Evaluation of low-ash poultry meal as a protein source in canine foods

Abstract

Eight mature female dogs (18.0 +/- 0.2 kg) were used in a replicated 4 x 4 Latin square experiment to determine the feeding value of low-ash poultry meal (PM) in a complete food fed to dogs. All foods contained graded concentrations of PM (10.4 to 32.5% DM), resulting in foods that were 10, 15, 20, and 25% CP. Daily DMI averaged 284 +/- 14 g/d. An increase in PM resulted in an increase in fecal moisture from 44.7 to 55.1% (linear; P < 0.01), and fecal DM output increased from 24.8 to 31.6 g/d (linear; P < 0.05). Ileal DM flow increased from 27.1 to 40.7 g/d (linear; P < 0.01). Small intestinal DM digestibility decreased from 90.4 to 86.1% (linear; P < 0.01) and total-tract DM digestibility decreased from 91.2 to 89.4% (linear; P < 0.01) as PM increased. Large intestinal DM digestibility increased from 8.4 to 21.1% with increasing PM (linear; P < 0.05). Fecal excretion of CP increased from 5.6 to 10.0 g/d (linear; P < 0.01) and ileal flow of CP increased from 6.9 to 15.6 g/d (linear; P < 0.01) as PM increased. Small intestinal CP digestibility was unaffected with treatment (P > 0.05). Large intestinal CP digestibility increased from 21.6 to 37.1% (linear; P < 0.05) with increasing PM. Total-tract CP digestibility increased from 81.0 to 86.6% (linear; P < 0.01) as PM increased. Arginine had the highest overall digestibility ranging from 88.5 to 91.3%, whereas cysteine had the lowest digestibility, ranging from 67.1 to 71.4%. These data indicate that PM is a highly digestible protein source for canine foods with inclusions of 10.4 to 32.5% of DM.

Full text

R. M. Yamka, U. Jamikorn, A. D. True and D. L. Harmon
Evaluation of low-ash poultry meal as a protein source in canine foods
2003, 81:2279-2284.J ANIM SCI
http://jas.fass.org/content/81/9/2279
the World Wide Web at:
The online version of this article, along with updated information and services, is located on
www.asas.org
by guest on May 24, 2011jas.fass.orgDownloaded from

Evaluation of low-ash poultry meal as a protein source in canine foods
1
R. M. Yamka, U. Jamikorn, A. D. True, and D. L. Harmon
2
Department of Animal Sciences, University of Kentucky, Lexington 40546
ABSTRACT: Eight mature female dogs (18.0 ± 0.2
kg) were used in a replicated 4 × 4 Latin square experi-
ment to determine the feeding value of low-ash poultry
meal (PM) in a complete food fed to dogs. All foods
contained graded concentrations of PM (10.4 to 32.5%
DM), resulting in foods that were 10, 15, 20, and 25%
CP. Daily DMI averaged 284 ± 14 g/d. An increase in
PM resulted in an increase in fecal moisture from 44.7
to 55.1% (linear; P < 0.01), and fecal DM output in-
creased from 24.8 to 31.6 g/d (linear; P < 0.05). Ileal
DM flow increased from 27.1 to 40.7 g/d (linear; P <
0.01). Small intestinal DM digestibility decreased from
90.4 to 86.1% (linear; P < 0.01) and total-tract DM di-
gestibility decreased from 91.2 to 89.4% (linear; P <
0.01) as PM increased. Large intestinal DM digestibility
Key Words: Amino Acids, Ash, Digestibility, Dogs
2003 American Society of Animal Science. All rights reserved. J. Anim. Sci. 2003. 81:2279–2284
Introduction
Poultry meal (PM) is of considerable value as a protein
source in canine foods. Information on the chemical com-
position and nutrient digestibility of poultry meal indi-
cates that it can be a variable product (Han and Parsons,
1990; Johnson et al., 1998). Two factors believed to affect
AA digestibility of animal meals are ash content and
processing temperature.
Results of research on apparent digestibility of AA
from various sources of PM have been inconsistent.
Johnson et al. (1998) found that the low-ash PM had a
slightly higher apparent digestibility of the essential AA
than the high-ash PM (68.0 vs. 66.9%). However, the
low-ash meat and bone meal was significantly lower in
apparent digestibility of AA than the high-ash meat and
bone meal (approximately 16 percentage units). From
this, Johnson et al. (1998) determined that any reduction
in protein quality with increased ash content was the
result of decreased concentrations of AA per unit of pro-
1
Published as publication No. 02-07-158 of the Kentucky Agric.
Exp. Stn.
2
Correspondence—phone: 859-257-7515; fax: 859-257-3412; E-
mail: dharmon@uky.edu.
Received August 29, 2002.
Accepted June 4, 2003.
2279
increased from 8.4 to 21.1% with increasing PM (linear;
P < 0.05). Fecal excretion of CP increased from 5.6 to
10.0 g/d (linear; P < 0.01) and ileal flow of CP increased
from 6.9 to 15.6 g/d (linear; P < 0.01) as PM increased.
Small intestinal CP digestibility was unaffected with
treatment (P > 0.05). Large intestinal CP digestibility
increased from 21.6 to 37.1% (linear; P < 0.05) with
increasing PM. Total-tract CP digestibility increased
from 81.0 to 86.6% (linear; P < 0.01) as PM increased.
Arginine had the highest overall digestibility ranging
from 88.5 to 91.3%, whereas cysteine had the lowest
digestibility, ranging from 67.1 to 71.4%. These data
indicate that PM is a highly digestible protein source
for canine foods with inclusions of 10.4 to 32.5% of DM.
tein, and not decreased digestibility. The results of other
poultry byproduct studies have varied. Zuo et al. (1996)
determined that apparent digestibility of essential AA
of poultry byproduct meal averaged 69.7% in dogs. Mur-
ray et al. (1997) found a higher apparent digestibility of
essential AA (81.0%) of poultry byproduct meal, indicat-
ing that the protein source was of higher quality when
compared with Zuo et al. (1996). Other studies have
shown digestibilities ranging from 77 to 89% of CP in
poultry based foods (Zuo et al., 1996; Murray et al., 1997).
Studies investigating the digestibility of PM in dogs have
ranged in concentrations of 7 to 32% of the total food
(Zuo et al., 1996; Murray et al., 1997; Johnson et al.,
1998). However, no individual study has investigated the
effect increasing PM has on apparent small intestinal
digestibility of AA in the dog. Therefore, the objective of
the present study was to determine the apparent small
intestinal digestibility of AA in response to increasing
protein from low-ash PM.
Materials and Methods
Dogs
Eight ileally cannulated (Walker et al., 1994) mature
female mongrel dogs with BW of 18.2 ± 0.2 kg were
used to evaluate protein and AA disappearance at the
by guest on May 24, 2011jas.fass.orgDownloaded from

Yamka et al.2280
Table 1. Crude protein and amino acid composition
of protein sources used to formulate
the low-ash poultry meal foods
a
Item, Low-ash Brewer’s
% of DM poultry meal rice
Crude protein 69.3 8.3
Arginine 4.37 0.69
Cysteine 1.32 0.19
Glycine 6.53 0.38
Histidine 1.71 0.28
Isoleucine 2.34 0.31
Leucine 4.77 0.70
Lysine 3.11 0.32
Methionine 1.13 0.24
Phenylalanine 2.69 0.42
Threonine 3.02 0.31
Tryptophan 0.52 0.10
Tyrosine 1.84 0.13
Valine 3.16 0.48
Aspartate 5.58 0.78
Serine 4.42 0.43
Glutamate 8.60 1.46
Alanine 4.30 0.55
a
Analyzed before formulation of foods.
terminal ileum and through the total tract. The dogs
were located in the Division of Laboratory Animal Re-
search Facility at the University of Kentucky (Lexing-
ton) and were cared for in accordance with Institutional
Animal Care and Use Committee protocols. Dogs were
housed in an environmentally controlled room at 22°C
with a light:dark cycle of 14:10. The kennels measured
1 × 1.5 m, with a slotted floor sitting 0.2 m above ground.
Each kennel was cleaned twice daily, following feeding
and allowing for 25 min of exercise and socialization with
other dogs and people. Water was available ad libitum
throughout the experiment.
Table 2. Ingredient composition of low-ash poultry meal foods
Crude protein in food, %
Ingredient, % 10 15 20 25
Corn starch
a
46.6 40.8 35.1 29.5
Low-ash poultry meal 10.4 17.8 25.0 32.5
Rice, brewers 25.0 25.0 25.0 25.0
Grease, choice white 9.5 8.8 8.0 7.0
Cellulose
b
2.5 2.5 2.5 2.5
Dicalcium phosphate 1.9 1.3 0.7 —
Calcium carbonate 0.4 0.3 0.2 —
Soybean oil 1.0 1.0 1.0 1.0
Palatability enhancer 1.0 1.0 1.0 1.0
Vitamin-trace mineral
c
1.7 1.5 1.5 1.5
a
Buffalo corn starch from Corn Products International, Westchester, IL.
b
Cellulose from J. Rettenmaier USA LP, Schoolcraft, MI.
c
Formulated to supply (at least) the following (g/kg of food): 0.6 Mg, 1.8 Na, 7.0 K, 7.6 Cl, (mg/kg of food)
211 Fe, 163 Zn, 13 Cu, 13 Mn, 0.4 Se, 1.5 I, (IU/g of food) 18.2 vitamin A, 1.0 vitamin D, 0.18 vitamin E,
(mg/kg of food) 0.3 biotin, 1,484 choline, 1.9 folic acid, 62 niacin, 18 pantothenic acid, 8.6 pyridoxine, 8.0
riboflavin, 41 thiamin, and 0.13 vitamin B
12
.
Feeding and Treatments
The ingredient and chemical compositions of each pro-
tein source and food are presented in Tables 1, 2, and
3. Each food was formulated, extruded, and kibbled in
accordance with the AAFCO (2000) nutrient guide for
dogs and balanced to meet maintenance requirements
(Tables 2 and 3); however, the 10 and 15% CP foods were
below the AAFCO minimum requirement of 18% CP.
Differences between the four foods were based on vary-
ing proportions of PM found in the dry food. The source
of CP was PM, and foods were 10, 15, 20, and 25% CP.
Chromic oxide was added to each food at 0.2% DM to
serve as an indigestible marker to determine digestibil-
ity. Each day, food was weighed and divided into two
equal portions and fed at 0700 and 1700 in stainless
steel bowls. Each dog was allowed 20 min to consume
the food. Bowls were removed after 20 min, and orts
were weighed and recorded. Throughout the experiment,
food samples were collected daily and pooled into plastic
collection bags for nutrient content analysis.
Sampling
The experiment was designed as a replicated 4 × 4
Latin square. Each experimental period was 14 d in
length. During the first 2 d of the period, dogs were fed
a 1:1 mixture of their current food and their respective
next experimental food in order to avoid meal refusal and
gastric problems. Dogs were allowed 6 d for adaptation to
each new food.
On the first day of fecal collection (d 7), all feces were
removed from the cages and discarded before 0730. Fecal
output was collected from this point on for the next 5 d
at each mealtime and placed into labeled plastic bags.
Samples were frozen as they were collected and pooled
by dog within each period.
The ileal sampling period consisted of the 3 d following
fecal collection. During ileal collection, Bite-not collars
by guest on May 24, 2011jas.fass.orgDownloaded from

Low-ash poultry meal in canine foods 2281
were placed on the dogs after the morning feeding and
removed after the last collection. These collars allowed
the dogs to drink water normally and prevented the
removal of their collection bags, which were attached
to the cannulas during sampling times. Ileal digesta
collection began at 0800 on d 12. Plastic, 28-g Whirl-Pak
collection bags (Nasco, Fort Atkinson, WI) were placed
on the animals’ cannulas to collect the ileal digesta. On
d 12 and 13, digesta were collected at 0800, 1000, 1200,
1400, and 1600. On d 14, samples were collected at 0900,
1100, 1300, and 1500. At each collection time, samples
were weighed, frozen, and added to a pooled sample.
Analyses
After collection, fecal and ileal samples were stored
frozen until they were lyophilized using a Dura-Dry MP
Freeze-Drier (FTS Systems, Stone Ridge, NY). Dry mat-
ter was determined as the difference in sample weight
before and after lyophilization. Fecal samples were then
ground through a 0.5 mm screen in a Cyclotec 1093
Sample Mill (Tecator, Hoganas, Sweden). Ileal samples
were ground using a mortar and pestle. Feed samples
were ground using a conventional blender (Hamilton
Beach/Proctor Silex, Washington, NC). The dried and
Table 3. Chemical composition of low-ash poultry meal foods
Crude protein in food, %
Item 10 15 20 25
Dry matter, % 93.6 94.0 93.9 94.2
Dry matter basis, %
Organic matter 95.5 95.4 95.2 94.8
Crude protein 10.4 15.1 20.4 25.9
Crude fat
a
12.5 12.6 12.8 12.8
ME, kcal/kg
a
3600 3600 3600 3600
Crude fiber
a
2.2 2.3 2.4 2.5
Calcium
a
0.8 0.8 0.8 0.8
Phosphorus
a
0.6 0.6 0.6 0.6
Essential amino acids
Arginine 0.69 0.97 1.29 1.59
Histidine 0.23 0.31 0.41 0.50
Isoleucine 0.17 0.31 0.49 0.62
Leucine 0.69 0.99 1.36 1.68
Lysine 0.49 0.74 1.05 1.34
Methionine 0.18 0.25 0.34 0.41
Phenylalanine 0.37 0.54 0.74 0.91
Threonine 0.41 0.58 0.81 0.98
Tryptophan 0.17 0.19 0.22 0.24
Valine 0.38 0.56 0.75 0.92
Nonessential amino acids
Alanine 0.71 0.97 1.26 1.53
Aspartate 0.87 1.24 1.69 2.05
Cysteine 0.13 0.16 0.21 0.24
Glutamate 1.47 2.08 2.75 3.40
Glycine 0.83 1.23 1.68 2.08
Proline 0.63 0.93 1.27 1.54
Serine 0.48 0.69 0.93 1.15
Tyrosine 0.27 0.37 0.50 0.62
a
Values are calculated.
ground samples were then stored in labeled plastic bags
at room temperature until further analysis.
Ileal, fecal, and feed samples were dried, ashed, and
digested as described by Williams et al. (1962). The solu-
tions were allowed to settle and were analyzed the follow-
ing day using an ATI Unicam 99 atomic absorption spec-
trophotometer (Cambridge, U.K.) to determine Cr con-
centrations in the samples. Protein content (N × 6.25)
of the samples were obtained using a Leco CNS2000
(Leco Corp., St. Joseph, MI) N analyzer (AOAC, 1995).
Amino acid analyses of feed and ileal samples were
determined according to AOAC (1995). A 10-␮L aliquot
was derivatized with 6-aminoquinolyl-N-hydroxy-
succinimidyl carbamate and the AA concentration was
determined by reverse-phase liquid chromatography us-
ing Millipore Waters AccQ Tag System, as described by
Liu et al. (1995).
Calculations and Statistics
Nutrient digestibility was calculated as described by
Merchen (1988) using chromium as an indigestible
marker. Digesta flows were adjusted for the amount of
marker recovered in the feces during the 5-d fecal col-
lection.
by guest on May 24, 2011jas.fass.orgDownloaded from

Yamka et al.2282
Table 4. Dry matter digestibility in dogs fed increasing
concentrations of low-ash poultry meal
Crude protein in food, % Contrasts
b
Item 10 15 20 25 SEM
a
Linear Quadratic
Body weight, kg 17.8 18.0 18.2 18.1 0.2 NS NS
DMI, g/d 278.8 269.4 294.5 295.1 7.6 P < 0.05 NS
Fecal moisture, % 44.7 49.6 51.3 55.1 1.1 P < 0.01 NS
Feces, g of DM/d 24.8 25.2 28.6 31.6 2.1 P < 0.05 NS
Ileal flow, g of DM/d 27.1 27.9 35.6 40.7 3.1 P < 0.01 NS
DM digestibility
Small intestine, % 90.4 89.9 87.8 86.1 1.1 P < 0.01 NS
Large intestine, %
c
8.4 8.8 15.5 21.1 4.6 P < 0.05 NS
Total tract, % 91.2 90.8 90.3 89.4 0.6 NS NS
a
Standard error of mean, n = 8.
b
Probability of a greater F- value.
c
Percentage of ileal flow.
NS = nonsignificant, P > 0.05.
Data were analyzed as a replicated 4 × 4 Latin square
using the GLM and regression procedures of SAS (SAS
Inst., Inc., Cary, NC). The experimental unit was dog,
the model included square, treatment, period (square),
and dog (square), and the error was residual error mean
square. Means were separated using polynomial con-
trasts for linear, quadratic, and cubic effects of PM inclu-
sion. Differences were considered significant when P <
0.05.
Results
All dogs remained healthy throughout the experiment.
There were no differences in BW during the experiment
(P > 0.05, Table 4). No differences in BW were expected
since foods were adjusted to supply the proper amount
of energy required for maintenance of BW each period.
Despite these attempts at equalizing intake, a linear
increase in intake (P < 0.05) with increasing PM oc-
curred. Fecal moisture increased linearly (P < 0.01), as
did fecal DM output and ileal DM flow (P < 0.05 and P
Table 5. Crude protein digestibility in dogs fed increasing
concentration of low-ash poultry meal
Crude protein in food, % Contrasts
b
Item 10 15 20 25 SEM
a
Linear Quadratic
CP intake, g/d 28.8 40.6 60.0 73.8 0.2 P < 0.01 NS
Feces, g of CP/d 5.6 6.3 8.1 10.0 0.1 P < 0.01 NS
Ileal flow, g of CP/d 6.9 8.8 12.5 15.6 0.2 P < 0.01 NS
CP Digestibility
Small intestine, % 76.3 79.3 79.4 78.1 2.3 NS NS
Large intestine, %
c
21.6 24.1 27.4 37.0 4.0 P < 0.05 NS
Total tract, % 81.0 84.5 86.3 86.6 1.3 P < 0.01 NS
a
Standard error of mean, n = 8.
b
Probability of a greater F- value.
c
Percentage of ileal flow.
NS = non-significant, P >0.05.
< 0.01, respectively), in response to increasing the PM
in the foods. Small intestinal DM decreased as PM in-
creased (P < 0.01). Large intestinal DM digestibility in-
creased linearly (P < 0.05) as PM increased. Total-tract
DM digestibility was not affected (P > 0.05) by increas-
ing PM.
Table 5 depicts CP (N × 6.25) digestibilities. As ex-
pected, CP intake increased (P < 0.01) with increasing
CP. There was also a linear increase (P < 0.01) in fecal
CP excretion and ileal flow of CP (P < 0.01). Small intesti-
nal CP digestibility was not affected (P > 0.05) by in-
creased concentrations of PM, whereas large intestinal
CP digestibility increased linearly (P < 0.05). Total-tract
CP digestibility increased linearly (P < 0.01) as PM in-
creased.
Amino acid disappearance as a percentage of intake
is shown in Table 6. Digestibilities for all AA were not
affected by increased PM, with the exception of isoleu-
cine and tryptophan. Arginine had the highest digestibil-
ity, ranging from 88.5 to 91.3%. Cysteine had the lowest
overall digestibility, ranging from 67.1 to 71.4%.
by guest on May 24, 2011jas.fass.orgDownloaded from

Low-ash poultry meal in canine foods 2283
Table 6. Disappearance of amino acids (percent of intake) in cannulated dogs fed
increasing concentrations of low-ash poultry meal
Crude protein in food, % Contrasts
b
Item 10 15 20 25 SEM
a
Linear Quadratic
Essential amino acids
Arginine 88.5 91.3 90.7 89.9 1.3 NS NS
Histidine 81.7 86.5 84.4 83.0 2.2 NS NS
Isoleucine 53.7 71.4 74.9 75.4 4.6 P < 0.01 NS
Leucine 78.3 83.5 83.5 82.6 2.3 NS NS
Lysine 77.1 83.0 83.0 82.0 2.6 NS NS
Methionine 86.3 89.0 90.3 89.0 1.6 NS NS
Phenylalanine 78.7 83.7 83.8 83.2 2.2 NS NS
Threonine 70.2 77.3 76.8 75.5 3.2 NS NS
Tryptophan 86.6 84.7 80.8 77.2 2.0 P < 0.01 NS
Valine 72.8 79.3 78.8 77.7 2.9 NS NS
Nonessential amino acids
Alanine 81.1 84.6 84.2 82.4 2.2 NS NS
Aspartate 68.9 76.0 72.8 69.4 4.0 NS NS
Cysteine 67.1 71.4 71.1 69.0 4.0 NS NS
Glutamate 80.2 84.5 83.3 81.8 2.3 NS NS
Glycine 80.3 85.6 83.8 81.7 2.4 NS NS
Proline 78.2 83.8 83.2 81.3 2.5 NS NS
Serine 70.1 77.6 76.2 75.3 3.2 NS NS
Tyrosine 75.6 80.0 80.0 78.7 2.7 NS NS
a
Standard error of mean, n = 8.
b
Probability of greater F-value.
NS = nonsignificant, P > 0.05.
Discussion
The purpose of this study was to determine the appar-
ent small intestinal digestibility of protein and AA in
response to increasing protein from low-ash PM. Total-
tract and small intestinal digestibility have been shown
to vary because of differences in processing conditions
and poultry byproduct sources (Muir et al., 1996; Zuo et
al., 1996; Murray et al., 1997; Johnson et al., 1998). The
results obtained in the present study are dissimilar to
the Johnson et al. (1998) study, which investigated low-
ash poultry byproduct meal as a protein source in canine
foods. Johnson et al. (1998) reported that DM small in-
testinal digestibility was 76% and CP small intestinal
digestibility was 68% for PM. Our values for small intes-
tinal and total-tract DM digestibility were approxi-
mately 7% higher (Table 4), indicating that the poultry
meal used in the present study may be of higher quality.
In another study, Zuo et al. (1996) fed an extruded
and kibbled food containing 32% poultry byproduct meal
to ileally cannulated dogs. The CP digestibilities were
approximately 10 percentage units lower (66% ileal di-
gestibility and 77% total tract) when compared with our
study. This lower digestibility suggests that the poultry
byproduct meal used in their study was lower quality
reinforcing the fact that poultry byproduct meal can be
highly variable.
The results from our canine AA digestibility study are
in agreement with Muir et al. (1996) and Murray et al.
(1997), who reported that poultry byproduct meal had
apparent digestibilities of AA ranging from 66 (aspar-
tate) to 89% (arginine) when poultry byproduct meals
were fed to dogs. Of the AA studied, arginine had the
highest small intestinal digestibility, whereas cysteine,
aspartate and isoleucine had the lowest. The small intes-
tinal digestibilities of AA observed by Muir et al. (1996),
Murray et al. (1997), and in the present study, are higher
than the digestibilities observed by Zuo et al. (1996) and
Johnson et al. (1998).
Variation in protein quality and AA availability
among major protein ingredients and the response to
varying levels of inclusion are of special concern to the
pet food industry. Because of differences in raw material
source and processing conditions, AA composition and
availability may be variable among animal meals. There-
fore, studies focusing on protein quality and AA avail-
ability of individual ingredients and different dietary
concentrations of these individual ingredients are
needed.
Increased processing time has been shown to decrease
digestibility and AA availability (Johnson et al. 1998).
Poultry byproduct normally contains only dry rendered
parts of the chicken, such as heads, feet, undeveloped
eggs, gizzards, and intestines, but not feathers, except
for the few that may be included from collection pro-
cesses. Renderers that provide poultry byproducts for the
pet food industry have different methods for determining
what will be utilized for byproducts. The differences in
sorting methods can lead to varying concentrations of
byproducts, resulting in a highly variable product (Mur-
ray et al., 1997). This variability can affect digestibility
and AA profiles, making it difficult to determine the
quality of the protein used to formulate canine foods.
by guest on May 24, 2011jas.fass.orgDownloaded from

Yamka et al.2284
This study indicates that PM fed at an inclusion level
of 10.4% (10% CP) of the food can supply adequate
amounts of digestible leucine, histidine, arginine, threo-
nine, tryptophan, and lysine when compared to NRC
(1985) requirements for canine maintenance. However
inadequate amounts of digestible methionine, isoleucine,
phenylalanine, and valine were supplied by the 10% CP
food. The requirements for threonine and valine were
not met until PM was included as 17.8% (15% CP) of
the food. Isoleucine and phenylalanine requirements
were not met until PM was included as 25.0% (20% CP)
of the food. Therefore, foods containing less than 25.0%
PM as a supplemental protein source would not meet
the minimum AA requirements for maintenance in the
dog. To be able to effectively utilize PM in lower protein
foods (<20% CP), the food would need to include a phenyl-
alanine and isoleucine supplement or utilize another
protein source (plant protein source combined with ani-
mal protein source) to effectively supply all the essential
AA needed for canine maintenance. Brewer’s rice was
included as 25% of the DM in each food and contributed
from 8 to 20% of total protein. It is believed that the
contribution of brewer’s rice to total protein did not affect
digestibility in this study; thus, PM digestibility was
maintained across a wide range of inclusions.
These data show the value of ileal-cannulated dogs
to determine digestibility. Total-tract CP digestibility
increased with increasing PM; however, no differences
in small intestinal CP digestibility were observed. This
would result in large changes of AA utilization in the
large intestine. Further, microbial transformation or
production of AA in the large intestine can also lead to
erroneous estimates of digestion and absorption (Wil-
liams, 1995). Crude protein or AA present in the feces can
be of dietary, endogenous, or microbial origin, making it
impossible to differentiate AA origin in the feces.
The general assumption in the pet food industry is
that animal protein usually has a higher digestibility
and is of higher quality when compared to plant protein
sources. Proteins of plant origin usually have a lower
digestibility than animal proteins because plant fiber
and carbohydrates lower digestion, due to a reduced deg-
radation rate of nutrients in the gut and increased bacte-
rial activity (Meyer, 1984; Neirinck et al., 1991; Murray
et al., 1997). The digestibility of PM in the present study
was investigated by adding increasing concentrations
of PM into the foods. A ranking of dietary treatments
according to apparent digestibility showed that ileal di-
gestibility of the 10% PM food for dogs tended to be
lower than that of 25% PM food. However, the impact
of endogenous protein and AA on apparent digestibility
would have been greatest for the 10% CP diet, and the
differences among digestibilities of all treatments were
small. These results show that PM is digested efficiently
at a wide range of concentrations in the dog.
Implications
For dogs, a high-quality protein source should contain
all the essential amino acids in proper amounts and be
readily bioavailable. The results of this study imply that
poultry meal in dietary inclusions of 10 to 32.5% of the
food can be an excellent source of protein for dogs; how-
ever, adequate amounts of digestible amino acids were
not supplied until poultry meal was incorporated as
32.5% (25% crude protein) of the dry matter. Comple-
mentary sources of protein may be needed to meet amino
acid requirements at lower protein intakes.
Literature Cited
AAFCO. 2000. Association of American Feed Control Officials: Official
Publication. The Association, Atlanta, GA.
AOAC. 1995. Official Methods of Analysis. Assoc. Offic. Anal.Chem.,
Washington, DC.
Han, Y., and C. M. Parsons. 1990. Determination of available amino
acids and energy in alfalfa meal, feather meal, and poultry by-
product meal by various methods. Poult. Sci. 69:1544–1552.
Johnson, M. L., C. M. Parsons, G. C. Fahey, N. R. Merchen, and
C. G. Aldrich. 1998. Effects of species raw material source, ash
content, and processing temperature on amino acid digestibility
of animal by-product meals by cecectomized roosters and ileally
cannulated dogs. J. Anim. Sci. 76:1112–1122.
Liu, H. J., B. Y. Chang, H. W. Yan, F. H. Yu, and X. X. Liu. 1995.
Determination of amino acids in food and feed by derivatization
with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate and re-
verse-phase liquid chromatographic separation. J. AOAC Int.
78:736–744.
Merchen, N. R. 1988. Digestion, absorption and excretion in ruminants.
Pages 188-189 in The Ruminant Animal: Digestive Physiology
and Nutrition. D. C. Church, ed. Prentice Hall, Engelwood
Cliffs, N.J.
Meyer, H. 1984. Nutrient digestibility and its relationship to alimen-
tary disorders in dogs. Pages 66–69 in Nutrition and Behavior
in Dogs and Cats. Permagon Press, Oxford, U.K.
Muir, H. E., S. M. Murray, G. C. Fahey, Jr., N. R. Merchen, and G.
A. Reinhart. 1996. Nutrient digestion by ileal cannulated dogs
as affected by dietary fibers with various fermentation character-
istics. J. Anim. Sci. 74:1641–1648.
Murray, S. M., A. R. Patil, G. C. Fahey, Jr., N. R. Merchen, and
D. M. Hughes. 1997. Raw and rendered animal by-products as
ingredients in dog diets. J. Anim. Sci. 75:2497–2505.
Neirinck, K., L. Istasse, A. Gabriel, C. Van Eenaeme, and J. M. Bienfait.
1991. Amino acid composition and digestibility of four protein
sources for dogs. J. Nutr. 121:S64–S65.
NRC. 1985. Nutrient Requirements of Dogs. Natl. Acad. Sciences,
Washington, DC.
Walker, J. A., D. L. Harmon, K. L. Gross, and G. F. Collings. 1994.
Evaluation of nutrient utilization in the canine using the ileal
cannulation technique. J. Nutr. 124:2672–2676.
Williams, C. H., D. J. David, and O. Iismaa. 1962. The determination
of chromic oxide in feces samples by atomic absorption spectropho-
tometry. J. Agr. Sci. 59:381.
Williams, P. E. V. 1995. Digestible amino acids for non-ruminant ani-
mals: Theory and recent challenges. Anim. Feed Sci. Tech.
53:173–187.
Zuo, Y., G. C. Fahey, N. R. Merchen, and N. L. Bajjalieh. 1996. Diges-
tion responses to low oligosaccharide soybean meal by ileally-
cannulated dogs. J. Anim. Sci. 74:2441–2449.
by guest on May 24, 2011jas.fass.orgDownloaded from

References
http://jas.fass.orghttp://jas.fass.org/content/81/9/2279#BIBL
This article cites 8 articles, 4 of which you can access for free at:
Citations
http://jas.fass.org/content/81/9/2279#otherarticles
This article has been cited by 3 HighWire-hosted articles:
by guest on May 24, 2011jas.fass.orgDownloaded from