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The senior horse

As horses get older their body changes and they become more prone to senior health issues such as weight loss, dental issues, arthritis or PPID.

Old age is not a disease. If a senior horse is losing weight, there’s a cause that can usually be addressed. The reason older horses become more prone to losing weight is that they become more prone to dental issues, PPID, insulin resistance and intestinal parasite infections. It is therefore important to maintain good preventative care:

Faecal egg counts once every season to stay on top of intestinal parasite infections
Yearly dental checks to stay on top of typical senior dental issues
Adjust the horse’s diet to one suitable for senior horses
Have your horse checked for PPID and/or insulin resistance
Do a Body Condition Score every 6 weeks, so that weight loss can be picked up early and loss of muscle mass can be prevented, as senior horses don’t build up muscle that easily anymore

Dental problems
Senior horses are more prone to develop certain dental problems. Horse’s teeth run very deep in the upper and lower jaw. In young horses 75% of their tooth sits inside the bone. Unlike in humans, cats and dogs, a horse’s teeth erupt throughout life, meaning that more of the tooth becomes exposed at the surface through time. The surface gets worn down by mastication of fibrous foods. As horses become old, they don’t have as much tooth left underneath the surface. This means that teeth may become loose, causing eating difficulties. Loose teeth may need to be pulled. When a tooth is pulled, the opposing tooth no longer gets grinded down and will keep on erupting into the free space where the pulled tooth used to sit. To prevent the opposing tooth from becoming too long and eventually causing damage the horse will need to get dental care every 6-12 months. If a horse has lost too many teeth, it won’t be able to chew forage properly anymore, which means its diet then needs to be adjusted. Our vets can help you with that.

Another issue is that the cheek teeth decrease in diameter towards their roots. This means that when these parts of the teeth come up at the surface, it may leave gaps between neighbouring teeth. These are called diastema. Food can get pushed into these gaps, but often can’t get out. The food then starts to rot, and the gums become inflamed. The gums retract, which leaves an even bigger hole for food to get trapped in. A vicious cycle starts and the problem becomes bigger. This process becomes quite painful, which can cause eating difficulties. Bacteria multiply and sit around the rotting food at the gumline. This causes periodontal disease, with infections below the gumline and tooth caries. The food pockets need to get cleaned out properly (they can run quite deep!) with specialistic equipment and infection needs to be treated so that the gums can heal. The gumline can restore itself if it’s rested long enough, but because of the diastema, the problem is likely to recur. This means that horses with diastema and food pockets may need to be seen every 4-6 months. Some diastema can be opened up further with a special burr, to see if food can fall out more easily. However, this only yields positive results in certain cases. In some cases it may be better to remove a tooth, so that there are no more small gaps. However, this may come with its own risks and also reduces chewing capacity. In other words, every case needs to be assessed individually to formulate the best treatment plan.

Another senior dental issue is something called “smooth mouth”. This is when the tooth has “run out”, and the surface no longer has proper grinding capacity. A horse’s tooth is composed out of different layers: enamel, dentin and cement. However, enamel (which gives the tooth a rough grinding surface) is only present in the crown, not the root. When the tooth is worn down to the root, it loses its sharp enamel edges, and mastication and digestion of forage becomes more difficult and less efficient. When a horse develops smooth mouth, it’s likely that it’ll need to have its diet adjusted. Unproperly digested rough forage can predispose horses to oesophageal choke or colic from intestinal impaction. Unproperly digested feed also can’t be absorbed properly by the gut, which means that the horse can’t take up its necessary nutrients. There are special geriatric feeds that can safely replace forages in the diet to make sure the horse receives enough fibre for its hindgut. These feeds are easily digestable and don’t need to be chewed.

Our vets can treat these senior dental issues and formulate the right diet for your senior horse to help keep your horse healthy longer.

Nutritional needs
A senior horse may have different nutritional needs. The age at which a horse starts to benefit from a senior diet depends on the individual. If you’re wondering about your horse’s diet, give us a call.

Studies have shown that older horses are more likely to develop health issues such as PPID (formerly known as Cushing) and insulin resistance. PPID occurs on 20% of horses over 20 years-old. Horses with PPID are prone to laminitis due to insulin dysregulation. However, horses that don’t have PPID can also develop insulin dysregulation.

Researchers that have studied PPID/Cushing and insulin resistance in old horses at the University of Kentucky’s Department of Animal and Food Sciences, found that a decrease in insulin sensitivity can occur as a normal part of aging. When they compared the results of two of their studies that used the exact same procedure to measure insulin sensitivity, they found that of the horses that did not have PPID, their 25 year-old horses had a 75% decrease in insulin sensitivity compared to the horses around 8 years old.

Horses with insulin dysregulation have different nutritional needs. Their feeds need to be regulated to make sure their sugar levels stay within normal limits. By changing their source of energy, we can help them keep their optimal body condition score without causing issues with their sugar levels.

When senior horses can’t chew properly anymore, the firbous portion of their diet might need to be replaced by a more digestable food source. There are special senior feeds available, but not every feed is suitable as a forage replacement. There are different types of fibres. The cellular walls of plants contain components such as cellulose, hemicellulose, lignin and pectin. These all have a different effect on the hindgut microflora. Beetpulp contains pectine, which stimulates fermentation and has a positive effect on the microflora of the hindgut. A certain fibre length is needed in forages to stimulate chewing, saliva production to buffer the stomach’s acid and intestinal mobility. If possible, a horse should still be offered some forage for this purpose. However, if fibrous feeds such as hay are not chewed down well enough it can cause oesophageal obstruction or impaction colic, so care should be taken.

Another way to improve fermentation is to feed a supplement that contains probiotics such as live yeast cultures. A horse that has a healthy gut might not need such supplements, but in horses that don’t eat a lot of forage, probiotics can be quite beneficial. Certain live yeast cultures protect against overgrowth of “bad bacteria” and aid stimulate the good bacteria, which helps digestion of fibre.

Older horses might not be able to properly chew certain hard feeds such as grains anymore either. Replacing such feeds with a pellet feed or a feed that contains extruded components increases nutrient digestability. Other options include feeding a vitamin/mineral pellet feed and adding vegetable oil to increase energy uptake.

Senior horses are not as good at gaining muscle as younger horses are. Especially if a horse can’t be worked anymore. Preventing loss of muscle is very important in the senior horse. A horse that’s on proper grass will receive more vitamin E and proteins than when the grass is of lesser quality or the horse can’t digest it properly anymore. A senior horse might benefit from a good protein and vitamin E source to support its muscles. Essential aminoacids such as lysine, threonine and methionine are important for muscle maintenance.

The immune system of older horses may not be as strong anymore. Vitamin C, which is produced by the liver, stimulates good immunity. In horses that have impaired liver function, extra vitamin C should be offered. The geriatric horse’s liver may not function as well anymore as a young horse’s, which is why vitamin C is often added to senior feeds.

Vitamin B and vitamin K are produced by the microflora in the hindgut. Some senior horses get hindgut issues due to changes in digestion of fibre. In such cases, it may be beneficial to supplement vitamin B and K.

Horses with arthritis often benefit form either a feed supplement or injectables. There are various options available, which you can discuss with your vet.

When does a horse become senior?
There’s no one age at which a horse becomes “senior”, as some horses show signs of old age at 17 years-old while others don’t show any changes untill they’re 25. By keeping a close eye on your horse and its body condition score and teeth, and having your horse checked by a vet yearly, signs of old age can be picked up early.

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