RESOURCE

Development of a body condition scoring

system for nonhuman primates using
Macaca mulatta as a model
Karen J. Clingerman, MS, DVM1 & Laura Summers, DVM2

The nutritional status of individual monkeys in research projects is an important yet

sometimes overlooked variable that complicates the interpretation of research findings.
The authors offer a framework for scoring fatness and muscularity in a semiquantitative
manner without special equipment and in a way that could easily be accomplished during
a routine physical examination. Body condition scoring can be used to assess the health
of individual animals as well as determine nutritional adequacy within groups of animals.

Body condition scoring (BCS) is a subjective, semi- nutritional support had the classification of cachectic
quantitative method of assessing body fat and muscle1. (BCS 1) or underweight (BCS 2) using a BCS scale of
Scoring of body condition assesses overall health, 1–5 (refs. 4, 5). Overweight or obese cats (BCS of 5 or 6,
nutrition, and performance in a wide variety of species respectively, on a scale of 1–6) were found to be more
including sheep, cattle, horses, dogs, cats, and mice1–12, likely to develop diabetes mellitus, lameness, and nonal-
and can readily be incorporated into a routine physical lergic skin disease. Underweight cats (cachectic or lean,
examination. BCS is generally independent of weight BCS of 1 or 2, respectively, on a scale of 1–6) were more
or frame size, and can provide additional animal health likely to have diarrhea9. In a research setting, the use of
information1,8. a 1–5 BCS scale for mice can aid in the determination of
Body condition scoring typically employs a 1–5, 1–6, experimental endpoints, with euthanasia recommended
or 1–9 scale, with mid-range values representing more for those animals having a BCS of 2 or 1 (thin or ema-
optimum body condition, lower values representing ciated). The scoring system is useful in mice in which
lean or emaciated conditions, and higher values repre- weight loss may be masked by organomegaly, a grow-
senting excessive body fat. Regardless of the scale used, ing tumor, or pregnancy3. BCS is an important part of
some assessments will always fall between two scores, dairy herd management and is used to make decisions
but for all practical purposes half-scores are sufficient8. regarding future feeding, breeding, and health manage-
Relative to most physical examination techniques, there ment. On a 1–5 scale, with 1 being very thin with no fat
is a learned art to assessing body condition. However, reserves and 5 being severely overconditioned, optimal
most protocols are easy to learn, especially when the scores are 3.5–4.0 at dry off and calving, and 2.5–3.0 at
scale is well described. peak lactation, with no cows changing by more than
Body condition scoring can be useful in making rec- one condition score over any lactation period11,12.
ommendations pertaining to nutrition or in assessing
the health status of an individual animal. BCS can also OTHER MEASURES OF BODY COMPOSITION
be a useful guide to the nutritional adequacy of an ani- Body composition may be assessed by morphometric
mal or group of animals and reflects the consequences data such as crown-rump or crown-heel length, arm
of food and nutrient intake during the previous weeks circumference, waist circumference, skin-fold thick-
or months1. Extremes in BCS may correlate with, or ness, and body weight. A body mass index can be cal-
be predictive of, certain disease conditions. Dogs and culated using crown-rump or crown-heel length and
cats seen at the University of Pennsylvania that required body weight measures. Imaging techniques such as

1The Scripps Research Institute, Department of Animal Resources, MB-18, 10550 N. Torrey Pines Road, La Jolla, CA 92037. 2California
National Primate Research Center, University of California, Davis, 1 Shields Ave., Davis, CA 95616. Correspondence should be addressed
to K.J.C. (karenc@scripps.edu).

LAB ANIMAL Volume 34, No. 5 | MAY 2005 31

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dual-energy x-ray absorptiometry (DEXA) to measure wing and gluteal surface of the body of the ilium will
specific body compartments such as fat and lean body feel concave because there is no muscle mass overly-
mass, and ultrasound to measure abdominal fat thick- ing the bony structures. The contours of the sacrum
ness, have also been used to assess body composition13– and ischium are easily palpable in thin to emaciated
16. Unlike BCS, these measures require additional tools animals. In overweight or obese animals, the borders
and imaging equipment. BCS can be a useful adjunct to of the wings of the ilium will be obscured and identifi-
these measures or provide a way to assess body compo- able only with deep palpation. The sacral region will
sition without additional tools or equipment. be rounded and soft, with bony structures difficult to
identify.
THE USE OF BCS IN NONHUMAN PRIMATES Visually assess the ischial callosities and rectal area.
This paper provides a well-described scoring system In thin to emaciated animals the ischial callosities may
to evaluate body condition in nonhuman primates be more prominent, while the anus is recessed into
(NHPs) based on similar systems that have been used the bony hollow between the callosities. In optimum
in other species. The BCS system provided (Table 1) to obese animals, no bony hollow is evident between
uses a 1–5 scale including half-scores with detailed the callosities and the anus is at or near the level of the
descriptions of each score. The scale design involves a ischial callosities.
one-page format with illustrations. A ‘stylized’ rhesus
monkey (Macaca mulatta) is used to depict the promi- Palpation of spine
nence of bony structures and the amount of muscle and Palpate over the lumbar and thoracic spine. Assess
fat that one palpates when assessing body condition, the prominence of spinous processes, presence of
with the caveat that an animal may not visually appear subcutaneous fat layer, and epaxial musculature. The
as drawn because of the presence of the haircoat. The spinous processes are easily palpable in thin to ema-
one-page summary provides a concise yet descriptive ciated animals. These animals also tend to have little
training tool for others who wish to adopt this system to no muscle mass, which makes the processes more
to evaluate nonhuman primates. pronounced than they would be when evaluating an
The physical examination can readily incorporate optimum or obese animal. Transverse vertebral pro-
the assessment of body condition. Animal care staff cesses in the lumbar area are also easily palpable in thin
can be trained to score animals, providing them with to emaciated animals. For animals in optimum con-
additional skills and expanding their role in promoting dition, the epaxial musculature will be well developed
animal well-being. The use of this BCS system can help and a subcutaneous fat layer will be present giving the
veterinarians make recommendations to investigators area over the spine a firm, rounded feel. Spinous pro-
regarding nutrition, endpoints, or additional diagnos- cesses can be distinguished on palpation but are not
tics. prominent whereas transverse vertebral processes may
Assessment of body condition in NHPs should be only be identified with firm palpation. Obese animals
conducted by palpation of an immobilized animal. will typically have well developed musculature and an
There should be no attempt to visually score nonimmo- abundant subcutaneous fat layer. On palpation, these
bilized animals, because haircoat and activity may make areas will feel rounded and soft. Bony structures may
visualization of bony prominences and muscle mass only be identifiable with deep palpation.
difficult if not impossible. For more reliable scoring, it
is helpful to develop a consistent routine for the evalu- Palpation of thorax
ation of each animal. Different individuals may choose Palpate over the rib cage and scapulae. Assess the prom-
different routines, but each routine should incorporate inence of the ribs and the presence of subcutaneous fat.
palpation of the following key elements: Palpate the scapulae for prominence, muscle mass, and
• Hips/Pelvis (ilium, sacrum, ischium) subcutaneous fat. The thorax is an optimal area to assess
• Spine (thoracic and lumbar) the subcutaneous fat layer, since there is normally little
• Thorax (ribs and scapula) muscle overlying the ribs. Any smoothing or obscuring
• Muscle mass (epaxials, gluteals, deltoids) of rib contours is predominantly due to the presence of
• Subcutaneous fat a subcutaneous fat layer.
• Fat deposits (abdominal, inguinal, axillary)
Palpation of muscle mass
Palpation of hips/pelvis It is best to assess muscle mass in association with
Palpate over the wings of the ilium, sacrum, and the palpation of the bony prominences (hips, spine,
ischium. Assess their prominence, presence of sub- scapulae). In these areas muscle mass or lack thereof
cutaneous fat layer, and muscle mass. The contours contributes to the degree of prominence. Additional
of the wings are easily palpable in thin to emaciated muscle masses that may be evaluated include the
animals. In animals with little to no muscle mass, the quadriceps, hamstrings, biceps, or triceps although

32 Volume 34, No. 5 | MAY 2005 www.labanimal.com

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TABLE 1 | Body condition scoring system for nonhuman primates. Stylized drawings of ambulating animals
and animals in right lateral recumbency attempt to visually depict bony prominences, muscle, and fat that
are palpated when scoring animals. Note that animals may not actually appear as drawn because of the
presence of the haircoat.
Ambulating Right lateral viewed
from back

EMACIATED – Very prominent hip bones (easily palpable and

likely visible), prominent facial bones, spinous processes, and
1 ribs. Minimal to no muscle mass is palpable over ilium or ischium.
Anus may be recessed between ischial callosities. Body is very
angular, no subcutaneous fat layer to smooth out prominences.

VERY THIN – Hips, spinous processes, and ribs are prominent.

Facial bones may be prominent. There is very little muscle present
1.5 over the hips and back. Anus may be recessed between ischial
callosities. Body is angular, no subcutaneous fat to smooth out
prominences.

THIN – Very minimal fat reserves, prominent hip bones and

spinous processes. Hips, spinous processes, and ribs are easily
2
palpable with only a small amount of muscle mass over hips and
lumbar region

LEAN – Overlying muscle gives hips and spine a more firm feel.
Hip bones and spinous processes are readily palpable, but not
2.5
prominent. Body is less angular because there is a thin layer of
subcutaneous fat.

OPTIMUM – Hip bones, ribs, and spinous processes are palpable

with gentle pressure but generally not visible. Well-developed
3
muscle mass and subcutaneous fat layer gives spine and hips
smooth but firm feel. No abdominal, axillary, or inguinal fat pads.

SLIGHTLY OVERWEIGHT – Hip bones and spinous processes

palpable with firm pressure but are not visible. Bony prominences
3.5
smooth. Rib contours are smooth and only palpable with firm
pressure. Small abdominal fat pad may be present.

HEAVY – Bony contours are smooth and less well defined. Hip
bones, spinous processes, and ribs may be difficult to palpate
4 because of more abundant subcutaneous fat layer. May have
fat deposits starting to accumulate in axillary, inguinal, or
abdominal areas.

OBESE – This animal will often have prominent fat pads in

the inguinal, axillary, or abdominal region. Abdomen will be
4.5 pendulous when animal is sitting or ambulating. Hip bones and
spinous processes difficult to palpate. Bony contours smooth and
poorly defined.

GROSSLY OBESE – Obvious, large fat deposits in the abdominal,

inguinal and axillary regions. Abdominal palpation is very
5 difficult due to large amount of mesenteric fat. Pronounced fat
deposits may alter posture/ambulation. Hip bones, rib contours,
and spinous processes only palpable with deep palpation.

LAB ANIMAL Volume 34, No. 5 | MAY 2005 33

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while having minimal subcutaneous fat, will tend to

have some mesenteric fat that will make the individual
bowel loops less prominent. In lean animals, there is a
thin layer of subcutaneous fat and the abdomen typi-
cally has adequate mesenteric fat, giving the abdomen a
more ‘doughy’ feel. Abdominal palpation of obese ani-
mals can be very difficult. The mesenteric fat deposits
may make the abdominal wall taut and obscure the
borders of internal structures. The abdominal fat pad
FIGURE 1 | Method of scoring an animal in lateral recumbency. is soft and pendulous, lying just outside of the body wall
and can extend from the xyphoid to the pubis.

evaluating muscle loss over long bones may be mis- POSITIONING AND EVALUATING THE ANIMAL
leading, because the muscle atrophy may be the result For consistency, it may be best to place any animals
of a primary condition (such as osteoarthritis) and evaluated in the same position every time. However,
may not be indicative of nutritional status. with practice it is possible to score animals in either
lateral or sternal recumbency.
Palpation of subcutaneous fat and fat deposits One technique is to place the animal in lateral recum-
One can palpate the subcutaneous fat layer over all bency (Fig. 1), with the animal’s head opposite or
locations described earlier. Presence of a subcutane- angled away from the evaluator. If the animal is in right
ous fat layer will tend to smooth out or obscure bony lateral recumbency, use the right hand to palpate over
prominences and contours. Fat will often accumulate the shoulder and spine, ilium, sacrum, and ischium
or form deposits in overweight to obese animals. The while the left hand palpates over the ribs and across the
first area for fat to accumulate or deposit is typically in abdomen. If the animal is in left lateral recumbency,
the abdominal fat pad. Other areas include the inguinal, use the left hand to palpate over the shoulder and spine,
axillary, or cervical region. ilium, sacrum, and ischium while the right hand pal-
pates over the ribs and across the abdomen.
Other areas When placing the animal in sternal recumbency
Head. In very thin to emaciated animals, the facial (Fig. 2), keep the animal as straight as possible, head away
bones (zygomatic arch, orbital bones) may be promi- from the evaluator with the knees flexed on either side of
nent. It is important to distinguish the ‘sunken-eyed’ the body. The evaluator should place his or her hands on
look in emaciation from possible dehydration. This each side of the thorax with the thumbs over the spine
appearance may not be as consistent, but, if present, and the fingers extended down across the ribs and run the
can aid in a body condition determination. hands down the length of the body and over the hips.

Abdomen. A deep abdominal palpation can provide SCORING THE ANIMAL

additional information with regard to body fat. In After the initial evaluation, the evaluator should be able
general, as the BCS of an animal increases it becomes to determine a tentative score for the animal based on
more difficult to localize individual structures within the descriptive criteria and scale (Table 1). Certain areas
the abdomen. Very thin or emaciated animals gener- may need to be reevaluated with the tentative score in
ally have little mesenteric fat. The decreased amount mind to reaffirm the criteria for that particular score.
of mesenteric fat deposits in these animals makes indi- It may be necessary to reposition the animal to bet-
vidual bowel loops readily palpable. Thin animals, ter evaluate certain anatomic sites, particularly if the
animal is in sternal recumbency. Other areas may be
assessed depending on the tentative score. For exam-
ple, a tentative score of 2.0 for an animal may prompt
a reexamination of the wing and body of the ilium for
evaluation of muscle mass or deep abdominal palpation
to evaluate mesenteric fat. The appearance of the peri-
anal region should also be a matter for consideration. In
another example, a tentative score of 4.0 for an animal
may prompt a reevaluation of the abdominal, axillary,
or inguinal regions for fat accumulation or deposits.
Once a score is determined, it should become part of
the physical examination data. Because the scoring sys-
FIGURE 2 | Method of scoring an animal in sternal recumbency. tem represents discrete values on a continuum of possible

34 Volume 34, No. 5 | MAY 2005 www.labanimal.com

 RESOURCE

body conditions, there may be times when it is difficult hips and spine, the ‘muscle’ score may be a 2.0. This is just
to settle on one score. A decision-making process should one recommended way to use the BCS for animals that
exist for determining a default score for animals that have do not readily fall within the described scale. Evaluators
features placing them between two defined scores. The who employ such a dual scoring system should describe
individuals working at a particular institution or with a it, indicating which score represents which aspect (i.e.,
particular model can define how to determine the default “muscle 2.0/5.0” and “fat 4.5/5.0”).
score. Since the BCS may be used to make recommenda-
tions pertaining to the animals’ care or use, consistency in CONCLUSIONS
determining the default score is particularly important. A wide variety of studies that use NHPs have the potential
The recommendation is to use the score that is most rep- to affect body condition. For example, animals may have
resentative. For example, if an animal is between a score of their food restricted as part of a training or operant-con-
2.0 and 2.5 but does not have a majority of characteristics ditioning protocol. A program for monitoring animals
associated with a 2.5 score, then the animal’s score is a 2.0. is an essential part of experimental protocols involv-
Conversely, if an animal is between a score of 2.0 and 2.5 ing food restriction17–19. Careful monitoring is crucial
and has a majority of characteristics associated with a 2.5 to ensure that food-restricted animals do not become
score, then the animal’s score is a 2.5. If it is helpful, the emaciated19. Adjustments of the restriction protocol or
evaluator can make a note next to the entry indicating that removing animals either temporarily or permanently
the animal is between the two scores or approaching the from food restriction are sometimes necessary17–19. BCS
higher score. The scale used should appear in the record criteria can be used as part of a monitoring program to
as in a score of 2.0 out of 5.0 (2.0/5.0), so that where the aid in this decision-making process. Another example
animal falls on the scale is more apparent to someone is animal models of potentially debilitating diseases.
reading the examination record. Animals infected with simian immunodeficiency virus
(SIV) may experience a decline in body condition. It has
SCORING A WIDE VARIETY OF ANIMALS been demonstrated that SIV infected juvenile rhesus
The BCS system as described can be applied to almost macaques exhibit changes in body composition depend-
any animal regardless of age or gender. Interpretation ing on the phase of infection. A progressive loss of fat is
of the significance of the BCS should be in light of the followed by a loss in lean body mass and then a marked
animal’s current age or reproductive status. For example, wasting in the terminal phases of the illness16. In a colony
juvenile animals tend to be lean or lanky, often scoring management situation, body condition assessment can
a 2.0 or 2.5. An animal that has just undergone a growth be used to make nutritional recommendations such as,
spurt may be evaluated as thin, scoring a 2.0, whereas nutritional supplementation for thin or emaciated ani-
one whose growth has stabilized may be lean, as muscle mals, or calorie restriction for overweight or obese ani-
mass catches up with previous bone growth. In another mals. Aging rhesus monkeys may develop spontaneous
example, a pregnant female may score a 3.5 or 4.0 as she obesity and diabetes. Dietary management to maintain
accumulates fat during pregnancy. Infants are similar to animals in a more lean body condition has been effective
juvenile animals in that it would be unusual to see an in increasing insulin sensitivity20,21. Classifying an ani-
overweight or obese animal. Ideally, an infant should mal at either extreme of the BCS spectrum may prompt
have an adequate subcutaneous fat layer that smooths additional diagnostics. Examples include evaluation of
bony prominences, and good muscle development. serum chemistry, complete blood count, and urinalysis
Healthy infants may typically score between 2.5 and 3.0. to check for systemic disease in a thin or emaciated ani-
The age group that may be the exception to routine mal or diabetes in an obese animal.
application of the scoring system is the geriatric animal. We have found the BCS system to be a useful adjunct
In many cases the scoring system as described can be use- to the physical examination. We routinely use the body
ful in describing geriatric animals. However, some ani- condition information to make nutritional recommenda-
mals in this age group may have incongruities between tions for NHPs. In particular, we are able to make nutri-
fat and muscle. For example, a geriatric animal may tional recommendations for animals before they reach
have a large abdominal fat pad but little muscle over the the extremes of body condition in an effort to return the
hips and spine. This particular animal may have mus- animals to a more optimum condition and to maintain
cle atrophy, which has resulted from decreased activity them within normal limits as representative research sub-
due to arthritis. The inactivity may have contributed in jects. BCS is also a useful monitoring tool, particularly
part to the animal’s obesity. There is no one score in the for animals under experimental protocols in which the
described scale that could be used for this scenario. In animals’ food intake may be altered or impaired. We hope
this case, it may be better to use two scores, one to repre- that, provided with a well-described BCS system, others
sent the ‘fat’ and one to represent the ‘muscle’. This par- can adopt this system and use it for monitoring of ani-
ticular animal, with a large abdominal fat pad, may score mals and to make recommendations regarding nutrition,
a 4.5 for ‘fat’. Because the animal has little muscle over the diagnostics, and experimental endpoints.

LAB ANIMAL Volume 34, No. 5 | MAY 2005 35

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COMPETING INTERESTS STATEMENT

The authors declare that they have no competing financial
interests.

Received 9 February 2005; accepted 4 April 2005.

Published online at http://www.labanimal.com
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