Waltham International Symposium:

Pet Nutrition Coming of Age

Intestinal Effects of Mannanoligosaccharides,
Transgalactooligosaccharides, Lactose and Lactulose in Dogs

1

Ju¨rgen Zentek,

2

Bettina Marquart and Tanja Pietrzak

Institute of Animal Nutrition, School of Veterinary Medicine Hannover, Hannover, Germany

EXPANDED ABSTRACT

KEY WORDS:

●

dogs

●

mannanoligosaccharides

●

transgalactooligosaccharides

●

lactose

●

lactulose

Carbohydrates that are indigestible by mammalian enzymes

can influence the composition and metabolic activity of the
intestinal microflora and are therefore of interest for the for-
mulation of pet food and specific veterinary diets. Mannan-
oligosaccharides are isolated from yeast cell walls (1). They are
not hydrolyzed by digestive enzymes but by different lactoba-
cilli and some bifidobacteria (2,3) and seem to be less ferment-
able by intestinal bacteria than are fructooligosaccharides
(4 –7). Galactooligosaccharides consist of

␤-1,6-linked galac-

topyranosyl units and an

␣-glycosidic bonding to a terminal

glycopyranosyl residue and have been shown to be fermentable
by canine intestinal microflora (6). Transgalactooligosacchar-
ides are produced by the

␤-galactosidase from Aspergillus oryzae

(8). Lactose can be regarded as a facultative fermentable
carbohydrate in dogs. The activity of intestinal lactase de-
creases age dependently with concomitant compensatory fer-
mentation by small intestinal and colonic bacteria (9). Lac-
tulose is an isomeric form of lactose with one galactose
molecule linked to fructose by

␤-1,4-linkage. In vitro investi-

gations demonstrated that lactulose is readily fermented by
bifidobacteria and lactobacilli, but also by Clostridium perfrin-
gens, Escherichia coli and Bacteroides sp. (10 –12). A decrease of
colonic pH and blood ammonia concentrations in dogs was
found after ingestion of lactulose (13,14).

In the present study mannanoligosaccharides, transgalac-

tooligosaccharides, lactose and lactulose were added to a
mixed diet for dogs and investigated for their effects on the
fecal quality, nutrient and mineral digestibilities and on some
products of intestinal microbial metabolism.

MATERIALS AND METHODS

Animals

Four adult female beagles with an average body weight of 11.7

⫾ 2.2 kg. Care and treatment of the animals was approved by

governmental commission according to the procedures of the ani-
mals’ protection law. The dogs were vaccinated and dewormed as
usual and housed individually.

Diet

The basal diet

4

(17 g/kg BW/d) was fed without added carbohy-

drates in the control periods I and II. Mannanoligosaccharides (MOS,
Bio Mos; Alltech, Bad Segeberg, Germany), transgalactooligosaccha-
rides (TGOS, Lactifit; Borculo Whey Products, Borculo, The Neth-
erlands), lactose (Variolac 99; Biolac GmbH, Harbarnsen, Germany)
or lactulose (Lactuverlan; Verla-Pharm, Tutzing, Germany) were
dosed individually for each dog (1 g/kg BW/d) and mixed with the
basal diet during four supplementation periods. The experiment was
designed as a 4

⫻ 4 Latin square and the dogs received the basal diet

without additives before and after the four diets were supplemented
with the fermentable carbohydrates. The adaptation periods lasted at
least 10 d before collection of the samples.

Variables

The apparent digestibility of crude nutrients [methods in Nau-

mann and Bassler (15) and macrominerals, by wet ashing in a mixture
of perchloric and nitric acid, atomic absorption spectrophotometry
for calcium and magnesium (16), flame photometry for sodium and
potassium (17), vanadate molybdate method for phosphorus (18)] was
measured after 5-d collection periods in a metabolism cage. Addi-
tional variables were a daily scoring of fecal consistency, determina-
tion of fecal dry matter (oven drying to weight constancy) and of

1

Presented as part of the Waltham International Symposium: Pet Nutrition

Coming of Age held in Vancouver, Canada, August 6 –7, 2001. This symposium
and the publication of symposium proceedings were sponsored by the Waltham
Centre for Pet Nutrition. Guest editors for this supplement were James G. Morris,
University of California, Davis, Ivan H. Burger, consultant to Mars UK Limited, Carl
L. Keen, University of California, Davis, and D’Ann Finley, University of California,
Davis.

2

To whom correspondence should be addressed.

E-mail: [e-mail].

3

Abbreviations used: BW, body weight;

IU

, international units; MOS, basal

diet with mannanoligosaccharides; TGOS, basal diet with transgalactooligosaccha-
rides.

4

Ingredients: dry greaves (35%), pressure-cooked rice (35%), fish meal (5%),

soya oil (20%), cellulose 3%, and vitamin and mineral supplement (2%; Vitakalk:
21% calcium, 8% phosphorus, 6% sodium, 1% magnesium; per kg: 500,000

IU

vitamin A, 40,000

IU

vitamin D3, 1000 mg vitamin E, 700 mg copper; Marienfelde

GmbH, Roth, Germany). Composition of the mixed diet (g/kg): dry matter, 945;
crude ash, 39.8; crude protein, 366; crude fat, 244; crude fiber, 49.5; calcium,
6.76; magnesium, 0.53; phosphorus, 5.06; sodium, 4.23; potassium, 3.06; chlo-
ride, 5.31.

0022-3166/02 $3.00 © 2002 American Society for Nutritional Sciences. J. Nutr. 132: 1682S–1684S, 2002.

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unbound water by centrifugation (weight of fluid after centrifugation
of 2 g of feces for 30 min, 30,000

⫻ g; Sorvall Superspeed RC2-B,

DuPont, Bad Homburg, Germany), and of pH (Knick-pH-Meter;
Knick, Berlin, Germany). Dietary effects on the metabolism of the
intestinal microflora were assessed by the fecal concentrations of
ammonia (ammonia-Electrode, Model IS 570 NH

3

; Philips, Kassel,

Germany) and volatile fatty acids (VFA) (capillary chromatograph
PU 4550; Pye Unicam, Offenbach, Germany; glass column, 2 m
length

⫻ 2 mm ID, packed with GP 10%/SP 1000/1% H

3

PO

4

on

100/120 Chromosorb WAW; Supelco, Deisenhofen, Germany) and
urinary nitrogen, indican (19) and urea excretion (Urea Kit, bio
Merieux, Nu¨rtingen, Germany). Fecal suspensions (1:10 in prere-
duced physiological saline) were incubated under nitrogen atmo-
sphere for 24 h with measurement of total gas formation and produc-
tion of VFA.

Statistics

Data were processed by EXCEL 5.0 and SAS 6.04 (20). ANOVA

and Tukey test were used for comparison of the Latin square with the
supplemented diets. Comparison of supplemented and basal diets I
and II was done by t-test. Probability values of

⬍0.05 were taken as

significant.

RESULTS AND DISCUSSION

The apparent digestibilities of dry matter, crude protein and

N-free extracts were lower with the mannanoligosaccharides
(Table 1) than those with the other dietary periods.

Apparent absorption rates of calcium (5–15%), phosphorus

(31– 46%), magnesium (9 –29%), sodium (93–97%) and po-
tassium (90 –95%) were not influenced by the type of diet.
Fecal consistency tended to get looser during the lactulose

period than during the basal period, whereas the other carbo-
hydrates had no negative effects on stool quality. The lowest
unbound water (5.5%) was found with mannanoligosaccha-
rides (Table 2), accompanied by a lower fecal pH (6.6). Fecal
ammonia concentration and excretion were higher with basal
diet I than with basal diet II. The ammonia concentrations
were lower after the addition of mannanoligosaccharides than
that in basal diet I and the lactulose period.

The fecal VFA concentrations ranged from 139 to 209

mmol/L with no differences attributed to diet (data not
shown). Dietary alterations did not influence the renal nitro-
gen (45– 60 mmol/kg BW/d), urea (18 –27 mmol/kg) or indi-
can (10 –16

␮mol/kg) excretion. Ammonia yield from anaer-

obic in vitro incubation of fecal suspensions for 24 h in dogs
fed lactulose was higher than that when either basal diet was
fed. There was a similar trend when the other three supple-
mented diets were fed (Table 3).

Total gas production was lowest in the initial control

period (basal diet I) compared with that of the other ex-
perimental diets. The concentrations of VFA (Table 3),
mainly of acetic acid, increased during the incubation,
whereas the proportion of propionic acid and n-butyric acid
decreased. There were no obvious dietary influences on in
vitro fermentation.

In conclusion, lactose, lactulose or transgalactooligosaccha-

rides did not alter the measures of microbial metabolism,
compared to those of the control periods. Higher intakes
might have induced clearer changes, but according to our own
preliminary experiments a dosage of 2 g lactulose/kg BW/d
induced diarrhea, which shows comparatively narrow limits

TABLE 1

Apparent digestibilities (means

⫾

SD

) of dry matter and crude nutrients (% of intake; n

⫽ 4)

1

Dry matter

Crude protein

Crude fat

Crude fiber

Nitrogen-free extracts

Basal diet I

85.0

⫾ 1.9

†

82.5

⫾ 3.2

†

96.2

⫾ 0.2

61.8

⫾ 8.2

94.8

⫾ 2.3

†

⫹ MOS

2

81.9

⫾ 0.6

b†

79.8

⫾ 1.9

b†

96.6

⫾ 0.5

a

69.1

⫾ 2.1

a†

83.1

⫾ 2.9

b

*

†

⫹ TGOS

3

87.2

⫾ 2.4

a

85.9

⫾ 3.6

a

96.9

⫾ 1.0

a

67.9

⫾ 1.7

a†

91.9

⫾ 1.2

a

⫹ Lactose

87.3

⫾ 2.8

a

86.2

⫾ 3.7

a

97.1

⫾ 1.0

a

67.4

⫾ 7.5

a

92.1

⫾ 0.7

a

⫹ Lactulose

86.5

⫾ 1.9

a

84.4

⫾ 1.0

a†

96.7

⫾ 0.7

a

71.0

⫾ 6.1

a†

91.4

⫾ 2.5

a

Basal diet II

89.5

⫾ 0.7*

91.3

⫾ 0.5*

96.8

⫾ 0.5

57.7

⫾ 2.6

92.5

⫾ 0.6*

1

Means within a column not sharing a common superscript are significantly different at P

⬍ 0.05.

2

Basal diet with mannanoligosaccharides.

3

Basal diet with transgalactooligosaccharides.

*

,

†

Significant difference from basal diets, period I (*) or II (

†

) (ANOVA and Tukey test for the supplemented periods, t-test for comparison of

supplemented and basal diets).

TABLE 2

Fecal consistency, dry matter, unbound water, pH and ammonia (means

⫾

SD

; n

⫽ 4)

1

Consistency

2

Dry matter, %

Unbound water, %

pH

Ammonia,

␮mol/g

Basal diet I

3.2

⫾ 0.7

35.7

⫾ 1.4

16.5

⫾ 5.1

6.9

⫾ 0.2

116

⫾ 7.8

†

⫹ MOS

3.6

⫾ 0.4

a

31.6

⫾ 1.0

a

*

†

5.5

⫾ 3.7

b

*

†

6.6

⫾ 0.1

b

*

†

78.4

⫾ 9.3

a

*

⫹ TGOS

3.5

⫾ 0.4

a

36.1

⫾ 3.9

a

11.7

⫾ 3.3

ab

6.9

⫾ 0.2

a

112

⫾ 31.8

ab

⫹ Lactose

3.5

⫾ 0.4

a

36.3

⫾ 4.2

a

11.5

⫾ 2.7

ab

7.0

⫾ 0.1

a

114

⫾ 29.8

ab

⫹ Lactulose

2.9

⫾ 0.5

a†

32.1

⫾ 4.3

a

17.4

⫾ 5.8

a

6.8

⫾ 0.1

ab

119

⫾ 9.6

b†

Basal diet II

3.7

⫾ 0.1

36.8

⫾ 1.4

12.6

⫾ 0.9

7.1

⫾ 0.1

83.8

⫾ 14.9*

1

Means within a column not sharing a common superscript are significantly different at P

⬍ 0.05.

2

Consistency: 1

⫽ diarrhea (liquid); 2 ⫽ unformed, wet; 3 ⫽ formed, but smeary; 4 ⫽ formed (optimum consistency); 5 ⫽ firm (hard, crumbly).

*

,

†

Significant difference from basal diets, period I (*) or II (

†

) (ANOVA and Tukey test for the supplemented periods, t-test for comparison of

supplemented and basal diets).

CARBOHYDRATES IN DOGS

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between tolerance and intolerance in dogs. Mannanoligosac-
charides resulted in a lower fecal pH, ammonia excretion and
apparent digestibilities of crude protein, nitrogen-free extracts
and dry matter, compared to those of the control periods and
the other carbohydrates. The percentage of total fecal water
increased and the unbound water decreased substantially dur-
ing this period, which can be interpreted as a change in the
physical properties of the intestinal chyme. This higher water
binding could have influenced the solubility of nutrients,
which might explain the lower digestibilities and also the
activity of the intestinal microflora. Further studies are war-
ranted to confirm these effects and the underlying mecha-
nisms.

LITERATURE CITED

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(1994)

Mannan-oligosaccharides: natural polymers with

significant impact on the gastrointestinal microflora and the immune system
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Nottingham, UK.

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(1994)

Biotechnology in the feed industry: 1994 and

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(1993)

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P. W. & Fahey, G. C., Jr.

(2000)

Glucose-based oligosaccharides exhibit

different in vitro fermentation patterns and affect in vivo apparent nutrient digest-
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(1995)

Effects of admin-

istration of galactooligosaccharides on faecal character in dogs and cats. Bull.
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(1987)

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application for food. Food Chem. 6: 87–94.

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(2001)

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Kan, T., Kuroda, A. & Sumihara, Y.

(1993)

Galactooligosaccharides. In: Oligo-

saccharides: Production, Properties and Applications (Nakakuki, T., ed.), vol. 3,
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(1992)

Laktosefu¨tterung bei Fleischfressern. Wien. Tiera¨rztl.

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(1986)

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11. Mitsuoka, T., Hidaka, A. & Eida, T.

(1987)

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(1993)

Growth of lactic acid

bacteria and bifidobacteria on lactose and lactose-related mono-, di- and trisac-
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beta-galactosidase. J. Dairy Res. 60: 557–568.

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(1971)

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(1990)

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(1993)

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(1968)

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(1963)

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TABLE 3

pH, ammonia, gas volume and volatile fatty acids after 24-h incubation of fecal suspensions (means

⫾

SD

; n

⫽ 4)

1

pH

Ammonia,

␮mol/mL

Gas volume, mL

Volatile fatty acids,

␮mol/mL

Basal diet I

6.83

⫾ 0.10

18.9

⫾ 7.03

5.5

⫾ 0.44

†

26.8

⫾ 3.84

⫹ MOS

6.45

⫾ 0.24

b †

25.3

⫾ 6.68

a

12.5

⫾ 3.07

a

*

41.3

⫾ 7.05

a †

⫹ TGOS

6.82

⫾ 0.16

a

29.2

⫾ 6.79

a

15.5

⫾ 6.24

a

36.4

⫾ 5.73

a

⫹ Lactose

6.85

⫾ 0.10

a

25.0

⫾ 2.31

a †

13.1

⫾ 4.81

a

*

33.1

⫾ 0.68

a

⫹ Lactulose

6.73

⫾ 0.22

ab

31.5

⫾ 4.89

a

*

†

13.3

⫾ 3.17

a

*

41.8

⫾ 5.09

a †

Basal diet II

6.92

⫾ 0.10

19.5

⫾ 3.09

13.4

⫾ 1.77*

26.2

⫾ 4.02

1

Means within a column not sharing a common superscript are significantly different at P

⬍ 0.05.

*

,

†

Significant difference from basal diets, period I (*) or II (

†

) (ANOVA and Tukey test for the supplemented periods, t-test for comparison of

supplemented and basal diets).

SUPPLEMENT

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