Basics

Introduction

The feeding of a horse consists of more than just procuring it with sufficient roughage, water and concentrate. Any horse needs to be fed according to its needs. What this means, is mainly that the rations need to be adjusted when the horse has had more or less work, or when a part of the feed is transferred to a foal, be it born or not.

In this course we try to explain some of the basics, in a simple, yet clear and thorough way. The feeding needs are one part of the equation, the way these needs are fulfilled, another important part. A good understanding of the anatomics of the digestive system of horses are a key element in understanding how digestion works. That’s why we direct our attention of this element first.

The digestive system

Horses are herbivores, plant eaters. Because herbivores feed on the structures with lot of fiber, such as grass, cereals, and so on their digestive system is adjusted to these circumstances. What characterizes a horses digestive system the most is its strongly developed bowels and a relatively small stomach.


Intake

The major factor in the intake process are the lips. A horses lips are extremely agile, which allows them to be very selective. Every horse keeper recognizes the example of the horse that manages to empty the entire feeding container but leave all the deworming medicine untouched. The advantage however, is that this ability enables it to get as much grass as possible out of the field, while avoiding the less tasteful or dangerous herbs. Contrary to cattle, horses do cut the grass with their incisors. As a consequence some horse meadows are grazed below the point where easy regrowth is possible. Grass needs a bit of leaf to grow, so one should not wait too long before relocating the horses.

Chewing

After the intake, the mastication is next. This process is slightly different from human chewing, as it is don by sliding the upper- and under jaw over one another, thus grinding the fibers. Because the under jaw is narrower than the upper jaw, a horse can only chew on one side at the time. The most common problems that arise when it comes to chewing are hooks on the teeth, dental degradation in older horses and the transition from milk teeth to permanent ones in younger horses. 
Hooks are sharp edges on the side of the teeth and can be prevented by procuring enough roughage. Otherwise the teeth are used irregularly and will be worn as such. Hooks can grow very sharp and diminish appetite and digestion.

The more structure the feed has, the longer the horses are forced to masticate, for a comparable amount of feed. This entails the production of saliva, which, at its turn, enables better digestion, of a feed that has been grinded better to begin with. On top of that, higher saliva production doubles as lubricant so that a regular transition through the bowels becomes possible. 
Saliva is physically basic, so extra saliva production makes the stomach less acid. An overly acid stomach kills a bigger part of the bacteria necessary for fermentation of the carbohydrates.
Water is vital for the production of saliva, so access to sufficient and clean water is more important to a horses diet than some people realize. Feeding at regular times is another interesting improvement to the overall feeding philosophy. It encourages the excretion of saliva, before the feeding begins, as the horse can anticipate and produce saliva, thus unknowingly improving digestion

The stomach

After the transition through the esophagus, the feed arrives in the alkali part of the stomach. This part is responsible for the processing of the easily digestible carbohydrates, by bacteria and enzymes. During the next stage, in the gastric mill, the proteins and fat are broken down. This is the acid part of the stomach, in which the bacteria from the alkali part do not survive. 

Stomach ulcers are a common problem with horses, usually caused by a stomach that keeps on producing acid when it is empty. A problem, however, that can be prevented by procuring sufficient roughage, so the horse can nibble all day long, as it would do in nature. 

We’ve mentioned before the stomach of a horse is small, relative to its bowels. For that reason it is wise o procure the food in smaller portions, spread over the day. Moreover, portions that are too big, combined with an eager or hungry horse, can cause serious digestive problems, such as colic.


Quite a lot of blood is used by the digestive system, when working. When the horse is demanded to work, shortly after feeding, the circulation system will draw blood from the intestines to the muscles, which will slow down digestion. This causes food to stay in the stomach for longer, which enables the production of gas. Gas that can not be evacuated quickly enough through the bowels and can cause colic all the same.

Small intestine

Food particles are further broken down in the small intestine, due to secretion of gall (liver), intestinal and pancreas fluids. A major part of the nutritional components are absorbed in the blood stream, through the intestinal wall. At this stage a healthy gut flora wit a good physical balance make sure the gut bacteria don’t survive, to avoid extra fermentation in the small intestine. Fermentation causes gas and gas causes colic, so this should be avoided.

Colon

Raw fiber is digested by micro-organisms in the colon. This process produces fatty acids, which serve as energy for the organism.
In case the horse has insufficient access to roughage, the amount of micro-organisms in the colon will be likely to decrease. It’s not difficult to understand that in this case, the positive effect of these organism will decrease subsequently

Te last part of the colon is responsible for resorption of water, salts and other resources of high nutritional value, after which only the indigestible parts are left to be excreted.
Excrements which lack consistency can be a sign of the food passing too fast through the digestive system of the horse. A problem that can be solved by adding raw fiber to the diet. Manure with a smell, less appealing than normal, are almost always a sign of problems in the intestinal canal of the horse.

Nutritional elements

Proteins

Proteins are one of the most important building blocks for new life. They play a vital role in the development of the fetus. In much the same way the lactating mare needs big quantities of protein for the milk she produces. Even growing youngsters still need higher dosage of proteins in their diet, to ensure good growth. 
Proteins are made of amino acids. The quality of the protein source is determined by the pattern and the digestibility of the amino acids. There is a difference between essential and nonessential amino acids. The difference between both being that essential amino acids are the ones the horses body can’t produce itself. They have to introduced via the feed. Most horse feeds have deficiencies in the essential amino acids Lysine, Methionine and Tryptofane. Those are the ones that can be found in soy, milk powder etc. and are the reason those elements are valuable assets in Lannoos horse feeds. 
In case of a protein surplus, the horses’ body has no storage facility. The protein is transformed into, which produces ureum, that will be evacuated through urine. 
Sport horses have no need for extra protein. A little known fact, and one that can have serious consequences on your horses’ health. Liver and kidneys have more work than they can handle, which results in exaggerated sweating and urinating. Symptoms of this problem can be; swollen legs, increased hearth rate, and skin rashes. 
Foals on the other hand do have an increased need for high quality proteins, due to the fact that their colon is still developing and very little microbial protein is produced.

Fat

Fat is very important as a source of energy. Furthermore, it’s responsible for body heath production, improving physical fitness and carrier of fat-soluble vitamins. 
Poli-unsaturated fatty acids (?-3-fatty acids) are produced from soy oil, corn oil and flax seed oil and contribute to a shiny skin and healthy appearance. 
Extra fat is fed to improve stamina in aerobe circumstances because of its glycogen saving effect. Up until 16% percent of a horses regime can be fat. Rates above 20 % have a negative effect on digestibility, with diarrhea as a possible consequence. 
Higher levels of fat can also have as side effect to reduce tastefulness of the feed.

Carbohydrates

Carbs are the main source of energy for horses. Carbohydrates is the eumbrella term for sugars, starch (in cereals) and the hard to digest cellulose (raw fibre in the cell wall of vegetable cells) 
the main source of sugars are beets and sugar beets. They are broken down in the intestines into glucose and fructose, both easily digestible. 
Starch also transforms into glucose, but not all starch is the same. When it originates from barley and oats, the digestibility is far beter than the starch out of corn and raw patatoes. 
Raw cellulose occurs mainly in feeds with a high stem and cell structure (grass, hay, straw..) The raw cellulose ends up allmost unchanged in the colon and is digested there, by micro organisms. 
A surplus of carbs in any diet can cause lactic acid fermentation in the colon, which causes a burning feeling in the gut. When large quantities of starch and sugars are ingested, the stress on the muscle glycogen can be so strong the aerobic catabolism releases dangerous amounts of lactic acid. In the equestrian world, this is known as 'tying up'. Muscle soreness can both be prevented and cured with addition of Dimethyl-glycine and Natri=bicarbonat to the horses diet.

Minerals

Calcium and phosphor

Calcium is vital in bone formation, muscle contractions and regulation of a large amount of cellular functions
Phosphor is equally important in bone formation, Furthermore it is needed in energy-rich compounds (ATP), proteins and phospholipids.
The calcium/phosphor ratio is of the utmost importance in horse feeding. The perfect ratio lies between 1.4 and 2. In case of calcium shortages (or phosphor surplus) calcium is taken from the bones, which causes bone deformations.
Vitamin D enables the intake of calcium and phosphor via the intestinal wall. Vitamin D, calcium or phosphor shortage can cause what people call 'rickets'. A disease that shows by the formation of less cartilage and excessive formation of bone, mainly in proximity of the joints.
Leguminous plants such as clover and lucerne contain high doses of calcium.

Potassium, sodium and chlorine

These minerals are electrolytes. They are excreted via transpiration. A natural consequence is that electrolytes should be added to the diet after heavy sweating. Salt (NaCl) is another mineral for which the needs are prone to fluctuations. By far the easiest solution to this problem is putting a salt block in reach of the horse. Normally a horse only licks from these blocks when he's in need of salt. When the horse bites into the block, taking larger peaces, the block should be removed immediately.
Potassium usually is abundantly present in most horse diets. Sodium on the other handrarely is. Salt shortage can cause loss of appetite, a rough looking coat, decrease in milk production and fertitlity.

Magnesium

Magnesium is an important factor in proficient brain and muscle functioning. Magnesium shortages can cause stress. Under normal circumstances magnesium shortages in horses are rare, but in sporthorses, an addition of Mg in the diet can be a good idea. The digestibility of magnesium decreases with the fat ratio in the diet. 

Lucerne hay, cereals and ceral byproducts are great sources of MG.

Trace elements

Selenium has a protective effect on cells and decreases the need for vitamin E. In case of over production of lactic acid or unsaturated fatty acids, the need for selenium increases, but also with increased work load. Selenium overload is just as harmful as a shortage and can result in symptoms such as hair loss, lameness, bad hoofs... 

Iron plays an important role in oxygen transport and is an important component of enzyms. Iron shortages are common in combination with blood worms. It's a common mineral in horse feeds, but usually in a form that's not so easily digestible. When horses are outed on acid meadows, they ingest a manganese (Mn) surplus. This causes iron (Fe) to be less likely to be digested, a phenomenon known as antagonism. 
Copper is an element enzyms need to produce elastin, collagen and hemoglobine. In case of copper shortage anaemia can occur. 

Intestinal bacteria need cobalt to synthesize vitamin B12.
Manganese is important in bone development and growth. For optimal fertility Mn is vital. Mn shortage doens't occur very commonly. Surplus on the other hand is rather common and can cause Fe- shortage. 
Zinc has a certain importance for a healthy coat and hoofs. It improves lactic acid discharge and reduces fatigue. 

Iodine is a component of the thyriod gland. Iodine deficiency can cause moult problems and swollen legs.

Daily needs
Horses w.500 kg	Maintenance	Work	Pregnant	Lactating	Growth	Stud
Calcium (g)	30	40	35	63	75	30
Phosphor (g)	20	30	25	40	45	20
Sodium (g)	8	25*	10	10	8	8
Potassium (g)	30	40*	30	35	25	30
Chlorine (g)	30	40*	30	35	25	30
Magnesium (g)	6.5	10	8	10	10	8
Copper (mg)	160	200	250	300	250	200
Iron (mg)	200	300	300	350	300	250
Zinc (mg)	500	600	750	950	750	600
Selenium (mg)	1	1.5	1	1	1	1
Iodine (mg)	1	1	1	1	1	1
Manganese (mg)	500	600	750	900	750	600
Cobalt (mg)	0.5	0.5	0.5	0.5	0.5	-
Salt (NaCl)	30	100*	30	40	25	30

Vitamins

Vitamins are small organic connections needed in small quantities for a well functioning metabolism. When horses suffer from vitamin shortages, this shows in slower reactions, blockages, and other vague symptoms.
Sport horses have higher needs in vitamins. Because of the sweating and stress they encounter, they drink more water, and lose more vitamins through sweat and urine.

Vitamins can be divided into two major groups, fat soluble and water soluble vitamins.

Fat soluble vitamins

Fat soluble vitamins are highly dependant on digestibility of the feed, when it comes to absorption. Fat soluble vitamins can be stored in the horses body, when a surplus is fed. When too much of a reserve is built up, however, vitamin poisoning is a real risk. Symptoms are much the same as that of a vitamin shortage. 


Vitamin A has an influence on growth, appetite, skin, respiration and cornea. It reduces tendon problems, bone deformations, nyctalopia and infections. Shortage in vitamin A can lead to fertility problems. A horses metabolism can turn carotene, present in fresh feeds, corn and carrots, into vitamin A. Carotene levels drop drastically when turning the feeds into hay or silage. In addition, breeding mares need bètacarotene for healthy oestrus cycles. 


Vitamin D3 stimulates absorption of Ca and P, thus preventing bone problems such as swollen joints, growth problems and leg flaws. Over dosage of it can lead to deposition of calcium in parts of the body, such as hart , liver en blood vessels. This might result in calcified vessels. Most horses never encounter vitamin D3 deficiency, as it is taken in from the sun, subcutanely. In winter, it is ingested through the sundried hay.

Vitamin E protects cell membrane, prevents muscle problems and enhances oxygen intake in the blood. This enables a better recuperation after heavy training. The need for vitamin E increases when the diet contains more unsaturated fats and when the horses workload increases; Grass and cereals usually contain high levels of vitamin E, levels drop drammatically in hay, older than a year, and oats that haven't been crushed recently. Low levels of vitamin E can cause lower performances and fertility.

Water soluble vitamins

Water soluble vitamins can't be stocked in the horses body. The surplus leaves the body via the urine; Vitamins B are synthesized through micro-organisms in the colon; but normal quantities are insufficient for sport horses. Extra vitamin B is a necessity in in sport horse feeds. Also for youngers horses and foals, additional vitamin B is vital, as the intestinal system isn't equiped for extracting the vitamins out of the feed.

Vitamin B1 or thiamine is essential in digesting carbohydrates and stops lactic acid production. It's used as a sedatif, in large quantities and is said to have benificial effects against roaring. 


Vitamin B2 or Riboflavine has a vital role in utilising nutrients in the feed, the nervous system and the metabolism, mainly concerning lipids and protein. It also activates the elimination of lactic acid. Shortage in Vitamin B2 rarely occurs.

Vitamin B3 or pantothenic acid plays a role in protein, lipid and carbs metabolism. It's essential for the growth of a dreat deal of micro organisms so, also for a healthy intestinal flora.

Vitamin B6 or pyridoxin has a role in the creation of blood blood celles and in some reactions with amino acids.

Vitamin B12 or cyanocobalamin is commonly administered in big quantities in order to improve oxygen transport in the blood, thus increasing the horses stamina.

Vitamin B15 or pangamic acid isn't well known in Europe. It's used frequently by the US equestrian team, following recommandations of Dr Robert Atkins. It also enhances oxygen transport in the blood and it's intake in muscles. Better physical condition and stamina are a possible result.

Vitamine M or folium acid is essential for the production of red blood cells. Other minerals and vitamins can contribute to this as well, but have no effect in case of folium acid shortage.

Vitamine PP or nicotine acid is important for the respiration of tissues.

Choline protects the liver and stimulates digestion.

Vitamin H or biotin is necessary for a shiny coat. High dosage, for a longer period (15mg/ day, for a couple of months) has positive effects on the quality of the hoofs (in combination with methionin, Vit. A, Vit. D3 and calcium) . Some plant materials like lucerne and grass meal are rich in biotin. The biotin in cereals is difficult to digest for horses. In fact, it is a major component in the creation of keratin, the basic material hoofs are made of. Sufficient amounts of biotin in the diet improves strength and elasticity of the hoof, and stimulates the process of keratin production.

Vitamin C or ascorbic acid is necessary for horses under continous physical or mental stress. Het improves the natural defense mechanism and is said to have a role in fertility. The horses metabolism produces large amounts of vitamin C on its own.

Daily need
Horse w. 500 kg	Maintenance	Work	Pregnancy	Lactation	Growth	Stud
Vitamin A (IE)	40000	40000	70000	70000	60000	50000
Vitamin D3 (IE)	4000	6000	5000	6000	6000	5000
Vitamin E (mg)	50	1000	150	250	150	1000
Vitamin K (mg)	-	-	1	1	1	1
Vitamin B1 (mg)	-	36	24	12	12	36
Vitamin B2 (mg)	-	60	40	60	20	60
Vitamin B3 (mg)	-	72	48	72	24	72
Vitamin B6 (mg)	-	12	12	12	12	12
Vitamin B12 (mg)	-	0.12	0.12	0.12	0.12	0.2
Vitamin B15 (mg)	-	75	50	75	50	75
Folium acid (mg)	-	20	12	18	6	18
Vitamin PP (mg)	-	180	120	180	60	180
Cholin (mg)	250	900	600	900	300	900
Biotin (mg)	-	0.5	0.5	0.5	0.5	0.5
Vitamin C (mg)	-	100	-	-	-	100

Fat soluble vitamins Water soluble vitamins

Water

Water is a very important in a horses diet. A horses body is made out of 70% of water, and moisture is excreted all the time. Through urine, sweating, manure, milk production... and logically it needs to be replenished accordingly. Clear and fresh water is to be recommended. 

A common mistake is trying to fulfill a horses huge need for water after a heavy workload in one serving. The ingestion of big quantities of cold water can cause colic.

Table: drinking water needs for horses in kg water per day, per animal

Foals	10-15 kg
Horse, light work	30-40 kg
Sport horse, heavy work	60-80 kg
Lactating mare	40-60 kg
Need per kg of dry matter roughage	3,5 kg
Need per kg of dry matter concentrate	3 kg