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When does an oversupply of calcium start to harm the horse?

Kristina Gehrdau-Schröder


4 Min. Lesezeit

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Disclaimer: The following text has been translated from German. It is important to note that if you have any inquiries regarding the feeding of your horse, it is always recommended to consult your veterinarian first.

Calcium is one of the bulk elements and is probably the most prominent representative of the minerals. The most important function of calcium in the horse's organism is to stabilise the skeleton. This is where 99 % of the calcium contained in the horse's organism is found. In addition to the mineralisation of the skeleton, calcium is also involved in numerous metabolic processes.

Secure a free feed sample of Equine 74 Gastric and help your horse to buffer  excess stomach acid, so it feels well again.

It all depends on the ratio to phosphorus


The most important antagonist to calcium is phosphorus. Therefore, it is not the absolute content of both minerals in the feed ration that is relevant, but the ratio of the two minerals to each other. A calcium deficiency can be caused by an absolute lack of calcium in the feed ration, but also by a relative excess of phosphate. In the total ration, the Ca:P ratio should be between 1.5-2:1 (however, the ratio should not be less than 1:1 and not more than 3:1), whereby an adult horse requires between 30-40 g of calcium per day, depending on its performance and body weight.

Sunlight is important for the calcium balance


The supply of vitamin D is of great importance for the absorption of calcium and phosphorus from the intestine. It is also responsible for the incorporation of calcium and phosphorus into the skeleton. Vitamin D can be produced by the horse itself. Sunlight is required to convert the vitamin D precursors into the active vitamin D. If a horse is mainly kept in a box and therefore does not receive enough sunlight, a calcium deficiency can occur, even though there is sufficient calcium in the horse's total ration and the Ca:P ratio is appropriate.

How do I recognise a calcium deficiency?


Many horse owners believe that they can judge from the blood count whether the Ca:P supply is correct or whether the horse has a calcium or phosphorus deficiency. However, this is only possible to a limited extent, as an inadequate calcium supply is compensated for hormonally via the feed. This is known as endogenous calcium supply. The parathyroid hormone releases calcium from the bones, making it available to the metabolism again.

What are the consequences of a calcium deficiency?

In young horses, a relative and absolute calcium deficiency can lead to deformation and dislocation of the limb bones. Cranial deformities are also possible. A long-term deficiency in adult horses leads to demineralisation of the bones.

Can an overdose of calcium also occur?

If there is an oversupply of calcium and a corresponding supply of vitamin D, most of the calcium is absorbed from the intestine. The excess calcium in the blood must then be excreted via the kidneys. This is done with the help of the hormone calcitonin, which is mainly produced by the horse in the C-cells of the thyroid gland. However, the risk of urinary calculus formation and disruption of erythropoiesis (formation of red blood cells) only increases from a 250-280% increase in oversupply.

How does a horse meet its calcium requirements?

Depending on the calcium content of the hay, the horse covers the majority of its calcium requirements. However, as the values can vary greatly and are between 3.5-5.5 g calcium per kg dry matter and many horses usually consume more phosphorus, supplementation via mineral feed is usually necessary to cover the horse's requirements.

Can supplementing Equine 74 Gastric lead to an oversupply of calcium or even harm the horse?

By supplementing Equine 74 Gastric, an adult horse consumes an additional 10 g of calcium when fed approx. 50 g per day. Assuming that the horse takes in between 30-40 g of calcium through the intake of hay and mineral feed, this results in a total intake of approx. 40-50 g of calcium. This would be an excess of about 10 g, which is harmless for the horse. Most of the excess calcium is absorbed from the intestine with an adequate supply of vitamin D and excreted via the kidneys with the help of the calcitonin produced by the horse.

If Equine 74 Gastric is fed at a higher level for a longer period of time (e.g. 100 g), the horse would absorb approx. 20 g of additional calcium. This corresponds to a 50-66 % increase in calcium intake. As an increased calcium intake can only be harmful to the horse from approx. 250 %, there is no danger when feeding 100 g Equine 74 Gastric per day. However, attention should be paid to the phosphorus supply at the same time in order to ensure the desired ratio of these two elements.

More about the topic

On our topic page about feeding horses with gastric issues, you will find a wealth of additional information about horse nutrition.

Horses with stomach problems require additional support. It is crucial to know which feed is suitable for your horse and which should be avoided.


Equine 74 Gastric

The long-term solution

Buffers the excess acid in the horse's stomach instead of blocking it.

Equine 74 Stomach Calm Relax

In case of acute stress

Supports the nervous horse stomach in stressful situations.