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Vitamins and Trace Minerals
Some Observations on the Dietary Vitamin D Requirement
of Weanling Pups1
R. D. KEALY,2 D. F. LAWLER AND K. L. MONTI
Ralston Purina Company, St. Louis, MO 63164
ABSTRACT A study was conducted to test the hy
pothesis that growing dogs do not require supplemen
tation with cholecalciferol (vitamin D-3) in a nonpurifled
extruded diet. Twenty-eight weanling pups from four
litters of English pointers and two litters of German
Shepherd dogs were allotted equally to two groups by
gender and weight. Dogs were raised in indoor-outdoor
kennel runs for the 102-wk evaluation. One group was
fed a diet that contained no added vitamin D while the
other group was fed the same diet to which had been
added 60.5 MScholecalciferol/kg diet. Both diets con
tained ~1.4% calcium and 1.0% phosphorus. Growth
as measured by body weight and length, serum calcium,
phosphorus and alkaline phosphatase and urine hy-
droxyproline were not significantly different (P > 0.05)
between the two treatment groups. There was no re
lationship between dietary treatment and nutritional
secondary hyperparathyroidism (NSH), rickets or other
skeletal abnormalities. The data support the concept
that addition of vitamin D to typical commercial dog
foods for purposes of prevention or amelioration of
rickets, NSH or other skeletal diseases is unnec
essary. J. Nutr. 121: S66-S69, 1991.
INDEXING KEY WORDS:
•symposium •dogs •uitamin D
Vitamin D rickets has been produced experimen
tally in the dog (1-5). Generally, there was an accom
panying deficiency in dietary calcium and/or phos
phorus, or the diets were imbalanced with respect to
calcium/phosphorus ratio (where percent calcium in
the diet was less than percent phosphorus). Vitamin-
D-deficiency rickets has also been reported in dogs
fed a diet reported to be adequate in calcium and
phosphorus (6). In most studies, the amount of ultra
violet light provided was not reported (1-5).
It has been suggested that the dog may not possess
the mechanisms for vitamin D synthesis in the skin
(7).In one study, rickets did not occur when 6-wk-old
pups were housed in total darkness for 8 wk while fed
nonpurified diets without added vitamin D (R. D.
0022-3166/91 $3.00 ©1991 American Institute of Nutrition.
Kealy, unpublished data). The results of another study
indicated that rickets in dogs cannot be prevented or
treated by ultraviolet radiation (6).
Nevertheless, the need for 1,25-dihydroxycholecal-
ciferol for intestinal calcium absorption in the dog has
been demonstrated (4).Also, 1,25-dihydroxycholecal
ciferol is produced by the kidney of the dog, as in other
mammalian species (8).
The purpose of this study was to investigate
whether pups of large breeds of dogs fed a nonpurified
diet for 2 y to which no vitamin D was added devel
oped rickets when housed in indoor/outdoor runs.
METHODS AND MATERIALS
Four litters of English pointers and two litters of
German Shepherd dogs were allotted to two groups
by gender and body weight, with 14dogs per treatment
group. Pups were weaned at ~6 wk of age. They re
ceived routine vaccinations and antiparasite treat
ments. All dogs were housed in indoor/outdoor kennel
runs (~2 X 19 m) with concrete floors. Food and water
were provided ad libitum.
Dry extruded nonpurified diets were prepared for
the study using a vitamin-mineral supplement (with
out added cholecalciferol) plus corn, corn gluten meal,
soybean meal, meat and bone meal, rice, animal fat,
corn gluten feed, calcium chloride, dicalcium phos
phate, sodium chloride and L-lysine hydrochloride. For
the treatment group of dogs, the base diet was sup
plemented with 60.5 Mgsynthetic cholecalciferol/kg
diet.3
1Presented as part of the Waltham International Symposium on
Nutrition of Small Companion Animals, at University of California,
Davis, CA 95616, on September 4-8, 1990. Guest editors for the
symposium were James G. Morris, D'Ann C. Finley and Quinton
R. Rogers.
2To whom correspondence should be addressed: Ralston Purina
Company, St. Louis, MO 63164.
3Hoffman-La Roche, Nutley, NJ.
S66
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DIETARY VITAMIN D REQUIREMENT OF DOGS S67
TABLE 1
Average composition oÃ-dry, extruded diets
{average of laboratory analyses?
Added cholecalcifol
diet)
60.5
n (samplesize)Moisture,
g/100gProtein,g/300gFat,g/100gCalcium,
g/IOOgPhosphorus,g/300 g158.527.012.11.351.00198.227.011.91.441.03
1The vitamin premix used in both diets included retinyl pal-
mitate, riboflavin, vitamin E, biotin, vitamin B-12, calcium panto-
thenate, folie acid, choline chloride, menadione sodium bisulfite
complex, niacin, pyridoxine hydrochloride and thiamine hydro-
chloride. Trace minerals included cobalt carbonate, copper oxide,
ferrous sulfate, manganese oxide, calcium iodate and zinc oxide.
Nutrient levels met or exceeded standards established by The Na
tional Research Council (11).
Multiple batches of each diet were produced. Rep
resentative samples from each batch were analyzed
using methods of the Association of Official Analytical
Chemists (Table 1). Dietary calcium contents were
determined by atomic-absorption spectrophotometry,
and phosphorus was determined by colorimetry. Vi
tamin D analyses of diets were not obtained.
Physical examinations were conducted on all dogs.
Blood was collected from all dogs at 11, 16, 30, 54, 80
and 108 wk of age. Blood was collected by jugular ven-
apuncture, allowed to clot and centrifuged at 1325
X g for 12 min. Urine was collected by catheterization
using aseptic techniques at all intervals except 80 and
108 wk of age. Analyses for serum calcium, phospho
rus, alkaline phosphatase (EC 3.1.3.1) and urine cre-
atinine were conducted on an autoanalyzer. Analysis
of urine for hydroxyproline was done by a previously
described procedure (9). The body weight and length
of the dogs were measured at intervals. Food con
sumption was measured by pen.
Development of the pelvis, hip joints and femurs
was examined by radiography at 30, 42, 54, 80 and
108 wk of age. Data were analyzed by analyses of vari
ance (10). Mean results plotted include all data avail
able at the time measurements were taken.
RESULTS
With one exception, all dogs remained healthy. One
German Shepherd dog was removed from the study
because of symptomatic hip dysplasia. This dog had
been fed the nonvitamin-D-supplemented diet. Two
other English pointers, one per treatment, were re
moved due to space/behavioral problems.
Regardless of breed, the dogs from the two treat
ments exhibited similar body weight, body length and
daily food consumption (Table 2). The weight trends
of dogs on both treatments were typical of their re
spective breeds (Fig. 1).
Serum calcium, serum phosphorus and serum al
kaline phosphatase were analyzed statistically to detect
differences between treatment groups in either or both
breeds studied. Over time, no significant differences
attributable to treatment were observed (P > 0.05).
Serum phosphorus and serum alkaline phosphatase
significantly decreased with time in each group (P
< 0.05) (Fig. 2). All blood serum values were within
reference intervals.
Urine hydroxyproline was expressed as hydroxy-
proline/creatinine ratio to adjust for variation in urine
output. Urine hydroxyprolinexreatinine did not differ
significantly (P > 0.05) by treatment (Fig. 1). However,
the ratio declined markedly during the first year of
growth.
Observations from radiographs of pelvis, hip joints
and femurs did not reveal any apparent dietary treat
ment effects.
DISCUSSION
The results of this study suggest that large breed
dogs housed in indoor-outdoor kennel runs do not re
quire added cholecalciferol when nonpurified diets are
fed during the first 2 y of life. The breeds in this study
were selected because developmental bone disorders
TABLE 2
Body weight, body length and food consumption of dogs fed
a diet with or without added cholecalciferol
from 6 wk until 2 y of age
Added cholecalciferol
(/ig/kg diet)
060.5
German Shepherddogs:nWeight,
kgLength,
cm2Food
intake/d,kgEnglish
pointers:nWeight,
kgLength,
cm2Food
intake/d, kg431.
7 ±1.2'113.7
±1.30.63824.5
±0.9091.6
±0.970.58530.2
±1.1111.0+1.10.64824.9
±0.8893.2
±0.940.58
1Values are means ±SEM.
2Body length was only taken until 54 wk of age.
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S68 KEALY, LAWLER AND MONTI
BODY
WEIGHT
(kg)
32
28
24
20
16
12
8
6 11 16 30 54
Weeks of Age IM
25
20
BODY
WEIGHT
(kg)
+ VitammD
0 Vitamin D
6 11 16 30 54
Weeks oÃ-Age
80 108
FIGURE 1 Weight change for eight English pointers
(upper panel) and four or five German Shepherd (lower panel)
dogs fed diets with or without added cholecalciferol. Values
are means ±SEM.
occur more frequently in the larger breeds of dogs
compared with many of the smaller breeds. The single
case of symptomatic hip dysplasia occurred in a dog
fed the nonvitamin-D-supplemented diet and was ap
parently unrelated to treatment.
Dogs fed diets with and without supplemental cho
lecalciferol did not differ in growth rate, food con
sumption or selected serum or urine values. Likewise,
there were no differences between the two groups in
the results of physical examination and radiographie
evaluation. The lack of response to added cholecalcif
erol was probably due to adequate levels of calcium
and phosphorus in the base diet and possible synthesis
of vitamin D. However, it is possible that some vita
min D could have been present in one or more of the
ingredients of the basal diet. It has been suggested that
dogs may only require additional vitamin D when
there is a mineral deficiency or imbalance in the diet
(11). However, one study reported canine rickets in
diets containing 1.2% calcium and 1% phosphorus (6).
It has been reported that carnivores may not possess
the mechanism of vitamin D synthesis in the skin (7).
Another study demonstrated that dogs fed a nonpu-
rified diet without added vitamin D under conditions
of total darkness did not exhibit bone defects (Kealy,
unpublished data). Previous reports did not record the
ultraviolet light status of the environment. It is not
u
u
SERUM
CALCIUM 2.7
(mmol L)
2.6
2.5
24
13
.Vitamin D
0 Vltimin D
5 10 24 36 48
Weeks of Test
74 102
SERUM
PHOSPHORUS
(mmol/L)
SERUM
ALKALINE
PHOSPHATASE
(p.kat/L)
3.00
2.50
24»
1-50
too
2.5
20
U
10
0.5
0.0
5 10 24 36 48
WMkl of Tut
74 102
5 10 24 36 48
Weeks of Test 102
URINE
HYDROXYPROLINE
80
70
00
n
40
11 16 42 M
Week»of Trat
FIGURE 2 Serum calcium (a)phosphorus (b)and alkaline
phosphatase (c)values and urine hydroxyprolinexreatinine
ratios (d) for dogs fed diets with or without added cholecal
ciferol (vitamin D). Urine hydroxyproline was corrected
against urine creatinine in the same urine sample (/ig hy-
droxyproline/mg creatinine). Values are means ±SEM for
12 or 13 dogs.
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DIETARY VITAMIN D REQUIREMENT OF DOGS S69
understood at this time how the dog acquires sufficient
vitamin D for metabolism. Part of the explanation ap
pears to be related to a very low vitamin D requirement
in the presence of adequate dietary mineral balance.
The observation that large breed dogs raised in in
door-outdoor kennel runs do not require added vita
min D is important because supplemental vitamin D,
calcium and phosphorus are frequently recommended
and used at levels in excess of the nutritional require
ments of the dog, presumably to enhance bone growth
and development. The data reported here suggest that
supplementation of nonpurified, commercially avail
able dog foods with vitamin D may not be necessary.
LITERATURE CITED
1. CAMPBELL,J. R. (1960) Calcium and phosphorus imbalance in
growing dogs. Vet. Ree. 11: 1153-1157.
2. CAMPBELL,J. R. & DOUGLAS,T. A. (1965) The effect of low
calcium intake and vitamin D supplements on bone structure
in young growing dogs. Br. /. Nutr. 19: 339-350.
3. OLDHAM,S. B., MITNICK,S. A. & COBURN,J. W. (1980)
Intestinal and parathyroid calcium binding proteins in the dog.
/. Biol. Chem. 255: 5789-5794.
4. BRICKMAN,A. S., CHILUMULA,R. R., COBURN,J. W., PASSORO,
E. P., JOWSEY,J. & NORMAN,A. W. (1973) Biologic action of
1,25-dihydroxy-vitamin D3 in the rachitic dog. Endocrinology
92:728-734.
5. KELLY,P. J. (1967) Bone remodeling in puppies with experi
mental rickets. /. Lab. Clin. Med. 70: 94-105.
6. HAZEWINKEL,H. A. W., How, K. L., BOSCH,R., GOEDEGEBUURE,
S. A. & VOORHOUT,G. (1987) Inadequate photosynthesis of
vitamin D in dogs. In: Nutrition, Malnutrition and Dietetics in
the Dog and Cat, (Edney, A. T. B., ed.), Waltham Center for Pet
Nutrition, Melton Mobray, Leicestershire, England, pp. 66-80.
7. WHEATLEY,V. R. & SHER,D. W. (1971) Studies of lipids of dog
skin. /. Invest. Dematol. 36: 169-170.
8. MIDGET,R. J., SPIELVOGEL,A. M., COBURN,J. W. & NORMAN,
A. W. (1973) Studies of calciferol metabolism. VI. The renal
production of the biological active form of vitamin D, 1,25-
dihydroxy cholecalciferol; species, tissue and subcellular distri
bution. /. CJin. Endocrino!. Metab. 36: 1153-1161.
9. KIVIRIKKO,K. I., LAITINEU,O. & PROCKOP,D. J. (1967)
Modifications of a specific assay for hydroxyproline in urine.
Anal. Biochem. 19: 249-255.
10. SEARLE,S.R. (1971) LinearModels. JohnWiley andSons, New
York, NY.
11. NATIONALRESEARCHCOUNCIL(1985) Nutrient Requirements
of Dogs. National Academy Press, Washington, DC.
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