What goes in, must come out. This is a sentiment all too familiar with those of us who muck out daily, yet this onerous task can provide vital information about a horse’s health. The importance of faecal monitoring should never be underestimated.
The basic anatomy of the digestive system is the same for all mammals. Horses have evolved as forage eaters who will graze for 16 to 18 hours a day, so the equine digestive system functions best when trickle fed in this way. However, the performance horse needs more energy than can be supplied by an all-forage diet. Health problems can soon arise when high levels of concentrates are fed infrequently and at the expense of forage.
The average horse will defaecate up to 12 times a day to produce 15 to 20kg of droppings, which is around nine tons per year. Stallions (who will use defaecation as a means of marking territory) and foals pass droppings more frequently than mares and geldings. The high-fibre diets of grazing or predominantly hay-fed animals have a lower digestibility and hence produce bulkier faeces, compared with those of horses on high-concentrate diets.
Knowing what is normal for your horse, such as his daily defaecation rate and the consistency of his droppings, is an essential part of good horsemanship and may provide an early and important clue that something is amiss. If the wheelbarrow contents look different to normal, then a phone call to your vet is always a sensible idea.
Look and learn
Healthy faeces should have a glossy shine and form firm, well-defined and moist balls that break up easily. They should not be dry, hard and dull looking, but neither should they resemble cowpats.
The frequency and appearance of droppings can be influenced by many factors. Certain identifiable characteristics will reveal a lot about a horse’s management and health status, such as:
- Colour: greenish, moist faeces are common for a horse on an alfalfa-based diet or predominantly at grass, especially on lush spring grazing; while yellow or brown faeces suggest that he is stabled and fed hay and concentrates. A reddish hue points to excessive beet pulp in the diet. Very dark or black droppings could indicate bleeding from the stomach or small intestine, although this is rare.
- Frequency: a reduced defaecation rate may be due to a lack of food. Fewer droppings will appear if a horse loses his appetite, perhaps through illness, or has difficulty eating because of dental issues. A sudden decrease in output could indicate an obstruction or impaction in the gastrointestinal tract and should be treated as a veterinary emergency.
- Content: intact grains or undigested fibre stems clearly visible in the droppings are often a sign of inadequate chewing, due to dental problems. A gritty appearance may point to potential sand colic, especially if the horse grazes in sandy locations, while the presence of fresh blood suggests injury to the wall of the colon or rectum. While visible redworms or roundworms in the faeces signify a worm burden, their absence does not rule out parasitism – hence the importance of routine microscopic faecal worm egg counts.
- Odour: an unusual smell, often accompanied by changes in colour and consistency, usually indicates an upset to the normal gut microflora. Foul-smelling faeces sometimes imply gastric or duodenal ulcers, or sudden dietary changes. A rancid smell may mean an excess of carbohydrate or protein in the diet.
- Texture: very dry, hard and small balls of a greyish colour, with a mucus covering and possibly some blood tingeing, may suggest constipation. This can quickly develop into potentially life-threatening impaction colic. Veterinary attention is also advisable if faeces vary between loose and liquid, because diarrhoea can create a serious risk of dehydration.
Keep it simple
The equine digestive tract works best if things are kept simple and regular, so sudden dietary changes can prompt diarrhoea.
Overfeeding, or the inclusion of indigestible roughage, dirt or sand in the diet, can soon cause diarrhoea in youngsters. In older horses, the more established bacterial population in the hindgut is sensitive to what passes through the intestines and will adapt to any changes, provided that they are introduced gradually. Dietary alterations that are inappropriate or too abrupt can have a profound effect on faecal consistency.
It is not unusual to see some change in faecal texture immediately after a dietary change; in most cases, this will improve as the horse adapts. If droppings remain loose, however, an intolerance should be considered and it may be necessary to eliminate one of the feedstuffs from the diet. Irritable bowel syndrome, which can be a significant challenge to manage, is now increasingly recognised, arguably as a result of presenting our horses with too much dietary variety.
There are a number of infectious and non-infectious causes of diarrhoea, including parasitism, salmonella and rotavirus. A sick horse with loose faeces is always an emergency.
Antibiotics are a well-known trigger for loose droppings, as they invariably have an impact on the hindgut microflora. In a recent study, researchers confirmed that antibiotic-associated diarrhoea (AAD) is attributed to the disruption of the normal flora of the hindgut, permitting the proliferation of pathogenic microbes – although not all the horses in the study were affected similarly. A probiotic supplement is often recommended when antibiotics are prescribed in an effort to combat AAD.
A horse who is excited or stressed may rapidly produce more droppings of an increasingly sloppy consistency. This is due to the “flight or fight response”, whereby the sympathetic nervous system prepares the body for a sudden need to flee a predator.
This response ensures that all sources of energy are diverted to the musculoskeletal system and also that the body isn’t weighed down by “unnecessary waste”. The resultant adrenaline surge not only “shuts down” the stomach and upper intestinal activity, but also increases lower bowel activity, stimulating the evacuation of any processed ingesta and lightening the body load.
The more rapid this response, the less time there is for ingesta water to be absorbed and the looser the droppings become. After any such episode, it is important to reintroduce forage gradually, so that the digestive process can pick up again, and to address fluid and electrolyte loss.
Foals who are still feeding from their dams, so are on a high-milk diet, will produce yellowish, pasty faeces. When the mare has her “foal heat”, eight to 10 days post-foaling, her foal may produce a yellow-brown, watery diarrhoea (scouring) that stains his hindquarters. This may last for a few days and is the result of the foal’s transition to a more mature bacterial gut flora.
Foals are often seen to eat the faeces of other horses, which is thought to help populate their own gut with microflora.
The daily digest
The digestive process begins with the first bite:
- Incoming food, or “ingesta”, is chewed and lubricated with saliva in the mouth, before passing down the oesophagus into the stomach where it is liquefied further.
- The ingesta enters the small intestine, where the extraction and absorption of nutrients (proteins, fats, sugars, vitamins and minerals) occurs.
- It passes through the large intestine, where the fibrous portion is broken down in the caecum and large colon with the help of billions of microorganisms. This fermentation process takes up to 36 hours and releases essential fatty acids, amino acids and vitamin K.
- These are absorbed in the large colon, together with some of the excess water.
- Remaining excess water is absorbed in the small colon, at the far end of the large intestine, before the resultant faecal balls are evacuated through the rectum and anus.
Ref Horse & Hound; 26 March 2020
