The Horse . Com Les Sellnow, October 10, 2001 HYPP

HYPP: Hyperkalemic Periodic Paralysis
by: Les Sellnow, October 10 2001, Article # 725
http://www.thehorse.com/

They gave the muscular Quarter Horse colt an ambitious name: Impressive. He lived up to the name in such dramatic fashion that it became a household word in Quarter Horse circles - especially among breeders and exhibitors involved in showing halter horses.

Impressive sons and daughters were big, bold, and beautiful with defined musculature. They took the halter show ring by storm, racking up championships from one part of the country to another. Just as quickly, sons and daughters of the great stallion were in demand for breeding programs.

Then, the Impressive ship hit the sand.

A number of owners of Impressive offspring and second- and third-generation descendants of the stallion reported that some of these horses seemed to have acquired a muscle disease. Some would exhibit muscle tremors and with others there was even paralysis.

Enter Sharon Spier, DVM, PhD, an associate professor of the Department of Medicine and Epidemiology at the University of California, Davis. Spier led the effort by researchers to find out more about the disease and what caused it. The project began in 1989 and was funded by the American Quarter Horse Association.

The results of that research produced a bombshell for the Quarter Horse industry. Spier and her associates reported that the disease involved was Hyperkalemic Periodic Paralysis, known industry-wide today by the acronym HYPP.

Merely identifying the disease and the way it functioned, however, was not the bombshell. The bombshell came when it was reported that every single horse found with the disease traced to one stallion--Impressive.

The researcher's report was published in the September 1992 issue of The Quarter Horse Journal, but Impressive was not identified by name. In the months that followed, there were rumors, speculation, and widespread concern within the industry.

The AQHA issued an official statement in the December 1992 issue of the Quarter Horse Journal, but it only fueled the flames. The statement said only that the disease affected a small percentage of the total horses registered by AQHA, and that it appeared to be limited to individuals from one bloodline. It further said that most of the individuals affected were bred for halter competition.

That issue of the magazine had already gone to press when Spier appeared on the program Nov. 30, 1992, at the annual convention of the American Association of Equine Practitioners. In answer to a question that followed her presentation on HYPP, she identified Impressive as the only bloodline that carried the mutant gene which causes HYPP.

The issue was now out in the open, and the Quarter Horse industry began to grapple with it. By the time research traced the disease back to him, Impressive had been siring foals for the better part of two decades, and his many descendants, now into the second and third generations, had become the mainstays of numerous breeding programs. Approximately 100,000 horses today carry the name Impressive in their pedigrees.

What is this disease that threatens to overshadow the show ring breeding legacy of such a great horse?

Spier has described it thusly:

"Hyperkalemic Periodic Paralysis is a muscular disease that affects both horses and humans. It is caused by a hereditary genetic defect that disrupts a protein called a sodium ion channel, a tiny gateway in the membrane of muscle cells. The genetic defect disrupts the channel's normal opening and closing, such that uncontrolled sodium influxes occur. These influxes, in turn, change the voltage current of muscle cells, causing uncontrolled muscle twitching or profound muscle weakness. High levels of potassium in the blood usually are present when the disruptions in the ion channel occur.

"Horses with HYPP can experience unpredictable attacks of paralysis which, in severe cases, can lead to collapse and sudden death. The cause of death usually is cardiac arrest and/or respiratory failure. The disease is characterized by intermittent episodes of muscle tremors manifested by generalized or localized shaking, trembling, and weakness.

"Occasionally, episodes are accompanied by respiratory noises resulting from paralysis of the muscles of the upper airway (larynx and pharynx). In cases of mild attacks, muscle tremors may be so subtle as to be detectable only by an experienced clinician performing EMG testing."
The disease, Spier further reported, was caused by a mutant gene.

"The original genetic defect causing HYPP was a natural mutation that occurred as part of the evolutionary process. The majority of such mutations, which are constantly occurring, are not compatible with survival. However, the genetic mutation causing HYPP produced a functional, yet altered, sodium ion channel. This gene mutation is not a product of inbreeding. The gene mutation causing HYPP inadvertently became widespread when breeders sought to produce horses with heavy musculature."

There is a bit of good news amongst all this. Spier and her associates made history when they were able to identify HYPP with DNA testing. HYPP is the first genetic disease that can be identified by a DNA test, and it is extremely reliable.

The American Quarter Horse Association, which struggled with how best to handle the disease in the early going, has now taken firm and definitive steps aimed at identifying and controlling it.
Following the 1996 AQHA convention in Seattle, Bill Brewer, executive director, announced the new rules set forth by the association's board of directors.

He had this to say:

"Beginning with the 1997 AQHA Official Handbook, HYPP will be listed in rule 205 among conditions commonly considered undesirable traits or genetic defects, such as parrot mouth or cryptorchidism. These conditions do not prevent a horse from being used as breeding stock or from participating in AQHA-approved events, subject to rules of the individual event.
"Beginning with 1998 foals, the rule requires the following notification to be placed on the registration certificates of foals descending from any bloodline determined to carry the HYPP gene: 'This horse has an ancestor known to carry HYPP, designated under AQHA rules as a genetic defect. AQHA recommends testing to confirm presence or absence of this gene.' "
Beginning in 1999, AQHA will test all foals that trace to Impressive for HYPP. The testing will be required prior to the foals being registered.

However, if the parents have tested negative for HYPP, the testing of the offspring might not be required.

Because HYPP is inherited as an autosomal dominant trait, it can occur in both males and females and is inherited from generation to generation with equal frequency. It does not get diluted out in succeeding generations.

In four years of testing for genetic mutation between October of 1992 and 1996, more than 27,000 samples were tested for HYPP. Of that group, 63% were normal (NN), 36% were heterozygous for HYPP (NH), and 1% were homozygous (HH).

Being heterozygous means the horse carries one copy of the HYPP gene. Being homozygous means the horse carries two copies of the gene.

Breeding an affected heterozygous horse to a normal horse, says Spier, will result in approximately 50% normal offspring, while 50% will carry the defective gene. Breeding an affected homozygote will result in all offspring carrying the gene mutation, regardless of the status of the other parent.

Normal negative offspring can be safely bred without fear of HYPP being inherited, unless, of course, they are bred to a horse that is positive. Thus, selective breeding of normal, negative horses to others that are also negative could entirely eliminate HYPP.

How can researchers be so sure that only the Impressive bloodline carries the mutant gene? First, they will only say that to date they have not found the troublesome gene in any other bloodline. However, one study pretty much solidified the already existing evidence.

Stored blood samples from 6,000 horses received between January of 1989 and December of 1991 that were on file in conjunction with blood-typing requirements of AQHA were available at the Veterinary Genetics Laboratory at the University of California, Davis. All samples were from horses bred and foaled before the availability of a genetic test for HYPP.

Following is the researcher's report:

"We used a computer program to choose, at random, 1,000 samples from the 6,000 available to test for the HYPP gene mutation. The samples were primarily from breeding stallions, but were otherwise not selected for bloodlines. Among the 1,000 samples, 22 were Thoroughbred (16 males and six females) and 978 were from Quarter Horses (882 males and 96 females). The foaling year with the largest number of tested horses was 1983 (109 horses).

"Forty-three horses (42 males and one female) tested positive for a single copy of the HYPP gene. No homozygotes were detected. All of the positive horses were Quarter Horses and all traced to the stallion Impressive as first-, second-, or third-generation descendants...

"The first foaling year with an HYPP-positive horse was 1977. The foaling years with the highest frequency of HYPP positives occurred between 1984 and 1987, for which the average frequency of positives per year over those four years was 10%.

"Among the 1,000 tested horses, 100 traced by pedigree to the stallion Impressive. All of the N/H (heterozygous) horses were Quarter Horses and all traced to Impressive as first-, second-, or third-generation descendants.

"This information provides substantial evidence to confirm that Impressive is the major, if not only, pedigree source of the HYPP gene in Quarter Horses, as proposed in previous studies...

"The overall frequency of HYPP positive among the Impressive subset was 43%. This frequency is much higher than expected if breeding stock is randomly selected with respect to HYPP from pedigrees tracing to Impressive.

"It is in the range of values expected, for example, from a set of matings in which one parent in every breeding pair was N/H. Since the majority of horses in this sample set that traced to Impressive were second- or third-generation descendants, for which only 50% or 25%, respectively, of breeding pairs could be expected to have one parent positive for the trait, the frequency of HYPP-positive horses is clearly higher than expected.

"From these data, we conclude the HYPP gene is infrequent among registered Quarter Horses, although its occurrence is substantially linked to pedigrees tracing to Impressive."

Unfortunately, horses do not outgrow HYPP. They are affected for life, but it does appear that symptoms might decrease with age. The disease also appears to be associated with periods of stress, such as being hauled, intensive training, dietary changes, illness or disease, general anesthesia, or the beginning of a training program which changes the afflicted horse's normal lifestyle.

Spier and her associates maintain, however, that HYPP in horses can be managed and incidents of mortality significantly reduced by proper diet and the administration of medication. It is their belief that horses afflicted with HYPP, if properly managed, can lead productive, useful lives.

The first step, obviously, is to have the disease properly diagnosed via the highly reliable DNA test. At present five laboratories meet AQHA requirements for conducting the test--University of California, Davis, the Oklahoma Blood Institute, Shelterwood Labs, Mann Equitest Labs, and NWS Agriculture. Contact the AQHA at 806-376-4811 for a request form for a hair collection kit. The AQHA no longer uses blood samples for testing. The test costs $35.

Following are management practices suggested by researchers that will assist in the control of HYPP:

1. Establish a regular feeding and exercise schedule. Avoid fasting and water deprivation. Horses do better if allowed access to a paddock or pasture rather than strict stall confinement. Daily or nightly turnout is helpful.

2. Adult horses do very well on grass or oat hay alone or pasture. If it is necessary to use alfalfa to balance the ration for growing horses, then mix alfalfa with grass hay or oat hay and grain (oats are best) to decrease potassium content of diet. Feed equal amounts of hay and grain two or three times daily. Avoid rapid changes in diet. Provide access to a white salt block or feed loose salt.

3. Administer acetazolamide (Diamox), a diuretic (2 mg/kg orally twice a day). Many halter horse owners continue alfalfa hay as the only roughage, but maintain their horses on this drug for all or most of their lives. (Please note, the researchers caution, thatacetazolamide is a forbidden substance under AQHA and AHSA regulations.)

4. Inform your veterinarian of HYPP condition prior to any general anesthesia, which might precipitate an episode of paralysis. Maintain acetazolamide therapy before and after surgery or anesthesia.

5. Use common sense while hauling. Be sure to stop and water horses frequently (every two hours).

The researchers also have suggestions for dealing with a horse which suffers a mild attack (when the horse is not down, but has muscle tremors). One or more of the following emergency treatments are recommended for mild attacks:

1. Exercise the horse, either by walking or longing. Exercise stimulates adrenaline, which helps replace potassium inside cells. However, one should use caution as the horse could stumble and fall while having muscle tremors.

2. Feed grain (oats, dry corn-oats-barley, or light Karo syrup) for glucose supplement. Feeding carbohydrates supplies glucose, which stimulates the release of insulin and promotes potassium uptake by cells.

3. Administer acetazolamide orally (3 mg/kg). This usually means six to eight tablets if the tablets are 250 mg each. Acetazolamide increases potassium excretion from the kidney and also affects glucose metabolism.

For severe attacks, the immediate procedure is obvious--call the veterinarian.

Another basic question surfaces: Is it dangerous to ride a horse known to carry the HYPP gene? After all, it already has been determined that episodes of weakness or paralysis are unpredictable.

Research on this subject also was carried out at the University of California, Davis. Nine horses, five of which had tested positive as heterozygous carriers of HYPP and four which were negative, completed four exercise trials using a high-speed treadmill at both aerobic and anaerobic intensities. The tests were carried out with and without the use of acetazolamide therapy.

The near-maximal exercise test consisted of a warm-up followed by two minutes of strenuous galloping. The submaximal exercise test consisted of 30 minutes of slow trotting at 60% maximal effort as determined by measurements of heart rate.

The results were upbeat, even though three of the five horses had episodes of muscle tremors during the rest period following exercise.

Here is what the researchers said:

"From this study, we can advise owners of affected horses that the chance of a paralytic episode occurring while the horse is being exercised appears unlikely.

"However, we did observe episodes of muscle tremors in the rest period after exercise. We recommend that only persons experienced with the symptoms handle and ride affected horses, and to use caution if any abnormal clinical signs are observed. Acetazolamide therapy decreased the appearance of clinical signs following exercise in two of the three horses which had episodes of muscle tremors during the rest period."

The researchers have done their part and are continuing to do it. They have identified the disease and have come up with a nearly foolproof test to determine whether a horse carries the mutant gene. They have also established procedures for dealing with afflicted equines so that they can be useful throughout their lives.

The rest is up to the breeders and owners of these afflicted horses. If they carry out sound breeding programs that do not include breeding HYPP carriers, the disease will be eradicated and Impressive-line horses which are free of HYPP can continue to shine and proliferate.

(Lynn here: The bold and italics are mine. It's absolutely unforgiveable that this could be extremely eradicated if it weren't for the $$$$ signs in the eys of the Quarter Horse world. Shame on anyone who is continuing to breed any horses that test h/h or n/h for this genetic mutation. This was first reported years ago. The article above was written in 2001. We need more people to do testing and stop breeding those that have the mutation.)

Tommy is awaiting test results. I took his samples and have shipped them to the lab in California. (Or they will be in first thing tomorrow morning.) Then I will know what to do.

Lost and Found: Local Tracking Dog Saves The Day For Escaped Horse

South Woodstock, Vermont
By Gareth Henderson
Vermont Standard Staff Reporter

A one-year-old tracking dog from South Woodstock, named Shiloh, has been trained for human search and rescue. But Shiloh and his owner, Lalita Karoli, had no idea this dog's skills would help save a horse last weekend.

Odyssey, a 16-year-old black Morgan horse, was missing in the woods for two days and was found on Sunday in Bridgewater, Vermont. He was upright and uninjured except for a bruise on his back and a slight cut on his hind leg.

Owner, Eunice, of Charlotte, Vermont, praised the Green Mountain Horse Association for their help.

"They mounted a very rapid and professional response."

She was also grateful for the search party led by Shiloh last Sunday. The team traversed difficult forested terrain for four hours to find the lost horse.

This dramatic story began during GMHA's fall foliage rides last week. On Friday, at around 11 a.m., Froeliger dismounted her horse, Odyssey, when he became flighty. Froeliger tried to lead him away, but the horse took off across a field. GMHA staff used vehicles and ATV's to search for the animal in remote areas over the next two days.

"A lot of people went out looking on Friday and Saturday," said GMHA Marketing and Horse Trials Manager Molly Hutchings. "We posted fliers in all of the general stores" and in Plymouth, Reading, Bridgewater and Killington.

GMHA also contacted the Vermont Horse Council, which sent out an e-mail to its extensive state network. The South Woodstock Fire Department, Woodstock Police and Bridgewater Rescue were also notified. Odyssey had last been seen entering the woods on Keeling Road.

However, by Saturday night, there were no further sightings. At that point, Ashley Packenham arranged a search party with eight hikers, led by Karoli's tracking dog, Shiloh. Froeliger and her husband, Robert, also joined the search. Packenham and Karoli emphasized that only professionals should undertake such efforts. The search party was essentially experienced hikers and outdoors experts led by a tracker and her trained dog. The stage was set for an intensive search once the party received permission from the Vermont Fish and Wildlife Department, the Vermont State Police and landowners Teresa Fullerton, John Connors and Peter Behr. Veterinarians Sandi Silva and Jeff Oney and tracker Harold Hutt were all on stand-by. South Woodstock Fire Chief Chip Kendall supplied radios to GMHA so they could keep in touch with the search party every half-hour.

The search party set out from Keeling Road at about 8:30 a.m. on Sunday morning. Karoli opened up a plastic bag with items carrying Odyssey's scent. All Shiloh needed was a sniff.

"I gave him the scent and said, 'Find it,' and he immediately was on the trail and dragging me," Karoli said.

Packenham said it was basically non-stop jogging throughout the morning.

"Literally we jogged through the woods for about four hours, stopping only for a small drink of water."

The distance was about 12 miles, Karoli guessed.

"I had to run a half-marathon in four hours, and so did the whole party."

The wet conditions in the woods made the search more difficult, but Shiloh was able to find tracks. The hikers put surveyor's tape on trees to mark their trail (which they removed later). Shiloh took the search party back and forth over the same terrain several times, since a lost horse often paces in different directions.

Shiloh and the team eventually came to the top of Old Baldy Hill, very close to the Calvin Coolidge State Park. Shiloh still had the scent and was pacing in an area near a steep raving. The party was thinking about following the scent down the slope, when Rick Walker, who hiked these woods as a child, saw two definite horse tracks nearby. There was also a spot where the vegetation was depressed and where Odyssey might have laid down. Shiloh became even more intense, with his whole body skimming the earth. At that point, the search had lasted over three hours, and it was time to tell the back-up tracker, Harold Hutt, that everyone was okay.

"Around noon, part of the party went back, and the five of us went forward to follow the track that Shiloh was indicating," Karoli said.

Shiloh was hot on Odyssey's trail and followed the scent further into the woods. Shiloh paced back and forth for a while and eventually found the horse at about 1 p.m. The impressive animal stood in the dense forest with his saddle hanging under his belly. Odyssey still wore a red bridle over his majestic black coat, though he had shed his reins.

"It was a magnificent creature," Karoli said. "He was standing in the shadows of the forest. His head was at half-staff and he was very tired."

Odyssey's owners Eunice and Robert Froeliger approached their horse that had been stuck in the cold, wet forest for two days.

"(Robert) had tears in his eyes," Karoli recalled.

And then there was the most touching moment in the entire ordeal.

"Shiloh got on his back feet and licked the horse on the mouth," Karoli said.

The search team walked another 30 to 40 minutes to a dirt trail that led to Curtis Hollow Road in Bridgewater. Paul Kendall of the Kedron Valley Stables arranged for Odyssey to be picked up at the intersection of Curtis Hollow Road and Route 4 and brought back to GMHA.

The entire search party that found Odyssey included Shiloh, Lalita Karoli, Claude Victor, Ashley Packenham, Gene Limlaw, Ray Johnson, Rich Walker, Victoria Thrane, Bob Anderson and Eunice and Robert Frolinger. Deborah Donahue, the trails coordinator for GMHA, kept in touch with the search party by radio every half-hour. The Froeligers were also critical to the search, since Eunice knew Odyssey's habits and the places he would venture or avoid.

The party's leader, Shiloh, is a one-year-old Plott hound. These fearless dogs have been used to track bears in the forest. In the southern United States, police have used Plott hounds to track escaped convicts.

Shiloh is currently being trained for human search and rescue. Last weekend's search was his first time tracking a horse. To his credit, Shiloh was not at all distracted by moose tracks on the trail or any possible bear scent he might have picked up. He was on Odyssey's trail for four hours and covered plenty of ground in the 21,000-acre state park.

Shiloh and his owners, Lalita Karoli and Claude Victor, train dogs at Woodstock Pet Care Services and are members of the Vermont Tracking Club.

Woo-hoo! Way to go. Glad to hear good news every once in a while!

Only Horse People....

* Believe in the 11th Commandment: Inside leg to outside rein.
* Know that all topical medications come in either indelible blue or neon yellow.
* Think nothing of eating a sandwich after mucking out stalls.
* Know why a thermometer has a yard of yarn attached to one end of it.
* Are banned from Laundromats.
* Fail to associate whips, chains and leather with sexual deviancy
* Can magically lower their voices five octaves to bellow at a pawing horse.
* Have a language all their own ("If he pops his shoulder, I have to close that hand and keep pushing with my seat in case he sucks back".)
* Will end relationships over their hobby.
* Cluck to their cars to help them up hills.
* Insure their horses for more than their cars.
* Will give you 20 names and reasons for that bump on your horse.
* Know more about their horse's nutrition than their own.
* Have neatsfoot oil stains on the carpet right next to the TV.
* Have a vocabulary that can make a sailor blush.
* Have less wardrobe than their horse.
* Engage in a hobby that is more work than their day job.
* Know that mucking stalls is better then Zoloft any day.

And then there was Water!

Wow. We have been at our house for 8 years yesterday. And I have always dreamed of having water in the barn. When my husband asked me to buy a frost-free hydrant so he could put water in the barn for me, I immediately ran to Home Depot and picked one up.

Only to discover, once we started digging in the cement, that there was water to the barn - and IT WORKED! We just needed to get a new faucet and run the dust out of the hose.

So, tonight when I was cleaning stalls and filling water buckets, guess what??!?!? I didn't have to run the hose from the house to fill the buckets. I got to fill the water from the hose in the barn!!!

Way too cool!

Headed off tomorrow to attend a Animal Cruelty Task Force Training for Large Animals. It's going to be a long day - I have to leave my house at 7 am and won't be home until after 6.

It's the third training I have attended and this one will be good as it specifically deals with the large animal rescue and reporting.

Have a Good Night

HYPP in Quarter Horses - what is it...

Tommy, the rescued quarter horse who was in earlier this week, has Impressive in his blood line. What does this mean? I've done some research on google and the horse.com . It is a genetic abnormality that is passed down . It was traced back to a single Quarter Horse named Impressive. (Personally, I think he looks like a hippo on steroids...)

It's a simple and easy fix. Except for one thing. It would cost people money. All the breeders of Quarter Horses and some Paint Horses would have to do is not breed any horse that is h/h or n/h for one generation. That's it. It is that simple. Only breed n/n horses.

The test isn't very hard. It only cost about $35.00. And it would save many people and animals much heartache.

Tommy is going to be tested. I am gathering the information I need and the hair sample that is necessary, along with the $35.00, to make sure I'm not going to be needing the assistance of a vet further down the road.

Do some research. The things I have read have made me cry. There is also a post on fuglyblog.com where this young man saved and worked and bought this horse, only to find that the horse is slowly deteriorating and will have to be euthanized.

Hmmm. All they would have to do is not breed any h/h or n/h horse for one generation to totally eradicate the disease.

Quit being so damn greedy and care for your horses more than you do your pocket books. Test your horses and don't breed any who are positive in any way. Stop this genetic disease at it's base. Quit your lame excuses of breeding 'just one more' and do what is right for the horse.

Argh....

Looking to Buy a Donkey?

Please think before considering the purchase of a donkey.
1. Don't buy an intact jack to guard or as a pet. Unless you are an experienced breeder, buy a gelding or a jennet.
2. Don't buy just one, these are herd animals and need the companionship of their own kind, preferably the same sex as well.
3. Budget the cost of feed, shots and farrier care. Don't believe that donkeys can be let alone and not cared for. They just don't need as much food as horses.
4. Good quality food, not weeds and throwaway hay, please.
5.Don't use a mini donkey as a guard. Dogs can do great harm to a mini donkey.
6. Budget time to work with the donkeys, there is nothing more miserable than trying to help an injured animal that has not been worked with.
7. Consider the fact that donkeys may live to be 45 years old.
8. No pet is disposable, in my opinion.
I may have forgotten something, but I feel that these are valid points.
Thanks for looking, Mary, mom to 2 rescue donkeys and 2 rescue mules

from an ad on craigslist

Group Riding Etiquette

Horseback Riding: Group Riding Etiquette
September 7, 2009
Learn how to keep you and your horse safe while riding with a group.
By Dennis Brouse

Manners are just as important — maybe even more important — while group riding as they are at the dinner table. There is nothing more aggravating or unsafe than someone who does not follow the rules of etiquette while riding the trails.

Here are the top 10 rules for being a courteous, safe and considerate trail rider:

1. The cardinal rule of group riding: Ride at the ability level of the least experienced rider or horse. If you have a new rider or a young, green horse in your group, do not ride too quickly or take trails that are too challenging for their comfort level and experience.

2. Keep at least one to two horse lengths between you and the horse in front of you. This will allow you to view the trail ahead and prevent your horse from being kicked.

3. If your horse is a known kicker, tie a red ribbon in his tail. This will alert any rider who comes up from behind that your horse may kick; however, never assume that all riders know what the red ribbon means. If an oncoming rider moves too close, let him or her know immediately that your horse may kick.

4. If you are the leader of the group, be watchful for trail hazards and relay them to those following you. Be specific when describing the hazard, such as: “Deep hole on the left side of the trail; stay to the right,” or “Watch out, there’s a low hanging limb ahead. Duck!”

5. Since many trails are designated as multi-use and are also enjoyed by those who hike, bike or ride ATVs, it is important to understand who yields to whom. As a general rule, all users should yield to horses. Be prepared for any reaction your horse may have to others. Always speak to those you meet with a simple “hello, there” or “good morning/afternoon” with the hope that they will return the greeting and your horse will recognize them as human and not be particularly alarmed by their backpacks, bicycles, etc! It is not discourteous to ask those you encounter to yield; however, it may be in everyone’s best interest if you move off of the trail to allow them to pass if they choose not to

6. When encountering others on a hill, the uphill group has the right of way and those going downhill should yield. Do not begin your descent if you see a group coming up. If you are already on the trail, safely move your horse off the trail with his hindquarters away from approaching traffic.

7. Always yield to oncoming groups that include children riders. Move off the trail and angle the hindquarters of your horse away from the trail.

8. When watering horses from a creek or other watering source, take turns and do not ride off until every horse has had an opportunity to drink. A thirsty horse will not drink if he is left behind.

9. If someone needs to dismount during the ride, everyone should stop and wait for the rider to remount before resuming the ride.

10. Be environmentally friendly. Carry out what you carry in. Do not ride off trail or cut across switchbacks unless it’s approved.

http://americashorsedaily.com/group-riding-etiquette/#more-8894

Then, I'll add another-

11. *One MAJOR courtesy that isn't covered is NEVER trot, canter OR gallop up behind or away from other horses. A horse running towards or away from them tells them there is danger and they may react accordingly!*





*As a side note, there are people I have ridden with in the last 12 years that I will NEVER ride with again. There are only three or four people I will ride my green-broke 7 year old paint morgan gelding with. Riding a green broke horse is never, ever a place to be worried about who you are riding with and what they might do.*