1. Introduction:

The horse's body condition marks the relationship between diet (energy input), exercise (energy output) and metabolic or pathological state (power management) and through that, we can determine:

– The horse's athletic performance

– The probability of growth problems in foals (up to 5-6 years depending on the breed).

– The likelyhood of obesity-related diseases such as insulin resistance, colic, laminitis or supercoriatitis, founder, tendonitis and / or arthritis, and infertility.

– The likelihood of cachexia related disorders such as immunosuppression and susceptibility to infection (Naylor and Kenyon 1981), hypothermia (Naylor 1999), reduced tissue repairing rate and fertility, hepato-renal problems, depression, gastrointestinal mucosa atrophy and other related problems (Lawrence et al 2004).

It is obvious therefore, that if we want to maximize the health of our horse and prevent a lot of diseases that reduce their athletic ability, quality and / or life expectancy we must help regulate the body condition of our horse and keep it in optimum condition, within known safe limits.

Determining the body condition, or optimal state, must be done in an objective way and based on the results of scientific studies of the subject. Therefore, we must avoid compromising the health and / or quality of life of our horses ignoring the subjective tastes or desires of the owner, rider or trainer - Because the health of the horse must always come first.

2. Live weight (LW) determination:

It is important to know the weight of the horse for the proper administration of drugs, determining the maximum weight that a horse can carry in a specific moment (to prevent musculo-skeletal problems the sum of the rider plus the saddle, halter, reins and other materials, should not exceed 15-20% of LW of the horse) (Powell et al 2008), to regularly check the increase or reduction of weight and to create a customized diet etc

There are two ways to accomplish this. The first is to determine the real weight, using a weighing scale (the most accurate way to determine the weight) and the second is through a formula. The formula that measures most accurately the real weight of a horse is the Hapgood formula, with a 97.559% accuracy, but because of its complexity is better to use the formula developed by Carroll & Huntington in 1988 with a precision of 95.349% . (Hapgood, 2001).

The left image shows the formula of Carroll & Huntington and how to take the measurements correctly (Carroll & Huntington 1988). In the image on the right we see a horse that is being weighed through the use of a balance equiscale (www.equiscale.com).

3. Determination of the optimal weight for my horse:

Once we know the weight of the horse, we must determine if it is below or above the optimal weight through the study of body condition, which indicates the fat % in the body and muscle mass at that particular moment. The most accurate way to determine the body condition is doing a plicometric study, but this method is not developed in horses, so we must settle for the indirect, inaccurate and interrelated measurement which has been scientifically proven (Carter et al 2008) in relationship with;

– Plasma glucose, insulin, triglycerides and leptin (0.4 to 0.5 p <0.001)– Fat deposits– Risk of suffering diseases such as RI and / or Supercoriatitis (laminitis)

Weight (Kg) = [G (cm)] x L (cm) 11877

In this image we can see an obese andalusian horse who therefore has an increased risk of suffering musculo-skeletal, metabolic and cardio-vascular problems that are going to reduce it's sporting life and badly effect it's quality of life (image taken from www.loscaballos.org).

3.1. Body Condition Score or BCS

This is a qualitative method of determining the horse's body condition, by examining the level of fat accumulation in 6 specific areas where the horse tends to accumulate fat (some breeds have a predisposition to accumulate a high % of the body fat in certain areas). Depending on the level of accumulation of fat the horse will receive a numerical qualification in a compressed scale between 0 and 9 (Henneke et al 1983). We can standardize that from one unit to the other exists a difference of 50 kg (38 to 55kg) (Carter et al 2008b)

We recommend using the BCS (Henneke 1983) because it has been scientifically proven that, despite being a qualitative method it keeps a close relationship with;

– Body Mass Index or BMI (Ewards et al, 2009)– The amount of subcutaneous fat (Gentry et al. 2002; Henneke et al. 1983)– The blood concentration of leptin (Buff et al., 2002)– The glucose tolerance test (Frank et al., 2006)– Insulin sensitivity (Vick et al., 2007, Hoffman et al., 2003).– The risk of laminitis (Treiber et al., 2006c)– Metabolic and reproductive problems (Vick et al., 2006).

The 9 Levels of the BCS are ( Kentucky Equine Research ):

1 - Poor:

Animal extremely thin. You can easily observe the spinous processes of the thoracic and lumbar vertebrae, ribs, sacrum, the coxal tuberosity and the ischial tuberosity. Easily palpable bony structures that make up the neck, withers and back, and the presence of any fatty deposits cannot be seen.

2 - Very Thin:

Very thin animal in which you can easily observe the spinous processes of the thoracic and lumbar vertebrae, ribs, sacrum, the coxal tuberosity and the ischial tuberosity. Easily palpable bony structures that make up the neck, withers and back, but there is a small layer of fat covering the spinous processes of thoracic vertebrae and the transverse processes of lumbar vertebrae, whose edges are still sharp.

3 - Thin:

A thin animal in which you can see a more muscular neck but still without any fatty deposits, the spinous processes can be seen but are difficult to individualize, ribs, sacrum, rounded coxal tuberosity can all be easily seen (the ischial tuberosity is no longer distinguishable). Palpable bony structures that make up the neck, withers and back, but there is a fat layer covering the spinous processes of thoracic vertebrae (transverse processes of lumbar vertebrae are not palpable) and ribs.

4 - Slightly Thin:

Mildly thin animal in which you can see a more muscular neck, a slight ridge in the lumbar area formed by the spinous processes but these are still difficult to individualize, not too obvious ribs, sacrum (depending on conformation), (or the coxal tuber and the ischial can be distinguished). Slightly palpable bony structures that make up the neck, withers and back, but there is a fat layer covering the spinous processes of thoracic vertebrae (transverse processes of lumbar vertebrae are not palpable), and the base of the tail.

In this image we can observe the different zones that are inspected and palpated for determining in which level of the BCS scale the horse is; A neck, B withers, C loins, D tail base, E ribs and F shoulder.

5 - Optimal Body Condition:

Animal in with an optimal amount of fat in which you can see a more muscular and rounded neck, withers and back which is flat also (or the spinous processes, and ribs, and the sacrum, or coccyx and ischial tuberosity cannot be distinguished). Ribs are easily palpable and there is a thin layer of fat covering the spinous processes of thoracic vertebrae (transverse processes of lumbar vertebrae are not palpable), and the base of the tail.

6 - Slightly obese:

Slightly obese animal in which all bony prominences are seen slightly rounded. You can feel a spongy layer of fat in the neck, cross over and between the ribs (but still can identify), and around the base of the tail.

7 - Obese:

Fat animal in which you cannot observe the bony prominences. A moderate layer of spongy fat is palpable in the neck, the withers, above and between the ribs (but still can identify each individual rib), and around the base of the tail.

8 - Very Obese:

Very fat animal in which you cannot observe the bony prominences. A moderate layer of hard fat palpable in the neck, the withers, above and between the ribs (not palpable), and around the base of the tail.

9 - Extremely Obese:

Hard fatty deposits that form lumps of varying size.

3.2. Body Mas Index or BMI:

If we want to maintain an objective, easy manageable and numeric control of our horses body condition, we must take measurements and apply some formulas. It's scientificaly proven that the morphometric formula has a higher correlation with the BCS is the Body Mas Index or BMI (0.64 to 0.68 p <0.001) (Carter et al 2008).

The left image shows how to perform the measurements on the horse and then apply them into the BMI formula to obtain a quantitative and comparable result. The box on the right shows the interpretation of BMI values obtained according to the chart developed in the study of Carter et al (2008).

BMI= G (cm) H (cm)

< 1,17 Thin (BCS 1,2,3)1,17-1,27 optimal (BCS 4,5,6)>1,27 obese (BCS 7,8,9)

3.3. Cresty Neck Score or CNS:

Although the BCS is a highly reliable formula to determine the body condition of a horse, certain breeds and / or certain horses (as individuals are unique and unrepeatable) tend to accumulate most lipids (fat) in the neck . This means that sometimes we can find a horse that has a BCS of 6, but if we pay attention to the neck will see that in reality has a BCS of 9.

It is therefore advisable to assess the CNS of a horse with his BCS because has also been scientifically proven that this index is closely related to the fat thickening of a horse and the risk of suffering insulin resistance, hyperinsulinemia and / or laminitis. (Frank et al., 2006; Johnson, 2002; Treiber et al., 2006c).

The 6 Levels of the CNS:

Level 0: You cannot feel any fat deposit palpating the nuchal ligament

Level 1: You can feel a little bit of fat in the nuchal ligament

Level 2: You can see and feel a slight accumulation of spongy fat distributed throughout the neck.

Level 3: You can see and feel an accumulation of fat located in the center of the neck, which begins to lose lateral mobility.

Level 4: You can feel a great accumulation of fat that is hard to hold with one hand across the deposit. A severe loss of lateral mobility

Level 5: There is so much hard fat in the neck that the neck droops to one side.

The left image shows the visual appearance of the 6 levels of CNS (Carter et al 2008).

3.4. Mean CNS:

Just as with the BCS, if we want to maintain a more objective, manageable and numerical control, we must take measurements and apply some formulas. It's scientifically proven that the morphometric formula which has a higher correlation with the CNS is the Mean CNS or MCNS (0.65 p <0.001) (Carter et al 2008)

The left image shows how to perform the measurements on the horse and then apply them into the formula of MCNS to obtain a quantitative result comparable over time. The box on the right shows the interpretation of MCNS values obtained according to the chart developed in the study of Carter et al (2008).

MCNS = [(Nc1+ Nc

2+ Nc

3) / 3]

H (cm)

< 0,6 thin (CNS 0)0,6-0,65 optimal (CNS 1,2)>0,65 obese (CNS 3,4,5)

4 - The optimal values:

Having identified the 4 default values, we must be able to interpret them and we must have a model which we get from the fusion of scientific studies in healthy populations of wild horses and other studies with great practical value. This mixture shows us that:

– The live weight: The mustangs of the Great Basin reach adult weight at 4-5 years old and the scientists have found this weight is between 350 and 550 kg (the most common values are those between 400-450kg). From that moment, the weight no longer depends on variables such as age, sex and breed, it depends only on environmental variables (Berger 1986)

– El BCS: Examining the annual BCS, we note that the Great Basin mustangs body condition fluctuates with environmental conditions such as temperature, wind, rain drought and the time of year - their weight being at its peak in the late autumn (5.5 to 6) and at its lowest point in the late winter (4 to 4.5) (Berger 1986). But if we examine the BCS from a multi-view (10 years), we see that in the feral horses of Namibia have the most repeated BCS of 4.5 (telan Greyling 2005).

Horses who are more likely to complete a highly demanding endurance race (Tevis for example) are those with a BCS of 4.5-5.5 (Garlingouse & Burril 1997, Garlingouse & Burril 1999, Lawrence et al 1990 ) because they have the optimal % of fat (up to 75%) that is going to support energy use during long term low medium intensity exercise like the ride, we can determine that the optimum BCS for the horse is between 4.5 and 5.5 and needs to fluctuate through the year.

– El BMI: Following the thinking that the optimal BCS is found between 4.5 and 5.5, the optimal BMI for the horse is between 1.20 to 1.25.

– El CNS: Thinking that the optimal BCS is found between 4.5 and 5.5, the optimal CNS for the horse is between 1-2.

– El MCNS: Thinking that the optimal BCS is found between 4.5 and 5.5, the optimal MCNS for the horse is between 0,6-0,65.

5. Obesity and its consequences:

Now that we know the optimal values, we are going to be able to detect the most common basic problem horses living in captivity have - obesity1. This occurs when you have a chronic condition in which the daily energy intake exceeds daily needed energy2. In a long term situation the energetic metabolism is placed in an anabolic state and the horse derives glucose into the tissues where they accumulate in the form of fat deposits (increased leptin in the blood) causing weight gain and, therefore, increased BCS, the CNS and their quantitative indices:

– The increase in the BCS, along with hiperlipemia3 alter the cardiovascular system (hypertension linked to increased uric acid in blood, risk of cardiac workload and reduced athletic performance ...) (Bailey et al 2008, Johnson et al 2007b).

– The BCS increase causes an increase in joint impact and the force exerted on the tendons, increasing the risk of arthritis, osteoarthritis and tendonitis. In endurance races it has been shown that horses with a BCS> 5.5 have a higher risk of being disqualified for lameness (Garlingouse & Burril 1997, Garlingouse & Burril 1999, Lawrence et al 1990).

– The increase in BCS reduces athletic performance because it causes early onset of fatigue (Garlingouse & Burril 1997, Garlingouse & Burril 1999), in fact, 10% more weight, represents a 15% increase in oxygen consumption (Thornton et al 1987).

– A BCS> 6 and / or CNS> 4, increases by 10 times the risk of insulin resistance, hyperinsulinemia and laminitis or supercoriatitis (Bailey 2007, Bailey 2008, Carter 2008, Coffman 1983, Jeffcot 1986, Treiber 2007b, 2006c Treiber, 2007b Asplin .)

Acknowledgements:

This article would not have been possible without the help and support of Cristina Ruiz Alonso, Luca Gandini, Caroline Wang-Andresen, the AANHCP, all the researchers who want the best for the horse and all the clients who are committed to the welfare of their horses and who give me enough energy to keep studying and writing.

1 In the USA, 19% of the horses are very obese (8-9) and the 32% are obese (7) (Thatcher et al., 2007).2 The horse, needs 28x10³ exceeding Kcal/day (18-30) to increase it's weight by 1 kg(Carter et al 2008b).3 Hyperlipidemia is the presence of elevated levels of lipids in the blood due to a metabolic imbalance secondary to a sedentary lifestyle or various

diseases and can contribute to many forms of disease, especially cardiovascular ones.

Namibian desert feral horse (Image taken by Williem Vijoel, 2009)

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