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4 Quarter Horse Bloodlines to Consider Avoiding

As the most popular breed in America, thousands of Quarter horses are bred each year. However, when breeding there are some Quarter horse bloodlines to avoid, as they are linked with diseases that are potentially fatal and even behavioral issues.

Though some of these Quarter horse bloodlines may be famous, they are linked to serious genetic and even temperament issues.

When breeding or buying any horse, it is important to study their bloodlines. However, it is also important to note that horses with these four bloodlines may not possess any genetic or behavioral issues and be wonderful, reliable horses. These specific bloodlines have produced many talented horses, but they also come with an increased risk of problems.

Quarter Horse Bloodlines to Avoid

1. Poco Bueno

Poco Bueno was a popular sire in the 1950s. He was powerful and fast, which led him to be a champion in the show ring.

Born in 1944, Poco Bueno was a successful cutting horse. He went on to sire an incredible 405 foals. Many of his offspring followed in his success, with 36 becoming AQHA champions. However, science has connected Poco Bueno to the fatal disease known as hyperelastosis cutis or hereditary equine regional dermal asthenia (HERDA)

HERDA is an inherited skin condition that is recognizable by hyperextensible skin, scarring, and severe lesions along the back of horses. The condition doesn’t normally become visible until horses are around two or three years old when they are starting under saddle. The horse’s skin will begin to tear, separate, and peel off from any form of pressure or even at random.

There is no cure for HERDA and it is not uncommon to euthanize horses with the disease. The disease was first recognized in 1971 and 95% of affected horses had Poco Bueno in both their sire and dam lines. Though the chances are relatively low if Poco Beuno is only on one side of a horse’s pedigree, they are much higher if he is on both sides.

Some of Poco Bueno’s most notable descendants, Dry Doc, Doc O’Lena, Great Pine, and Zippo Pine Bar, were carriers and have all sired at least one foal with HERDA. Fortunately, testing is available to find out if a horse is a carrier for HERDA. There are still many fans of the Poco Bueno line, as many of his descendants are durable and talented.

2. Impressive

Impressive, Famous Quarter Horse stallion linked with hyperkalemic periodic paralysis (HYPP)

Impressive was a sorrel Appendix Quarter horse stallion born in 1969, who achieved his full AQHA registration in 1971. He lived up to his name with an incredible show career, winning the 1974 AQHA World Champion Open Aged Halter stallion.

Impressive also had a phenomenal career as a breeding stallion, siring a whopping 2,250 foals. Nearly 30% of his offspring went on to win world champion titles themselves. However, in 1992, researchers linked Impressive as the carrier of hyperkalemic periodic paralysis (HYPP).

All the horses that researchers found that had HYPP were descendants of Impressive. HYPP causes mild to severe muscle shaking and twitching. Horses with the disease may also experience weakness, “dog sitting”, high serum potassium levels, behavioral issues, sweating, and yawning. In severe cases, some horses may suffer from respiratory paralysis or respiratory failure, which can lead to suffocating to death.

HYPP is caused by a mutation in the muscle’s sodium channel. The severity for a horse with one copy of the gene can vary. However, horses with two copies of the gene are more severely affected by HYPP. In fact, you can not register horses with the AQHA if they have two copies of the mutated gene. Testing is available to see if a horse is a carrier of HYPP.

3. King

King, famous Quarter Horse

King, also known as King P-234, was a famous Quarter horse sire who played an important role in the early years of the breed. The bay stallion was born in 1932 and excelled in ranch work and roping.

King sired some of the most notable horses in the breed including Royal King, Martha King, King’s Pistol, Power Command, and also Poco Bueno. However, his line is connected to the deadly Glycogen-branching enzyme disorder (GBED).

GBED prevents a horse from properly storing sugar, as the cells are unable to recognize the GBR gene, making the body unable to produce the GB enzyme. Oftentimes, the disease leads to late-term abortions or stillbirths.

Foals that are born with GBED may appear healthy at first, but may develop seizures or be unable to stand due to weakness. No foal born with GBED has ever made it past 18 weeks.

Horses with King in their bloodlines can still make great show horses or working horses. However, if you are wanting to breed horses with King in their bloodlines, be sure to get them tested first to make sure they are not a carrier of GBED. Chances of a horse being a GBED carrier are higher if King is on both the sire and dam sides.

4. Joe Hancock

Joe Hancock quarter horse

One of the most famous and perhaps the most controversial Quarter horse bloodline is Joe Hancock. Though Joe Hancock has many notable descendants and some highly recommend his bloodline, others suggest staying away.

Joe Hancock was born in 1926 to a half Percheron mare and to a stallion out of the notable Peter McCue. He was famous for his level-headed personality and strong work ethic. Joe Hancock proved to have talent in both racing and working cattle.

The sorrel stallion went on to sire several quality roping horses, with solid conformation and strong work ethics. However, several descendants of Joe Hancock have also been known to be temperamental and prone to bucking. This has been especially prominent in horses out of his son Roan Hancock.

In addition, some descendants of Joe Hancock have Polysaccharide Storage Myopathy (PSSM). PSSM is a form of exercise intolerance where horses are reluctant to move, experience stiffness, pain, tremors, and excessive sweating.

There are two types of PSSM, with Quarter horses more prone to PSSM 1. PSSM 1 is connected with the semi-dominant variant of the GYS1 gene. The variant of the enzyme is overactive, leading to excess glycogen storage in muscle tissue.

Depending on who you ask, some people will swear by Joe Hancock bloodlines, where others say to steer clear. There are many reliable horses that have Joe Hancock in their bloodlines and others that are prone to bucking and being difficult to work with.

Quarter Horses with Halter Lineage That Carry Malignant Hyperthermia (MH)

Malignant Hyperthermia (MH) is another genetic disorder known within the Quarter horse breed. MH is an inherited autosomal dominant disease that causes a life-threatening condition when a horse receives anesthesia. In rare cases, it may occur from stress or excitement. 

Symptoms include high body temperature, metabolic failure, and in severe cases even death. MH is often more severe in horses that have PSSM 1. Though it may not be common, testing is available to see if a horse has this genetic disorder. It is most common among Quarter horses with halter bloodlines.

Also read our guide about the legendary Quarter Horse, Doc Bar.

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