Vitamin D for Horses

Vitamin D is one of the fat-soluble vitamins, meaning it can be stored up in the body.  It is often referred to as the “Sunshine Vitamin”, since the easiest way for both you and your horse to get your daily dose is a little time in the sun.  Horses receiving a few hours a day of sunlight will meet their needs easily, and they also receive a dose from eating hay that has not been stored for more than six months.

It is fairly common to see a small amount of Vitamin D added to horse feeds, mainly to help those horses who are stabled and receive little or no turnout time and are often fed hay that has been stored for a lengthy period of time.

Vitamin D plays a role in helping calcium to be absorbed. Deficiency may result in rickets and weak bones.  However, excessive Vitamin D may be toxic and may cause abnormal calcium deposits, which could contribute to conditions like spavins, ringbone and sidebones.

Feeding Tips for Horses with Laminitis

Laminitis in short, is the inflammation of soft tissue in the hoof causing damage to or death of the laminar cells, resulting in the loss of the foot’s mechanical integrity.  The severity of damage is unique to each case with the worst damage resulting in founder which is the sinking of the coffin bone.

Overall management and feeding of horses with laminitis requires special care, since factors such as body weight, starch intake, mineral and energy balance, as well as metabolic function can have a profound effect on the fragile environment of the damaged tissue of the hoof.  If you are managing a horse currently being treated for laminitis or one with a history of laminitis, the most important element of overall care is staying connected to your vet and farrier.  When it comes to feeding, here are some nutrition tips to help you along the way.

  • Weight: weight control and regular exercise help any horse physically and mentally, but the laminitic horse in particular.  Excess weight and stagnation add unneeded stress to an already fragile situation. Once the acute phase has passed, regular turn out and exercise provide essential blood flow to the foot, which provides the nutrients for tissue repair.  Activity is also helpful in managing weight.
  • Pasture:  Lush pasture access should be limited by a grazing muzzle for horses prone to laminitis or those currently being treated for it.  If a grazing muzzle is not available, the horse should be limited to access later in the day when plant sugar (fructans) levels in grass are lower, or be kept on a dry lot.
  • Forage: High quality grass hay is the ideal forage for a horse prone to laminitis.
  • Feed: A product specially formulated for metabolic issues or a ration balancer are the best bet to feed your laminitic horse.  Micro nutrients such as vitamins and minerals are essential for tissue repair, so be sure to check that the feed is balanced for these as well as the essential amino acids.   Avoid feeds which provide high levels of starch per meal as these horses tend to be sensitive to increases in blood sugar and insulin.
  • Supplements: Horses with laminitis may benefit from supplemental magnesium and chromium, both of which assist in sensitivity to insulin.
  • Water: Often overlooked as a nutrient, water is one of the best allies in the defense of laminitis in your horse.  Fresh, clean tepid water is a key to overall health as well as circulation of nutrient rich blood.

Following these guidelines for feeding and management, as well as working closely with your veterinarian and farrier should provide you with the tools you need to manage laminitis in your horse.  With extra care and help from the trusted professionals in your life, your horse with laminitis can live a happy, balanced life.

Vitamin A for horses

Vitamin A is one of the fat-soluble vitamins, meaning it is stored up in the body. It is potentially the most commonly deficient vitamin for horses that do not receive commercial feeds or do not have access to green forage.

Roughages that are green, leafy and not too old will contain carotene, which can be converted to vitamin A by the horse, but roughages that are bleached, or have been weathered and are dark and dusty will not contain sufficient vitamin content to be considered. If good green forage is available, the horse will generally have sufficient Vitamin A to meet its needs. However, if a horse is fed poor quality roughage, supplemental Vitamin A is needed.

Since so many horses are fed hay that is stored for many months, most all commercially prepared grains contain Vitamin A to help combat this deficiency. It is important to remember that horses can develop a toxicity situation with Vitamin A, if high-potency vitamin supplements are fed on top of an already well-fortified grain base.

Total Dietary (ie. Hay + Grain) Requirements for 1100lb horse, According to 2007 NRC Guidelines:

  • 15,000 IU per day for maintenance horses
  • 22,500 IU per day for moderately active horses
  • 30,000 IU per day for pregnant/lactating mares

Times that are especially critical for additional Vitamin A are the last 90 days of pregnancy and during lactation. High performance horses and weanlings also need additional Vitamin A.

The most common signs of Vitamin A deficiency are dry, scurfy skin and hair coat, and runny eyes and night blindness are other symptoms. A few studies have been done that have shown night blindness can actually be induced by depriving the horse of Vitamin A and then fixed by adding sufficient Vitamin A back in to the diet. Hooves may be dry and scaly. There’s also a slower resistance to respiratory infections, stress and diarrhea. Toxicity symptoms can include dry hair, anemia, and increased bone size.

Types of Vitamins in Horse Diets

There are two main classes of vitamins: fat-soluble and water-soluble.

Fat-Soluble Vitamins:

The fat-soluble vitamins are A, D, E, and K, and they are listed on horse feed tags as IU/lb. This stands for “International Units per Pound”. They are able to be built up and stored in the body fat and other tissues, and thus are not absolutely required on a daily basis, but should be considered an important part of your horses’ regular nutritional program.

Water-Soluble Vitamins:

Water soluble vitamins, which are the b-vitamins such a niacin, thiamine, folic acid, biotin and many others, are excreted from the body on a daily basis in the urine. All of the B-complex vitamins are essential to horses, but they are synthesized by bacteria in the cecum and colon from ingested feed. After microbes form the vitamins, they are absorbed through the intestinal wall and are available for use by the horse’s body cells. Bacteria in healthy adult horses generally produce adequate levels of the B-complex vitamins.

While none of the vitamins are required by law to be listed on a feed tag, more and more feed companies ARE guaranteeing the levels included in the feeds.  These are generally listed on the tag in either mg/kg or mg/lb, so it is important when comparing feeds or supplements to make sure you are comparing the same unit of measurement.

In coming blog posts, we will look at several of the vitamins individually to learn more about what they are each responsible for.

Calcium and Phosphorus Levels in Horse Diets

Where do calcium and phosphorus come from, and what can you as a horse owner do to balance the diet?

As always, first examine your hay source.  Legumes are better sources of calcium than are the grass hays, but neither legumes nor grass hays are very good sources of phosphorus.  Legumes tend to have a significantly higher Ca:P ratio, with many coming in at around 6:1.  Grass hays, however will have a Ca:P ratio that is about 1:1 and often are even shown to be slightly lower in calcium than phosphorus.  The best way to know what is in your hay is to have it tested.  Check with your local Extension Office for places to get your feed tested.

Next, take a look at your grain source.  For cereal grains (oats, corn, etc.) the reverse is true in terms of calcium and phosphorus relative to roughages. The cereal grains are poor sources of calcium, but are moderate sources of phosphorus.  Oil seed meals, by-product feedstuffs from the distilling and brewing industry, and protein concentrates are often low to moderate in calcium but are excellent sources of phosphorus.  Commercially available feeds should have levels and ratios in balance, but don’t forget to check any supplements you are using. If you are feeding a straight grain, such as oats, or if you are using feed from local grain elevator, which do not always guarantee calcium and phosphorus levels, it is a good idea to have your grain tested along with your hay.

From these two points, it is easy to see where a horse on a grass hay and oats diet – still one of the most common equine diets in use – could suddenly be suffering from an calcium and/or phosphorus deficiency.  Sadly, a deficiency of either of these two minerals is not something that will show up quickly in a manner that is visible to the horse owner.  Years of this imbalanced diet will lead to demineralization and weakening of the bone structure, which can result in increased susceptibility to lameness and injuries.

Calcium and Phosphorus in Horse Diets

Horses are more likely to suffer from a lack of calcium (Ca) and phosphorus (P) than of any other minerals.  Considering the detrimental effect on bone development that a deficiency of these two minerals can have, every horse owner should investigate where their horse’s diet is at in regards to them.

One of the first things any animal science student learns in their Animal Nutrition 101 course is that an animal must always supply calcium in a higher amount than phosphorus, no matter what the species.  The reason for this is that phosphorus will bind up calcium in the animal, making calcium unavailable for use in bones, teeth, and other areas it is needed for.  If there is more phosphorus than calcium available to the horse, then the phosphorus will start to pull calcium away from wherever in the body it can, including the all-important bone structure! 

The reverse situation has very little in the way of detrimental effects, however.  As long as there is more calcium than phosphorus, there is very little risk of getting in to a calcium toxicity situation.   In horses, the ideal ratio is to have between 1.2:1 and 2:1 Ca:P.  Studies have shown up to a 6:1 Ca:P ratio not having an ill effect on horses.

One other note of interest in regards to calcium: it is also essential for proper tubule formation and cell attachment in the hoof wall of the horse. These parts of the hoof wall provide resiliency to the hoof and attach the wall to the sole of the foot, and inadequate calcium or poor calcium-to-phosphorus ratios can cause brittle hooves or tenderness on one or more feet. Proper balance of calcium and the addition of protein to horse rations can help produce strong hooves with well-defined tubules.

Hoof Health and Nutrition

If your horse has ever had issues with his/her feet, the old adage, ‘no hoof, no horse’ could not ring truer.  When considering hoof health, multiple factors influence the state of your horse’s feet including nutrition, conformation, environment, use and overall management and care.  When assessing your nutrition program in relation to hoof health, there are many key components that need to be present for healthy hoof maintenance and growth. 

  1. Water is the most important nutrient for horses overall.  Specifically for feet, adequate amounts of water provide tissue hydration and promotes the circulation needed to deliver nutrients to the living hoof tissues.
  2. Balanced energy in the diet is important to support metabolic activity, the growth and function across the entire body system, including the feet. 
  3. Balanced proteins (aka amino acids) provide structural strength and function for hoof tissues. Lysine, Methionine and Threonine are the three most commonly associated with hoof growth.  It is imperative that amino acids be present in balanced levels along with key minerals and vitamins.  The ability for the body to absorb these critical nutrients is dependant on the delicate balance of them and too much of one or another can disrupt the utilization of these key nutrients.
  4. Macro minerals include calcium, phosphorus, sodium, potassium and sulfur.  The appropriate balance of macro minerals play a key role in skeletal development and maintenance, blood clotting, muscle contraction, temperature regulation, enzyme activity regulation, glandular secretion and cell membrane integrity. 
  5. Micro minerals (aka trace minerals) include zinc, copper, manganese, cobalt, selenium and more. Trace minerals help with the synthesis of proteins, immune system activity, synthesis and maintenance of elastic connective tissues, the integrity of skeletal bone tissue, antioxidant activity and much more.
  6. Vitamins, both fat and water soluble, play a key role in the formation, maintenance and repair of hoof tissues. Vitamin A,D and E aid in bone and muscle growth, maintenance of healthy epithelial tissue, calcium metabolism control, immune response and activity.  Vitamins C and B-biotin, both water-soluble vitamins, aid in antioxidant activity, lipid metabolism, as well as growth and maintenance of tissues. Biotin aids in the cell-to-cell adhesion in the outer hoof layer.

If you are feeding a commercially produced complete feed, check the guaranteed analysis for these nutrients.  It is also important to check that you are following the feeding directions so the proper levels of nutrients are making it in your horse.  Feed companies formulate the nutrient density and balance based on their feeding directions.  Feeding less than recommended amount means your horse is likely not getting enough of the balanced nutrients he needs.

Hoof supplements are widely available and varied.  If you are feeding a complete feed from a commercial manufacturer that guarentees levels of the nutrients listed above,  you likely do not need to supplement for hoof quality. However, special cases require additional nutrient supplementation.  It is best to work with your vet, farrier and a qualified nutrition consultant to determine the best feed and supplementation program for your horse.

Feeding a horse that has established foot issues such as laminitis takes special care,  as he needs the nutrients in feed but likely not the energy provided.  Excessive levels of starch and sugar per meal increase spikes in glucose and insulin which may have a negative impact on feet.  A low calorie feed or ration balancer  fully fortified with vitamins, minerals and amino acids is your best bet for these special cases. 

Finally, if you have specific questions about your feeding program, check with a qualified nutrition consultant for more information.  A combination of regular hoof care , the right nutrition and proper management for your horse will go a long way in keeping him or her sound for years to come.

Understanding Laminitis

If you suspect laminitis, call your vet immediately!

Spring is upon us and hopefully warmer weather has arrived where you are! Many of our horses will soon begin to receive a substantial amount of their daily nutrients from new growth pasture.

While it can be a relief to turn horses out on green pasture after a long winter (for both the horse and the owner), these horses can be faced with a challenge that strikes terror in the hearts of horse owners everywhere: Laminitis.

Laminitis is a specific disease of the foot, which is characterized by damage or inflammation at the junction between the sensitive and insensitive laminae. This important area allows for the attachment of the hoof wall to the coffin bone within the hoof. Laminae become inflamed when an accumulation of toxins and lack of blood flow is found in the hoof. Although laminitis can be caused by a myriad of different things, we classify it in two ways:

  1. Metabolic laminitis
  2. Mechanical laminitis

Metabolic laminitis is more common of the two types and often coincides with some sort of toxemia in the body. It has been reported that approximately 45% of laminitis cases were triggered by lush, green growing pasture. While lush grass is one known cause, laminitis can also be caused by grain-overload (think feeding meals that are way too large, or your horse breaking into the feed room) or even by a retained placenta in a broodmare.

It can be hard to make the connection between something that the horse eats to a hoof disease, so let’s walk through an example: Your horse has been turned out on lush spring pasture that he hasn’t had access to all winter. He over consumes the rich grass which in turn overwhelms the upper digestive tract, and leaks into the hind-gut (cecum/large colon). Certain microorganisms in this part of the GI tract rapidly ferment the starches and sugars that leaked into the hind-gut resulting in an alteration in the pH. This change in the pH level kills off critical populations of cecal and colonic bacteria (good bugs) that help in the digestion process. Not only is the digestion process inhibited, but these dead bacteria release endotoxins which get into the horses blood. The endotoxins in the blood restrict blood flow to the hoof, damage those delicate laminae tissues and result in laminitis.

The second type, mechanical laminitis, is usually trauma induced. Overload on a horse’s foot from excessive body weight, riding on a hard-surface, or where the horse is trying to lessen the pain from a separate injury by shifting more weight to the good leg can all be causes of mechanical laminitis. A well known example of mechanical laminitis is Barbaro, the 2006 Kentucky Derby Winner.

In either metabolic or mechanical situations laminitis can happen in any foot, but most commonly it will occur in the front feet of horses on pasture. They will have a tender footed stance and act like they are “walking on egg shells”. A close inspection may show that the horse is shifting their weight—maybe backwards or even from side to side in an effort to compensate for the pain that they are experiencing in their affected leg or legs. If you find your horse in this situation, or suspect laminitis for any reason, contact your veterinarian immediately!

Types of Minerals Used in Horse Feeds

In the case of minerals found in a bag of commercially prepared feed, the form of mineral used as an ingredient can be looked at.  There are a variety of types of minerals that can be used as ingredients, with varying levels of bioavailability, or ability to be absorbed by the animal, for each of them. 

  1. Inorganic trace minerals, namely oxides and sulfates, are the most common, with oxides having about half the bioavailability of sulfates, except in the case of copper and zinc.  These would be seen on a feed tag as “zinc oxide” or “copper sulfate”. 
  2. Organic* trace minerals, namely “chelates” and “complexes”, are two forms of minerals that are gaining popularity in horse feeds due to their increased digestibility. 
    1. Chelates are a mineral molecule tied to a string of general amino acids. These are seen on feed tags as “zinc amino acide chelate”.
    2. Complexes (the more bioavailable of the two) are minerals tied to a specific amino acid that is known to assist in the availability.  These are seen on feed tags as “zinc methionine complex”. 

Premium horse feeds often contain one of the two forms of organic trace minerals, as they are the more bioavailable forms. They are generally used in combination with the inorganic forms to acheive the desired level, without skyrocketing the price of the feed.

For more information on trace minerals in horse feed, visit ZinPro’s website – ZinPro is a key supplier of trace minerals in the feed industry.

*Please note that “organic” is not referencing certified organic products like you would purchase at a grocery store – instead it is a scientific reference to the chemical makeup of the mineral.

Minerals in Horse Feeds

There are a variety of minerals that are important in horse nutrition.  As we learned in previous blog posts, it is important not to put too great of an emphasis on any one particular mineral, although some do require greater supplementation than others.  For example, rarely will iron or iodine be seen listed in the guaranteed analysis on a horse feed tag, but most all commercially prepared feeds will have guaranteed levels of copper and zinc.  The reason for this is that some nutrients are naturally present in most forages, but others are often not present in high enough levels to fulfill the needs of today’s horse – a horse with the demands of performance placed on it. 

Also, it is important to note that when looking at a feed tag, just because a particular mineral is not listed on the guaranteed analysis, that does not mean that it is not present in the feed.  Many minerals are naturally occurring in the ingredients used to produce the feed, and in some cases does not need to be supplemented on top of the other ingredients.

Below is a quick guide to some of the basic minerals and what their function is in the horse:

Magnesium is necessary to reduce stress and irritability. Although rare, deficiency may occur in horses on high grain diets or animals in high-stress situations. If deficient, horses are high-strung, and jumpy. Rations with significant forage generally have no problem with magnesium deficiency.  Grass tetany as seen in cattle is not an issue in horses, as horses absorb magnesium much more efficiently than cattle do.  Toxicities are not generally seen in horses.

Potassium has a major function in muscle activity, and acid-base balance. It may be deficient in horses on high-grain diets. Deficiency symptoms may be reduced intakes, muscle weakness, diarrhea, and a slow-down in growth. Forage is important to prevent potassium deficiency. Toxicity is not generally an issue if adequate water is provided, as excesses are excreted in the urine.

  • Potassium has gained most of its notoriety with the onset of HYPP in the quarter horse world. Feeding elevated levels of potassium can induce an attack in an HYPP-positive horse. Total dietary potassium in a HYPP-positive horse should be kept to less than 1%.

Cobalt is necessary for synthesis of vitamin B12 in the intestinal tract. However, the requirement is very low.

Copper is necessary for hemoglobin formation, along with iron and vitamin B12. Anemia and abnormal bone development in foals may be symptoms of deficiency. Often deficiencies occur in suckling foals, as the mare’s milk has very low levels of copper.  Care should be taken with pregnant mares to feed a diet sufficient in copper during the last 3-4 months of gestation, when the unborn foal is laying down stores of copper in it’s liver to get through the nursing period without problems. Copper levels are also of great interest in developmental orthopedic diseases.  Toxicity is very rare in horses, and deficiencies in mature horses are also not seen often.

Iodine is needed to make thyroxin, which controls the ratio of body metabolism. When iodine is deficient, foals may be born dead. Mares may be unable to nurse or have higher than normal naval ill when iodine is deficient.  Both toxicity and deficiency lead to hyperthyroidism, due to the fact that a toxicity impairs/inhibits release of thyroid hormones, while a deficiency doesn’t allow for sufficient hormone production.

Iron is necessary for the formation of hemoglobin, which enables the blood to carry oxygen. Iron deficiency anemia is a deficiency symptom. Horses under the heavy stress of racing or showing may develop deficiency symptoms, as well as horses with chronic blood loss from parasite damage.  Symptoms of toxicity can include depression, diarrhea, or increased susceptibility to bacterial infections.

Manganese is essential for bone formation, growth and reproduction. Manganese deficiency symptoms may be poor growth, lameness or bowing of legs, as well as reproductive dysfunction. Most feedstuffs are rich in manganese. 

Selenium is associated with white muscle disease and the death of foals. Deficient animals have muscle disorders, such as tying-up. However, greater than 5 ppm selenium in the ration may be toxic to the horse.  Feed companies are not allowed to supplement selenium at a rate that would give more than 0.3 ppm in the total daily intake when fed as directed.  Should be fed with Vitamin E, as they work together in the body.

Zinc gives gloss or “bloom” to hair coat and is needed for protein synthesis and metabolism.  Needs to be kept in ratio with copper, with the ideal ratio being between 1:3 and 1:4 copper to zinc.  Zinc is also being heavily looked at in relation to the occurrence of developmental orthopedic diseases.