Oils: Why, Which One and How to feed?

Written by Briony Witherow MSc, BSc, RNutr.

What are fats and oils?

We often hear the terms fat and oil used interchangeably, and while their basic chemical structure is technically the same, their properties are slightly different. A key difference is that fats are solid at room temperature and tend to be higher in saturated fats, while oils are liquid at room temperature and tend to be higher in unsaturated and polyunsaturated fats.

Both fats and oils are classed as lipids, the building blocks of which are fatty acids. Depending on which fatty acids make up a triglyceride and how they are connected, will change how they are classified; some examples include saturated, unsaturated, and polyunsaturated fats.  Polyunsaturated fats (or “PUFAs”) are a source of two well-known categories of fatty acids: omega 3 and omega 6.

Essential and Non-Essential Fatty Acids

As the name suggests, essential fatty acids are required for basic function of the body and therefore need be provided for in the ration. These include omega 3, 6 and 9. Within each omega ‘family’ group, there are members (forms of omega fatty acids) that are very useful (readily useable in the body), and those that are not so useful. The most common form of omega 3 is Alpha Linolenic Acid (ALA) and for omega 6 is Linoleic Acid (LA), and while these can form more useful forms, the method through which they achieve this is thought to be inefficient. You can choose to supplement sources which directly provide readily usable forms, for example algae oil contains EPA and DHA. Alternatively, linseed oil is an excellent source of ALA. 

Omega 3 vs Omega 6

The useful forms of omega 3 (EPA and DHA) and omega 6 (AA and DGLA) produce prostaglandin (hormone-like substances responsible for regulating body functions) which play an important role in mediating inflammation. Omegas 3 and 6 have slightly different roles in this process - omega 3 is anti-inflammatory and omega 6 is pro-inflammatory.  While the benefits of anti-inflammatory responses are more obvious, pro-inflammatory responses are also key. These help to maintain the immune system and are essential during times of injury, infection, or sickness.  Due to their shared role in inflammation and immunity, the ratio of omega 3 to 6 is thought to be important (however the optimum ratio is – as yet -  unknown).

What we do know is that the ration of the domesticated horse is likely to be significantly higher in omega 6, in comparison to the natural diet which would likely have been higher in omega 3. Omega 3 fatty acids naturally occur in forage but are found in higher concentrations in linseed and fish oil (the latter often less palatable), while Omega 6 fatty acids are abundant in cereals, corn oil, rice-bran and soya oil. Subsequently, domesticated horse rations are often higher in omega 6 than omega 3.

As such, when we consider overall fatty acid content, those on poor quality or restricted forage may be deficient, and for those on large quantities of concentrate feed, the intake of omega 6 is likely to be significantly in excess of omega 3 (more so if these rations are also low in forage).

Benefits of Omega 3

• Improves skin and hair coat quality
• Decreases joint pain in arthritic individuals
• Reproductive benefits
• Anti-inflammatory benefits for horses with gastric ulcers and equine metabolic syndrome
• Alleviates allergic hyperactivity (e.g., sweet itch)

Fat and Oil as an Energy Source

Fat or oil is an excellent alternative for supplying energy/calories where starch and sugar levels need to remain low for clinical (laminitis, gastric ulcers) or behavioural reasons. It is also very calorie/energy dense – oil provides 2.5 times the amount of energy/calories as the same quantity of cereals, and therefore can be a good solution for adding calories/energy without causing a significant increase in meal size.

In addition to being an excellent alternative to starch and sugar, due to the way it is metabolised, oil does not produce as much heat when it is digested, so can be a useful calorie/energy source for horses competing in hotter climates.

As the horse does not have a gall bladder, it can take upwards of 6 weeks for optimal utilisation of oil. When introducing it to the diet, increase the quantity gradually, and be aware that beneficial effects may not be evident until the diet has been supplemented for at least a month.  

Beware of Excess Calories

While small amounts of dietary fat in the diets of most horses is beneficial, care must be taken when supplementing fat to those with low energy requirements and good doers (particularly those with metabolic issues such as EMS). Oil are very calorie dense and therefore care needs to be taken to not feed more than an individual’s energy (calorie) requirements.

Adding Oil to the Diet

Oil should be introduced gradually over a period of 10-14 days

• If feeding oil for coat condition and shine, recommended feeding rates range from 20-60ml per day.
• If feeding oil for additional calories/energy, larger quantities can be fed: up to 100ml per 100kg bodyweight (up to 500ml for a 500kg horse). However, many horses would find these quantities unpalatable. When feeding more than 100ml of additional oil per day, it is advisable to feed an additional antioxidant supplement (such as vitamin E) to help neutralise free radicals (unless this is already accounted for in the formulation of the product).

What are free radicals?

Free radicals (also known as reactive oxygen species (ROS)) are reactive substances produced in the process of everyday bodily metabolic function. This production can increase in times of illness or injury, stress and where exercise levels are increased. Fat supplementation also causes increased fat oxidation during submaximal exercise, resulting in the increase of free radicals creating a need for additional dietary antioxidants. Left to their own devices, free radicals can cause damage to cells and cell membranes.

Take Home Points

• Fats and oils are well digested by the horse
• They provide an energy dense ingredient meaning that meal size can be kept to a minimum while increasing calorie/energy content
• They are a ‘slow release’ energy source which can be used in place of cereals (starch and sugar) to provide energy/calories. This can be ideal for those with clinical or behavioural issues needing a low starch and sugar diet.
• Remember that adapting to a high oil diet can take 6 weeks or more.