Free roaming horses in our manmade world . Stress hormones and happy hormones (and neurotransmitters) . Ulcers . Colic . Laminitis . Equine digestion . Evolution of the modern horse .
If you are seeking medical advice for your horse talk to a professional. This is for interest only, I cannot guarantee this is wholly accurate.
All this information is widely available on the internet, I have drawn from many sources, referenced after each section. I have tried to bring it together here in a clear digestible fashion.
In their natural habitat wild horses would spend many hours per day with their head down, grazing on wild grasses and other vegetation, and occasionally snoozing too. They would also browse shrubs and trees and move seasonally to find healthy vegetation. They would eat small amounts on and off, they don’t need to eat all the time. Over a 24 hour period they may spend 15-18 hours eating and only 3-5 hours sleeping and not all at once, they mostly sleep standing and must lie down for REM sleep.
Unfortunately, this isn’t possible for many domesticated horses, particularly competition horses where, in some cases, what they are given to eat and when they can eat it may be more aimed at winning than the health of the horse. So, we ought to find a best compromise between what they need for good health and what we are able or want to provide.
Hays and haylage vary in nutrient content, and we supplement with mineral licks and grains, particularly for competition horses requiring a high calorie intake. Many fields lack a natural variety of vegetation, with grasses that are too nutritious and fast growing for horses, and in winter months they may hardly be growing at all. A diet based mainly on good nutritional forage and turn out on well established organic grazing could be best for digestive health.
Dopamine (neurotransmitter), Norepinephrine (neurotransmitter)
and Epinephrine 'Adrenaline' (hormone mainly, also a neurotransmitter).
A group of chemicals produced (one from the other in that order) in a complex
chain of chemical actions, from tyrosine an amino acid obtained by eating
These first three have roles in the instant energetic response. One of dopamine’s jobs is motor control, it plays a part in pulling your hand away from a hot surface. Too much of it and your jittery hyperactive, severe deficiency causes Parkinson's disease.
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It drives motor control, motivation, learning, memory, and gives reward. Dopamine release is increased during fight or flight and afterwards.
• Focuses attention.
• Motor control in response to sensory input such as pulling away from danger.
Dopamine release is mostly increased in anticipation of a reward, the greater the anticipation the greater the release. To keep getting that 'high' more and more rewarding things are sought.
• Thought processing, memory. Remembering you like chocolate bars,
or remembering something that was dangerous.
• Increases motivation. The drive, the need, to want something like a chocolate bar, or to get away from danger.
• Reward. Happiness and euphoria. One of the feel-good hormones (neurotransmitter mainly). Reward for achieving a goal such as finding a hidden chocolate bar, achieving a personal best, or reaching a place of safety.
• Panic attacks
• Raised blood pressure
• Addiction. Read the last three good effects again, and again, and…
• Increases alertness
• Focuses attention
• Can cause restlessness
• Elevated blood pressure and heart rate
• Irregular heartbeat
• Anxiety etc.
Neurotransmitter in small amounts involved in the instant reaction to danger.
Hormone in larger amounts from the adrenal glands.
• Increases the heart rate.
• Elevates the blood pressure.
• Directs blood to important muscles and organs
• Dilates the airways. Think EpiPens for anaphylactic shock.
• Triggers blood sugar release, the same as cortisol.
• High blood pressure
• Sweating and shaking.
Released from the adrenal glands, to prepare the body for
further physical effort after the immediate reaction.
• Tells the liver to convert its stored protein and fat into glucose and release it into the blood.
• Tells the pancreas to release insulin. Insulin enables the body’s cells to take up glucose from the bloodstream, so the muscles get extra energy for running away.
• Suppress functions not needed when running, including digestion.
• Away from stress it acts on your circadian rhythm, rising in the morning to get you going.
• Can lead to excess insulin, which can lead to insulin dysregulation, which is a well known cause of Metabolic Laminitis (3.1), amongst other bad things.
• Suppresses or disrupts digestion in various ways.
• It can also have a negative effect on the stomach lining mucus, (1.1 Gastric Ulcers).
• Interrupts pain signals to the brain. The body’s own opiate pain killers. Entomology “endogenous,” meaning from the body, and “morphine”.
• A feel good neurotransmitter. Boosts mood and self-esteem.
• Reduces stress, depression, and anxiety
• There aren’t any from the amount the body can produce.
Mood stabiliser. Wellbeing and happiness.
Important for brain function
Important role in regulating the digestive system.
Brings on sleep in the circadian rhythm.
Similar to those of too much of a catecholamine.
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1.1 Stomach (gastric) Ulcers. Typically caused by physical or emotional/psychological stress, also by higher than recommended NSAID doses, particularly on an empty stomach, same as us.
1.2 Colonic Ulcers. Are much less common. Researchers say they can occur in any part of the colon, though usually these are the causes and locations…
Colic for horses is regarded as pain in the gastro-intestinal system. There are many types and causes. Here are the most common causes.
A symptom, not an illness. Is pain from the lamellae tissues bonding the outer hoof to the bone. A painful condition something akin to a toenail coming off but far more serious. Laminitis is not a disease in itself but a symptom of other health issues, some short term, some long term, requiring greater management. So, what has it got to do with digestive health? Have you ever noticed white patches, ridges, bumps, and thin areas on your fingernails after lengthy illness? Your nails are affected by your health too.
What are lamellae? Without getting too medically technical here, the outer hoof as it grows down is bonded to the last bone in the foot, the coffin bone (pedal bone in US), by interlocking scaley tissues, the lamellae (laminae US) on each part, with a gluey layer in between.
There are numerous often interacting causes. Poor digestive health is a major factor in inflammatory laminitis, and a contributing factor in metabolic laminitis. Another form or cause is overload laminitis. Inflammatory laminitis Is pain from this firm tissue, lamellae, becoming swollen, enflamed, “itis” means inflammation. Metabolic laminitis is pain from the lamellae due to the bone beginning to separate from the inner hoof wall. The lamellae are weakening, lengthening, and beginning to break down due to lack of nutrient from blood sugars, they can no longer transfer the weight to the hoof. As it gets worse the coffin bone begins to peel away from the hoof inner wall and point down and sink down in the foot. Overload laminitis is pain from the lamellae from standing too much weight on that foot for long periods, usually because of pain or injury in another leg.
3.1 Metabolic laminitis
So what causes insulin dysregulation? Three common causes for horses are EMS, PPID (Cushing’s Disease), and poor digestive health which is also important when considering the first two.
3.2 Inflammation laminitis
The acid produced from digestive problems such as colic, diarrhoea, or a sudden large intake of sugars can cause lesions, weakening of the intestinal walls. This can result in bacterial toxins getting into the blood, and the immune system releasing inflammatory cells (disease fighting cells) into the blood. These bacterial toxins can cause infection around the body including the lamellae, and the increase of blood flow to these infected cells, caused by the immune system cells going to fight the infection, cause inflammation. The resulting inflammation in the lamellae causes pain due to the immense pressure from the weight of the horse. The pressure will restrict blood flow. Add on flow restriction due to the volume of toxins and immune system cells in the blood, and you have the beginnings of metabolic laminitis type symptoms.
3.3 Overload laminitis
Overload laminitis can lead to inflammation laminitis symptoms, and then to loss of blood flow resulting in metabolic laminitis like symptoms.
Sources: Royal Veterinary Collage London, University of Liverpool, The Laminitis Site, American Association of Equine Practitioners.
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All domesticated animals have been selectively bred over
hundreds, in some cases thousands of years, for the physical and behavioural attributes
we desire. Compared to the pace of evolution these have been rapid changes. Many
things about all breeds are still basically the same as their wild ancestors,
including their digestive systems.
The equine digestive system is defined in two parts, the foregut which includes the stomach and small intestine, and the hindgut or large intestine which includes the caecum, large and small colon. For an adult 500kg horse the whole system is about 30m long with a capacity of about 180L.
Teeth. Horses chew in a complex sweeping action of both side to side and forward backward movement as well as up and down, and the upper jaw is wider than the lower jaw, creating more area for this action to grind fibrous foods. A diet high in grains and low in forage requires less lateral chewing action that does not pass beyond the outer edges of the teeth, resulting in sharp points developing on the outside edges. If these are not filed down or ‘floated’, they can cause significant effect on efficient chewing, rate of eating, mood, and poorly chewed forage may get stuck causing choking. Less forage and more grain also means the continuously growing teeth will not be worn down by the silica content of the grasses and need regular filing/floating.
1.1 Oesophagus. They have a long neck and oesophagus. For food to pass easily along this it must be well chewed and contain plenty saliva. Preventing horses bolting their food down is important to avoid choking.
1.2 Stomach. Horses have only one chamber to their stomach, it does have an upper and lower part, and it is the smallest stomach in proportion to body size of all domesticated animals, about 7.5-15 Litres, and only 10% of the whole system. The small size is because they eat little and often so don’t need to store food, which normally passes quite quickly through, the stomach is also not very stretchy as it doesn’t need to be. Gas colic can be a problem as horses cannot burp or be sick, because the valve at the stomach entrance remains tightly shut. The only way out for gasses is the back way!
Not much of the fibrous food they eat can be digested by the stomach, mainly digestion of proteins and fats starts here. The main function is adding acid and gastric juices to break down the fibrous food into smaller parts and make it easier to pass on into the intestines where most of the digestion occurs. The acid is secreted continuously in the lower half of the stomach which has a special lining which releases a thick layer of mucus containing bicarbonate that resist the acid. The upper half of the stomach, which is basically an expansion of the oesophagus separated by a band of tissue, does not have this acid resistance and is where, without a steady flow of food taking the acid away, ulcers will occur if acid gets up there.
An unnatural diet high in grains and low in forage can cause problems throughout the system. Because of their lack of bulk grains can pass quickly through the stomach leaving it empty again and vulnerable to acid attack, and get stuck low down in other parts. Grains and pellets are mostly rapidly digested in the small intestine and can give a horse a sugar rush, some horses have learned to get this by refusing to eat until they get their grains. If some passes quickly on into the hindgut it can create a lot of gas causing painful gas colic.
.1.3 Small intestine. About 20-25m long with a volume about 5 times that of the stomach and is about 30% of the whole system. Food again normally passes relatively quickly through here. This is where enzymes digest soluble carbohydrates, the sugars from starches, amino acids from proteins, fatty acids, and vitamins A, D, and E.
This is where equine digestion has really evolved. How to digest cellulose that ruminants need a four chambered stomach, lots of chewing the cud, and lots of time sitting around and sleeping, to do. The hindgut is about 62% of the whole system, where the bulk of the food spends most of its time. Its where fibres are broken down by fermentation by microorganisms (bacteria, protozoa, and fungi) more or less the same as in ruminant stomachs.
The caecum and large colon are where most fibre is digested, in a similar way to ruminant stomach chambers, into Volatile Fatty Acids (a fermentation biproduct of the bacteria’s digestion of the cellulose), from which the horse gets a lot of its energy.
2.1 Caecum. About 1m long and 30L, a kind of large muscular sac with one way entry and exit valves both at the top and is often where impaction colic can occur if a lot of forage is eaten too quickly, as it will pass through the foregut too fast and not be broken down enough and be too dry.
2.2 Large colon. About 3.5m and 55L, is where microbial fermentation digestion continues and absorption of B vitamins and trace minerals occurs.
2.3 Small colon. About 3m and 18L, is where water is reclaimed back into the body before the remainder passes out as poo.
Sources: Edinburg University, American Association of Equine Practitioners, My Horse University, Equine Wellness Mag, Equisearch.
Domesticated and wild, horses, donkeys, zebras etc, have a unique digestive system, due to a change in the environment of their very early ancestors 20 million years ago. Unlike most other grazing animals, they only have one stomach chamber and it’s a small one. And no, it’s not because they are a fast animal, antelopes have 4, kangaroos have 2, and rhinos have 1.
56 million years ago you came onto this website wondering if you might buy one of our feeders. You must have read the testimonials on the more relevant pages about 55 million years ago. Save yourself and see if you can find a feeder you like in our shop.
A time of evolution of many animal groups including mammals. The climate was warm and humid, plant life was widespread lush forests and very little grass lands. Digestive systems don’t show in fossil records, so little detail is known of their evolution.
A hoofed browsing mammal about 5 hand high, with 4 padded toes or hooves at the front and the rear 3. Fossils have been found in North America and Europe and they were so different to modern horses that it was sometime before the connection was made via later discoveries. It had a single small stomach system well adapted to the abundance of easily digested high energy fruits and lush leaves at the time.
From Eohippus there evolved many branches, many extinct. The main evolutionary changes then were of the teeth, the animal itself changed little. More and larger molars appearing for specialist adaptations to its browsing diet. All modern equids still have these teeth today, though very adapted to grazing.
From Eohippus fossil records suggest the continued evolution towards the modern horse occurred mostly in North America. Mesohippus was becoming more horse like, still only 6 hands high and still browsing.
In the early Miocene the climate cooled and became drier, in North America forests were dying off and dry course low nutrition grasslands were spreading.
Some branches spread north and across into Eurasia. Remaining in North America the Parahippus evolved into a grazing animal and went on to become the modern horse. Their molars and pre-molars became more adapted to the side-to-side motion required to grind down grasses, developed larger and stronger protrusions, and a greater depth of crown material to longer withstand the abrasive nature of grasses due to their high silicon content.
The transition to grazing teeth was complete. Merychippus was about 10 hands high, the lower leg bones had fused for fast running and ligaments attaching the remaining central toe to the ankle and leg bones became strong and spring like. still with three toes.
Pliohippus was single toed.
Finally, all forms of Equus evolved with even springier ligaments and longer straighter teeth. This included Equus Caballus, the modern horse.
Equus successfully spread all over North America, some into South America, and north across the Bering land bridge all over Eurasia and into Africa.
They disappeared from North and South America and non could spread back from Eurasia because sea level had risen submerging the Bering land strip. It’s not known why they disappeared and there are various theories, humans had been there since 20,000 years ago, so hunting is one possibility.
In Central Asia and Eastern Europe Equus Cabullus thrived and various breeds developed. Of these it’s thought Przewalski’s Horse of Central Asia (there is some debate as to whether these are wild or ferral), the Tarpan of Eastern Europe and the Ukranian Steppes, and the Forest Horse of Northern Europe formed the origins of the domesticated horse. From the first two came the southern “warm-blood” horses. And from the Forrest Horse the heavier “cold-blooded” horses.
Horses finally returned to their ancestral lands with the Spanish.
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