People often ask me, ‘What is the best type of forage to feed to my senior horse?’ My answer, in recent times, is: ‘As many different forages as you can find!’ My meaning is that it is best to feed multiple types of forages simultaneously to your horses.

You see, the more different types of forage we can get into our horses’ diets, the more their diets are like their wild ancestors. They roamed free, grazing and browsing on grasses, shrubs, herbs, forbs, trees, and various other fibrous plants. This diet created significant fibre diversity in their gut. And that gave rise to microbe diversity … which we are starting to recognise as one of the cornerstones to horse health.

So, when selecting pasture species to plant or hays to buy, you should go for as much variety as you can manage. Select forage species that are safe, palatable, and suitable for your particular horse.

Which raises the question … which forage species are suitable for senior horses?

Exploring all of the forage species options is not an undertaking for a short article.

In the following information let’s focus on some specific characteristics of some warm season grasses and consider when they may, or may not, be suitable for seniors.

Warm Season Grass Characteristics

#1 – Digestible Energy

When at a comparable stage of maturity, warm season grasses (think kikuyu, bermudagrass/couch, teff, Rhodes grass, buffel grass, digit grass) are typically lower in energy than their close relatives the cool season grasses (think ryegrass, prairie grass, timothy, fescue, orchardgrass/cocksfoot).

This potentially lower energy characteristic is owing to their tendency to accumulate higher levels of lignin, which then lowers fibre digestibility.

Lower energy is useful when your senior needs to be on a weight control diet or needs to lose weight. The lower energy warm season forages, and particularly hay made from mature warm season grasses, allows you to feed bulk to these good doers. This keeps their guts full and to keep them chewing for long periods of the day without overfeeding calories. In these situations, warm season forages could be used to make up the majority or all of their forage requirements. And are, in fact, wonderful for this purpose!

A couple of points to consider, however, are that warm season grasses are typically low in sugars. This makes them less sweet and less palatable for some horses. This usually isn’t an issue for horses on calorie restricted diets, but occasionally may be.

And, owing to the higher lignin and less digestible fibre content, some warm season grasses—and particularly Bermudagrass—may put horses at a higher risk of impaction colic.

If your senior needs to gain weight or has trouble holding weight, early vegetative warm season grasses (lush green pasture or soft leafy hay) may work well and could also be fed as a majority of the forage in your seniors diet. This is providing they don’t have any metabolic conditions that require them to have a very controlled intake of non-structural carbohydrates … see below.

But, mature warm season grasses may not have enough digestible energy to meet the poor doers increased calorie needs if fed as the primary forage in the diet.

In these situations, if mature warm season forage is all the grass forage you have access to, you can simply add some higher quality, higher energy legume forages like lucerne/alfalfa hay into the diet to increase the overall nutrient value of the forage portion of the diet.

Supplement with some digestible, high-energy feed ingredients (think well-formulated senior feeds, beet pulp, lupin hulls, rice bran, oils, extruded grains where safe and appropriate, and copra meal) to meet calorie requirements.

#2 – Protein

At the same stage of maturity, warm season grasses typically have lower quality protein than cool season grasses and legumes. Lower quality protein means that they are lower in bioavailable essential amino acids. Which means they are not as capable of meeting a seniors essential amino acid requirements.

And this means that seniors may have more problems maintaining muscle mass on diets containing significant amounts of warm season grasses (see Equine Muscle Mass: Detecting and Monitoring Changes for details on an equine muscle mass scoring system).

But, this is an easy situation to fix! If you do find your senior needs additional protein to maintain muscle mass on a diet based on warm season grasses, add some high-quality protein from sources like soybean meal or well-cooked full fat soybean, whey protein, lupins (we love these in Australia!), faba beans, well-cooked peas, or use senior feeds containing these high-quality protein ingredients.

And, add some lucerne/alfalfa to the diet. The lucerne brings in beautiful protein and adds the all-important fibre variety! Lucerne also adds calcium to the diet, which is really important on warm season grasses. Keep reading to find out why!

#3 – Fibre

Good-quality (soft and leafy) warm season grass hay can be fed in small amounts to add fibre variety to any senior’s diet. This is a particularly useful thing to do when your senior is grazing lush, green, cool season pastures or when your senior has access to only a limited number of other fibre sources.

Do keep in mind that warm season grasses become very fibrous as they mature. This may make them difficult for older horses with poor dental health to chew. And, there is a possibility of an increased risk of impaction colic, especially if yours senior aren’t great at keeping themselves hydrated.

If your senior’s teeth are wearing and you would like to use a small amount (0.5 to 2 kg/day) of warm season grass hay to add fibre variety to their diet, choose only soft, leafy warm season grass hay.[PH1] 

#4 – Calcium

The bioavailability of calcium in some warm season grasses is poor owing to their high oxalate content (a compound that loves calcium so much it will steal it from your horse).

On these grasses, your senior is at high risk of severe calcium deficiency and will require a carefully balanced diet to ensure requirements are met and severe calcium deficiency is avoided.

For details on the risks and the management required to prevent severe calcium deficiency please read Warm Season Grasses and Senior Horse Safety.

#5 – Non-Structural Carbohydrates

It is this feature of warm season grasses that earns them a place on my ‘very useful ingredients’ list for horses.

Why?

Because they have a ‘controlled’ carbohydrate storage system. Which usually makes them safe for seniors who need a low non-structural carbohydrate diet.

Very quick plant physiology recap for you … Plants use light from the sun, carbon dioxide, and water in a process called photosynthesis to make their own food in the form of carbohydrates (which is super clever when you stop to think about it!).

Warm season grasses have specialised cells where they store their food, which is primarily in the form of starch. Once those cells are full, they stop making food for themselves until they have more room to store it. So, they tend to have low levels of non-structural carbohydrates and are, more often than not, safe to feed to metabolic syndrome, PPID, PSSM, or laminitis prone horses (without soaking!).

In contrast, cool season grasses are physiologically ‘allowed’ to stuff their food (primarily sugars and fructan) wherever they want to store it. Under the right conditions, they can accumulate 30%-plus of their dry weight in these non-structural carbohydrates. Which spells almost certain disaster for any horse that requires a low non-structural carbohydrate diet.

Warm season grasses are my almost fail-safe go-to for laminitic horses. However, they can still sneak a few extra snacks into their stems and leaves and occasionally we will find warm season grasses that have accumulated more starch than normal (it’s like comfort eating for plants!!). So, it is wise to always test your hay or buy hay that comes with a reliable non-structural carbohydrate analysis.

If you have a senior who requires a very controlled non-structural carbohydrate diet that has access to grazing, early morning grazing—from 2 hours before sunrise until 2 hours after sunrise—is going to be safest!

If you live in a climate where you have bright sunny days and overnight temperatures that can dip very low, be wary. Even in the very early hours of the morning, pastures may be too high in non-structural carbohydrates to be safe. Although this is more of a concern with cool season grasses, it is still important to be aware of even on warm-season grass pastures. And it is a particular concern in spring when the sunlight hours are longer but the cold nights are still lingering!

#6 – Vitamins and Minerals

Warm season grasses, like all grasses, are typically low in the trace minerals copper and zinc. And, depending on where you are in the world, may also be low in phosphorus, selenium, iodine, and manganese.

In addition, mature warm season grasses, like all grasses, will be low in natural vitamin content, with the exception of vitamin D that tends to increase with increasing forage maturity.

And, like all hays, warm season grass hay will lose vitamin content as time of storage increases, with all hays having virtually zero vitamin value left after 12 months.

With these nutrient characteristics in mind, it is important to ensure you are balancing your senior horse’s diet with vitamins and minerals.

A high-quality balancer pellet is ideal for easy keepers. A well-formulated complete feed may work well  for horses that need additional energy and protein to maintain weight.

Horses for Courses

Whether warm season grasses are suitable for your senior really depends on your individual seniors and their needs.

If you have a senior that tends to get fat easily and/or needs a low non-structural carbohydrate diet, then warm season grasses may be their saviour. Those often provide a safe forage that can be eaten in bulk without readily oversupplying calories and keeping non-structural carbs under control.

If on the other hand, if your senior is a poor doer and needs a lot of help to maintain weight, then warm season grasses may only have a small role to play in adding some fibre variety to the diet.

You will need to consider your horses’ dental health and any dental conditions your seniors may have before selecting appropriate forages (see Tips on Feeding Older Horses with Dental Issues ).

If you are still competing, be aware that it is recommended you avoid teff hay due to the risk of a positive swab to synephrine.

Final Words

Warm season grasses are some of my favourite forages, but you do need to be aware of their shortcomings to use them well!

The key to using them successfully is to feed them in a well-balanced diet that is meeting calorie, protein/essential amino acid, mineral, and vitamin requirements, and one that has as much forage variety as possible!

For more detailed information on warm season versus cool season grasses read Nutritional and Non-Nutritional Aspects of Forage.

Further Reading

  • Nerida McGilchrist, PhD
    Nerida McGilchrist, PhD, has more than 20 years experience as an equine nutrition specialist. She has worked with horses ranging from top-level competitors to backyard senior ponies.
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