J. Nutr.-2002-Dobenecker-1665S-7S

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Waltham International Symposium:Pet Nutrition Coming of Age

Influence of Calcium and Phosphorus Intake on the Apparent Digestibility

of These Minerals in Growing Dogs1,2

Britta Dobenecker3

Institute for Physiology, Physiological Chemistry and Animal Nutrition, Ludwig-Maximilians Universitat,Munich, Germany

EXPANDED ABSTRACT

KEY WORDS: symposium dogs developmental skeleton disease minerals digestibility

Skeletal diseases are often diagnosed in growing dogs, most

commonly in large and giant breeds. The connection betweenmistakes in feeding regime and disturbances of bone develop-ment has been illustrated by the negative effects of a lack incalcium (Ca4)4 intake (1) and the consequences of an over-supply of energy and/or Ca for skeletal health (14). Theinability of puppies to decrease the digestibility of Ca tocompensate for a threefold oversupply has already been shownby Hazewinkel and coworkers (3). In the literature there isonly limited information about the digestibility of Ca andphosphorus (P) in puppies with an insufficient intake of thoseminerals, especially regarding the ability to make optimumfeeding recommendations after a period of malnutrition ingrowing dogs.

MATERIALS AND METHODS

To determine and quantify the ability of growing dogs to alter theapparent digestibility (aD) of Ca and P at various degrees of over- andundersupply at different ages during growth, a feeding trial with 20healthy Beagles from three litters (10 m/10 f) was carried out fromweaning until 6 mo of age. Four groups were formed to carry out threetrials of approximately 6-wk duration each (42 to 49 d). The dogs ofeach group were housed together in a large kennel with access to anoutdoor area. A diet based on tripe, rice and cellulose and supple-mented individually with minerals and vitamins was fed (Table 1).

The amount of the basic ration was given based on the energy

requirement of the dogs (5) and the energy content in the diet (6).The intake of Ca, P and the other minerals and vitamins wasdetermined and balanced individually and exactly with the help of aspecial supplement for all groups: every single dog of each group gotan especially mixed mineral and vitamin supplement, which groupwas given according to actual body weight and age. Depending on thesources of Ca and P in the supplements were CaCO3, Ca-phosphateand Na-phosphate. All but the nutrients in question were supplied tomeet or exceed the requirements per kg body weight (5).

The course of trials was as follows (Table 1). The Ca intake wasadjusted to 15, 50, 100 (control), 150 and 300% of the requirement(the Ca and P content in the control diet at the beginning ofTrial 1 was approximately 11 g Ca and 8 g P/kg DM; and at the endof Trial 3 approximately 10 g Ca and 7 g P/kg DM). The P intake metthe requirements, that is, the Ca/P ratio was altered accordingly whenthe Ca intake was adjusted. After Trial 1 and without a break inbetween, the feeding of groups A to C was changed to Trial 2 diets,from oversupply to undersupply and vice versa. In both trials the fivedogs of the control group were fed according to the requirements(100%) (i.e., all nutrients met the requirements). After Trial 2 alldogs were changed to a 100% diet for another 6 wk (Trial 3). At theend of each feeding period a balance period of 7 d was carried out;thus there was a washout period of a minimum of 5 wk before thebalance period. During the balance period the dogs were housedseparately in cages that allowed sampling of feces and urine. The feceswere collected quantitatively, then weighed, lyophilized and groundfor further analysis. The Ca content was measured with flame emis-sion photometry (7) and the P content by photometry after acidhydrolysis (8). Body weight was determined every day before feeding.

Data are expressed as means SD. Means were compared byTukeys test to determine significant differences between the groups

(P

0.05 was considered a significant difference). The study wasapproved by the Regierung of Oberbayern, which is the properauthority according to German laws on animal welfare (Tierschutzge-setz).

RESULTS AND DISCUSSION

As intended, no impairment of bone health was evident: noclinical symptoms of disturbances of skeletal development

1 Presented as part of the Waltham International Symposium: Pet NutritionComing of Age held in Vancouver, Canada, August 67, 2001. This symposiumand the publication of symposium proceedings were sponsored by the WalthamCentre for Pet Nutrition. Guest editors for this supplement were James G. Morris,University of California, Davis, Ivan H. Burger, consultant to Mars UK Limited, CarlL. Keen, University of California, Davis, and DAnn Finley, University of California,Davis.

2 Supported by Gesellschaft zur Forderung Kynologischer Forschung , Ger-many.

3 To whom correspondence should be addressed.E-mail: [email protected].

4 Abbreviations used: aD, apparent digestibility; Ca, calcium; DM, dry matter;f, female; g, gram; kg, kilogram; m, male; n, number of animals; P, phosphorus;tD, true digestibility.

0022-3166/02 $3.00 2002 American Society for Nutritional Sciences. J. Nutr. 132: 1665S1667S, 2002.

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were noticeable in any of the Beagle puppies. The weightcurve was not influenced systematically by the feeding regime.In contrast to the aD of Ca, which was highly variable andshowed only a tendency to decrease, the aD of P decreasedsignificantly with the age in the control group (100%), asexpected (9); so the highest values were measured in theyoungest puppies. At the age of 6.5 to 13.5 wk of age (Trial 1)no statistically significant differences in the aD of Ca wereseen among the groups (Table 2). This shows that during thisage the puppies are not able to adjust the aD according to theintake, as has already been shown by Hazewinkel and cowork-ers (3) in the case of an oversupply with Ca. The first time adifference between the groups could be measured was in olderpups, that is, in Trial 2 (13.519.5 wk of age). Here, in the15% group (group B), a significant higher digestibility of Cacompared to the 300% group (group A) was measured. Neither

the control group (100%) nor group C, which was fed with aration to meet 50% of the Ca requirements, was significantlydifferent from the other two groups. Consequently, no down-regulation of the aD of Ca was detectable in the oversupplied

group (300%) relative to the control group. In the case of ahigh Ca intake there is little difference between aD and truedigestibility (tD) because endogenous losses can be assumed tobe relatively small when compared to the levels of intake andfecal excretion. In addition, endogenous fecal losses have beenrepeatedly estimated by regression analysis and they appear tobe fairly constant in dogs (9). If the Ca intake is low, the aD

is considerably lower than the tD. Therefore it is most unlikelythat a significantly higher aD in a group with reduced Caintake is an effect of endogenous losses. In contrast, thedifferences in the tD are likely to be more distinct than thosein the aD. Trial 3 showed no significant differences in the aDof Ca. At this age the digestibility seemed to be unaffected bythe preceding feeding, which makes the influence of carryovereffects less likely.

In contrast to the influence of the diets on the aD of Ca, theaD of P was influenced significantly in the youngest dogs (Trial1). When the Ca intake or the Ca/P ratio did not meet therequirements as in groups A to C, a difference in the valueswas measured. The aD of P was significantly lower in the caseof a Ca oversupply in Trial 1, as Jenkins and Phillips (10) have

already described. A distinctly higher mean value for the aD ofP was detectable in puppies on a Ca undersupply (15%) and aCa/P ratio far below 1:1 compared to that of the other groups.A potential mechanism for this observation might be a possi-ble elevation of the blood level of PTH and, as a consequence,a stimulation of the kidneys to form active vitamin D, whichleads to a higher absorption of both elements from the gastro-intestinal tract. Trial 3 showed no significant differences in theaD of P.

The results demonstrate that dogs younger than 4 to 5 moare not able to adjust the digestibility of Ca in relation to theCa intake at 100% of requirements. Not only the inability todownregulate the aD but also the inability to increase theuptake in the case of an insufficient intake in young growing

dogs makes it necessary to adjust precisely the daily supply ofCa to the requirements. In contrast, an ability to alter theapparent digestibility of P was already observed in very youngdogs.

TABLE 1

Composition and average nutrient content (% dry matter)

of the basal diet fed to 20 growing Beagles

Component Amount (%)

Basal ration

Tripe 60Cooked rice 39Cellulose 1

Supplement Vitamin-mineral mixture Individual supplementation

Average nutrient content, % dmDry matter 31.2 3.7Crude protein 33.7 5.6Crude ash 2.3 0.6Crude fat 28.8 8.9Crude fiber 5.1 1.9N-free extracts 31.0 11.9

TABLE 2

Apparent digestibility (aD, mean SD, %) of calcium and phosphorus in 20 Beagles (from weaning to 6 mo of age)

in relation to age and daily intake of these elements

Trial(age of dogs, wk ) Group n

Feeding regime(% ca ) Ca/P aD Ca aD P

1 (6.513.5) Control 7 1001 1.5/1 65.6 8.4 79.5*a 3.0

A 5 15 0.2/1 46.2 32.9 93.4b 1.1B 5 300 4.8/1 54.1 10.5 73.1c 2.7C 3 150 2.4/1 47.7 3.5 66.9d 2.0

2 (13.519.5) Control 6 100 1.6/1 56.0ab 15.9 65.5*a 11.7 A 5 300 5.0/1 52.0b 9.3 62.5a 10.3B 5 15 0.2/1 73.8a 9.3 92.0b 0.4C 3 50 0.9/1 57.3ab 0.8 72.2a 1.3

3 (19.525.5) Control 6 100 1.6/1 43.3 20.1 62.2* 9.0 A 5 100 1.6/1 55.7 12.2 71.4 8.6B 5 100 1.6/1 54.4 9.4 69.8 6.4C 3 100 1.6/1 45.0 9.9 63.5 7.2

1 Balanced diet concerning all minerals and vitamins; one puppy was removed from the group for other then trial reasons.* Significant differences between the three trials in the control group were determined by Tukeys test (P 0.05). Letters identify differences

between more than two groups; means not sharing a superscript letter are significantly different (Tukeys test, P 0.05).

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LITERATURE CITED

1. Marek, J. & Wellmann, O. (1931) Die Rhachitis, Pathologischer Teil.Gustav Fischer Verlag, Jena, Germany.

2. Hedhammar, A., Wu, F. M., Krook, L., Schryver, H. F., De Lahunta, A.,Whalen, J. P., Kallfez, F. A., Nunez, E. A., Hintz, H. F., Sheffy B. E. & Ryan, G. D.(1974) Overnutrition and skeletal disease. An experimental study in growinggreat Dane dogs. Cornell Vet. 64(suppl. 5): 9150.

3. Hazewinkel, H.A.W., Goedegebuure, S. A., Poulos, P. W. & Wolvekamp,W.Th.C. (1985) Influences of chronic calcium excess on the skeletal develop-

ment of growing great danes. J. Am. Anim. Hosp. Assoc. 21: 377391.4. Meyer, H. & Zentek, J. (1998) Ernahrung des Hundes. Parey Verlag,

Berlin, Germany.

5. Meyer, H. (1992) Ernahrung des Hundes. Ulmer Verlag, Stuttgart,Germany.

6. Kienzle, E., Opitz, B., Earle, K. E., Smith, P. M., Maskell, I. E. & Iben, C.(1998) The development of an improved method of predicting the energycontent in prepared dog and cat food. J. Anim. Phys. Anim. Nutr. 79: 6979.

7. Gehricke, S. & Kurmies, B. (1926) Die kalorimetrische Phosphorsau-rebestimmung mit Ammonium-Vanadat-Molybdat und ihre Anwendung bei derPflanzenanalyse. Z. Pflanze. Dung. Boden. 59: 235247.

8. Hermann, R. & Alkemade, C.T.J. (1963) Flame Photometry. Inter-science Publishers, New York/London.

9. Meyer, H. (1978) Ubersich. Tierernahr. 6: 3154.10. Jenkins, K. J. & Phillips, P. H. (1960) The mineral requirement of the

dog. J. Nutr. 70: 235246.

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