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If you have a horse that is overweight or at a possible risk of laminitis, you need to take a closer look at what your four-legged friend eats during the day. Healthy horses should also be monitored, taking a closer look at the hay as it is the ultimate source of nutrients. In this article, we take a closer look at the exact values that are important when analysing hay and how much of what my horse needs.

It should look nice and smell good

From a purely sensory point of view, good hay should first of all look clean greenish in colour, dry and coarse to touch. It should contain lots of (hard) stems and not just (soft) leaves, smell fresh and of course be free of poisonous plants. Pulling tufts of hay apart should not create dust or even stick together. If the mould is already visible as grey or white sticky patches, then it is recommended to discard of the hay completely instead of feeding parts of it to your horse. Mouldy hay has far-reaching negative effects on the metabolism, feeding good quality hay is of upmost importance. As a layman it’s easy to evaluate the hay to this point by yourself, but what exactly does the hay provide in terms of nutrients?

Knowledge as to what is inside

If you want to know what exactly is in your hay, you can send it to a laboratory that offers hay analysis, there are several companies in the UK offering this service. The basic analysis includes the most important parameters, such as dry matter, protein and sugar content. Mineral and trace element content can also be determined. If there is uncertainty whether the hay smells as it should, a microbiologically analysis, i.e. for bacteria and fungi can be performed.

Fresh hay in the meadow
From a purely sensory point of view, good hay should first of all look clean greenish in colour, dry and coarse to touch. © Adobe Stock/Mak

Sugar, fiber, protein and Co

First of all, the hay analysis gives you an indication of how dry the hay is. Ideally, the value should be over 85% dry matter (DM), i.e. 1kg of hay should ideally contain less than 15% water. This value is important as all subsequent measurements are usually based on this value. So if I have hay with 85% dry matter and 10% sugar content per kilo of dry matter, this means that 1kg of hay, as I feed it to my horse, contains 85g of sugar. If my horse gets 10kg of hay per day, it therefore gets 850g of sugar from the hay.

Carbohydrates: sugar, starch, fibre

This sugar is usually referred to as ‘water soluble carbohydrate’ (WSC). This is absorbed by the horse in the small intestine and therefore also has a direct influence on the blood sugar level, while non-fibre carbohydrates (NFC), i.e. non-soluble carbohydrates, are utilised by the microbiome in the large intestine. You can find out exactly how this works and which values are good for your horse in our article on fibre digestibility [CF1] [CF1] . When it comes to water-soluble carbohydrates, it may be necessary to differentiate between starch, sugar and fructan. Starch plays a subordinate role in hay samples, as it is not present or only present in very small quantities. Fructan can also be disregarded, as the values are at their lowest at the time of hay harvest. The sugar content is important, as it plays a key role in maintaining health and weight management, especially in good-doers horses.

For water-soluble sugar, 6-10% is acceptable for regularly exercised leisure horses. A good-doer slightly on the heavier side, hay with <6% sugar content is recommended. Hay with >10% sugar content can contribute to many horses being/becoming overweight and increase the risk of insulin resistance or laminitis.

The general rule for horse hay is: the less sugar, the better. The sugar content in hay is largely responsible for feeding behaviour (‘greed’), obesity and metabolic problems in our horses. The recommendation would be to monitor regularly. The recommendation would be to monitor regularly. You can find a simple quick test for the sugar content in your hay HERE.

Protein – it depends on where it is digested

The results from the laboratory will show several values for protein. Essentially, you get two values, one of which represents the total protein in the tested hay, also known as crude protein. Ideally, this is between 6 and 9%. In addition, the pre-caecal digestible protein is given, usually referred to as pcv XP. This refers to the proportion of the total protein that is digested and absorbed by the horse in the small intestine. In contrast, the term ‘digestible protein’ describes the sum of the protein that is utilised in the course of the entire intestinal passage, i.e., both the proportion that the horse digests in the small intestine and the proportion that the microbiome in the large intestine utilises but is not available to the horse at all. The amount of pre-caecally digestible protein is particularly important for non-species-appropriate feedstuffs, such as those frequently used in mixed feeds. This is because these may have high total protein values (high RP value) but may be of lower quality so that the protein is not necessarily utilisable by the horse (low pcv XP) value).

The daily crude protein requirement of a normal leisure horse with 500kg actual weight is approx. 350g. If I now have a hay with a 6% protein content (RP), calculated on the basis of dry matter, that is 510g of crude protein (15% residual moisture in the hay) for 10kg of hay that my horse receives per day. Even if not all is available in the small intestine – see pcv XP – the 6% should still be sufficient. This is because the proportion of pcv XP in hay and grass is comparatively high and is usually around 3.5-7% pcv XP, based on dry matter. The more species-rich the hay, the higher the proportion of pcv XP. As the pcv XP values are only calculated on the basis of certain assumptions and no actual measurement data to be evaluated in the hay analyses, it is naturally difficult to calculate the exact protein content in the ration. Nevertheless, it can be assumed that with species-appropriate ad libitum feeding, a horse with 500kg body weight will eat between 2-3% of its weight in hay and can therefore consume between 290g and 890g of pre-caecally digestible protein. The fewer nutrients there are in the hay, the more a horse will eat, so there is no need to worry about “too little” protein for a healthy horse with normal protein levels in the hay.

However, if other factors such as illness are added, protein may need to be supplemented. Stallions, broodmares and young horses also have a higher protein requirement. The quality of the protein also plays a major role. The amino acid lysine is usually the limiting factor. So, if the value is at the lower end of my protein content, protein in the form of sainfoin or lucerne with their high lysine content should be added or a mixture of amino acids essential for the horse such as OKAPI’s Lymeth.

If the crude protein values in my hay are above 9%, then the hay is only suitable for sport horses in the upper performance range. For leisure horses and good doers, hay with high crude protein values often leads to obesity.

two horses eat hay
Ideally, the crude protein should be between 6 and 9%. © Alexia Khruscheva / Adobe Stock

Hay also contains fat

The term “crude fat” in the analysis refers to the fats/oils stored in the plant, which are usually present as tiny fat droplets, especially in the fat stores of the plant cells, for example in the seeds. The crude fat content varies greatly depending on the time of harvest and the plant population and is usually between 1 – 2.5% in hay. As horses do not develop a fatty acid deficiency even under experimental conditions, this value plays a lesser part.

“raw ash” has nothing to do with normal Ash

The “crude ash” also contains all minerals and trace elements, which can also be determined. The crude ash content does not say much at first, as it also measures sand and soil deposits in addition to the minerals and trace elements. This terminology does not break down which minerals are present in which quantities, it is only the overall sum. Anyone who is after the exact values can have the minerals and trace elements analysed. Iron or calcium, for example, are usually present in quantities well above the requirement, while others such as copper or phosphorus may be present in small quantities. Any mineral deficiencies can be counteracted with a balanced mineral feed.

All values together provide the digestible energy

The digestible energy is known as DE (digestible energy) and usually also the energy actually utilised by the horse as metabolisable energy ME (metabolisable energy). So if the ME in our example hay was 7MJ/kg, then 10kg of hay would provide 70MJ of energy. This would be more then sufficient to our 500kg leisure horse.

Not everything that is mathematically in the hay reflects in the supply for the horse

When analysing hay and calculating a ration, you must always bear in mind that the presence of nutrients, minerals or trace elements does not necessarily mean that the horse can absorb enough of them. If the intestinal flora or the function of the horse’s intestinal mucosa is disturbed, a deficiency can develop despite optimal nutrition. If the horse is low in their pecking order and has to fight for its hay intake within a herd, deficiencies can also develop.

Of course, hay from different harvests and different locations also contains different nutrients. Therefore, a sample should be taken from each batch of hay that is fed over the winter and either sent in separately or mixed with the samples from all batches and then sent in to obtain an average value.