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Dietary Poultry Fat and Gastrointestinal Transit Time of Feed
and Fat Utilization in Broiler Chickens
A. GOLIAN1 and D. V. MAURICE2
Department
of
Poultry
Science,
Clemson
University,
Clemson,
South
Carolina 29634-0379
ABSTRACT An experiment was conducted with broiler chicks to determine
the effect of 0,5,10, and
20%
supplemental poultry fat and age on gastrointesti-
nal transit time (GTT) and the effect of supplemental fat on fat utilization and
growth. Mean GTT, measured with chromic oxide or ferric oxide, was not
affected by supplemental fat. There was a curvilinear relationship (rising ogive)
between mean
GTT
and
age.
It increased from an estimated lower plateau of 170
min to an upper plateau of
211
min with the inflexion point at
3.23
wk. At
6
wk
of age, birds receiving supplemental fat consumed more energy and were
heavier and more efficient. Total lipid digestibility increased with supplemental
poultry fat but digestibility of poultry fat was not altered. The AME of poultry
rat ranged from 8.1 to 8.4 kcal/g at 5 to 20% inclusion in the diet.
(Key
words:
dietary poultry fat, fat utilization, gastrointestinal transit time,
apparent metabolizable energy, age)
1992 Poultry Science 71:1357-1363
INTRODUCTION
Numerous factors influence the transit
of ingesta through the gastrointestinal
tract. Fasting, drugs, ileal obstruction,
irradiation, diet composition, and enteric
parasitism alter gastrointestinal transit
time (GTT) of feed in laboratory animals
(Summers et al, 1970; Castro et al, 1976).
Factors reported to affect GTT in poultry
include excitement (Henry et al, 1933), age
(Hillerman et al,
1953;
Vergara et al, 1989),
temperature (Wilson et al, 1980), genotype
(Cherry and Siegel, 1978), amount of feed
consumed (Sibbald, 1979; Wilson et al,
1980),
and diet composition (Monson et al,
1950;
Hillerman et al, 1953; Stokstad et al,
1953;
Larbier et al, 1977; Mateos and Sell,
1981).
Diet is the most important factor affect-
ing GTT (Duke, 1989). Food may contain
specific cathartics or the qualitative and
Received for publication December 23, 1991.
Accepted for publication March 31, 1992.
1On sabbatical leave from School of Agriculture,
Ferdowsi University of Mashhad, Mashhad, Iran.
2To whom correspondence should be addressed.
quantitative differences in carbohydrates,
proteins, fats, and additives may alter
transit time. Penicillin in feed slowed GTT
in chickens and turkeys (Hillerman et al,
1953) and in purified diets aureomycin
retarded feed passage in a sucrose-based
diet but not in glucose- or starch-based
diets (Stokstad et al, 1953). Different
carbohydrates have a distinct effect on
GTT in chickens. Diets containing sucrose
and lactose passed through the tract faster
than diets containing either glucose or
starch (Monson et al, 1950; Stokstad et al,
1953;
Tuckey et al, 1958; Mateos and Sell,
1981).
The effect of supplemental fat on GTT
in chickens is equivocal. Yellow grease
included at 0 to 30% in the diet delayed
transit time of feed in White Leghorn hens
in egg production (Mateos et al, 1982). In
contrast, neither animal fat supplements at
levels up to 12% in the diet of
4-wk-old New Hampshire pullets (Tuckey
et al, 1958) nor corn oil at levels up to 10%
in the diet of White Leghorn mixed-sex
chicks from day old to 3 wk influenced
GTT (Golian and Polin, 1984). The slowing
in the rate of passage induced by supple-
mental fat (yellow grease) in laying hens
1357
1358 GOLIAN AND MAURICE
TABLE 1. Composition and calculated analysis of experimental diets
Ingredients
and analyses 0%
71.30
25.73
.05
.80
1.40
.25
.40
.05
.02
18.53
2.08
Added
5%
61.81
30.00
5.00
.07
.75
1.65
.25
.40
.05
.02
19.86
6.79
(%)
fat
10%
52.35
34.24
10.00
.09
.80
1.75
.25
.45
.05
.02
21.17
10.80
20%
33.50
42.70
20.00
.13
.80
2.05
.25
.50
.05
.02
23.84
21.49
Yellow corn
Soy bean meal
(48.5%
CP)
Poultry fat
DL-methionine
Limestone
Deflourinated phosphate
Vitamin mix1
Salt
Mineral mix2
Ethoxyquin
Chemical analysis
Protein
Fat
Calculated analysis
Energy, kcal AME/g 3.02 3.21 3.41 3.81
Vitamin mix provided per kilogram of diet: retinyl acetate,
2.27
mg;
cholecalciferol,
.04
mg;
DL-oc-tocopheryl
acetate, 5.5 mg; menadione sodium bisulphite, 1.45 mg; riboflavin, 6.6 mg; pantothenic acid, 11 mg;
cyanocobalamin,
.01
mg; choline,
550
mg;
folic acid,
.7
mg;
thiamin mononitrate, 1.1 mg; pyridoxine, 1.1 mg; and
niacin, 33 mg.
2Mineral mix supplied per kilogram of
diet:
manganese,
65
mg;
zinc,
40
mg;
copper, 5 mg; and iodine,
.5
mg.
fed sucrose-based diets results in more
complete digestion (Mateos and Sell,
1980a) and enhanced energy utilization
(Mateos and Sell, 1980b). These observa-
tions have been extended to all classes of
poultry and proposed as an explanation
for the extracaloric effect of fat in poultry
diets (Summers, 1984).
Supplemental fat is an important com-
ponent in the diet of broiler chickens. The
objectives of the present study were: 1) to
determine the effect of supplemental fat
on GTT in broiler chickens at different
ages using two different markers; and 2)
to ascertain the influence of supplemental
fat on performance and lipid utilization.
The level of supplemental fat (poultry fat)
used in the present study ranged from 0 to
20%
and the diets were fed from day-old
to 6 wk of age.
MATERIALS AND METHODS
Animals and Husbandry
Mixed-sex, day-old broiler chicks (Peter-
son x Arbor Acres) were obtained from a
commercial hatchery. The 120 chicks were
identified with wing-bands and allocated at
random to
24
pens in an electrically heated,
wire-floored, battery brooder. At 3 wk the
birds were moved to wire-floored grower
cages.
In the brooder unit each bird was
provided
650
cm2 of living space with
22
cm
of head room, and 6 cm of waterer space.
The growing unit provided 1,070 cm2 of
living space in cages 36 cm high, 16 cm of
feeder space, and 16 cm of waterer space.
These space allowances were in compliance
with recommendations for laboratory
animals (United States Department of
Health, Education, and Welfare, 1980). The
units were maintained in a controlled
environment and exposed to a 24-h photo-
period and light intensity of about 10 lx.
Feed and water were provided for
ad libitum
consumption.
Diets
The experimental diets (Table 1) were
introduced at day-old and fed for the
duration of the experiment. The diets were
designed to evaluate the effect of 0, 5, 10,
and
20%
supplemental poultry fat in broiler
chicken diets. The diets were formulated so
that the ratios of major nutrients to AME
remained constant. The diets were pre-
sented in mash form. Chromic oxide (.4%)
DIETARY POULTRY FAT AND TRANSIT TIME OF FEED 1359
was mixed into a portion of each diet and
this was used each week to measure GTT
and was also used to measure lipid digesti-
bility in the 3rd wk.
Measurements
Body weight and feed consumption were
recorded weekly. Body weight was mea-
sured on a pen basis following a feed
withdrawal of
12
h.
The
GTT
was measured
as the difference between the time of
presenting the marked diet or administra-
tion of the marker per os and the first
appearance of the marker in excreta. Time
of initial appearance of marker is a superior
end-point when compared with final clear-
ance of marker because of greater reprodu-
cibility (Lutwak and Burton, 1964).
Chromic oxide (.4%) was used in feed
(Dansky and Hill, 1952) and ferric oxide
(200 mg/kg body weight) in a gelatin
capsule given per os (Golian and Polin,
1984).
Ferric oxide capsules were adminis-
tered to the same birds each week to reduce
variation. In the case of chromic oxide, the
birds were starved for 1 h, offered the
marked version of the diet until the first
appearance of the marker in excreta, and
then returned to the equivalent unmarked
diet until the next week.
Each week, GTT was first measured with
ferric oxide and the next day with chromic
oxide. A clean dropping pan was used each
time and examined every
10
min during the
2nd h after offering the marker and then
almost continuously until the end-point
was recorded for each pen. The gross
energy of poultry fat, chromic oxide con-
centration, and fat in feed and excreta were
determined (Maurice et ah, 1985) between
the 3rd and 4th wk. Lipid digestibility and
metaboUzable energy value of poultry fat
were calculated (Young, 1961). Percentage
utilization of total fat in the diet (Uf) was
calculated as follows: Uf = 100 - 100
[(percentage fat in excreta + percentage fat
in feed) x (percentage Cr2C>3 in feed +
percentage
Cr2C»3
in excreta)]. Digestibility
(D) was calculated as follows. D = Uf x
(percentage total fat
+
percentage test fat) -
percentage utilization of fat in basal x
(percentage fat in basal + percentage test
fat).
Experimental Design and
Statistical Analysis
The four dietary treatments (0,5,10, and
20%
supplemental fat) were arranged in a
randomized block design with six
blocks.
A
pen of five birds constituted the experi-
mental unit for purpose of analysis. The
data were subject to analysis of variance
(Mead and Curnow, 1983) and least signifi-
cant difference used to separate means. The
relationship between gastrointestinal tran-
sit time (y) and age (x) was modeled by a
logistic equation of the rising ogive form
p(x) with the relationship function y(x)
ranging from a lower plateau (d) to an
upper plateau (g):
p(x) = 1/(1 + exp) (bxm-bxx)
y(x) = d + (g - d) x p
where b is a rate parameter; and m is the
point of inflection (Draper and Smith, 1981).
The logistic ogive was fitted by nonlinear
least squares method using an iterative
process until convergence criteria were met.
The criterion (F statistic) used throughout
for detecting statistically significant effects
was based on a level of protection against
Type I error set at P < .05.
RESULTS
The effect of dietary fat on the perform-
ance of broiler chickens is shown in Table
2.
An age by diet interaction was detected.
Added fat did not affect body weight up
to 2 wk, thereafter, birds receiving supple-
mental fat were heavier. Feed to gain ratio
was lower in birds fed diets supplemented
with fat. An interaction between age by
diet for feed:gain ratio was not evident.
The best feed:gain ratio was observed in
birds fed the diet containing 20% supple-
mental fat. The addition of fat to the diet
brought about a significant increase in
energy intake when compared with the
control diet. Mean daily energy intake was
not altered as the amount of added fat
increased from 5 to 20%.
The average GTT of feed in broiler
chickens fed diets with or without supple-
mental poultry fat was not different (Table
3).
The mean GTT measured with chromic
oxide were not different from those ob-
tained when ferric oxide was used. The
1360 GOLIAN AND MAURICE
TABLE 2. Dietary poultry fat and performance
of broiler chickens at 6 wk of age1
Supplemental
fat
(%)
0
5
10
20
SEM5
Body
weight2
(g)
l,603c
l,779b
l,830*b
1,870*
20.4
Feedyjain
ratter
(g:g)
2.00*
1.83b
1.81b
1.76c
.044
AME
intake4
(kcal/
day)
216b
242*
242*
258*
6.6
a-cMeans in a column with no common super-
scripts are significantly different (P < .05).
^ata based on six pens of five birds each.
2An age by diet interaction was detected (P < .05).
Added fat did not affect body weight in the first 2
wk. Thereafter, birds receiving supplemental fat were
heavier.
3A significant interaction of age by diet was not
detected.
4Added fat did not affect AME intake in the 1st
wk, thereafter, birds receiving supplemental fat had
higher AME intake.
5Pooled SEM.
variation in GTT measurements was lower
when chromic oxide was used as marker
compared with ferric oxide (SE of 3.7
versus 7.1).
The average with both markers was not
different at 1, 2, and 3 wk of age. There
was a marked change after 3 wk of age
and GTT was increased at 4, 5, and 6 wk
of age as compared with the first 3 wk of
life.
A diet by marker interaction was not
detected. The relationship between GTT
and age was modelled by a rising ogive
(Figure 1). Mean GTT increased from an
estimated lower plateau of 170 min to an
estimated upper plateau of
211
min at 4 to
6 wk of age with the inflexion point at 3.23
wk.
Total lipid digestibility was improved
substantially when poultry fat was added
to the diet (Table 4). The addition of 20%
fat increased the total fat digestibility as
compared with 5% added fat. Total lipid
digestibility increased linearly as the level
of supplemental fat increased from 5 to
20%.
The digestibility of poultry fat, at
levels of inclusion of 5, 10, and 20%, was
not different and varied from 91 to 94%.
The apparent ME of poultry fat was also
not affected by the amount of supplemen-
tal dietary fat from 5 to 20%.
DISCUSSION
Substitution of 0, 5,10, and 20% poultry
fat at the expense of corn and soybean
meal in practical diets did not produce a
longer GTT in broiler chicks measured by
using either chromic oxide or ferric oxide
as markers. This is in agreement with
Tuckey et
al.
(1958) and Golian and Polin
(1984),
who did not observe any increase
in GTT with the addition of 10 to 12% fat
to the diet of chicks. The present results
are at variance with the linear increase in
GTT observed by Mateos and Sell
(1980a,b) and Mateos et al. (1982) when
hens in egg production were fed supple-
mental yellow grease at 0 to 30%. There-
fore,
the higher body weight and in-
creased feed efficiency in broiler chickens
fed fat-supplemented diets must be
ascribed to the higher energy concentra-
tion and not related to the GTT of feed.
Golian and Polin (1984) detected no differ-
ences in GTT but detected an extra body
weight gain in birds fed diets with 10%
supplemental fat when they used equica-
loric diets. The current results confirm the
report of Washburn (1991) that there is
little correlation between rate of passage
of feed through the digestive system and
feed efficiency.
TABLE 3. Dietary fat and gastrointestinal transit
time of feed in broiler chickens1
Supplemental fat
(%)
0
5
10
20
SEM3
Transit time2
(min)
195
187
194
192
4.7
^ata are the means of six pens of six birds each
measured weekly to six weeks of age. Neither a main
effect (diet or marker) nor diet by age interaction was
detected (P > .05).
2Transit time was measured as the difference
between the time of giving the marker and the first
appearance of the marker in excreta. In the case of
chromic oxide ((^03) the birds were starved for 1 h
prior to offering the marked diet. Ferric oxide
(Fe2C>3) was administered in capsules and the same
birds were used each week.
3Pooled SEM.
DIETARY POULTRY FAT AND TRANSIT TIME OF FEED 1361
240-
225-
I /.
'•£3 • / •
r /
150
^ , , , , , ,
0 12 3 4 5 6
Age (wk)
FIGURE 1. The relationship between gastrointes-
tinal transit time and age. The fitted response was
obtained from a logistic equation. The parameters of
the logistic equation (d = lower plateau; g = upper
plateau; b = a rate parameter; and m = point of
inflection) and their standard errors were: d = 170 ±
3.1;
g =
211
±
3.0;
b = 3.65
±
2.325;
and m = 3.23 ± .195.
• = control (no added fat); • = 5% fat; O = 10% fat; •
= 20% fat.
The type of fat may influence the
response of GTT to supplemental fat. The
current authors used poultry fat, whereas
Mateos and Sell (1980a,b, 1981) used
yellow grease. However, Tuckey et al.
(1958) reported an inconsistent effect of
saturated fat up to 12% of the diet. The
other reason may be the age and type of
birds that were used. The present study
used broiler chickens at 1 to 6 wk of age
but Mateos and Sell (1980b, 1981) used
mature hens. The type of bird may not be
a determinant because mean retention
time of feed in the entire gastrointestinal
tract of broiler chicks (338 min) and
Leghorns (360 min) are similar (Shires et
al, 1987).
The results of the current experiment
and others (Golian and Polin, 1984;
Tuckey et al, 1958) indicate that in the
chick and young broiler chickens, unlike
the hen, GTT is not influenced to any
great extent by fat in the diet. Therefore,
the improved absorption of fats and
increased ME of diets detected in chicks
(Gomez and Polin, 1974; Polin and Hus-
sein, 1982) cannot be explained by the
TABLE 4. Lipid digestibility and metabolizable
energy value of poultry fat
Supple- Total Poultry AME
mental lipid fat of
fat digestibility1 digestibility fat2
(kcal/
(%) kg)
0 45.2C
5 76.9b 91.0a 8,117
10
83.8ab
94.3a
8,413
20 88.2a
92.8a
8,277
SEM3 313 Z14 191.2
a_cMeans in a column with no common super-
scripts are significantly different (P < .05).
1Total lipid digestibility (percentage) was calcu-
lated by the method of Young (1961).
2 AME = Digestibility of poultry fat x gross energy
of poultry fat.
3Pooled SEM.
effect of fat on GTT. Total lipid digestibil-
ity increased as the rate of inclusion of
supplemental fat increased. There was no
evidence that AME of poultry fat declines
with increasing rate of inclusion, as re-
ported by Wiseman and Lessire (1987).
The digestibility or AME value of poultry
fat did not change as the level of fat
increased, in agreement with the results of
Fedde et al. (1960), using chicks, and
Hoagland and Snider (1941), using rats.
The level of fat did not have any effect on
GTT of diet or on digestibility of poultry
fat. Hence, an alternative explanation
must be sought for the extrametabolic
effect of fat in broiler chicken diets.
Age has a definite effect on the GTT of
feed (Shires et al, 1987; Vergara et al,
1989).
In the current study, GTT exhibited
a curvilinear response with age rising
from a lower plateau to an upper plateau
at 3.23 wk. This may be one of the reasons
for the reported improvement in fat diges-
tion with age (Duckworth et al, 1950;
Renner and Hill, 1960). Alternatively,
development of the digestive tract with
age (Kantongole and March, 1980) may
promote enhanced digestion, which in
turn alters gut motility and transit time.
ACKNOWLEDGMENTS
The authors thank P. N. Burrows,
Department of Experimental Statistics for
1362 GOLIAN AND MAURICE
advice and assistance with the experi-
mental design and statistical analyses. The
authors are grateful to S. F. Lightsey,
Poultry Nutrition Laboratory for technical
support, Ann Miller for tending the birds,
and Gloria Freeman for secretarial assis-
tance. This paper is Technical Contribu-
tion Number 3219 of the South Carolina
Agricultural Experiment Station, Clemson
University, Clemson, SC 29634.
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