Nutrient Digestion by Ileal Cannulated Dogs as Affected by Dietary
Fibers with Various Fermentation Characteristics
H. E. Muir*, S. M. Murray , G. C. Fahey, Jr.*, ,1, N. R. Merchen*, ,
and G. A. Reinhart!

Department of Animal Sciences and *Division of Nutritional Sciences, University of Illinois,
!
Urbana 61801 and The Iams Company, Lewisburg, OH
ABSTRACT: We studied the effects of dietary ileum was similar for all groups, except for lysine,
fibers with various fermentation characteristics on
which increased ( P < .05) in digestibility as dietary
nutrient digestion at the distal ileum and in the total
cellulose concentration increased. Dogs consuming
tract of dogs. The following high-protein (34%), high-
LCM had lower apparent ileal digestibility values for
fat (23%) diets were fed: 1) a control treatment
all nutrients, including most amino acids, than dogs
(CON) with 0% supplemental fiber; 2) beet pulp
consuming HCM or SF. Total tract digestion of DM
(BP), 7.5%; 3) low-cellulose mixture (LCM), 2.5%
and OM by dogs fed supplemental fiber was less ( P <
cellulose + 5.0% pectin; 4) high-cellulose mixture
.05) than for dogs fed the control diet. The BP
(HCM), 5.0% cellulose + 2.5% pectin; or 5) Solka
treatment was higher than other fiber treatments in
FlocŁł (SF), 7.5% cellulose. Nutrient intakes by fiber-
total tract digestion of OM ( P < .10) and total dietary
supplemented dogs were similar among treatment
fiber ( P < .05). Total tract digestibilities of all
groups but greater ( P < .05) than for dogs fed the
nutrients exhibited either linear or quadratic
control diet. Digestion of nutrients at the distal ileum
responses to dietary cellulose concentrations. Appar-
was similar among groups except for fat: the dogs fed
ent ileal and total tract nutrient digestion was
BP digested less fat than those fed the other sources of
dietary fiber. Digestion of amino acids at the distal influenced by the source of dietary fiber consumed.
Key Words: Dog, Fiber, Digestion, Ileum
J. Anim. Sci. 1996. 74:1641 1648
Introduction to the production of greater quantities of nitrogenous
constituents. A precise estimate of N and amino acid
Research conducted in our laboratory showed that digestibility can be obtained using dogs cannulated at
an increase in the percentage of dietary beet pulp, a the distal ileum. Therefore, the objectives of this study
moderately fermentable fiber source, leads to a were to investigate the effects of dietary fibers of
decrease in apparent N digestibility by dogs (Fahey et various fermentation capacities on nutrient and
al., 1990b). Also, selected fiber sources fed to dogs energy intake, digestion before the distal ileum, total
resulted in different apparent N digestibilities (Fahey tract digestibility, and pH and SCFA concentrations in
et al., 1990a). Sunvold et al. (1995) showed that ileal contents.
poorly fermentable fiber sources resulted in higher
apparent N digestibilities than did moderately fer-
Experimental Procedures
mentable fiber sources in dogs. From these data, one
could infer that moderately fermentable fibers act to
Animals and Diets. Five diets (Table 1) containing
inhibit N digestion.
either 0% supplemental fiber (control), 7.5% Solka
Microbial growth in the large bowel adds to the
FlocŁł ( SF; Fiber Sales and Development Corporation,
quantity of N present at that site; much of this N is
St. Louis, MO), 7.5% beet pulp ( BP; Michigan Sugar,
subsequently excreted as feces. Fermentable fibers
Saginaw, MI), a blend of 5.0% cellulose and 2.5%
encourage microbial growth and thus could contribute
pectin (high-cellulose mixture, HCM; TIC Gums,
Belcamp, MD), or a blend of 2.5% cellulose and 5.0%
pectin (low cellulose mixture, LCM) were tested in a
1
To whom correspondence should be addressed.
5 � 5 Latin square design with periods lasting 11 d.
Received September 25, 1995.
Accepted February 7, 1996. All diets were extruded. Five female dogs with hound
1641
1642 MUIR ET AL.
Table 1. Ingredient composition of the basal diet fed
Larger abscesses required subcutaneous injections of
to ileal-cannulated dogs
antibiotics (Polyflex, G. C. Hanford Manufacturing,
Syracuse, NY) twice daily.
Sampling Procedures. During the collection phase,
Ingredient % DM basis
ileal digesta and feces were collected. A 4-d collection
Gelatinized cornstarch to 100
phase was used with three collection times for ileal
Chicken protein sourcea 40.26
digesta daily. Each collection lasted for 1 h. For
Chicken fat 6.22
Egg 3.25 example, on d 1, sampling took place at 0700, 1100,
Vitamin-mineral premixb 1.90
and 1500. The sampling times advanced 1 h for the
Herring meal 1.00
three remaining days. Total feces excreted on each of
Brewer s dried yeast 1.00
the 4 d were collected from the floor of the pen,
Chicken liver meal .50
weighed, composited, and frozen at -4�C. Ileal digesta
DL-Methionine .45
Fiber sourcec 7.50 was collected by attaching a Whirlpak bag (Pioneer
a Container, Cedarburg, WI) to the cannula hose clamp
Combination of chicken and chicken by-product meal.
b
Provided the following (per kilogram of diet): vitamin A, 26,400 with a rubber band. Before attachment of the bag, the
IU; vitamin E, 136 IU; vitamin D3, 1,760 IU; thiamine, 16.5 mg;
inside of the cannulas was scraped clean with a
riboflavin, 29.0 mg; niacin, 58.0 mg; d-pantothenic acid, 35.3 mg;
spatula and initial digesta discarded. Dogs were
biotin, .52 mg; folic acid, 1.4 mg; choline, 2,295 mg; vitamin B12, .25
mg; monosodium phosphate, 6 g; potassium chloride, 5 g; choline encouraged to move around freely during ileal collec-
chloride, 3 g; Mn, 42.2 mg; Zn, 203 mg; Cu, 29.2 mg; Co, .5 mg; Se,
tions. Elizabethan collars were utilized at collection
.26 mg.
c times so that dogs would not pull the bag from the
0% supplemental fiber control; 7.5% beet pulp; 7.5% Solka Floc;
a blend of 5% Solka Floc and 2.5% pectin (high-cellulose mixture; cannula. Immediately after collection of ileal digesta,
HCM); a blend of 2.5% Solka Floc and 5% pectin (low-cellulose
pH was recorded. Samples then were frozen in their
mixture; LCM). Fiber sources were added to diets at the expense of
individual bags at -4�C. After completion of the trial,
the gelatinized cornstarch.
all of the digesta collected was composited for each dog
in each period and refrozen at -4�C. A portion of the
composited ileal digesta was frozen separately for
bloodlines and an average BW of 31 kg were fitted
analysis of short-chain fatty acids ( SCFA).
with simple T-type ileal cannulas according to the
Ileal digesta and feces were freeze-dried in a Tri-
method of Walker et al. (1994). Surgical and animal
Philizer�� MP microprocessor-controlled lyophilizer
care procedures for the experiment were conducted
under a research protocol approved by the Institu- (FTS Systems, Stone Ridge, NY). After drying, foods,
orts, ileal digesta, and feces were ground through a
tional Animal Care Advisory Committee, University of
2-mm screen in a Wiley mill.
Illinois, Urbana-Champaign. Dogs were allowed a
minimum of 2 wk recovery before experiment initia- Chemical Analyses. Foods, orts, ileal contents, and
feces were analyzed for DM, OM, and ash content
tion. Dogs were housed individually in clean floor pens
using AOAC (1984) procedures. Crude protein was
in a temperature-controlled room with a 12-h dark:
calculated from Kjeldahl N values (N � 6.25) for all
12-h light cycle. Dogs were adjusted to their respective
diets during a 7-d adaptation phase followed by a samples (AOAC, 1984). The total lipid content of
4-d collection period. diets, orts, ileal digesta, and feces was determined by
All dogs were offered 250 g (as-fed basis) of their acid hydrolysis followed by ether extraction according
respective diet each day at 0700 and 1900, for a total to the procedures of AACC (1983) and Budde (1952).
of 500 g/d for the first period. Because some dogs were The total dietary fiber ( TDF) content of diets, orts,
losing weight by the end of Period 1, diet offerings ileal digesta, and feces was determined according to
were increased to 300 g per feeding for a total of 600 g/ the method of Prosky et al. (1985). The ileal digesta
d for the remaining four periods. Diets were balanced pH was measured with a flat-glass electrode. Gross
to meet or exceed nutrient requirements of dogs at energy content of diets, orts, ileal digesta, and feces
their physiological state (NRC, 1974). was determined by bomb calorimetry (model 1261,
Chromic oxide was used as a digestion marker. Parr Instrument, Moline, IL). Ileal and fecal samples
Beginning on d 3 of each period, dogs were dosed were prepared for Cr analysis according to the method
orally with a capsule containing .5 g of chromic oxide of Williams et al. (1962), and Cr concentrations were
at 0700 and 1900, before feeding, for a total of 1 g of measured using an atomic absorption spectrophotome-
marker per day for the duration of the period. Water ter (model 2380, Perkin-Elmer, Norwalk, CT). For
was available ad libitum. Throughout the trial, all orts amino acid analysis, approximately 100 mg of food
were collected at the time of each feeding (i.e., at each and 150 mg of ileal contents were hydrolyzed in 15 mL
12-h period) for subsequent analyses. of 6 N HCl for 22 h at 105�C according to the
Small abscesses around the cannulas were treated procedure of Spitz (1973). The amino acid composi-
topically with Panalog cream (SOLVAY Animal tion of the resulting hydrolysate was measured on an
Health, Mendota Heights, MN) and were washed amino acid analyzer (model 126, Beckman Instru-
daily with Betadine solution (Becton Dickinson Acute- ments, Palo Alto, CA) using sodium citrate buffers
Care Division, Franklin Lakes, NJ) and warm water. and a ninhydrin detector. Short-chain fatty acids were
VARYING FIBER SOURCES IN DOG FOOD 1643
Table 2. Chemical composition of diets fed to ileal-cannulated dogs
Dieta
Item CON BP LCM HCM SF
Dry matter, % 91.5 92.8 92.2 93.1 93.3
% DM
Organic matter 93.0 92.2 92.8 92.8 92.6
Crude protein 34.2 34.7 33.7 33.8 34.3
Fat 23.6 23.1 24.2 23.2 22.5
Total dietary fiber 2.6 8.6 9.7 9.7 8.7
Gross energy, kcal/g 5.6 5.5 5.6 5.5 5.5
Amino acids
Essential
Arginine 2.4 2.4 2.2 2.3 2.3
Histidine .81 .84 .75 .76 .80
Isoleucine 1.5 1.5 1.4 1.4 1.4
Leucine 2.6 2.7 2.4 2.5 2.5
Lysine 2.4 2.5 2.1 2.2 2.3
Methionine .80 .71 .56 .68 .76
Phenylalanine 1.5 1.5 1.4 1.4 1.4
Threonine 1.4 1.4 1.3 1.3 1.3
Valine 1.8 1.9 1.7 1.7 1.7
Non-essential
Alanine 2.3 2.4 2.2 2.2 2.3
Aspartate 3.3 3.4 3.1 3.2 3.2
Glutamate 5.1 5.2 4.7 4.9 5.0
Glycine 3.2 3.3 3.0 3.1 3.1
Proline 2.2 2.3 2.0 2.1 2.1
Serine 1.5 1.5 1.4 1.4 1.4
Tyrosine 1.0 1.1 .93 .98 .99
a
CON = 0% supplemental fiber control; BP = 7.5% beet pulp; LCM (low-cellulose mixture) = a blend of
5% pectin and 2.5% Solka Floc; HCM (high-cellulose mixture) = a blend of 5% Solka Floc and 2.5% pectin;
SF = 7.5% Solka Floc.
analyzed by gas-liquid chromatography. Samples were procedure of SAS (1989). Model sums of squares were
prepared according to the method of Erwin et al. separated into treatment, period, and dog effects.
(1961). Concentrations of individual and total SCFA Sums of squares for diet effects were separated further
in the diluted supernatants were determined with a into orthogonal contrasts. Orthogonal contrasts used
gas chromatograph (model 5890A, Hewlett-Packard, were 1) control vs. supplemental fiber treatments; 2)
Avondale, PA) equipped with a flame-ionization BP vs. LCM, HCM, and SF; 3) linear cellulose effect,
detector. The column used was packed with GP 10% and 4) quadratic cellulose effect. Least squares means
SP1200/1% H3PO4 on 80/100 ChromasorbW AW (Su- (because of occasional missing data points) were
pelco, Bellefonte, PA). The column was 1.83 m in calculated for nutrient and energy intakes, ileal and
length and had an internal diameter of 4 mm. apparent total tract nutrient digestibilities, ileal pH,
Nitrogen was used as a carrier gas with a flow rate of and ileal SCFA. Level of probability for statistical
75 mL/min. Oven temperature was 125�C, and detec- significance was defined as P < .05 unless otherwise
tor and injector temperatures were 180�C and 175�C, stated.
respectively. For all procedures, samples were ana-
lyzed in duplicate.
Calculations. Dry matter (g/d) excreted as feces Results and Discussion
was calculated by dividing the Cr intake (mg/d) by
fecal Cr concentration (mg Cr/g feces). Nutrient flows
Chemical composition. The chemical composition of
at the ileum and nutrients in feces were calculated by the diets is presented in Table 2. Diets contained
multiplying the DM flow by the concentration of the similar concentrations of DM (92.6% on average), OM
nutrient in the ileal or fecal DM. Ileal and apparent (92.7% of DM), fat (23.3% of DM), CP (34.1% of
total tract nutrient digestibilities were calculated as DM), and gross energy (5.5 kcal/g DM). All sup-
nutrient intake (g/d) minus the ileal or fecal (respec- plemental fiber-containing diets had similar levels of
tively) nutrient flow (the quantity) divided by TDF (range, 8.6% for the diet containing BP to 9.7%
nutrient intake (g/d). for the diets containing the LCM and the HCM).
Statistical Analyses. Data were analyzed as a 5 � 5 Fahey et al. (1990a) fed 30 English pointers meat-
Latin square design by the General Linear Models based diets with beet pulp added at levels of 0, 2.5,
1644 MUIR ET AL.
Table 3. Nutrient intakes and digestibilities by ileal-cannulated dogs
Dieta
Item CON BP LCM HCM SF SEM
Intake, g/d
Dry matterb 368 421 423 447 459 20.4
Organic matterb 373 418 425 445 455 20.7
Crude proteinb 126 146 143 154 157 7.3
Fatb 87 96 105 105 103 5.1
Total dietary fiberb 10 36 40 43 39 2.7
Gross energy,b kcal/d 2,042 2,324 2,353 2,500 2,528 120.0
Digestion at ileum, %
Dry matter 76.6 67.8 64.1 74.0 73.4 5.0
Organic matter 83.6 74.9 71.5 79.2 78.7 3.8
Crude protein 73.4 70.9 66.1 76.7 77.8 4.4
Fatc 95.0 93.2 93.8 96.1 95.7 .93
Total dietary fiber -12.4 -23.4 -22.3 -8.1 -9.8 24.2
Gross energy 85.6 79.2 76.3 82.8 82.5 3.2
Total tract digestion, %
Dry matterbd 85.3 81.5 82.4 77.1 78.5 1.3
Organic matterbcd 90.9 86.3 86.7 82.2 83.1 1.0
Crude proteine 85.1 83.9 83.2 82.4 86.7 1.2
Fatf 95.1 94.3 94.0 94.9 95.3 .36
Total dietary fiberfg 23.8 35.0 47.8 5.0 -12.5 7.1
Gross energybd 91.1 87.4 87.7 84.8 85.8 .80
a
CON = 0% supplemental fiber control; BP = 7.5% beet pulp; LCM (low cellulose mixture) = a blend of
5% pectin and 2.5% Solka FlocŁł; HCM (high cellulose mixture) = a blend of 5% Solka FlocŁł and 2.5%
pectin; SF = 7.5% Solka FlocŁł.
b
CON vs BP, LCM, HCM, and SF ( P < .05).
c
BP vs LCM, HCM, and SF ( P < .10).
d
Quadratic cellulose effect ( P < .10).
e
Linear cellulose effect ( P < .10).
f
Linear cellulose effect ( P < .05).
g
BP vs. LCM, HCM, and SF ( P < .05).
5.0, 7.5, 10.0, and 12.5%. They found that inclusion of diet. Intake of nutrients was highest usually for dogs
dietary beet pulp at levels up to 7.5% resulted in no fed SF and HCM diets.
No differences among diets were noted in apparent
severe reductions in total tract nutrient digestibility
ileal digestibilities of DM, OM, CP, TDF, or GE (Table
or energy utilization and seemed to be an acceptable
3). However, dogs fed the LCM diet had numerically
source of dietary fiber in a meat-based dog diet.
lower ( P > .10) ileal digestibilities of all these
Similar TDF concentrations across treatments allow
constituents, except TDF, than did dogs fed the other
comparisons of digestive responses to different sources
diets. In addition, as regards the supplemental fiber
of dietary fiber. Diets contained similar concentrations
treatments, both the HCM and the SF treatments
of individual amino acids, with essential amino acids
resulted in numerically higher ( P > .10) ileal digesti-
ranging, on average, from a high of 2.5% for lysine to a
bilities of DM, OM, CP, fat, TDF, and GE compared
low of .70% for methionine, and with non-essential
with the LCM treatment. Atallah and Melnik (1982)
amino acids ranging, on average, from 1 to 5% for
fed growing rats purified diets containing various
tyrosine and glutamate, respectively.
pectins added at the 10% level. These pectins differed
Intake and digestibility. Intakes of DM, OM, TDF,
in molecular weight ( MW) and degrees of esterifica-
fat, GE, and CP did not differ among fiber-sup-
tion. These researchers noted that pectin-containing
plemented treatment groups (Table 3). Dogs ingest-
diets led to a decrease of eight percentage units, on
ing the control diet consumed less ( P < .05) food than
average, in apparent total tract digestion of N;
dogs consuming the other treatments. Fahey et al.
digestibilities ranged from 79.4% for the pectin with
(1990a) fed dogs meat-based diets with increasing
the highest MW and degree of esterification to 87.4%
levels of added BP and noted a linear increase ( P <
for the pectin with the lowest degree of esterification.
.05) in DM intake as level of dietary BP increased.
Their control diet, which contained no pectin, had an
This was attributed to a dilution in nutrient supply
apparent total tract N digestibility of 92%, thus
and slightly increased DM levels in diets sup-
indicating that pectin has the ability to significantly
plemented with the higher concentrations of fiber.
depress N digestibility. Li et al. (1994) fed pigs
Thus, as dietary energy content was diluted by the isonitrogenous diets with Solka Floc included at levels
presence of DF, dogs consumed a greater amount of of 4.3, 7.3, 10.3, or 13.3% in cornstarch-based soybean
VARYING FIBER SOURCES IN DOG FOOD 1645
meal-containing diets. Apparent ileal digestibilities of CP, respectively, by pigs fed pectin. Again, this is in
N averaged approximately 73% across treatments. agreement with apparent total tract OM (86.7%) and
Apparent ileal and total tract digestibilities were not CP (83.2%) digestibility values obtained for dogs fed
affected by the inclusion of Solka Floc at levels up to the LCM. Total dietary fiber digestibilities indicate
13.3%. The trend ( P > .10) for decreased digestibili- that soluble fibers are better energy substrates for
ties by dogs fed LCM, as well as the numerically gastrointestinal microorganisms than are insoluble
higher ( P > .10) digestibility values for dogs fed HCM fibers. Another aspect of digestion important in dog
or SF, agrees with the results of these two studies. nutrition is the moisture content of fecal material and
Apparent total tract digestibilities of DM, OM, and the amount of feces excreted by the animal. In this
GE by dogs fed fiber-containing diets were lower ( P < study, dogs fed the control, BP, LCM, HCM, and SF
.05) than values for dogs consuming the control diet. treatments had average fecal DM concentrations of 45,
Apparent total tract DM and GE digestibilities 29, 39, 45, and 47%, respectively. Average wet fecal
decreased quadratically ( P < .10) as the level of outputs (g wet feces excreted/d) were 118, 267, 191,
dietary cellulose increased. Burrows et al. (1982) 238, and 203, respectively. Inclusion of BP in diets
noted a linear decrease in apparent total tract resulted in the highest fecal moisture content as well
digestibility of DM when dogs were fed a meat-based as the greatest fecal volume. Treatments high in
diet with Solka Floc added at increasing levels (0, 3, cellulose also resulted in high fecal volumes. The
6, and 9%). Apparent total tract digestion of OM results of our study agree with the conclusion drawn
followed a similar pattern. In our study, digestibility by Eggum (1995) that the inclusion of dietary fiber,
of OM in BP-containing diets was higher than the in general, decreases apparent protein digestibility;
mean value for the other supplemental fiber-contain- insoluble fiber increases fecal bulk and N excretion
ing diets. Fahey et al. (1990a) reported a DM due to increased excretion of cell wall-bound protein,
digestibility of 86.2% and an OM digestibility of 89.0% and soluble fiber increases fecal bulk and N excretion
when apparent total tract digestibilities were meas- due to increased microbial N excretion.
ured in dogs fed a meat-based diet with 7.5% Amino acid intakes and digestibilities. To our
supplemental BP. The DM and OM apparent total knowledge, this is the only study in which amino acid
tract digestibilities observed in this trial (81.5 and ileal digestibility has been determined in dogs. Amino
86.3%, respectively) for dogs fed the BP treatment acid intakes were similar among supplemental fiber
were slightly lower. This difference could be attributed treatment groups, but greater than intakes of dogs
to age and(or) breed of dog, housing arrangements consuming the control diet for all amino acids
(metabolism cage vs run), marker usage, or cannula- measured except methionine (Table 4). A positive
tion of the dog. Apparent total tract digestibility of GE linear cellulose effect was noted for intakes of
was 87.7% for dogs consuming the LCM, whereas dogs methionine ( P < .05), lysine, and tyrosine ( P < .10),
consuming the HCM and SF had an average GE total perhaps reflecting OM and CP intake patterns. Amino
tract digestibility of 85.3%. Data indicate that diets acid intake data generally followed the pattern noted
containing higher concentrations of soluble fiber have for CP intake.
two to four percentage units greater total tract DM Amino acid digestion at the distal ileum was
and OM digestibility than diets with higher concentra- similar among treatments, and was not affected by
tions of insoluble fiber. treatment for all amino acids except lysine, for which
Apparent total tract digestibility of TDF was higher a positive linear effect ( P < .05) of cellulose concentra-
( P < .05) for dogs fed BP compared with the other tion was noted (Table 5). A trend ( P > .10) for SF
fiber treatments. However, this was largely due to the having the highest ileal amino acid digestibilities and
low TDF digestibility values for the HCM and SF the LCM having the lowest ileal digestibilities for all
treatments. Also a negative linear effect of cellulose amino acids was noted. These results agree with those
concentration was noted ( P < .05). The negative of the study by Mosenthin et al. (1994), in which pigs
digestibility for the SF-containing diet indicates that fed 7.5% pectin had significantly lower ileal amino
none of this fiber source was digested by the dogs. acid digestibilities than the control. Those researchers
Apparent total tract digestion of fat ( P < .05) and CP noted an average decrease in apparent ileal digestibil-
( P < .10) exhibited positive linear responses to dietary ity of 14.1 percentage units for essential amino acids
cellulose concentrations. Mosenthin et al. (1994) and 17.6 percentage units for non-essential amino
reported apparent ileal digestibilities of 74.1 and 69% acids when pectin was included in the diet. The
for OM and CP digestion, respectively, for a diet depression in apparent ileal digestibility of amino
containing 7.5 g pectin/100 g cornstarch-based diet fed acids noted for dogs fed the LCM was 5.9 percentage
to ileal-cannulated pigs. This agrees well with the units, on average, for essential amino acids and 7.5
apparent ileal digestion values for OM (71.5%) and percentage units, on average, for non-essential amino
CP (66.1%) when dogs were fed the LCM, which acids. When Li et al. (1994) included Solka Floc at
contained 5% pectin and 2.5% cellulose. In the same levels of 4.3, 7.3, 10.3, and 13.3% in an isonitrogenous
study, Mosenthin et al. (1994) reported apparent cornstarch-based soybean meal-containing diet for
total tract digestibilities of 94.7 and 85.8% for OM and pigs, no differences ( P > .05) were noted among
1646 MUIR ET AL.
Table 4. Amino acid intakes (g/d) by ileal-cannulated dogs
Dieta
Item CON BP LCM HCM SF SEM
Essential amino acids
Arginineb 8.7 10.4 9.4 10.3 10.6 .5
Histidineb 3.0 3.6 3.2 3.4 3.6 .2
Isoleucineb 5.4 6.5 5.7 6.2 6.6 .3
Leucineb 9.6 11.6 10.4 11.2 11.7 .6
Lysinebc 8.7 10.7 9.1 9.9 10.8 .6
Methionined 2.9 3.0 2.4 3.0 3.5 .2
Phenylalanineb 5.3 6.5 5.8 6.2 6.4 .3
Threonineb 5.4 6.5 5.9 6.3 6.6 .3
Valineb 6.6 8.0 7.0 7.6 8.0 .4
Non-essential amino acids
Alanineb 8.4 10.1 9.1 9.9 10.4 .5
Aspartateb 12.1 14.6 13.1 14.2 14.9 .8
Glutamateb 18.5 22.2 20.0 21.7 22.7 1.2
Glycineb 11.6 13.9 12.7 13.9 14.3 .7
Prolineb 7.9 9.7 8.6 9.5 9.7 .5
Serineb 5.4 6.6 6.0 6.4 6.6 .4
Tyrosinece 3.8 4.6 3.9 4.4 4.5 .2
a
CON = 0% supplemental fiber control; BP = 7.5% beet pulp; LCM (low-cellulose mixture) = a blend of
5% pectin and 2.5% Solka Floc; HCM (high-cellulose mixture) = a blend of 5% Solka Floc and 2.5% pectin;
SF = 7.5% Solka Floc.
b
CON vs. BP, LCM, HCM, and SF ( P < .05).
c
Linear cellulose effect ( P < .10).
d
Linear cellulose effect ( P < .05).
e
CON vs. BP, LCM, HCM, and SF ( P < .10).
Table 5. Amino acid digestibilities (%) at the distal ileum of cannulated dogs
Dieta
Item CON BP LCM HCM SF SEM
Essential amino acids
Arginine 86.8 87.3 83.4 87.9 88.7 2.8
Histidine 76.2 75.4 68.7 77.6 80.0 4.9
Isoleucine 77.9 78.3 71.1 79.1 81.5 4.3
Leucine 78.9 79.1 74.1 81.0 82.6 4.0
Lysineb 80.3 80.0 68.2 78.6 83.5 4.6
Methionine 86.0 87.2 86.2 86.7 87.7 3.3
Phenylalanine 75.2 72.8 69.0 77.4 78.0 5.4
Threonine 69.0 67.2 62.7 72.0 73.6 6.0
Valine 74.7 74.7 68.9 77.2 79.0 4.7
Non-essential amino acids
Alanine 80.1 79.6 74.4 81.6 82.7 4.0
Aspartate 66.1 60.0 53.3 65.0 68.1 7.9
Glutamate 79.1 78.3 71.9 80.2 81.8 4.4
Glycine 76.6 74.9 68.2 77.3 77.7 5.2
Proline 75.8 75.2 69.6 78.0 78.4 4.8
Serine 68.6 66.5 62.2 71.7 71.7 6.5
Tyrosine 72.9 72.2 67.0 76.4 77.3 5.8
TEAAc 78.7 78.3 72.3 80.0 82.0 4.3
TNEAAd 74.6 72.9 66.9 76.0 77.3 5.4
TAAe 76.4 75.3 69.3 77.8 79.4 4.9
a
CON = 0% supplemental fiber control; BP = 7.5% beet pulp; LCM (low-cellulose mixture) = a blend of
5% pectin and 2.5% Solka Floc; HCM (high-cellulose mixture) = a blend of 5% Solka Floc and 2.5% pectin;
SF = 7.5% Solka Floc.
b
Linear cellulose effect ( P < .05).
c
TEAA = total essential amino acids.
d
TNEAA = total non-essential amino acids.
e
TAA = total amino acids.
VARYING FIBER SOURCES IN DOG FOOD 1647
Table 6. Short-chain fatty acid (SCFA) concentrations and molar proportions in
digesta from the distal ileum and pH at the ileum of cannulated dogs
Dieta
Item CON BP LCM HCM SF SEM
Ileal pH 7.15 7.43 7.16 7.19 7.22 .09
Total ileal SCFA, mMb 2.3 3.2 1.8 2.4 2.0 .53
SCFA molar proportions,
mol/100 mol
Acetate 76.7 72.7 77.7 76.3 77.8 2.4
Propionateb 14.6 17.7 15.7 14.8 16.1 .9
Isobutyrate 0 .6 0 .5 0 .3
Butyrate 7.7 7.7 5.5 7.4 5.5 1.4
Isovalerate .9 1.3 1.1 1.1 .5 .6
a
CON = 0% supplemental fiber control; BP = 7.5% beet pulp; LCM (low-cellulose mixture) = a blend of
5% pectin and 2.5% Solka Floc; HCM (high-cellulose mixture) = a blend of 5% Solka Floc and 2.5% pectin;
SF = 7.5% Solka Floc.
b
BP vs. LCM, HCM, and SF ( P < .10).
treatments in apparent ileal amino acid digestibilities. isovalerate, and valerate were not present in any
These workers noted average apparent ileal amino significant amounts. Propionate molar proportion was
acid digestibility values of 78.9 and 77.9% for essential lower ( P < .10) for cellulose treatments than for the
and non-essential amino aids, respectively, for those BP treatment.
animals fed 7.3% Solka Floc. In our study, dogs fed In conclusion, incorporation of dietary fiber at a
7.5% Solka Floc had ileal digestibility values of 82.0 level of 7.5% did not adversely affect apparent ileal
and 77.3% for the essential and non-essential amino
digestibilities of DM, OM, TDF, fat, GE, CP, or amino
acids, respectively. Data from the two studies are in
acids. Specifically, apparent ileal digestibilities of CP
general agreement. Total essential amino acid digesti- and amino acids were not affected by fiber inclusion,
bility ( TEAA) at the ileum ranged from 72.3% for the
regardless of its solubility, viscosity, or fermentability.
LCM to 82% for SF; total non-essential amino acid
Greater variability in data obtained with ileal digesta
( TNEAA) apparent ileal digestibility ranged from
and use of marker techniques compared with total
66.9% for the LCM to 77.3% for SF; total amino acid
fecal collections may have contributed to this lack of
( TAA) digestibility at the ileum ranged from 69.3%
effect; however, interesting biological trends were
for the LCM to 79.4% for SF. The TEAA, TNEAA, and
noted in the data. Indeed, much of the CP and amino
TAA digestibilities were not affected by supplemental
acid intake and digestibility data showed significant
fiber treatment, but the trend ( P > .10) indicated that
effects among treatments if a P value between .10 and
SF inclusion in the diet resulted in the highest ileal
.20 was accepted. These effects were expressed
digestibilities of amino acids, whereas the LCM
primarily as a negative influence of soluble, fermenta-
treatment resulted in the lowest ileal digestibilities.
ble fiber (pectin) on ileal amino acid and CP
Perhaps this was due to the soluble-viscous-fermenta- digestibilities. Apparent total tract digestion of
ble nature of the pectin, which could alter rate of
nutrients was influenced by the presence of fiber as
passage of digesta through the small intestine, as well
well as by the mixtures of dietary fibers fed.
as the viscosity of the intraluminal contents (as
previously described), or to small intestinal fermenta-
tion. In addition, the viscous nature of pectin limits Implications
access of digestive enzymes to substrates, and this
could have a bearing on our results as well. Inclusion of pectin in meat-based dog diets tended
Short-chain fatty acids and pH. Averaged across to depress apparent nutrient digestibilities at the
treatments, ileal pH (7.23) was not affected by distal ileum but had little effect on apparent total
inclusion of fiber in the diets (Table 6). Total ileal tract nutrient digestibilities, apparently as a result of
SCFA ranged from 1.8 mM for the LCM to 3.2 mM for active microbial fermentation occurring in the large
BP; a difference ( P < .10) between BP and the other bowel of the dog. Cellulose incorporation into diets had
treatments was noted. These values indicate a limited little effect on apparent nutrient digestibilities at the
amount of microbial fermentation occurring in the ileum but resulted in lower apparent total tract
small intestine. Acetate was present in the highest digestibility values for nutrients due to the refractory
molar proportion (average 76.2 mol/100 mol), fol- nature of cellulose and its general lack of susceptibil-
lowed by propionate (average 15.8 mol/100 mol) and ity to microbial fermentation in the large bowel.
butyrate (average 6.8 mol/100 mol). Isobutyrate, Amino acid nutrition of dogs could potentially be
1648 MUIR ET AL.
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Li, S., W. C. Sauer, and R. T. Hardin. 1994. Effect of dietary fibre
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