Small Animal Clinical Nutrition
Small Animal Clinical Nutrition
Small Animal Clinical Nutrition
Chapter
Old dogs, like old shoes, are comfortable. They might be a bit out of shape
and a little worn around the edges, but they fit well.
Bonnie Wilcox Old Dogs, Old Friends
INTRODUCTION
For a number of reasons, the mature segment (six to eight years
of age and older) of the pet dog population is growing. More
than 35% of dogs in the U.S. are at least seven years old and, in
Europe, the number of dogs older than seven years increased by
about 50% from 1983 to 1995 (Lund et al, 1999; Kraft, 1998).
In this chapter, mature dogs include dogs that are middle aged
and older. In people, middle age is often considered as being
approximately the third quarter of the average lifespan.
Aging increases vulnerability (Mosier, 1989; Hayflick, 1994).
Aging isnt a disease; however, morbidity increases with age
because normal changes make animals more vulnerable to diseases (Hayflick, 1994). The influence of nutrition on vulnerability to chronic or acute disease is difficult to evaluate, and has
not been explored thoroughly in dogs. In people and companion animals, nutrition may be one of the more important
aspects of geriatric care because delay or elimination of the two
or three leading causes of death would profoundly affect life
expectancy (Hayflick, 1994a). In dogs, the three leading nonaccidental causes of death are cancer, kidney disease and heart
disease (Bronson, 1982; MacDougall and Barker, 1984; MAF,
1991, 1998). Other diseases and disorders are also common
(Table 13-1). Moreover, older animals seldom suffer from a single disease and one problem may markedly influence the course
of another (Mosier, 1990).
The overall feeding goals for mature adult dogs are to opti-
274
the length of life of mature dogs through nutritional management. An important example is cognitive dysfunction (Chapter
35). Nutritional intervention in combination with mental stimulation can halt and even reverse its progression.
There is considerable interest in the potential benefits of pet
nutrition on the part of pet owners. In one survey, 51% of
respondents indicated that they were interested in learning
about clinical signs and treatments for older pets and 47% were
interested in pet nutrition (MAF, 2005).
PATIENT ASSESSMENT
History and Physical Examination
A thorough history should be taken and a physical examination
performed to identify potential areas of nutritional concern. All
of the considerations discussed for young adult dogs in Chapter
13 (i.e., breed, gender and health status) should be considered
Water
Mature dogs are more prone to dehydration due to possible
osmoregulatory disturbances, medications (diuretics) and
chronic renal disease, with compromised urine concentrating
ability. Therefore, continuous access to a fresh, clean water supply is very important and water intake should be routinely
monitored.
Energy
With increasing age, lean body mass decreases, subcutaneous
fat increases, basal metabolic rate gradually declines and body
temperature may decrease. As dogs age, they become slower
and less active, and their thyroid function may be impaired
(Siwak et al, 2000; Armstrong and Lund, 1996; Finke, 1991;
MacDougall and Barker, 1984; Mosier, 1990; Meyer, 1990;
Sheffy et al, 1985). All these changes result in a 12 to 13%
decrease in daily energy requirement by around seven years of
age (Chapter 13, Table 13-2) (Kienzle and Rainbird, 1991). For
mature dogs, a daily energy intake of 1.4 x resting energy
requirement (100 kcal [418 kJ] metabolizable energy/BWkg0.75)
is a good starting point (Leibetseder, 1989). This amount
should be modified if a dog tends to lose or gain weight when
fed at the recommended level. Very old dogs are often underweight and may have inadequate energy intake (Armstrong and
Lund, 1996; Kronfeld, 1991; Donoghue et al, 1991).
Underweight, very elderly people increase body weight when a
food of higher caloric density is provided (Olin et al, 1996).
Thus, it may be appropriate to feed a more energy-dense food
to very old dogs. Because of the potential for mature dogs to
have different energy needs, energy densities in foods recommended for this age group may vary from 3.0 to 4.0 kcal (12.6
to 16.7 kJ)/g dry matter (DM).
Fat
A relatively low fat intake helps prevent obesity in healthy
mature dogs. However, some dogs may need different foods at
seven years of age than they will at 13 years of age. Very old
dogs may have a tendency to lose weight (Armstrong and
Lund, 1996; Kronfeld et al, 1991). For these dogs, increasing
the fat content of the food increases energy intake, improves
palatability and improves protein efficiency (NRC, 1985;
Schaeffer et al, 1989).
Research in people has indicated that increased energy intake
can correct immunosenescence due to mild protein-energy
malnutrition (Morley, 1994). The general condition of elderly
people improved significantly by increasing the energy density
of the food (Olin et al, 1996). Thus, a good balance should be
275
Table 14-2. Key nutritional factors for foods for mature dogs.
Recommended food levels*
Normal weight and
Inactive/
body condition
obese prone
Water
Free access
Free access
Energy density (kcal ME/g)
3.0-4.0
3.0-3.5
Energy density (kJ ME/g)
12.5-16.7
12.5-14.6
Crude fat (%)
10-15
7-10
Crude fiber (%)**
2
10
Protein (%)
15-23
15-23
Phosphorus (%)
0.3-0.7
0.3-0.7
Sodium (%)
0.15-0.4
0.15-0.4
Chloride (%)
1.5 x Na
1.5 x Na
Antioxidants (amount/kg food)
Vitamin E (IU)
400
400
Vitamin C (mg)
100
100
Selenium (mg)
0.5-1.3
0.5-1.3
Food texture (VOHC Seal
Reduced
Reduced
of Acceptance)
plaque
plaque
accumulation
accumulation
Key: kcal = kilocalories, kJ = kilojoules, ME = metabolizable
energy, VOHC = Veterinary Oral Health Council Seal of
Acceptance (Chapter 47).
*All foods expressed on a dry matter basis unless otherwise
noted. If the caloric density of the food is different, the nutrient
content in the dry matter must be adapted accordingly (Chapter
1).
**Crude fiber measurements underestimate total dietary fiber
levels in food.
Factors
Fiber
Mature dogs are prone to develop constipation (Twedt, 1993),
which may justify increased fiber intake. Additionally, fiber
added to foods for obese-prone mature dogs dilutes calories.
Fiber also decreases postprandial glycemic effects in diabetic
dogs (Nelson, 1989). Very old dogs that tend to lose weight,
however, should be offered a food with increased caloric density. The recommended levels of crude fiber in foods intended for
mature dogs are at least 2% (DM).
Protein
Recommendations for protein intake in mature dogs are controversial, which parallels the debate in people (Pellet, 1990).
The decrease in lean body mass, seen with age, together with
alterations in protein synthesis and turnover have been the
basis for the argument that protein intake in mature dogs
should be higher than for younger adults (Grandjean and
Paragon, 1990; Kronfeld, 1983; Wannemacher and McCoy,
1966). In contrast, other investigators have recommended
reduced protein intake because of the increased prevalence of
276
Phosphorus
Some degree of clinical or subclinical renal disease is often present in mature dogs; as many as 25% of all dogs may be affected
(Oehlert and Oehlert, 1976; Rouse and Lewis, 1975; Shirota et
al, 1979; Leibetseder and Neufeld, 1991; Bloom, 1954; Crowell
and Finco, 1975; Mller-Peddinghaus and Trautwein, 1977).
Excessive phosphorus intake should therefore be avoided
(Finco et al, 1992). Researchers have observed that dogs with
advanced renal disease had slowed progression and reduced
severity of renal disease when phosphorus levels in foods were
decreased, thereby improving survival time (Brown et al, 1991;
Finco et al, 1992; Lopez-Hilker et al, 1990). The minimum
recommended DM allowance of phosphorus for foods for adult
dogs is 0.3% (NRC, 2006). Therefore, foods for mature dogs
should contain 0.3 to 0.7% DM phosphorus.
Antioxidants
The consequences of prolonged oxidative stress (i.e., free radical damage) to cell membranes, proteins and DNA contribute
to and/or exacerbate a wide variety of degenerative diseases
including those listed in Table 13-1. In addition to these diseases, cognitive dysfunction was shown to affect 28% of dogs
between 11 and 12 years of age and 68% of dogs 15 to 16 years
old. Cognitive dysfunction is responsive to certain combinations of antioxidants (Chapter 35).
The consequences of free radical damage to cells and tissues
have also been associated with the effects of aging. Although
aging is a complex, multifactorial process, one explanation for
many of the degenerative changes associated with aging is the
free radical theory of aging (Harman, 1956). This theory proposes that free radicals produce cell damage and that agedependent pathologic alterations may, at least in part, be the
cumulative result of these changes.
Many phenomena initiate free radical formation within the
body. Although environmental pollutants and radiation are
direct and indirect sources of free radicals, the primary source is
endogenous from normal oxidative metabolism. However, the
body defends itself against the effects of free radicals through a
complex network of protective antioxidant compounds.
Antioxidants protect biomolecules by scavenging free radical
compounds, minimizing free radical production and binding
metal ions that might increase the reactivity of poorly reactive
compounds. In addition, many antioxidants exhibit second
messenger regulatory function, cell cycle signaling and control
of gene expression (Chapter 7). Also, combinations of antioxidants are more effective in relieving oxidative stress than are
individual antioxidants.
Food Texture
Oral disease is the most common health problem in mature
dogs and may predispose affected patients to systemic complications (DeBowes et al, 1996). Both veterinary care and home
care are important in the treatment and prevention of periodontal disease. Foods designed to reduce the accumulation of dental
substrates (e.g., plaque) and help control gingivitis and malodor
are an important part of an oral home-care program for mature
dogs (Chapter 47). If the labels of such foods carry the
Veterinary Oral Health Council (VOHC) seal for plaque control, they have been successfully tested according to specific protocols and shown to be clinically effective in reducing accumulation of plaque. However, with older dogs, it is best if an adequate periodontal management program is in place (veterinarian/client/patient) so that there is sufficient periodontal health to
ensure that the patient can chew the product (Chapter 47).
FEEDING PLAN
Mature dogs are more prone to obesity, degenerative joint disease, cardiac disease, renal disease, cognitive dysfunction and
metabolic aberrations. They also are usually less active than
young adult dogs. The feeding plan should be based on potential risk factors and information attained in the assessment.
Because of the larger variation in health among mature dogs,
more attention should be paid to individual needs. Nutritional
surveillance is more important for mature dogs than for young
adult dogs; therefore, the number of veterinary assessments per
year should be increased. Goals remain the same as listed in the
introduction; however, each patient should be evaluated individually.
277
278
Table 14-3. Comparison of recommended levels of key nutritional factors for foods for mature adult dogs with levels in selected
commercial foods.*
Dry foods
Energy
density
(kcal/cup)**
Energy
density
(kcal ME/g)
Recommended levels
(normal body condition)
3.0-4.0
Hills Science Diet
363
4.0
Mature Adult 7+ Original
Hills Science Diet
273
3.8
Oral Care Adult
Iams Eukanuba
350
4.6
Medium Breed Senior
Medi-Cal Dental Formula
280
na
Nutro Natural Choice Senior 267
3.8
Purina ONE Senior
375
4.1
Protection Formula
Purina Pro Plan
408
4.2
Chicken & Rice Senior
Royal Canin MINI
378
4.3
Aging Care 27
Moist foods
Energy
Energy
density
density
(kcal/can)** (kcal ME/g)
Recommended levels
(normal body condition)
3.0-4.0
Hills Science Diet
164/5.8 oz.
Gourmet Beef
368/13 oz.
4.0
Entre Mature Adult 7+
Hills Science Diet
369/13 oz.
4.1
Gourmet Turkey
Entre Mature Adult 7+
Hills Science Diet
155/5.8 oz.
Savory Chicken
347/13 oz.
3.8
Entre Mature Adult 7+
Dry foods
Energy
Energy
density
density
(kcal/cup)** (kcal ME/g)
Recommended levels
(inactive/obese prone)
3.0-3.5
Hills Science Diet
295
3.3
Light Adult
Iams Eukanuba
275
4.2
Medium Breed
Weight Control
Iams Weight Control
328
4.2
Medi-Cal Weight
320
na
Control/Mature
Nutro Natural Choice Lite
244
3.4
Purina Pro Plan
337
3.7
Chicken & Rice
Weight Management
Royal Canin MINI
326
3.8
Weight Care 30
Moist foods
Energy
Energy
density
density
(kcal/can)** (kcal ME/g)
Recommended levels
(inactive/obese prone)
3.0-3.5
Hills Science Diet
322/13 oz.
3.4
Light Adult
Medi-Cal Weight
370/396 g
na
Control/Mature
Fat
(%)
Fiber
(%)
Protein
(%)
P
(%)
10-15
15.8
2
4.2
15-23
19.3
15.5
10.1
25.1
0.65
12.8
2.2
29.3
12.7
12.1
14.0
5.3
2.2
3.4
15.6
Na
(%)
VOHC
Se
plaque***
(mg/kg) (Yes/No)
Vit E
(IU/kg)
Vit C
(mg/kg)
400
700
100
271
0.5-1.3
0.41
No
0.24
564
175
0.62
Yes
0.95
0.40
236
83
na
No
19.7
23.1
32.3
0.9
1.21
1.12
0.4
0.27
0.30
na
275
1,012
na
99
na
na
0.49
0.99
No
No
No
2.3
30.4
1.14
0.44
na
na
na
No
17.4
1.7
29.3
0.71
0.33
717
326
0.22
No
Fat
(%)
Fiber
(%)
Protein
(%)
P
(%)
Na
(%)
Vit E
(IU/kg)
Vit C
(mg/kg)
10-15
15-23
400
100
0.5-1.3
14.4
1.6
18.8
0.52
0.16
316
na
0.70
No
12.8
2.1
19.4
0.62
0.17
426
na
0.83
No
13.1
1.6
18.4
0.57
0.16
520
na
0.82
No
Fat
(%)
Fiber
(%)
Protein
(%)
P
(%)
Na
(%)
Vit E
(IU/kg)
Vit C
(mg/kg)
7-10
8.8
10
14.6
15-23
24.5
400
586
100
276
0.5-1.3
0.45
No
10.5
1.9
21.3
0.76
0.50
206
42
0.34
No
12.5
8.5
2.8
4.0
22.2
19.5
0.85
0.8
0.37
0.2
103
na
44
na
0.35
na
No
No
7.2
10.2
4.4
2.7
16.7
30.5
1.22
1.06
0.33
0.27
161
503
67
na
0.44
0.33
No
No
12.0
6.2
32.6
0.82
0.33
652
326
0.16
No
Fat
(%)
Fiber
(%)
Protein
(%)
P
(%)
Na
(%)
Vit E
(IU/kg)
Vit C
(mg/kg)
7-10
8.6
10
9.7
15-23
19.5
400
385
100
na
0.5-1.3
0.78
No
10.0
5.5
21.5
na
na
na
No
0.3-0.7 0.15-0.4
0.58
0.18
0.3-0.7 0.15-0.4
0.3-0.7 0.15-0.4
0.58
0.23
0.3-0.7 0.15-0.4
0.51
0.31
0.6
0.3
VOHC
Se
plaque***
(mg/kg) (Yes/No)
VOHC
Se
plaque***
(mg/kg) (Yes/No)
VOHC
Se
plaque***
(mg/kg) (Yes/No)
Key: ME = metabolizable energy, na = information not published by manufacturer, Fiber = crude fiber, Se = selenium, P = phosphorus, Na =
sodium, VOHC = Veterinary Oral Health Council, na = information not available from manufacturer, g = grams.
*From manufacturers published information or calculated from manufacturers published as-fed values; all values are on a dry matter basis
unless otherwise stated.
**Energy density values are listed on an as fed basis and are useful for determining the amount to feed; cup = 8-oz. measuring cup. To convert
to kJ, multiply kcal by 4.184.
***An adequate periodontal management program should be in place (veterinarian/client/patient) to ensure that there is sufficient periodontal
health to enable the patient to chew these products.
The manufacturers of most of the foods listed for inactive/obese-prone dogs recommend these foods for young adults.
REASSESSMENT
Nutritional status for healthy mature dogs should be assessed at
least every six to 12 months. Immediate reassessment should
take place if clinical signs arise that indicate the current nutritional regimen is inappropriate or if the dogs needs change due
to altered use.
ENDNOTE
a. Zicker SC. Hills Pet Nutrition, Inc., Topeka, KS. U.S.
Marketing Research Summary: Omnibus Study on Aging
Pets. Data on file. November 2000.
REFERENCES
The references for Chapter 14 can be found at
www.markmorris.org.
279
CASE 14-1
Feeding a Mature Miniature Pinscher
Jacques Debraekeleer, DVM
Hills Science and Technology Center
Etten Leur, The Netherlands
Kathy L. Gross, PhD
Hills Science and Technology Center
Topeka, Kansas, USA
Patient Assessment
An eight-year-old intact male miniature pinscher was examined as part of a routine health maintenance program. The owners saw
a magazine article recently promoting preventive health programs for mature dogs. They realized that their dog was aging but had
not noticed any specific problems.
The dog weighed 4.5 kg and had an optimal body condition score (BCS 3/5). Physical examination was normal except for a
slightly enlarged prostate gland, mild periodontal disease and a grade II/VI holosystolic cardiac murmur loudest over the mitral
valve. Results of a complete blood count, serum biochemistry profile, urinalysis and ocular fundic examination were normal.
Thoracic radiographs were normal with no evidence of cardiomegaly or pulmonary disease.
280
Questions
1. What are the key nutritional factors that should be considered in this patient?
2. Outline a feeding plan (foods and feeding method) for this dog.
3. How should the owners concern about the reduction in appetite be addressed?
Progress Notes
The food was changed to a commercial moist specialty brand food formulated for mature dogs (Science Diet Mature Adult 7+
Caninea). The dog was fed three-fourths of a large can per day. The commercial jerky-type treats and ice cream were discontinued
and replaced with a dry treat formulated for mature dogs. The dog was given two treats per day. A thorough oral examination
including dental prophylaxis and polishing was recommended.
Endnote
a. Hills Pet Nutrition, Inc., Topeka, KS, USA.