rein attached to the bottom of the cheek is pulled, the cheek acts as a lever, generating a significant amount of pressure on the top end, which is inside the horse’s mouth. The pull also tightens the cheek pieces of the bridle into the sensitive poll area, thereby applying additional pressure on the horse’s head.
2. Curb chain: As the cheek of the bit moves backwards, the curb chain is elevated into the soft chin area. It ‘squeezes’ the lower jaw, inducing the horse to bend more at the poll and draw its nose towards its chest. It also encourages the horse to relax its jaw, neck, and back, shifting more weight onto its hindquarters, thus promoting a more ‘collected’ outline.
   Disclaimer: Misuse of the curb chain can endure undue discomfort and stress on the horse, thrusting it in various directions.

Riding Technique Using Curb Bits

Curb bits like Pelhams are typically used with two reins.

Doubling bridle usage: Riders implement a very light contact on the rein attached to the curb bit and predominantly use the snaffle, or the ‘bridoon’ bit.

Pelham usage: In Pelham, the top rein produces no ‘lever’ effect and is frequently employed. The bottom rein exerts more severity and is sparingly used when the horse’s attention is required.

The following table summarises the different components of curb bits and their effects: