How to add condition and weight to “hot, fizzy” horses

It’s a question that comes up time and again – How do I safely put weight onto my horse without making it fizzy? Thankfully there are ways to minimize the risk of a change in feed, affecting your horse’s behaviour.

As a starting point, it's important to stress that every horse is an individual and a feed that one horse accepts without issue may trigger a behavioural change in another.

Having said that there are certain ingredients that are ‘more likely’ to provoke a ‘feisty’ response from your horse and so avoiding these and identifying alternatives may provide you with the best opportunity to add the desired condition whilst steering clear of unwanted behaviour.

The 4 Sources of Energy

Whilst the mere mention of the word ‘energy’ can strike fear into the hearts of many nervous horse owners, the reality is that without energy a horse cannot function, move, breathe or survive at all.

In simple terms, if a horse utilizes more energy than it takes in through feed or pasture then it will lose condition. If it consumes more energy than it uses then it will gain weight. It is therefore necessary for us to either provide more energy to a horse that requires condition or reduce its output. The actual source of energy is the key to how behavior will be affected.

This leads us to the primary sources of energy that we can feed a horse.


Whether it is pasture, hay, chaff, or a superfibre such as beet pulp or lupin hulls, fibre remains the most essential source of energy in the diet. The ‘heating’ potential of fibre can vary wildly as anyone with a spring flush of clover will attest to. Cereal hays such as Oaten and Wheaten as well as cool season grass hays such as rye/clover can be extremely high in sugar and provoke an excited response accordingly. Lucerne is generally lower in sugar yet excellent for conditioning however some horses may also react negatively to this higher protein option.

Most likely the safest sources of fibre from a behavioural point of view and which also provide excellent conditioning are soluble fibres such as unmolassed beet as well as products based on lupin hulls. In addition it is recommended that ‘fizzy’ horses be provided with a base hay that is lower in sugar such as Rhodes Grass, Teff or indeed Barley straw.


Starch is a non structural carbohydrate and is primarily sourced from cereal grains such as oats, corn, barley and wheat. Once consumed the longer chain glucose molecules are transformed into available sugars and as such are the energy source of choice for high performance horses such as those that race, event, jump or are involved in any high level equestrian pursuits.

Starch provides rapid energy. For a horse prone to ‘fizzy’ behavior it is likely to make matters worse and so is generally not the energy source of choice for such horses. Oats and Corn in particular are more likely to be problematic from a behavioral point of view however there may be instances where a highly digested form of barley (eg micrbarley) may provide the conditioning benefits of carbohydrates without excessive fizz. Again this will be very much an individual response but particularly in the case of thoroughbreds the application of some micronized barley is worth a try.


Protein is essential for life itself. More specifically the amino acids that are the building blocks of protein are essential in the repair and redefining of muscle and topline and so any desire to add healthy condition must include protein. Aside from pasture and legume hays such as lucerne, protein is also readily provided through ingredients such as soyabean meal, lupins, tick beans and sunflower seeds. All of these sources are high in protein and relatively low in starch and so generally provide a lower ‘fizz’ type of energy.

However, whilst protein is an important element in topline conditioning it should not be wholly relied upon as a singular energy source as it is both expensive and can provoke ‘deamination’ which sees excessive amino acids transformed into ammonia. Such a scenario can be of concern to a stabled horse in particular.


Fat is best fed to horses via plant based oils. It is the most dense of all energy sources yet is generally found to be the least ‘heating’ from a behavioral point of view. Oils are highly efficient with 100ml’s providing as much energy as 250-300 grams of oats and also have the added benefit of improving coat quality and are effectively ‘starch sparing’ as they diminish the dependence on carbohydrates as an energy source.

Fats/Oils are often referred to as ‘slow release’ as they can be utilized aerobically and are devoid of the quick acting sugars that can impact glycemic index so intensely.

Oil should always be a significant part of any diet that seeks to add condition and stamina with minimal excitability.

HYGAIN® PERFORMA 3® is a rich, natural source of Omega 3, 6 & 9 fatty acids. By combining Omega 3 rich vegetable and fish oils with added garlic, PERFORMA 3® contains high levels of usable EPA and DHA's.

Which weight gain feeds should I avoid feeding my hot, fizzy horse?

The first type of energy that we should attempt to avoid is one that is high in either starch or sugar. Feeds coated in excessive molasses or those containing oats or corn should be avoided. Although barley is a cereal grain containing starch, a small amount of correctly processed barley (e.g. micronised) may be suitable for thoroughbreds in poor condition. However the horse's response will be very much a case by case basis.

How to put weight on your horse (the smart way!)

With knowledge of potential energy sources we can look at practical ways we can formulate a diet to add the condition with minimal ‘fizz’.

As with any diet we always start with fibre, be it pasture, hay or chaff. The more a horse can rely on fibre the better and so a combination of a low sugar pasture along with approximately 1.5 to 2% of the horse’s bodyweight in a low sugar hay is an ideal base.

We should then endeavor to maximise feed efficiency by providing at least 2 feeds per day consisting again of an efficient low sugar fibre source such as Micrbeet, Fibressential or Fibre Protect and then a balanced blend of fat, protein and ‘cooler’ carbohydrates.

An appropriate premixed feed with full micro nutrient profile will also avoid the need to add more supplements on top.

The following is a very basic example of a commonly recommended ‘low heating’ diet for a 450kg horse requiring condition without the fizz. There are a plethora of other options but this one is probably the simplest starting point for a horse of this size and breed.


4 Biscuits of a lower sugar hay per day (eg Teff, Rhodes or specific low sugar grass blend). May also include some lucerne if the horse does not react negatively to it.

Added Feed Per Day (split over minimum of 2 feeds)

500g of Micrbeet (Dry Weight) Soaked to be approx. 2kg’s

1.2kg of Fiber Protect

2.5kg’s Tru Care

30g plain salt

Tips when looking for a cool feed for weight gain

Firstly, let’s consider that each horse is different. What works for keeping one horse “cool headed”
will not necessarily work for another. Horses also have varying tolerance levels for starch. One horse may tolerate a medium level of starch (between 10-20%) whilst another horse may be better suited to a low starch feed (<10%).

Keep in mind that starch and sugar levels also contribute to condition. It follows that a transition from a high starch feed to a low starch feed may result in a drop in condition.

Look for a feed that is lower in starch, but high in fat and fibre so that condition is maintained or added.

The best of both worlds – Premixes that add weight with “cool energy”

Tailoring your own feed ingredients is one option. Another option is to select a premix that is specifically formulated to provide cool energy, condition and balanced nutrition. Such mixes are subject to comprehensive analysis to ensure they provide everything your horse needs. The benefit of a premix is that it provides the convenience of a “ready to feed” blend and the confidence that the mix is consistent from one bag to the next. A premix is likely to also offer a saving on time and money compared to the “do it yourself” option.

Quality is still very important when choosing a premix. Between manufacturers there are varying degrees of quality assurance, production methods, processing and ingredients. Hygain® are proud of their commitment to high quality and modern processing methods.

Feeds for hot fizzy horses

The key to slow, steady weight gain

Adding weight should be done in a way that avoids shocking the horse’s system. A sudden influx of calorie rich feeds can upset the digestive system and further compromise a horse’s condition. Gradually increase any new feed and opt for smaller, more frequent meals in preference to one big dinner.

It can be tempting to chase a rapid result by shoveling weight-gain feed into a horse, but a slow, steady approach aligned with the manufacturer’s recommended feeding rate is the best way to safely add condition.

If it’s not the feed...what else can make a horse hot and fizzy?

Whilst energy dense feed is an obvious trigger for behavioural change, it’s important to consider other factors and the overall “big picture.”


Check if your horse’s paddock has had a seasonal change to its pasture. Flushes of sugar-rich green grass in Spring and Autumn are notorious for bringing on hyperactivity and “naughtiness.” Grass can hold a surprising amount of sugar and is often overlooked as a suspect when it comes to identifying behaviour causes.

Pasture can also be mycotoxin affected, meaning your horse is ingesting microscopic toxic fungi. Such toxins can have an effect on behaviour (amongst other systemic issues.) A broad-spectrum toxin binder such as Safeguard EQ® may be beneficial in resolving this problem.

Think about the effect of any recent changes to herd dynamics. Does your horse have a new friend that he may be focusing on instead of his work? Perhaps the removal of a friend has placed your horse under a period of stress. Both situations tend to resolve given time and/or training.

Consider your horse’s living conditions. If your horse is stabled, then its excitable behaviour could be the result of inactivity. Give your horse more to occupy its mind and body with increased access to exercise. Even fairly short periods of turnout or in-hand walking for 30 minutes can make a difference to the horse’s physiological and psychological wellbeing.

Nutritional imbalance:

A diet deficient in Magnesium or B Vitamin (Thiamine) can make a horse nervous, anxious or spooky. Whilst it's uncommon for a diet to be lacking in Magnesium or Thiamine, it’s not a difficult fix and is achieved through feed or supplement.

The individual horse:

Take a closer look at the type of negative behaviour your horse is exhibiting and rule out other causes such as pain. It’s important to remember that a horse has limited ways in which to communicate, so jogging, spooking, bucking and rearing may be an indicator of pain instead of simply excess energy.

Natural disposition and workload

Let’s not forget that horses are individuals. If you are basing a new horse’s diet on one that worked for another horse, then you could be setting yourself up for a real eye-opener. What one horse tolerates (e.g. grain) can be completely the wrong fit for another horse. Horses vary in their ability to digest starch and therefore have different blood sugar reactions from one individual to the next.

If you have reduced your horse’s workload but not adjusted its feed, then it may have an excess of energy. Excess energy can be expressed under saddle, on the ground, or in the paddock.

On the other side of this equation are horses that lack condition and have an undersupply of energy. Their deficiency leaves them lethargic, which may be mistaken for a quiet disposition. When such horses have their diets balanced then it stands to reason that more energy will make them feel more “energetic.” In such cases it’s important to re-evaluate the horse’s baseline for normal behaviour and apply training and/or further exercise as appropriate.

Is your horse spooky, anxious or nervous? This is a great time to check in with your equine nutritionist and make sure your horse’s diet is still the right fit. You can access a free diet analysis and advice service through Nutrikey. Click here to book a time to talk.


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