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The WALTHAM International Nutritional Sciences Symposia

Effect of Fecal Water and Dry Matter Excretion on Fecal Mineral Excretion in Dogs Studied in a Fiber Model1–3 Ellen Kienzle,4 Britta Dobenecker, Brigitta Wichert, and Simone Schuster Institute for Physiology, Physiological Chemistry, and Animal Nutrition, Ludwig-Maximilians Universita¨t, D-80539 Munich, Germany EXPANDED ABSTRACT

a microwave digestion unit (MLS Ethos-1600). Magnesium was measured by atomic absorption spectrometry (Unicam 939/959). Sodium, potassium, and calcium were determined by flame emission spectography, and phosphorus photometrically with ammonium molybdate and ammonium vanadate in HNO3 (4). Fecal pH was measured in fresh feces (dilution 1:5 in distilled water) with an electronic pH meter. The Government of Upper Bavaria, the proper authority according to German law on animal welfare (Tierschutzgesetz), approved the study. A 2-way ANOVA (Sigmastat 3.0) with the factors dog and diet was carried out before regression analysis to make sure that there were no significant effects of the individual dog. There were significant effects of diet but not of dog.

The present study was originally designed to study fiber effects on feces quality (1,2). The use of various celluloses with differing water-binding capacity, a fiber-free negative control diet, and a guar-containing positive control accidentally created a model to study the effect of fecal dry matter and water excretion on fecal mineral excretion.

MATERIAL AND METHODS In the present study the effect of 6 cellulose types (microcrystalline versus fibrous: fiber length 60, 300 mm, each from beech as well as from pine and a mixed cellulose) and guar on fecal mineral excretion was investigated in feeding trials with 10 adult beagles (1–6 y, 11–15 kg body weight, .7 dogs/trial, total number of observations n ¼ 64). On a dry-matter basis the basal diet consisted of 55.7% heat-dried meat by-product meal, 38.5% isolated corn starch (gelatinized by cooking), and 5.8% sunflower oil. Cellulose was added as 10% dry matter, and guar was added as 6% of dry matter to the basal diet. Mineral content did not significantly differ among the diets used. Mineral intakes (mg kg-1 d-1) were: Ca 126–146, P 114–134, Mg 16–18, Na 66–79, K 52– 59. Details of the composition of the basal diet and cellulose types are described elsewhere (1). Each trial started with a 13-d adaptation period followed by a 7-d fecal collection period. Chromic oxide (0.5% dry matter) was used as a fecal marker. Dogs were fed to maintain weight. Food and feces were freeze-dried, ground, and stored for analysis. Chromic oxide was determined by the method of Petry and Rapp (3). For mineral analysis, wet digestion of samples was carried out in

RESULTS Amount of daily fresh feces varied from 7.8 6 0.9 g/kg body weight in the basal diet to 16.1 6 2.2 g/kg body weight/d in one of the cellulose diets. Fecal dry matter excretion ranged from 2.1 6 0.2 g/kg body weight in the basal diet to 4.8 6 0.8 in a cellulose diet. Fecal daily water excretion ranged from 5.7 6 0.9 g/kg body weight in the basal diet to 11.3 6 1.8 g/kg body weight in a cellulose diet. Fecal dry matter content was lowest in the guar diet (21.3 6 2.7%) and highest in a cellulose diet (33.3 6 2.5%). Fecal pH remained unchanged for cellulose (basal diet 7.3 6 0.3, cellulose diets 7.3 6 0.1), but it decreased significantly (P , 0.001, 1-way ANOVA, Holm-Sidak-test, Sigmastat 3.0) after the addition of guar (6.5 6 0.2). Fecal excretion of sodium was correlated to the amount of feces, to the fecal dry matter excretion, and to the fecal water excretion (Figs. 1–3). In all cases, an exponential function gave the best fit. Fecal excretion of potassium was also correlated to the amount of feces, to the fecal dry matter excretion, and to the fecal water excretion (Figs. 1–3). Again, an exponential function gave the best fit. Fecal magnesium excretion was exponentially correlated to fecal dry matter excretion (r ¼ 0.58) but not to fecal water excretion. Fecal phosphorus excretion was exponentially correlated to fecal dry matter excretion (r ¼ 0.74) and to some extent to the amount of fresh feces and to fecal water excretion.

1 Published in a supplement to The Journal of Nutrition. Presented as part of The WALTHAM International Nutritional Sciences Symposium: Innovations in Companion Animal Nutrition held in Washington, DC, September 15–18, 2005. This conference was supported by The WALTHAM Centre for Pet Nutrition and organized in collaboration with the University of California, Davis, and Cornell University. This publication was supported by The WALTHAM Centre for Pet Nutrition. Guest editors for this symposium were D’Ann Finley, Francis A. Kallfelz, James G. Morris, and Quinton R. Rogers. Guest editor disclosure: expenses for the editors to travel to the symposium and honoraria were paid by The WALTHAM Centre for Pet Nutrition. 2 Author disclosure: No relationships to disclose. 3 Supported by Phricolat Chemische Erzeugnisse GmbH, Siegburg, Germany. 4 To whom correspondence should be addressed. E-mail: kienzle@tiph. vetmed.uni-muenchen.de.

0022-3166/06 $8.00 Ó 2006 American Society for Nutrition. J. Nutr. 136: 2001S–2003S, 2006.

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KEY WORDS: fecal water excretion fecal dry matter excretion fecal mineral excretion fiber dog

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FIGURE 1 Relations between fecal bulk (x, g/kg body weight) and fecal sodium excretion (Na, mg/kg body weight) and fecal potassium excretion (K, mg/kg body weight). n, Na; h, K; solid line, Na ¼ 1.44 3 e0.137x, r ¼ 0.88, n ¼ 65; wavy line, K ¼ 2.52 3 e0.073x, r ¼ 0.76, n ¼ 65.

FIGURE 2 Relation between fecal dry matter excretion (x, g/kg body weight) and fecal potassium excretion (y, mg/kg body weight). n, Na; h, K; solid line, Na ¼ 1.93 3 e0.398x, r ¼ 0.81, n ¼ 65; wavy line, K ¼ 3.36 3 e0.179x, r ¼ 0.59, n ¼ 65.

Fecal calcium excretion was correlated to fecal dry matter excretion (r ¼ 0.62) but not to fecal water excretion.

DISCUSSION Potential reasons for an increase of mineral excretion with increasing fecal bulk, fecal water, or dry matter excretion are numerous. They range from decreased passage time and effects of dilution to potential subclinical damage to the enteral mucosa as described by Reinhard et al. (5). For practical application the question is, however, whether the relations among fecal bulk, dry matter, and water are an effect of the model used ¨bler or whether they are consistent over a variety of diets. Gru

FIGURE 3 Relation between fecal water excretion (x, g/kg body weight) and fecal potassium excretion (y, mg/kg body weight). n, Na; h, K; solid line, Na ¼ 1.65 3 e0.179x, r ¼ 0.85, n ¼ 65; wavy line, K ¼ 2.55 3 e0.102x, r ¼ 0.77, n ¼ 65.

et al. (6), Meyer et al. (7), and Kienzle et al. (8) published data on fecal excretion of sodium and potassium as well as fecal bulk, dry matter, and water in dogs fed different diets. Meyer et al. (9) investigated the influence of breed on the same parameters. Even across such a variety of conditions in the trials, the relation between fecal bulk and sodium excretion (Fig. 4) and the relation between fecal water and potassium excretion were significant (Fig. 5). For calcium, magnesium, and phosphorus, there was mainly an effect of fecal dry matter excretion on fecal mineral excretion. In these minerals, guar is likely to have an effect that is independent of its effect on fecal dry matter excretion. Fermentable fiber with a low precaecal digestibility such as lactose or guar may increase the absorption of all 3 minerals in various species (10–14). Part of this effect is believed to be ¨hlum a result of acidification of the ingesta. For comparison, Mu (12) and Kienzle et al. (13) fed rations containing carbohydrates poorly digestible precaecally with different poorly digestible carbohydrates. Some increased fecal bulk and decreased fecal pH; others decreased fecal pH without increasing fecal bulk. Intake of calcium, phosphorus, and magnesium may be a major determinant for fecal excretion. Mineral intake was more or less constant in the present investigation, whereas it varied

FIGURE 5 Relation between fecal water excretion (x, g/kg body weight) and fecal potassium excretion (K, mg/kg body weight). Current data and data from references 6–9. n, current data; n, 6; 1, 7; 3, 8; *, 9; solid line, K ¼ 3.32 3 e0.096x, r ¼ 0.72, n ¼ 127.


FIGURE 4 Relation between fecal bulk (x, g/kg body weight) and fecal sodium excretion (Na, mg/kg body weight). Current data and data from references 6–9. n, current data; n, 6; 1, 7; 3, 8; *, 9; solid line, Na ¼ 3.38 3 e0.088x, r ¼ 0.73, n ¼ 127.

FECAL MINERAL EXCRETION IN DOGS

LITERATURE CITED

Multiple regression calculations between fecal dry matter and mineral intake (independent variables), and fecal mineral excretion (dependant variable) for calcium, magnesium, and phosphorus1

1. Wichert B, Schuster S, Hofmann M, Dobenecker B, Kienzle E. Influence of different cellulose types on feces quality of dogs. J Nutr. 2002;132: 1728S–9S. 2. Schuster S. Wirkung verschiedener cellulosen im vergleich zu guarmehl auf na¨hrstoff- und bruttoenergieverdaulichkeiten sowie kotqualita¨t beim hund [Dissertation]. Munich: Ludwig Maximilians Universita¨t; 2003 3. Petry H, Rapp W. On the problem of chromium oxide determination in digestion studies. Z Tierphysiol Tierernahr Futtermittelkd. 1971;27:181–9. 4. Gericke S, Kurmies B. Die kalorimetrische phosphorsaürebestimmung mit ammonium-vanadat-molybdat und ihre anwendung bei der pflanzenanalyse. Z pflanzenern du¨ng Bodenkd. 1952;59:235–47. 5. Reinhart GA, Moxley RA, Clemens ET. Source of dietary fiber and its effects on colonic microstructure, function and histopathology of Beagle Dogs. J Nutr. 1994;124:2701S–3S. 6. Gru¨bler B, Meyer H, Koch-Erhorn B. Eignung verschiedener komponenten fu¨r adipositasdia¨ten beim hund. In: Meyer, H., Kienzle, E. editors. Erna¨hrung, fehlerna¨hrung und dia¨tetik beim hund. Institute for Animal Nutrition, Tiera¨rztl. Hochschule Hannover, Germany 1988; p. 214–217 7. Meyer H, Behfeld T, Schu¨nemann C, Mu¨hlum A. Intestinaler wasser-, natrium- und kaliumstoffwechsel. Adv Anim Physiol Anim Nutr. 1989;19: 109–19. 8. Meyer H, Zentek J, Habernoll H, Maskell I. Digestibility and compatibility of mixed diets and faecal consistency in different breeds of dog. Zentbl Vetmed Reihe A. 1999;46:155–65. 9. Kienzle E, Dobenecker B, Eber S. Effect of cellulose on the digestibility of high starch versus high fat diets in dogs. J Anim Physiol Anim Nutr (Berl). 2001;85:174–85. 10. Outhouse J. The relative effects of certain saccharides and of vitamin D on mineral metabolism in rats. J Nutr. 1938;15:257–68. 11. Zentek J. Untersuchungen zum mineralstoffhaushalt der katze unter besonderer beru¨cksichtigung des magnesiums. [Dissertation]. Hannover (Germany): Tiera¨rztliche Hochschule; 1987 12. Mu¨hlum A. Untersuchungen u¨ber die praecaecale und postileale verdaulichkeit verschiedener kohlenhydrate beim hund. [Dissertation]. Hannover (Germany): Tiera¨rztliche Hochschule; 1987. 13. Kienzle E. Untersuchungen zum intestinal- und intermedia¨rstoffwechsel von kohlehydraten (Sta¨rke verschiedener herkunft und aufbereitung, mono- und disaccharide) bei der hauskatze (Felis catus). [habilitation]. Hannover (Germany): Tiera¨rztliche Hochschule; 1989 14. Beynen AC, Kappert HJ, Yu S. Dietary lactulose decreases apparent nitrogen absorption and increases apparent calcium and magnesium absorption in healthy dogs. J Anim Physiol Anim Nutr (Berl). 2001;85:67–72.

Regression equation

SEM

r

48.0

0.95

2.5

0.78

16.9

0.96

mg/kg body weight

Mg P

Fecal Ca excretion = 33.8 1 13.6 3 fecal dry matter excretion 1 0.78 3 Ca intake Fecal Mg excretion = 0.06 1 0.44 3 fecal dry matter excretion 1 0.83 3 Mg intake Fecal P excretion 60.2 1 0.83 3 fecal dry matter excretion 1 4.9 3 P intake

1 All coefficients of regression and multiple correlation coefficients are significant, P , 0.01. Current data plus data from Mu¨hlum (12) and Kienzle et al. (13); n ¼ 84.

¨hlum (12) and Kienzle et al. considerably in the rations of Mu (13). To account fo this, multiple regressions were calculated ¨hlum [12], Kienzle et al. [13], and the (pooled data from Mu present investigation) with the fecal excretion of either mineral as the dependant variable or the intake of the mineral as well as the fecal dry matter excretion as the independent variables. Calcium/phosphorus ratio was not included in the calculations because the variation was within the recommended limits. The results of the regression calculations (Table 1) demonstrate that fecal dry matter excretion has a significant influence on fecal excretion of calcium, magnesium, and phosphorus.


TABLE 1

Mineral

Ca

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