Comparison of equine dietary iron requirements to iron concentrations of 5,837 hay samples
N. Richards and B.D. Nielsen, 2018
Introduction
Iron is essential for the production of red blood cells. According to the 2007 Horse NRC, Fe requirements are 50 ppm for growing foals, lactating and pregnant mares, and 40 ppm for all other classes of horses. The 2005 NRC suggested a maximum tolerable Fe concentration of 500 ppm using data from other species. It is claimed that excess dietary Fe is causative of horses becoming insulin resistant.
Athletic horses, and particularly those in Thoroughbred racing, are often supplemented with Fe in an attempt to improve performance. Supplementation is commonly carried out without any formal analysis of the diet to determine if additional iron is required. Forages are typically high in iron and supply a majority of iron in all equine diets.
This study looks at the iron concentration in forages typically fed to equines and whether iron from forage is enough to meet the iron requirement of an athletic horse.
Methods
Nutrient concentrations from hay samples submitted for analysis in 2017 and for which Fe was measured were obtained from Equi-Analytical representing 3,060 grass, 1,193 legume, and 1,584 mixed hay samples.
Iron concentration was measured using inductively-coupled plasma mass spectrometry (ICP). Analysis methodology is available from Dairy One. Statistical analysis was performed using Proc MEANS of SAS.
Results
Iron was highest in Legume and Mixed Mainly Legume Hays and lowest in Grass Hay (Table 1). All hay types had a mean iron concentration more than five times that required by athletic horses and a median iron concentration more than three times.
From all hay samples (n = 5,837), 707 contained Fe at or above the suggested tolerable threshold of 500 ppm, while only 81 contained Fe at less than 50 ppm. Further, only 15 contained Fe at less than 40 ppm.
Discussion
A 500 kg horse in heavy work has an iron requirement of 500 mg/day (NRC 2007; based on a daily feed intake of 2.5% bodyweight and a requirement of 40 ppm). Forage intake is often restricted by Thoroughbred trainers. But even when fed at 1% of bodyweight to a 500 kg horse, these hays will supply an average 1,060 mg to 2,230 mg of iron per day, supplying more than 200% of daily iron requirements in the forage component of the diet alone.
Fortified grain concentrates are fed at an average 2.5 kg/horse per day in Australian Thoroughbred racing stables (Richards 2003). These concentrates have an average iron concentration of 190 ppm (FeedXL.com), adding an additional 475 mg/day of iron to the diet of these horses. Almost 60% of Australian Thoroughbred trainers then add an iron supplement to their horses’ diets (Richards 2003). It is expected similar trends would be found in the USA.
Based on this broad diet analysis, forage is able to meet the daily iron requirement of athletic horses. When iron from fortified feeds and supplements is added, there would be few racehorses receiving less than 300% of their daily iron requirement. It’s not unexpected that many horses would be receiving in excess of 500% of their daily iron requirement
What About Insulin Resistance
Given the dearth of Thoroughbred racehorses that are insulin resistant, despite Fe supplementation in combination with diets that can easily supply amounts beyond requirements, it seems unlikely excess Fe causes insulin resistance. However, it is recognized insulin resistant horses may have elevated serum ferritin.
References
Council NR. Nutrient Requirements of Horses: Sixth Revised Edition. Washington, DC: The National Academies Press, 2007.
Richards N, Hinch G, Rowe J. The effect of current grain feeding practices on hindgut starch fermentation and acidosis in the Australian racing Thoroughbred. Aust Vet J 2006;84:402-407.
HUGE THANKS to Equi-Analytical for providing the data to write this paper, which was presented as a poster at the recent International Conference on Equine Exercise Physiology (ICEEP).
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Vitamin C, also known as ascorbic acid, is a water-soluble vitamin. It is an important antioxidant and broadly plays a vital role in immune function, collagen synthesis, and hormone production.
Do horses need it?
Did you know that vitamin C is not considered an essential nutrient in your horse’s diet? Unlike humans, who will get scurvy and die if they don’t eat enough of it, horses make their own vitamin C in their liver from glucose.
While healthy horses synthesise enough of it to meet their body’s own requirements, there are some situations whereby a horse’s own synthesis may not be sufficient to meet their normal needs or where an underlying cause requires more vitamin C. Such situations include aged horses, post-operative cases, horses that suffer from respiratory conditions, during periods of illness, high-performance horses (particularly those stabled for prolonged periods), and during times of stress (such as transport).
What about vitamin C supplements for horses?
Based on studies, a recommended supplemental dosage of vitamin C for horses is 10-20mg per kg of body weight (5,000-10,000mg for a 500kg/1100lb horse).
There are different forms of vitamin C available, and they all have similar absorption and efficacy. However, stabilised forms appear advantageous over straight ascorbic acid as they are less acidic and may be gentler on the digestive tract. To find a stabilised form, look for coated ascorbic acid, ascorbyl palmitate, or those composed of phosphate esters of ascorbic acid (also called “buffered” ascorbic acid). These buffered forms include sodium ascorbate, calcium ascorbate, or magnesium ascorbate.
Keep in mind that if you’ve been supplementing with vitamin C for more than 10 days, don’t stop abruptly. Instead, taper off slowly over 7 days to allow your horse’s body to upregulate its own production again.
For FeedXL Premium Plan members, you can track how much supplementary vitamin C is in your horse’s diet via the Additional Nutrients tab in the Review Results step.
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We are frequently asked about how to add Vitamin E to a horse’s diet when all other nutrient requirements are being met. Vitamin E is abundant in fresh green forages and many horses will meet their daily requirement of Vitamin E with adequate intake of good quality pasture. Vitamin E declines over time in stored feeds including preserved forages. Most commercial pre-mix feeds and vitamin & mineral supplements account for this and are formulated with supplementary Vitamin E.
At times when pasture is average or poor quality, overgrazed or simply not available, diets which previously had adequate Vitamin E may become low as a result. Sometimes even with a good quality pre-mix feed or vitamin and mineral supplement, the Vitamin E levels may still not be adequate within the diet.
How FeedXL Can Help
Additional vitamin E can be safely added to diets and can be found in FeedXL’s blue ‘Balancers & Supplements’ tab under ‘Antioxidants’. Antioxidant supplements commonly contain both selenium and vitamin E. Unless the diet requires additional selenium, look for supplements which contribute only vitamin E to your horse’s diet.
To find vitamin E-only supplements, click on ‘Complete Data’ which is located below the ingredient name when editing diets or browsing ingredients and FeedXL will show you which nutrients that product contains. (See the image in this post).
Another consideration when choosing a suitable Vitamin E supplement is the form of Vitamin E to supplement with. Natural vitamin E is reported to be more effective in raising plasma Vitamin E concentrations when compared with a synthetic source. To know which is which you will need to read the manufacturer supplied information for each product on their website or product labels.
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This little vitamin, B6, is not talked about much in equine nutrition, mainly because we still don’t know exactly what a horse’s dietary requirement is. We also assume a large part of their requirement is fulfilled by the Vitamin B6 produced by the bacteria in their hindgut.
We do know B6 is important for building muscle. A published paper has looked at Vitamin B6 supplementation and muscle development in rabbits. (https://www.publish.csiro.au/AN/AN15807…)
Even though a rabbit is a very different animal to a horse, from a gut physiology and nutrition perspective they are actually really similar, so it is worth a look to see what the researchers found.
Vitamin B6 supplementation was shown to significantly alter protein metabolism and increase the ratio of fore + hindleg muscle weight to body weight (i.e. supplemented rabbits had more leg muscle). Interesting!
How FeedXL Can Help
We do track a horse’s vitamin B6 intake in our Premium FeedXL plans … this just reinforces how important a horse’s base diet is when it comes to achieving specific outcomes. For example, if you are wanting your horse to build muscle but you aren’t meeting basic nutrient requirements (like vitamin B6) you could add all the fancy muscle building supplements you like to the diet and they won’t help!
You can’t build muscle unless you get your basics right first! Here at FeedXL, we can help you with that! Take a look at our plans and pricing here.
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4 things to consider when feeding chickpeas to horses
Chickpeas do contain anti-nutritional factors including trypsin inhibitor, which is the same as the main anti-nutritional factor found in soybeans. Trypsin inhibitor does exactly as its name suggests, it inhibits/stops trypsin, an enzyme in the small intestine which chops up protein into smaller pieces so it can be absorbed. Too much trypsin inhibitor in the gut can reduce protein digestion to such an extent that protein deficiency will become apparent. This doesn’t sound good for chickpeas!
BUT, on reading about the amount of trypsin inhibitor in chickpeas it is much, much lower than soybean. In the published literature there are values of 15 TUI (Trypsin Units Inhibited – reflects quantity of trypsin that has its activity inhibited) for chickpeas while values for soybean are more like 80 TUI. Reading papers and interpreting units is challenging as it seems everyone likes to express their TUI units in slightly different ways so just be careful with this!
Chickpeas have been fed raw to pigs at levels of up to 88% without affecting measured parameters to determine growth and feed conversion. A pretty good indication the anti-nutritional factors aren’t too anti-nutritional as growing pigs will show us very quickly if something is not right. This study did however find that adding additional methionine improved growth performance in chickpeas.
Chickpeas are routinely used uncooked in pig diets in Australia at levels up to 20% of the diet without any ill effect. They typically aren’t fed to younger pigs less than 20 kg bodyweight.
Updates in FeedXL…
Based on all of this we have now updated our information in FeedXL to read:
Chickpeas are classified as a pulse, which is a seed from a leguminous plant. Chickpeas are rarely included in horse diets but can be fed as a protein and energy supplement in much the same way lupins or faba beans are used. The protein is of moderate to good quality with good concentrations of the essential amino acid lysine. They may however be too low in methionine for some classes of horses.
Like most pulses, chickpeas appear to contain some anti-nutritional factors including a trypsin inhibitor, which blocks the activity of the protein digesting trypsin enzyme in the gut and can negatively affect protein digestion. The anti-trypsin activity of chickpeas is however much lower than that of soybean, with chickpeas expected to ‘block’ around 15% of trypsin enzyme activity in the gut compared to more than 80% of trypsin activity being blocked when raw soybean is fed.
Chickpeas should therefore be safe to feed without any form of heat treatment to mature horses at levels of no more than 20% of their ‘hard feed’. If larger amounts were to be fed, heat treatment is recommended. Chickpeas would be best heat treated prior to feeding if being fed to horses younger than 12 months of age.
As always our information is quite conservative, but we prefer to play it safe with so many people using our service with so many varied scenarios.
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A lot of you use them, and while there is theoretical justification for their use there is still very little science that actual shows a proven benefit in feeding them.
A study just published does however lend some nice information in this area. It is both blinded (i.e. the people feeding the horses, the people assessing the horses for various measures of movement and levels of comfort don’t know if the horses were on the joint treatment or not at the time of assessment so it couldn’t influence what they ‘saw’ and recorded. And the author who analyzed the data was blind to which horse was on what treatment so they too could not be influenced) and is also a crossover study where each horse in the study was on both the joint treatment and the placebo and assessed on both so you could see changes in the same horse as opposed to changes between two different groups of horses where one group is treated and one group given a placebo.
This study also used ‘objective’ measurements of gait using high speed motion capture to assess movement of the hind legs at the trot.
The results are interesting, with significant improvements in lameness scores (less lameness in treated horses), less response to flexion tests and improvements in muscle tone reported (plus many other results).
A good time to remember too that not all joint supplements are created equally as far as the ingredients and amount of ingredient per dose they contain. The supplement used in this study was ‘FlexAbility’, from Science Supplements, UK; it contains chondroitin sulfate 162 g/kg, glucosamine 190 g/kg, vitamin C 80 g/kg, methyl sulfonyl methane 256 g/kg, docosahexaenoic acid 66 g/kg, eicosapentaenoic acid 34 g/kg For those of you who use FeedXL, if you look in the ‘Health’ tab in your results you will see a breakdown there of the various joint nutrients and how much of each are in your horse’s diet when you use a joint supplement.
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Hard working horses have enormous requirements for energy that are traditionally filled using high grain rations fed together with chaff and hay. However, feeding large amounts of grain does come with its own set of issues which can include colic, hindgut acidosis, nervous or fiery behaviour, tying up and loss of appetite. Oil has gained popularity in recent years as a substitute source of energy for working horses, but is it effective? How much can be fed? Are all oils equal in the benefits they can provide? And do they cause any health issues of their own?
A little bit goes a long way
The biggest benefit oils provide working horses is their very high energy content relative to grains. Oils contain nearly 3 times more energy than oats, with 400 mls of vegetable oil providing as much energy as 1 kg of oats. The real benefit in this is you can reduce the size and sheer bulk of feed a horse has to consume without reducing calorie intake, allowing you to get enough ‘feed’ into horses with poor appetites. The end result being these horses can hold their weight and continue to train and compete for longer than they otherwise would on a more traditional diet.
Reducing heat load
Oils generate less heat during the digestive and metabolic processes than an equivalent amount of grain or forage. Feeding oil also means that you can feed less grain and still meet energy requirements. Combined, this means that high oil diets place less of a heat load on working horses, reducing electrolyte losses and the amount they need to sweat to stay cool, a big bonus for hard working horses, especially those training and racing in hot environments or working over very long distances.
Saving glycogen
Fatty acids from oils are the preferred fuel for muscles during slow and medium pace work while glycogen is the only source of energy a muscle can use during sprints and strenuous exercise. Once a horse runs out of glycogen its muscles fatigue and the horse will slow down and lose the ability to perform at the level it is capable of. Feeding oil in diets provides a source of fatty acids for muscles to burn during the warm up and slower phases of a competition, meaning muscles are able to conserve valuable glycogen and avoid fatigue.
Problem solving
‘Problem horses’ and particularly those that tie up or get excited and nervous on high grain diets will often benefit from rations that provide a portion of the dietary energy from oils. It is thought that the positive effects seen in these horses on high oil diets is due more to the reduction in grain intake as opposed to the addition of oil, but using oil in the diet allows you to reduce grain intake without compromising energy intake and performance.
Oils aint oils
All oils contain virtually the same amount of digestible energy, but there are other differences you may want to consider when looking to purchase an oil, including:
Essential Fatty Acid Content: Horses need omega 3 and omega 6 fatty acids in their diet. Grains are naturally high in Omega 6, so for horses on a high grain diet, it is preferable to choose an oil with some omega 3 content. The table below shows the amount of omega 3 and omega 6 in some commonly used oils. Linseed and canola oil contains the highest omega 3 fatty acid content of the natural vegetable oils.
Ingredient Name
Omega 3 (%)
Omega 6 (%)
Linseed (Flax) Oil
57
13.9
Cod Liver Oil
25
2
Canola Oil
10
20
Soybean Oil
7
52
Corn Oil
1
55
Olive Oil
1
11
Rice Bran Oil
1
39
Sunflower Oil
0.3
60
Coconut Oil
0.1
2
Palatability: Some linseed oils and fish oil including cod liver oil are notoriously unpalatable for horses, so while these oils are useful for providing omega 3 fatty acids, they can’t be fed in large amounts as most horses simply won’t eat them.
Processing Method: Oil is extracted from oilseeds in two main ways; cold pressing where oil is squeezed out of seeds, often in a water-cooled environment to keep the oil at less than 60C; and solvent extraction where a solvent like hexane is added to extract oil from seeds. The oil is then heated to remove the hexane. Cold pressed oils tend to be higher in quality as more of their essential fatty acids and natural antioxidants are left intact in comparison to solvent extracted oils.
It takes time
Horses need time to adapt to digesting and metabolising oils. Oils should always be introduced into a diet slowly, starting with ¼ cup of oil per day and increasing this by ¼ cup every 5 days until you reach the full amount you want to feed. Introducing oil into a diet too quickly can result in soft manure and reduced fibre fermentation in the hindgut.
It will take a minimum of 3 weeks before a horse starts to really benefit from the oil in its diet and it could take up to 3 months before the full benefits of oil are realised.
How much can you feed?
Horses can be fed up to 20% of their total energy intake as oil, which in real terms means just over 3 cups of oil per day for a 500 kg horse in full work. While this level of oil is useful for horses that tie up, very few horses are fed this much oil per day. Feeding between 1 and 2 cups of oil per day is enough to give horses the benefits discussed above without making diets messy, unpalatable or unnecessarily expensive.
Good Stuff
Oils are ‘good stuff’ for working horses. They reduce reliance on grains, make the amount of feed a horse needs to eat smaller, keep horses cooler, allow horses to conserve muscle fuel for sprinting, give horses that tie up a safer and more effective source of energy and provide essential fatty acids in the diet.
For the best results, introduce oils slowly into the diet and select oils based on the following: their omega fatty acid content with oils containing some omega 3 fatty acids preferred; palatability, be aware that some oils including linseed and fish oils can be unpalatable; and method of processing, with cold pressed oils preferred over solvent extracted oils.
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As a horse exercises its muscles generate heat. To prevent its body from dangerously overheating, the horse sweats to allow evaporative cooling to dissipate the heat being produced. As a horse sweats, water and electrolytes, including sodium, chloride, potassium, magnesium and calcium are lost from the body.
For effective sweating to occur, the horse must be well hydrated and have an ample supply of electrolytes in its body. The electrolytes and water lost through sweating must be replaced following exercise to prevent electrolyte depletion and dehydration.
In this blog post we will look at what electrolytes are and why they are important, how much ‘electrolyte’ a horse needs, where horses get electrolytes from in the diet and when to use an electrolyte supplement.
What are electrolytes?
Very simply, electrolytes are minerals, which, when present in a watery solution like body fluids, become positively or negatively charged particles that have the ability to conduct electricity. Electrolytes maintain fluid balance and circulatory function, facilitate muscle contractions, trigger nerve functions and maintain the body’s acid-base balance. The most important electrolyte minerals are sodium, chloride, potassium, magnesium and calcium.
What happens if a horse becomes electrolyte deficient?
Electrolyte deficiencies are associated with fatigue, muscle weakness, lethargy and reduced feed and water intakes, resulting in weight loss and dehydration. In addition, electrolyte deficient horses may experience reduced sweating, which can result in hyperthermia (over-heating) and compromised performance. Studies in England have also linked electrolyte deficiencies to the incidence of recurring bouts of tying-up (Harris et al. 1992).
Please Note: severe electrolyte deficiency can result in complete exhaustion, colic, synchronous diaphragmatic flutter (commonly known as the ‘thumps’), collapse and death if not treated. Severe electrolyte deficiencies are a veterinary emergency requiring IV fluids, electrolytes and specialist care so please call your vet immediately if you suspect your horse is acutely dehydrated and electrolyte deficient.
How much ‘electrolyte’ does a horse need?
All horses have a small daily requirement for electrolytes to replace the obligatory losses from the body in the urine and faeces. This requirement is termed a horse’s ‘maintenance requirement’ and is reflected in FeedXL’s recommended daily intakes for horses not in work.
Sweating increases a horse’s requirement for electrolytes above their maintenance requirement, as large quantities of sodium, potassium and chloride and smaller quantities of magnesium and calcium are excreted in sweat (amounts are given in the table below):
Electrolyte
Sodium
Potassium
Chloride
Magnesium
Calcium
Quantity in sweat* (grams/L)
3.1
1.6
5.5
0.05
0.12
The amount a horse sweats, and therefore its electrolyte requirement, will be determined by the amount of work it is doing, the intensity of work it is performing and the climatic conditions in which the horse lives and works. Individual horses also vary considerably in their tendency to sweat. As an indication, in a moderate climate, a racing thoroughbred will lose between 5 and 10 litres of sweat during a daily workout and an endurance horse will excrete between 5 and 10 litres of sweat per hour when travelling between 12 and 18 km/hour. Sweat losses of up to 15 litres/hour can occur during high intensity exercise where horses are travelling at between 30 – 35 km/hour.
FeedXL calculates your horse’s electrolyte requirements for you based on a sweat loss of 1.6 L per day for horses in light work, 4.4 L per day for horses in moderate work, 6.7 L per day for horses in moderately heavy work and 8.9 L per day for horses in heavy work.
How does climate affect requirements?
Hot and particularly hot and humid climates increase a horse’s need for electrolytes as horses will sweat more under these conditions. As a general guide, if the temperature is 30C (86F) supply 140% of your horse’s recommended daily intake (RDI) calculated by FeedXL for sodium, potassium and chloride . If the temperature is 35C (95F), supply 170% of your horse’s calculated requirement for these minerals and if the temperature is 40C (104F) or over you should supply 200% of their requirements. Also be sure to have a salt lick available at all times.
Where do electrolytes come from?
Pastures and forages are almost always a rich source of potassium and are commonly a good source of magnesium. However they tend to contain variable and often unknown concentrations of chloride and typically low concentrations of sodium. Common table salt contains 39% sodium and 61% chloride and is frequently used as a readily available, palatable and cheap source of these electrolytes in a horse’s diet. Potassium chloride (50% potassium, 47% chloride) can be used to supply additional potassium and chloride where required and magnesium oxide is a readily available and cost effective source of magnesium where additional magnesium is needed. Grains contain only very small amounts of all the electrolyte minerals and it is high grain diets that are most commonly ‘electrolyte deficient’.
When should you feed an electrolyte supplement?
In many situations horses can get enough electrolyte minerals from a forage based diet that has plain table salt added for additional sodium and chloride. Some horses on high grain/low forage diets may benefit from an electrolyte supplement that contains potassium or need potassium chloride added to their feeds. On a day to day basis though, most horses won’t need a commercial electrolyte supplement.
Commercial electrolyte supplements are however very handy in situations where your horse is away from home, not grazing or eating as much hay as he normally would and/or working a lot harder or longer and sweating more than usual. Well formulated supplements (ones that contain the same proportion of electrolytes as those found in equine sweat) can be used in these situations to quickly replace electrolytes lost in sweat. Where prolonged exercise occurs (for example endurance riding or long days of stockwork or trail riding) it may be necessary to provide some electrolytes during the period of exercise.
Well formulated electrolyte supplements will provide enough electrolyte minerals in a 60 gram dose to replace the salts lost in 5 litres of sweat. There is debate over how much electrolyte replacer you should give to working horses with no firm recommendations available given it does depend so much on the climate, intensity of work and the horse as an individual. If a horse is sweating consistently over a long period of time AND will have access to water frequently you can give 60 grams of electrolyte every hour to two hours. If water is not available on a frequent basis give 60 grams of electrolyte when you know the horse will have access to water and can have a good drink. Don’t give more than 60 grams per dose as you may overload the horses ability to absorb the salts you give.
Well formulated electrolyte supplements will contain 20 – 25% sodium, 43 – 48% chloride, 10 – 12% potassium and smaller amounts of magnesium and calcium (normally 1 to 2%). These higher quality products will also have less than 20% glucose or other base or filler.
Some practical tips for using electrolyte supplements
Always make sure your horse has access to water after being given electrolytes as they will get thirsty and need to be able to drink. Failure to provide water will result in dehydration because the salts will pull water out of the body and into the gut.
If it is possible, wait for your horse to have a drink of water before giving it electrolytes.
Never give electrolytes to an already dehydrated horse that isn’t drinking as you will worsen the dehydration. Call your vet in these situations.
Don’t add electrolyte supplements to a fussy horse’s feed as chances are it won’t eat them. Instead mix the electrolyte with apple sauce and give it over the tongue (beware they will spit it all over you!).
During endurance rides where feed intake is also important, allow your horse to eat before giving him electrolytes as a paste as it will often stop a horse from eating for a little while which may affect your gut noise scores.
Always have a salt lick available to allow your horse access to extra sodium and chloride at any time.
If you want to use an electrolyte to help make your horse drink when away from home try it out at home to see if it works – if you dose your horse with electrolytes and he doesn’t drink he will actually end up more dehydrated than when you started.
To increase water intake, offer slightly salty water to your horse as its first drink after exercise. Research has shown (Schott et al 2003) that horses who drink slightly salty water (0.9% salt, 90 grams of salt per 10 litres of water) initially will drink more water and rehydrate themselves faster after exercise than horse who drink plain water as their first drink. You will likely need to train your horses to drink the salty water, a touch of molasses might help.
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Several different forms of carbohydrates form what we call ‘fibre’. These carbohydrates include cellulose, hemicelluloses and lignin. Fibre cannot be digested in a horse’s small intestine. Instead, the horse relies on the billions of bacteria that live in the hindgut to digest the fibre by fermentation. Fibre, which is also called ‘structural carbohydrate’, is essentially provided by the pasture, hay, chaff, haylage and high fibre feeds like sugarbeet and legume hulls in your horse’s diet. Fibre is the single most important component of a horse’s diet (after water) as without it, their digestive tract can’t function as it should. So why is it so important and what will happen if your horse doesn’t get enough?
Why do horses need fibre?
Fibre plays 3 very important roles in the diet of horses. These are:
Fibre provides a source of energy/calories for horses. While the horse itself cannot ‘digest’ the carbohydrates that form fibre (because like humans they don’t have the necessary digestive enzymes to break it down in the small intestine), the horse houses billions of bacteria in its hindgut that do the job of digesting fibre for it. So, the horse provides the bacteria somewhere safe and warm to live and in return the bacteria pass on to the horse most of the energy contained in the fibre.
As well as providing the horse with energy, important vitamins like vitamin B1, biotin and vitamin K are produced during the bacterial fermentation of fibre in the hindgut.
Fibre provides the horse with ‘gut fill’. The horse’s gastrointestinal tract is an ENORMOUS organ and it needs to be kept full. The fibre in a horse’s diet is what provides the bulk to keep the gut full and healthy.
Fibre soaks up and holds water in the gut to act as a water reserve when horses need it.
What happens if a horse doesn’t get enough fibre?
Diets that don’t provide a horse with enough fibre can cause major problems including:
Colic – if a horse’s gastrointestinal tract is not kept full it is prone to twisting about and moving in ways that it can’t normally when it is full of fibre. Unfortunately for the horse this can lead to serious colic that can only be resolved (if the horse is lucky) by surgery.
Diarrhoea – low fibre diets very often result in loose sloppy manure, which in-turn affects the whole dynamic of how the gut works. Horses with diarrhoea digest what fibre they do get less efficiently and they are prone to problems with dehydration and electrolyte deficiency.
Dehydration – horses on a low fibre diet don’t have a readily available water reserve in their gut, meaning if they sweat heavily or spend an extended period of time away from water they are more prone to dehydration than a horse on a high fibre diet. Problems with diarrhoea as discussed above make this issue worse.
Energy deficiency – horses that aren’t being fed enough fibre are also most likely not being fed enough energy (calories) so they may be losing weight or having difficulty gaining weight. The energy value of fibre is often underestimated, with forages like oaten hay or chaff often being viewed simply as a ‘filler’ when in fact they are a valuable source of energy for horses.
Vitamin Deficiency – the bacteria that ferment fibre in the hindgut also produce several vitamins including vitamin B1, biotin and vitamin K for horses. If horses aren’t fed enough fibre the bacteria are unable to produce the amount of vitamins they normally would and a deficiency may result leading to problems like loss of appetite and poor quality hoof growth.
Boredom – horses on low fibre diets will often have a lot of spare time to fill in during the day that ordinarily they would be spending eating. This boredom will often lead to problems like cribbing, weaving and chewing on strange objects or eating dirt.
Gastric ulcers – the horse’s stomach is constantly releasing gastric acid and the horse relies on eating fibrous feeds to help prevent gastric ulcers. Chewing high fibre feeds like pasture or hay generates a lot of saliva which acts to buffer the gastric acid. Fibre also provides a raft in the stomach that helps to stop acid from the lower portions of the stomach from splashing up and damaging the unprotected upper portions of the stomach. Low fibre diets can’t provide this protection for horses.
Constant hunger – because fibre is the part of the diet that provides the ‘gut fill’ a diet low in fibre will leave a horse always feeling hungry, which then causes its own set of problems including behavioural issues and even sand colic (see below).
Sand colic – when horses are fed low fibre diets it increases the chance that sand and dirt will accumulate in their hindgut and cause colic or diarrhoea. Feeding large amounts of forage is one of the most effective ways to remove sand and dirt from the hindgut. The increased risk of sand colic in horses on low fibre diets is also partly also related to the fact that horses on low fibre diets are often hungry and if housed on dirt or sand will be going around vacuuming everything off the ground, and picking up large amounts of dirt and sand in the process.
What types of feed are high in fibre?
As you can see fibre is absolutely essential in a horse’s diet. Feeds that contain a lot of fibre include:
All types of hay and chaff
Most pastures (very lush green pastures are quite low in fibre)
Haylage
Sugarbeet pulp
Legume hulls including soybean and lupin hulls
Copra meal
Seed hulls including oat and sunflower seed hulls
How much fibre does a horse need per day?
Recent recommendations are that horses should be fed a minimum of 1.5% of their bodyweight per day in forage (pasture, hay, chaff, haylage; Harris et al. 2017). This is equivalent to 1.5 kg/100 kg bodyweight or 1.5 lb per 100 lb bodyweight (which equals 7.5 kg/day for a 500 kg horse; 16.5 lb/day for an 1100 lb horse). Essentially though the more fibre you can feed in your horse’s diet the better. Use FeedXL to see if you can meet your horse’s energy requirements with high fibre feeds alone (focussing mainly on pasture and hay) and then just top up whatever vitamins and minerals are missing using a vitamin and mineral supplement.
It isn’t always possible to feed like this however and horses that are working hard need higher energy feeds like oils and cereal grains in their diet. Even for these horses it is still critically important that they are fed 1% of their bodyweight in high fibre forage.
Any of the feeds listed above can be used to provide ‘fibre’ in a horse’s diet. A second good rule of thumb to follow is to provide at least half of the fibre in your horse’s diet as long stem fibre in the form of hay or pasture. The long stem fibre takes the horse longer to eat (so keeps them happier) and also makes them chew more, which encourages more saliva production, which is important for gut health too. These long stem fibres also contain what is known as effective fibre, which is fibre that remains undigested as it passes through the gut. Effective fibre is important for allowing the horse to produce manure and shift unwanted material like sand out of the hindgut.
What other nutrients do forages provide?
High fibre forages (like pasture, hay, chaff and haylage) are a valuable source of protein. In fact for many horses these forage are more than capable of meeting 100% of their energy and protein requirements – FeedXL will show you if this is the case for your horse. Forages are particularly rich in the electrolyte mineral potassium (and sometimes contain too much of this minerals, read our FeedXL Newsletter ‘Is Pasture Affecting your Horse’s Behaviour’) and also contain good amounts of calcium, phosphorus and magnesium and varying amounts of other trace minerals (we recommend having your forages tested so you know exactly what your forage is providing your horse, then you can use FeedXL to just add what is needed). Fresh green forages are also particularly rich in vitamin A, E and K and the B-group vitamins and they are an excellent source of omega 3 fatty acids.
The final straw
Horses evolved eating a high fibre diet and fibre is still the single most important component in your horse’s diet aside from water. If your horse isn’t getting enough fibre it can be facing serious consequences including colic, dehydration, diarrhoea, ulcers, vitamin deficiency, weight loss and behavioural problems. So be sure to feed enough, it will keep your horses much healthier and far more content.
Do you have a question or comment? Do you need help with feeding?
We would love to welcome you to our FeedXL Horse Nutrition Facebook Group. Ask questions and have them answered by PhD and Masters qualified equine nutritionists and spend time with like-minded horse owners. It’s free!
Protein is a very important component of all horse diets and as discussed in our post ‘Understanding Protein Quality’, the quality of protein used in diets will largely determine how well that diet can support functions that rely on protein including growth, reproduction, athletic performance and muscle building.
But can we get carried away with protein in a horse’s diet? Can too much protein be fed? And are the very high protein pastures that are so common nowadays a problem for horses? The answer to those questions is ‘yes and no’, it all depends on the circumstances your horse find itself in. Let’s look in more detail at when high protein diets may be a problem.
Protein is expensive!
When protein is fed in excess of protein requirements the horse will simply chop the protein up, remove the nitrogen and use what is left as a source of energy, so it isn’t completely wasted. BUT feeding protein as a source of energy is sort of like using notes of money instead of old newspaper to get a fire started. It will do the job, but it is an expensive way to do it. So when formulating a diet, use FeedXL to keep protein intake as close to requirements as is practically possible.
Wet and smelly bedding
Horses on high protein diets will, as discussed above just chop the protein up and burn it essentially like a carbohydrate. But they then need to get rid of the nitrogen they didn’t need from the protein. To do this, nitrogen is turned into urea and excreted in the urine. Getting rid of waste nitrogen requires a lot of water so horses on high protein diets tend to drink AND urinate a lot. Now, this isn’t a problem if your horse has ready access to water and lives outside. But for horses in stables, feeding too much protein is going to mean a whole lot of extra wet bedding for you to muck out every day, which is time consuming and can be expensive depending on what you pay for bedding.
Perhaps a bigger issue for stabled horses on high protein diets is the strong smell of ammonia that develops as the excreted urea is converted to ammonia in the bedding. Ammonia can irritate airways and cause respiratory issues, especially in poorly ventilated stable areas, so meeting but not unnecessarily exceeding protein intakes is particularly important for horses confined to stables for long periods of time.
Heat production
The digestion and metabolism of protein generates more heat than the digestion and metabolism of fat and carbohydrate. So a horse on a high protein diet that is burning a lot of protein as a source of energy will need to get rid of more body heat and in doing this will sweat more. This increased rate of sweating, together with the extra urine production needed to remove the waste urea from the horse’s body combine to increase a horse’s water requirement.
If the horse in question is only in light work, has free access to water and doesn’t live in a hot climate, the high protein diet really won’t pose an issue. However, if a horse is in moderate to heavy work, and particularly if that work is endurance type work or the horse lives in a hot climate the excess heat production from the high protein diet could lead to problems with dehydration and heat stress. Connysson et al (2006) observed that protein intakes of 160% of requirements did disrupt fluid balance (by increasing water loss through sweating and urination) so keeping working horse protein intakes below this level may assist with maintaining good levels of hydration. These researchers observe no negative impact of this level of protein on performance in the horses studied.
Hyperactivity
Protein is sometimes blamed for making horses ‘hot’ and some horse owners will actively select low protein feeds in an effort to keep their horses calm. This however is mostly a wives tale. Diets that are higher in energy than a horse’s true energy needs can and often will make a horse hyperactive. If you are feeding a very high protein diet, chances are this diet is also going to be a high energy diet … AND all the horse is going to do with the extra protein it is being fed is cut it up and burn it for energy. So it isn’t the protein, as such, causing problems with behaviour, but instead the amount of energy in the diet.
What about the liver and kidneys?
High protein diets have also long been blamed for damaging liver and kidney function. There is no evidence (that I can find) to suggest that healthy horses with a fully functioning liver and kidneys suffer any kind of harm to these organs on a high protein diet. However if a horse has a pre-existing problem with either its liver or kidneys a low protein diet that meets but does not exceed protein requirements is recommended.
Managing protein intakes on high protein pastures
Most of the time when protein intake is indicated as being excessive in FeedXL it will be due to a very high protein pasture playing a prominent role in the diet. This may not be a problem if your horse is healthy, living in a temperate or cool environment, living outdoors and in light work, breeding, growing or not doing anything at all. However, if your horse is stabled for periods of time, living in a hot climate or is in moderate to heavy work it would be advisable to try and reduce protein intakes by reducing pasture intake. This is often best done by keeping the horse off pasture for a period of time during the day or night and providing a lower protein grass hay. The use of lucerne/alfalfa hay should also be minimised or stopped altogether when horses are grazing high protein pastures.
Use high quality protein
When feeding protein a major consideration is whether that protein is meeting your horse’s requirement for essential amino acids. Using the best quality protein you have available will allow you to meet lysine (and other essential amino acid) requirements without having to feed excessive amounts of crude protein. Using low quality protein will mean you have to feed more crude protein to meet essential amino acid requirements and the higher level of crude protein may interfere with your horse’s hydration, heat load and air quality as discussed above.
Take Home Message
If your horse:
lives in a hot climate
is stabled all or part of the time
is in moderate to heavy work; and/or
has a pre-existing liver or kidney disease
You should keep protein intakes within the acceptable limits for protein set by FeedXL (and in the case of liver or kidney disease keep intakes as close to 100% of requirements as possible) to avoid the issues discussed above.
However, if your horse is:
healthy
living in a temperate or cool environment
living outdoors; and
in light work, breeding, growing or not doing anything at all
Excess protein in the diet will simply be chopped up and used for energy. However you should still avoid feeding more protein than you need to because it is expensive and doesn’t provide any benefit to your horse.
Do you have a question or comment? Do you need help with feeding?
We would love to welcome you to our FeedXL Horse Nutrition Facebook Group. Ask questions and have them answered by PhD and Masters qualified equine nutritionists and spend time with like-minded horse owners. It’s free!
