In the early 21st century, this annual event attracted considerable attention and controversy because of issues linked to abuse of horses that was practiced to enhance their performance in the show ring.

The two basic categories of Tennessee Walking Horse show competition are called "flat-shod" and "performance", distinguished by desired leg action.

Performance horses are shod with built-up pads or "stacks", along with other weighted action devices, creating the so-called "Big Lick" style.

The United States Equestrian Federation and some breed organizations now prohibit the use of stacks and action devices at shows they sanction.

[2][3] The hindquarters are of "moderate thickness and depth", well-muscled, and it is acceptable for the hind legs to be slightly over-angulated, cow-hocked or sickle-hocked.

[6] The Tennessee Walking Horse has a reputation for having a calm disposition and a naturally smooth riding gait.

Some members of the breed perform other variations of lateral ambling gaits, including the rack, stepping pace, fox trot and single-foot, which are allowable for pleasure riding but penalized in the show ring.

By the stallion Allendorf (from the Hambletonian family of Standardbreds) and out of a Morgan mare named Maggie Marshall, he became the foundation sire of the Tennessee Walking Horse breed.

In 1950, the United States Department of Agriculture recognized the Tennessee Walking Horse as a distinct breed.

[21] The two basic categories of Tennessee Walking Horse show competition are called "flat-shod" and "performance".

[24]: 12 Performance horses, sometimes called "padded" or "built up", exhibit flashy and animated gaits, lifting their forelegs high off the ground with each step.

[27] In the early 21st century, this form of shoeing is now prohibited at shows governed by the National Walking Horse Association (NWHA),[22]: 3  and the United States Equestrian Federation (USEF).

Tennessee Walkers are also shown in both pleasure and fine harness driving classes, with grooming similar to the saddle seat horses.

Hats are not always mandatory, but use of safety helmets is allowed and ranges from strongly encouraged[23]: 9  to required in some pleasure division classes.

[29] Congress delegated statutory responsibility for enforcement to the management of sales and horse shows, but placed administration of the act with the Animal and Plant Health Inspection Service (APHIS) of the United States Department of Agriculture (USDA).

The USDA certifies certain Horse Industry Organizations (HIOs) to train and license Designated Qualified Persons (DQPs) to complete inspections.

[32] Between 1978 and 1982, Auburn University conducted research as to the effect of applications of chemical and physical irritants to the legs of Tennessee Walking Horses.

The study found that chains of any weight, used in combination with chemical soring, produced lesions and pain in horses.

[33] Soring can be detected by observing the horse for lameness, assessing its stance and palpating the lower legs.

Trainers who sore their horses have been observed leaving the show grounds when they find that the more stringent federal inspection teams are present.

[35] Although illegal under federal law for more than 40 years, soring is still practiced; criminal charges have been filed against people who violate the Act.

The President and executive committee of the TWHBEA voted to support this legislation, but the full board of directors chose not to.

Opponents included members of the Performance Horse Show Association, and the Tennessee Commissioner of Agriculture.

[41] In 2016, the USDA proposed new rules independent of the PAST Act, banning stacks and chains, and providing stricter inspections at training barns, auctions, and shows.

[42] Controversies over shoeing rules, concerns about soring, and the breed industry's compliance with the Horse Protection Act has resulted in the development of multiple governing organizations.

[37] The NWHA was in the process of building its own "tracking registry" to document both pedigree and performance achievements of horses recorded there.

[17] In the early 21st century, the Celebration has attracted large amounts of attention and controversy due to the concerns about violations of the Horse Protection Act.