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.

Measuring Minerals in Horse Diets

Minerals are generally listed in two ways on a feed tag guaranteed analysis. 

  1. Macro minerals, or those needed in larger quantities, are expressed as a percentage. They include calcium, phosphorus, sodium, chlorine, potassium, magnesium, and sulfur. 
  2. Micro minerals, or those needed in smaller amounts, are expressed as “parts per million” which is what the “ppm” on the tag stands for.  Occasionally a feed tag will list these in “mg/kg”, which converts directly to ppm – 1 ppm is equal to 1 mg/kg.  These minerals include selenium, iodine, copper, zinc, manganese, and iron.

When analyzing a feeding program, it is of great importance to make sure that the same units of measurement are being used.  Often times, test results for a hay sample that has been analyzed will not be expressed in the same unit of measure as the nutrients guaranteed on a bag of feed.  So, in order to know what the entire diet is providing, make sure you are comparing apples to apples!

Powering Ponies

It is very exciting to see the popularity of ponies increasing among adults and children across disciplines, but specifically in the FEI ones such as Eventing and Dressage.  Some notable ponies of late include Theodore O’Connor, Hideaways’sErin Go Bragh, and North Forks Cardi.  Ponies may be shorter in stature, but they are no less in heart and mind than a big horse.  With modern pony breeders focusing on increasing performance traits, more ponies are in the competition limelight. Though they can hold their own amongst the ‘big kids’, ponies do come with a few adjustments to care and nutrition.

Most of us have seen the proverbial fat pony. Then it’s no surprise that one of the most common concerns among pony owners is their pony’s weight.  Most ponies are considered by their owners to be easy keepers, meaning they gain weight just by looking at their feed (or so it seems!) which makes sense when you consider the origination of many of the pony breeds. 

Most breeds were developed in harsh conditions, the Welsh, Connemara, and Dartmoor to name a few, and are recognized for their hardiness and ability to exist on a relatively low plane of nutrition.  Modern ponies are metabolically efficient and adjustments need to be made as they should not be fed as their full-sized counterparts. 

Special care should be taken when selecting the appropriate feed for your pony.  Due to high incidence of insulin resistance and other metabolic disorders among ponies, feeds which provide large amounts of starch and sugar per meal should be avoided.  It is important to note that ponies don’t generally require a different feed than their larger counterparts, rather they simply require less of that feed. 

For low activity ponies, a ration balancer fortified with vitamins, minerals and amino acids along with a high quality grass forage are ideal.  Daily turnout for these ponies is also advised, though be cautious not to allow excessive grazing on lush pasture.  Exposure should be limited either a dry lot or use of a grazing muzzle if lush pasture rich in fructans and soluble sugars is all that is available.

For a pony in work, a feed that provides energy from high levels of soluble fiber and  fat, fortified with vitamins, minerals and amino acids is ideal.  Active ponies in regular work or strenuous exercise should consume forage at a rate of about one pound per 100 pounds of body weight, per day.  For a 700 pound pony, that would be approximately seven pounds of hay per day.  Good quality grass hay is ideal roughage for ponies. 

As with horses, it is important to monitor the body condition and weight.  A general guideline to follow for the body condition score for a pony is 5.0-5.5.  Their smaller size can be deceiving when it comes to dishing up feed, therefore it is very important to weigh feed and follow the recommended feeding directions.   

By keeping a keen eye on your feeding and management program, your pony can live a healthy, productive life in trim shape, and can excel in whichever discipline you choose – whether it’s in a dressage arena, or just a competition to see who’s got the prettiest pasture ornament!

Mineral Levels & Ratios in Horse Diets

Mineral Interactions in Horses

A major factor to consider when looking at the mineral profile of a feed is the interaction of different minerals. Not only are the levels of each individual mineral important, but so are the ratios in which those minerals are present with each other.

As you can see from the image at right, the level of copper (Cu) present has a direct effect on Zinc (Zn), Iron (Fe), Molybdenum (Mo), and Sulfur (Su). This effect is the reason that single nutrients should not be focused on unless there is a known and quantified deficiency or excess of a certain mineral in the animal. Addition of a single nutrient in large quantities may visually solve one problem in a horse (i.e. their coat got shinier), but what else is going on behind the scenes is often hard, if not impossible, to tell.

Of course, this is not meant to downplay the fact that individual levels of minerals are important as well.  Depriving or overdosing a horse for a short time may not have a significant effect immediately that is visible to the average horse owner (termed “clinical signals”).  However, it does not take long for “subclinical” deficiencies or toxicities to begin to occur.  These are not visible to the naked eye, but still can have a profound effect on the health of an animal.  Eventually, they will show up, but there is no guarantee that if the deficiency or toxicity is fixable by the time the clinical symptoms are seen. 

Deficiencies over time in a horse's diet

A prime example of this would be a pregnant mares diet, and it’s effect on the foal.  A mare in the first two trimesters of pregnancy needs a quality diet, but it doesn’t have to be much higher than a maintenance level diet.  However, many requirements increase by 50% or more when that mare hits the last trimester of pregnancy and after that when she goes in to lactation.  Not feeding her a balanced diet designed for the stage she is in may not leave her looking bad in the immediate time frame, but improper mineral levels or ratios could be severely detrimental to the foals health, to the mares health down the road, or even her ability to re-breed efficiently.

Supplementing Horse Diets with Omega Fatty Acids

As you look at your horses’ diet, it is important to remember that horses need a balance of both omega-3 and -6 fatty acids for optimal health and performance.  One isn’t necessarily better than the other; they simply have different roles in the body and must be in balance with each other for optimal health.

As herbivores and nomadic grazers, horses are naturally adapted to a diet rich in omega-3 fatty acids (ALA).  The little bit of fat found in forages, particularly fresh pasture, is naturally high in ALA (omega-3) whereas oils from some grains and seeds tend to be higher in LA (omega-6).  

Total diets (forage + grain concentrates + supplements/treats) that include supplemental fat in addition to grain concentrates tend to have a total dietary fatty acid ratio that provides higher omega-6 fatty acids to omega-3 fatty acids.

Scientists have not yet pinpointed the ideal total dietary intake or ratio of omega-3 and omega-6 fatty acids for horses. Limited research suggests that providing supplemental sources of ALA or EPA/DHA, in addition to a well-balanced forage plus grain concentrate, may provide some key benefits to your horse. Start by basing your horse’s diet on a good quality forage plus a quality complimentary feed that provides omega 6 and omega 3 fatty acid guarantees on the feed tag . Supplementation on top of what the base diet is providing may be worth discussing with a trusted equine veterinarian or nutritionist when supporting horses with pro-inflammatory conditions (e.g. skin allergies or hypersensitivity, joint pain, etc.).

As always, when adding dietary supplements to the horses feeding program, make sure the total diet (forage + concentrates/treats) stays balanced and that changes are made gradually so the horse’s digestive track has time to adjust.  Benefits from providing omega fatty acids in the diet are not realized immediately, but take 30 – 90 days of supplementation before benefits are detectable, so be patient and make sure your expectations are realistic.

 

 

DIETARY SOURCES OF POLYUNSATURATED FATTY ACIDS
Omega-6 fatty acids Omega-3 fatty acids
Corn oil (LA) Flaxseed (linseed) oil (ALA)
Safflower oil (LA) Fish oil (EPA, DHA)
Rice bran oil (LA) Soybean oil (ALA)
Sunflower oil (LA) Canola oil (ALA)
Borage (starflower) oil (LA) Mustard oil (ALA)
Cottonseed oil (LA)
Grapeseed oil (LA)
Peanut oil (LA)
Primrose oil (LA)
Sesame oil (LA)
Soybean oil (LA)