Download Changes in chemical composition in male turkeys

METABOLISM AND NUTRITION
Changes in chemical composition in male turkeys during growth
V. Rivera-Torres,*† J. Noblet,‡§ and J. van Milgen‡§1
*Techna, BP10, F-44220 Couëron, France; †AgroParisTech, UFR Nutrition animale, qualité des produits et
bien-être, Département Sciences de la Vie et de la Santé, F-75005 Paris, France; ‡INRA, UMR1079 Systèmes
d’Elevage, Nutrition Animale et Humaine (SENAH), F-35590 Saint Gilles, France; and §Agrocampus Ouest,
UMR1079 SENAH, F-35000 Rennes, France
ABSTRACT In growing animals, requirements for many
nutrients (and energy) are determined by the retention
of these nutrients. During growth, this retention changes in an absolute way and also between nutrients and
energy, resulting in changing nutrient requirements.
The objective of this study was to describe the changes
in chemical composition in male growing turkeys. The
serial slaughter technique was used to determine the
composition of amino acids, lipid, ash, and water in
feather-free body (FFB) and feathers in male turkeys
offered feed ad libitum from 1 to 15 wk of age. Allometric relations were used to describe changes in body
composition. The feather content in the body decreased
from 6% at 1 wk of age to less than 3% at 15 wk of age.
The water and protein content in FFB decreased with
increasing FFB mass, with allometric scalars (b) of,
respectively, 0.967 and 0.970, whereas the lipid content
increased with increasing FFB mass (b = 1.388). The
water, protein, and ash content in fat-free FFB was
constant and represented, respectively, 71.6, 24.2, and
4.2% of the fat-free FFB mass. The amino acid content
of FFB protein was relatively constant and only the
Cys content decreased between 1 and 15 wk of age,
whereas the Ile content increased. Feathers were mostly
composed of protein, and the protein content did not
change during growth. During growth, the Lys, Met,
Trp, His, Tyr, Asp, and Glu contents in feather protein decreased, whereas the Cys, Val, and Ser contents
increased. The contribution of feathers to whole-body
amino acid retention ranged from 5% for His to 33%
for Cys. On average, the weight gain of FFB contained
21.3% protein and 12.7% lipid, corresponding to an energy content of 10.1 kJ/g. The weight gain of feathers
contained 87.4% protein, corresponding to an energy
content of 20.4 kJ/g. The results of the present study
can be used in a factorial approach to determine nutrient requirements in growing turkeys.
Key words: turkey, growth, body composition, amino acid, allometry
2011 Poultry Science 90:68–74
doi:10.3382/ps.2010-00633
INTRODUCTION
mined at different ages, and measurements have to be
performed in different conditions to determine the effects of environment and nutritional strategies (Fatufe
et al., 2004; Lumpkins et al., 2007; Samadi and Liebert,
2007). The expression of amino acid requirement as a
percentage in the diet or relative to dietary energy also
requires information on energy utilization. Especially
in turkey nutrition, these measurements are costly and
time-consuming because of the sexual dimorphism associated with a long production cycle.
The composition of BW gain contributes largely to
the nutrient requirements of growing animals. A description of the dynamics of protein and amino acid
retention can therefore be helpful in determining amino
acid requirements. Although this approach has been
used in broilers through allometric relations (Gous et
al., 1999) and modeling (King, 2001), little information is available in turkeys (Firman and Boling, 1998).
Hurwitz et al. (1983) used the factorial method to determine the amino acid requirements of turkeys, but
Poultry meat is a major source of animal protein produced in the world. Although the production efficiency
is high relative to other animal production systems,
improving the efficiency remains a key issue to reduce
production costs, the use of natural resources, and the
impact on the environment. An excess supply of protein
in the diet compared with the amino acid requirement
of the bird is the main cause of the inefficient use of
dietary nitrogen. In poultry nutrition, amino acid requirements are usually based on empirical definitions
of the amino acid levels that optimize a response criterion such as maximization of BW gain, carcass yield, or
feed efficiency (e.g., Moore et al., 2004; Barbour et al.,
2008; Dozier et al., 2008). The requirements are deter©2011 Poultry Science Association Inc.
Received January 6, 2010.
Accepted October 4, 2010.
1 Corresponding author: [email protected]
68
BODY COMPOSITION IN MALE TURKEYS
recommendations were given for different age classes,
rather than being based on the dynamics of BW gain.
Emmans (1989) described the change in body composition in male and female turkeys as a function of
whole-body mass or protein mass of carcass and feathers. In addition, he described the amino acid requirement for maintenance and growth in feather-free body
and feathers. However, a possible change in the amino
acid profile of feathers and the feather-free body was
not considered. As observed by Ferket et al. (1997),
the amino acid profile of the feather-free body does not
seem to change during growth, in contrast to that of
feathers. The objective of this study was to determine
the composition of BW and BW gain in male growing
turkeys, with emphasis on the change in the relative
contributions of feathers and carcass during growth.
MATERIALS AND METHODS
Birds and Diets
The experiment was carried out at the same time as
an experiment in which we measured the energy expenditure by indirect calorimetry (Rivera-Torres et al.,
2010), and turkeys from the same batch were used in
both experiments. In brief, 2 groups of medium-size
male turkeys (B.U.T. 9) were obtained from a hatchery (France Dinde, Saint Hervé, France) on the day of
hatching. Turkeys were housed in flat-deck cages and
given ad libitum access to feed and water throughout
the experiment. Four different diets were used during 4
successive periods of 4 wk each, and the nutrient supply
of these diets met or exceeded NRC (1994) recommendations during each period. The anticipated digestible
Lys contents were 1.48, 1.32, 1.08, and 1.00% for diets
distributed during periods 1 through 4.
Measurements and Sampling
The change in body composition was determined
by periodically slaughtering turkeys from each group.
From 1 wk of age onward, 2 turkeys from each group
were slaughtered every 2 wk so that at the end of the
experiment, 4 replicate measurements were obtained at
8 different ages. Turkeys that were selected for slaughter were kept in a light room for 4 to 6 h before slaughter, with ad libitum access to water but without access
to feed. They were then killed by intravenous injection of a mixture of embutramide, mebezonium, and
tetracaine chlorydrate (T 61, Intervet SA, Beaucouzé,
France) after anesthesia by an intravenous injection of
ketamine (Imalgène 1000, Merial, Lyon, France). Each
turkey was weighed immediately after this procedure.
The body was then soaked in hot water (60°C) for 2
min, plucked, and placed in a room at ambient temperature until the skin was dry. The feather mass was
calculated as the difference between BW before and
after plucking. The birds were then eviscerated manually. The viscera included both the empty gastrointestinal tract and internal organs (including reproductive
69
organs). The feather-free body (FFB; i.e., carcass plus
empty viscera) was stored in plastic bags and frozen
at −20°C. During plucking, some feathers of each bird
were picked from different parts of the body to create
a sample representative of the feathering of the body.
Feather samples were then pooled by age and ground
with a cutting mill (Grindomis GM200, Retsch, Newtown, PA). A subsample was further ground using an
ultracentrifugal mill (ZM100, Retsch), whereas another
subsample was ground with a ball mill (Vangoumil 300,
Merck, Darmstadt, Germany) for amino acid analyses.
The individual frozen FFB samples were cut into
smaller pieces. For turkeys weighing less than 1 kg,
this was done manually, whereas for turkeys weighing
more than 1 kg, a cutter-slicer was used (RF15, Hobart,
Marne la Vallée, France). The samples were then ground
twice (4346SF, Hobart) using, respectively, a 5-mm
and a 2-mm die. After manual homogenization, a 600-g
sample was taken for heavier turkeys, whereas all material was used for turkeys weighing less than 1 kg. The
FFB samples were weighed, freeze-dried, and weighed
again. The samples were then minced and stored in a
cold room. The freeze-dried FFB samples were later
ground with an ultracentrifugal mill (ZM100, Retsch)
for chemical analyses. Subsamples of these were taken,
pooled by age, and ground with a ball mill (Vangoumil
300, Merck) for amino acid analyses.
Chemical Analyses
Chemical analyses were carried out in samples of individual turkeys for FFB and in samples pooled by age
for feathers. Samples were analyzed for DM (ISO 64961983), ash (ISO-5984), N [NF V18-120, 1997 (with a
LECO3000 instrument, Leco, St. Joseph, MI)], and
fat (NF V18-117, 1997) using methods of the International Organization for Standardization (ISO methods,
http://www.iso.org) and the AFNOR group (NF methods, http://www.afnor.org/en). The fat content was not
determined in feathers. The DM content of FFB corresponded to the product of the DM contents determined
during freeze-drying and oven-drying. Energy content
was measured with an adiabatic bomb calorimeter
(ISO 9831-1998; IKA C5000, IKA, Staufen, Germany).
Amino acid analyses were performed by the Ajinomoto
Eurolysine S.A.S. laboratory in Amiens (France) with
a JLC-500/V AminoTac Amino Acid Analyzer (JEOL,
Croissy-sur-Seine, France) after hydrolysis with 6 N
HCl at 110°C for 23 h under reflux. The Cys and Met
contents were obtained after performic acid oxidation
before hydrolysis. The Trp content was determined after hydrolysis at 120°C for 16 h with barium hydroxide
and separation by reverse-phase HPLC and fluorometric detection.
Statistical Analyses
All statistical analyses were performed using the
GLM and NLIN procedures of SAS (SAS Inst. Inc.,
70
Rivera-Torres et al.
Cary, NC). A Gompertz growth function was used to
describe the change in BW (BWt, in kg) as a function
of age (t, in d). The function was log-transformed to
account for heteroscedasticity of the errors:
log (BWt) = log(BWm
× exp{−exp[−B × (t − t*)]}), [1]
where BWm is the BW at maturity (kg), B is the rate
of maturing (d−1), and t* is the age at maximal growth
rate (d). A high value of B implies an early-maturing
animal.
Body composition traits were analyzed by analyses
of variance with age as a fixed effect. Traits were also
analyzed using allometric equations to describe the development of a tissue relative to a reference compartment (e.g., empty BW). When described as a mass, the
equation is
Y = a × Xb,
[2a]
where Y is the mass of a tissue or a nutrient (g) and
X is the mass of the reference compartment (g). The
parameters a and b are the shape and scale parameters
of the allometric equation, respectively. Because most
of the traits were measured as contents (e.g., amino
acid content in FFB protein), a transformed equation
was used:
Y/X = a × X(b−1).
[2b]
When the scale parameter b differs from unity, the
content increases (b >1) or decreases (b <1) with increasing mass. The allometric analysis differs from the
ANOVA in that mass (and not age) is seen as a driving
force for potential changes in composition. Several authors have reported important changes in body composition during the first week after hatching (Leeson and
Summers, 1980; Ferket et al., 1997). We also observed
that body composition in the first week differed from
that later on (see below). Therefore, the allometric
analysis was carried out using data from 3 wk of age
onward.
The results of the Gompertz function and the allometric relations were used to determine the average
composition of BW gain between 3 and 15 wk of age.
In addition, the allometric relations were used to determine the average contribution of feathers to wholebody amino acid retention. The ash, water, and protein
masses in FFB were described as a function of fat-free
FFB mass, as indicated in equation 2a.
RESULTS
Daily gain was in line with the performance potential
provided by the breeder and averaged 140 g/d between
1 and 15 wk of age. With the Gompertz function (equation 1), the estimated mature BW (BWm) was 18.1 ±
0.9 kg, whereas the rate of maturing (B) was 0.0274 ±
0.0009 /d. The age at maximal growth rate (t*) was
estimated at 62 ± 2 d.
The viscera and feather contents generally decreased
with increasing age (Table 1), resulting in an increase
in carcass content from 75.2 to 90.2% of BW between
1 and 15 wk. These tendencies are also reflected in the
scale parameter (b) of equation 2b, which was greater
than unity for the carcass and lower than unity for the
viscera and feathers (Table 2). The allometric scalar for
viscera was lower than that of feathers, indicating that
the viscera content decreased more rapidly than the
feather content.
In general, the protein and ash contents in FFB declined with increasing age, whereas the lipid content,
and consequently the gross energy content, increased
substantially from 3 wk of age onward (Table 1). The
composition of FFB at 1 wk of age appeared to be different from the general tendency observed at the other
ages. The water content in particular was low (60.3%)
at 1 wk of age, resulting in relatively high values for
protein, ash, and lipid contents. This justifies the differentiation in body composition between 1 wk of age
and later ages in the allometric analysis (Table 2). The
changes in chemical composition of FFB were reflected
in the allometric scalars (for FFB), which were lower
than unity for the protein and water contents and were
greater than unity for the lipid and gross energy contents. In addition, the scalars for water, ash, and protein were very similar (0.966 to 0.970), meaning that
their ratios in FFB gain were relatively constant and
that the composition of fat-free FFB would be constant
during the growing period. That was further illustrated
in the allometric relationships (Equation 2b) for water,
ash, and protein content relative to the fat-free FFB
mass, for which the allometric scalars did not differ
significantly from unity. The fat-free FFB contained on
average 71.6, 4.2, and 24.2% water, ash, and protein,
respectively. Feathers were mostly composed of protein
(Table 1) and the protein content did not change with
feather mass (Table 2), resulting in an average protein
content of 88.6% in feathers. Similarly, the gross energy
content in the feathers did not vary during growth (P =
0.19) and corresponded to 20.64 kJ/g of feathers. The
ash content decreased with increasing feather mass,
whereas the water content increased (Table 2).
The amino acid profile differed between FFB and
feather protein (Tables 3 and 4). The Lys, Met, Trp,
and His contents in FFB protein were at least 2-fold
greater than those in feather protein, whereas the Cys
content was 6-fold greater in feathers than in FFB protein. The variation in the amino acid contents of protein from 3 to 15 wk of age (from 0.8 to 14 kg of BW)
appeared to be greater in feathers than in FFB, as indicated by the allometric scalars (Tables 3 and 4). The
amino acid composition of FFB was relatively constant
during growth and only the Cys and Ile contents were
affected by FFB protein mass. In feathers, the Cys,
Val, and Ser contents increased with increasing protein
71
BODY COMPOSITION IN MALE TURKEYS
Table 1. Body composition of male turkeys from 1 to 15 wk of
age1
Significance2
Age (wk)
Item
Empty BW (g/bird)
Empty body (% of BW)
Carcass3
Viscera
Feathers
Feather-free body (%)
Water
Ash
Protein (N × 6.25)
Lipid
Gross energy (kJ/g)
Feathers4 (%)
Water
Ash
Protein (N × 6.25)
Gross energy (kJ/g)
1
3
5
7
9
11
13
15
186
75.2
18.5
6.3
60.3
4.5
26.3
8.4
9.34
10.8
1.9
86.7
20.56
862
77.1
18.9
4.0
66.7
4.1
23.2
5.5
7.61
11.6
1.4
88.5
20.11
2,310
84.3
11.3
4.4
67.7
3.5
20.9
7.5
7.89
11.4
1.6
88.6
21.17
4,112
86.7
10.7
2.6
63.9
4.1
23.7
6.1
8.64
9.5
1.1
90.5
21.49
6,463
91.7
5.3
3.0
64.7
3.7
20.4
8.7
8.86
10.5
1.4
89.5
21.08
8,947
92.0
4.7
3.3
64.4
3.9
22.0
6.8
8.72
11.9
1.1
88.2
20.77
11,840
89.5
7.6
2.9
61.1
3.6
21.1
12.5
10.16
11.4
0.9
88.6
19.86
13,944
90.2
7.2
2.6
60.9
3.5
20.8
14.2
10.44
13.5
1.2
86.5
19.95
RSD
P-value
754
4.3
4.1
1.2
1.8
0.3
1.1
2.7
0.69
NA
NA
NA
NA
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
NA
NA
NA
NA
1Values
correspond to the average of 4 replicate measurements per age (for feathers: 1 pooled measurement per age).
= residual SD; NA = not applicable. P­= probability of an age effect.
3Feather-free eviscerated body.
4No statistical analysis was carried out because there was no replicate measurement.
2RSD
mass, whereas the Lys, Met, Trp, His, Tyr, Asp, and
Glu contents decreased. Threonine, Leu, Phe, and Arg
were the only amino acids that remained constant in
both FFB and feather protein.
The allometric relations were used to determine the
average composition of BW gain (Table 2) and the average amino acid composition of whole-body protein
retention (Figure 1). As expected, BW gain was mainly
due to carcass gain, and viscera and feathers represented only a minor part of BW gain (4.7 and 2.6%,
respectively). The FFB gain mostly consisted of water,
and contained 21% protein, 13% lipid, and 4% ash.
Feather gain mostly consisted of protein (87%). Lysine,
Leu, and Arg were the most abundant essential amino
acids in the deposited protein, each representing more
than 6%. Most amino acids were deposited in FFB,
but the contribution of FFB and feathers varied largely
between amino acids. Feathers contributed only marginally (6%) to whole-body Lys and Met retention, but
they represented 33% of whole-body Cys retention.
Table 2. Allometric relations describing the change in body composition during growth in male turkeys from 3 to 15 wk of age
Parameter estimate2
Item1
Empty body
Carcass
Viscera
Feather-free body
Feathers
Feather-free body
Water
Ash
Protein
Lipid
Gross energy
Feathers
Water
Ash
Protein
Gross energy
1The
a (SD)
0.539 (0.052)
3.687 (2.334)
0.915 (0.018)
0.120 (0.061)
0.848 (0.047)
0.050 (0.008)
0.281 (0.032)
0.003 (0.003)
3.36 (0.56)
0.089 (0.010)
0.020 (0.003)
0.913 (0.012)
21.6 (0.71)
b (SD)
RSD3
Composition
of gain4
1.057* (0.011)
0.558* (0.082)
1.007* (0.002)
0.846* (0.062)
0.967* (0.007)
0.966 (0.020)
0.970* (0.013)
1.388* (0.102)
1.114* (0.02)
1.049* (0.021)
0.907* (0.032)
0.994 (0.003)
0.991 (0.006)
0.045
0.043
0.011
0.011
0.021
0.004
0.014
0.032
0.776
0.011
0.002
0.011
0.608
92.9%
4.5%
97.4%
2.6%
62.4%
3.6%
21.3%
12.7%
10.1 kJ/g
11.5%
1.1%
87.4%
20.4 kJ/g
values for each subitem (Y) are expressed relative to that of the main item (X).
the allometric relation Y/X = a·X(b−1), where a and b are the shape and the scale parameters, respectively, and both Y and X are expressed in grams (gross energy is expressed in kilojoules). Body composition was
determined at 7 different ages with 4 replicate measurements per age (1 measurement per age for feathers). An
asterisk (*) indicates the value is significantly different from 1 (P < 0.05).
3RSD = residual SD.
4Average composition of BW gain from 3 to 15 wk of age calculated from the allometric relations from 0.8 to
14 kg of BW.
2From
72
Rivera-Torres et al.
Table 3. Amino acid composition (%) in feather-free body protein in male growing turkeys and allometric relations describing the
change in amino acid composition during growth1
Parameter estimate2
Age (wk)
Amino
acid
1
3
5
7
9
11
13
15
Lys
Thr
Met
Cys
Trp
Ile
Leu
Val
His
Phe
Tyr
Arg
Gly
Ser
Ala
Asp
Glu
Pro
Total
6.82
3.92
1.93
1.10
1.08
3.88
6.96
4.57
2.42
3.81
3.15
6.68
8.23
4.05
6.24
8.29
13.05
5.19
91.4
6.94
3.83
2.04
1.05
1.09
3.87
6.83
4.46
2.60
3.65
2.99
6.42
7.76
3.80
6.15
8.20
12.87
5.02
89.6
7.23
3.92
2.04
1.02
1.07
3.99
7.01
4.55
2.67
3.73
3.07
6.52
7.69
3.89
6.26
8.43
13.21
5.11
91.4
6.95
3.81
2.02
0.99
0.99
3.96
6.80
4.50
2.57
3.63
2.93
6.52
8.02
3.73
6.23
8.25
12.97
5.31
90.2
7.13
3.83
2.00
0.96
1.04
4.07
6.92
4.65
2.69
3.67
2.96
6.55
7.98
3.64
6.38
8.38
13.26
5.24
91.4
7.10
3.76
2.02
0.98
1.03
4.02
6.80
4.52
2.63
3.56
2.92
6.39
7.63
3.56
6.21
8.23
13.07
4.98
89.4
7.19
3.79
2.01
0.97
1.04
4.07
6.84
4.55
2.62
3.59
2.89
6.43
7.68
3.66
6.21
8.27
13.16
5.09
90.1
7.31
3.86
2.04
0.94
1.04
4.07
6.93
4.51
2.65
3.62
2.95
6.50
7.65
3.69
6.26
8.38
13.42
5.10
90.9
a (SD)
0.059
0.041
0.021
0.017
0.014
0.031
0.069
0.042
0.025
0.041
0.036
0.065
0.084
0.051
0.059
0.080
0.114
0.050
(0.006)
(0.004)
(0.001)
(0.001)
(0.002)
(0.002)
(0.005)
(0.003)
(0.003)
(0.003)
(0.004)
(0.004)
(0.011)
(0.007)
(0.004)
(0.006)
(0.008)
(0.008)
b (SD)
1.012 (0.006)
0.996 (0.005)
0.997 (0.003)
0.968* (0.006)
0.982 (0.010)
1.015* (0.003)
1.000 (0.005)
1.004 (0.005)
1.003 (0.006)
0.992 (0.005)
0.988 (0.006)
1.000 (0.004)
0.995 (0.008)
0.980 (0.009)
1.004 (0.004)
1.002 (0.004)
1.009 (0.004)
1.001 (0.010)
1Amino
acid composition was determined in samples pooled by age (4 turkeys per pool).
the allometric relation 100·Y/X = a·X(b−1), where a and b are the shape and scale parameters, respectively, 100·Y/X is the amino acid content (%), and X (g) is the feather-free body protein mass. Only data between 3 and 15 wk of age were used in the analysis. An asterisk (*) indicates
the value is significantly different from 1 (P < 0.05).
2From
DISCUSSION
Growth functions, such as the Gompertz function,
are frequently used in biology to describe the change
in BW as a function of time. Because of the simplicity
and robustness of this function, the parameters may
be compared among different studies. Emmans (1989)
estimated the mature BW in different strains of turkeys from 1942 (Asmundson, 1942) to 1980 (Leeson and
Summers, 1980), and he suggested that genetic selection for greater BW resulted in an increase in mature
BW and in earlier maturing turkeys. This hypothesis
was confirmed later by Anthony et al. (1991), who compared randombred turkeys and turkeys selected for increased BW at 16 wk of age. Although the estimated
BW at maturity was close to the estimate by Emmans
for 1980 data and to that of Anthony et al. (1991), the
rate of maturing (B) was greater than those estimated
Table 4. Amino acid composition (%) in feather protein in male growing turkeys and allometric relations describing the change in
amino acid composition during growth1
Parameter estimate2
Age (wk)
Amino
acid
Lys
Thr
Met
Cys
Trp
Ile
Leu
Val
His
Phe
Tyr
Arg
Gly
Ser
Ala
Asp
Glu
Pro
Total
1Amino
1
3
5
7
9
11
13
15
2.24
4.37
0.65
6.58
0.74
4.67
7.58
7.32
1.62
5.32
4.72
7.27
8.05
10.49
3.85
7.32
10.90
9.03
102.7
1.77
4.49
0.50
6.95
0.52
4.68
7.99
7.95
0.78
5.18
3.61
6.81
7.93
11.10
4.70
7.03
10.53
9.58
102.1
1.74
4.51
0.43
7.16
0.51
4.81
8.10
8.29
0.75
5.18
3.43
6.84
7.95
11.05
4.62
6.95
10.52
9.83
102.7
1.67
4.54
0.41
7.16
0.49
4.81
8.15
8.24
0.74
5.32
3.41
6.95
7.88
11.32
4.70
7.00
10.50
10.12
103.4
1.53
4.37
0.39
7.21
0.42
4.76
7.88
8.20
0.72
NA
NA
6.84
7.64
11.05
4.43
6.77
10.00
9.89
92.1
1.52
4.54
0.43
7.27
0.42
5.03
8.21
8.37
0.74
5.33
3.13
7.09
7.79
11.83
4.36
6.70
10.35
10.11
103.2
1.29
4.34
0.37
7.69
0.43
4.86
8.21
8.47
0.65
5.31
3.10
6.97
8.03
11.90
4.59
6.73
10.02
9.87
102.8
1.25
4.43
0.34
7.43
0.38
4.86
8.28
8.48
0.66
5.32
3.02
6.95
8.14
11.79
4.61
6.70
9.98
10.16
102.8
a (SD)
b (SD)
0.100 (0.047)
0.051 (0.006)
0.025 (0.011)
0.045 (0.006)
0.025 (0.010)
0.037 (0.004)
0.069 (0.008)
0.058 (0.004)
0.018 (0.005)
0.044 (0.003)
0.095 (0.010)
0.059 (0.005)
0.075 (0.012)
0.072 (0.012)
0.061 (0.011)
0.096 (0.006)
0.143 (0.017)
0.077 (0.009)
0.866* (0.034)
0.990 (0.009)
0.871* (0.032)
1.034* (0.010)
0.878* (0.028)
1.020 (0.008)
1.012 (0.008)
1.025* (0.005)
0.934* (0.020)
1.012 (0.005)
0.924* (0.007)
1.012 (0.006)
1.004 (0.011)
1.033* (0.012)
0.980 (0.013)
0.976* (0.004)
0.977* (0.009)
1.018 (0.008)
acid composition was determined in samples pooled by age (4 turkeys per pool). NA = not applicable.
the allometric relation 100·Y/X = a·X(b−1), where a and b are the shape and scale parameters, respectively, 100·Y/X is the amino acid content (%), and X (g) is the feather protein mass. Only data between 3 and 15 wk of age were used in the analysis. An asterisk (*) indicates the value
is significantly different from 1 (P < 0.05).
2From
BODY COMPOSITION IN MALE TURKEYS
by Emmans (1989) and Anthony et al. (1991). Genetic
selection resulted in early-maturing birds with a rapid
growth rate.
Although the allometric relation indicated that the
viscera content in BW decreased with increasing body
mass, viscera content was not a continuously declining
fraction of BW because it decreased by 40% during the
first 5 wk of age, but increased again after 11 wk of
age (Table 1). Similar to our observations, Leeson and
Summers (1980) and Hurwitz et al. (1983) observed a
sharp decline in viscera content during the first 5 wk of
age. At later ages, the viscera content in BW appeared
to remain stable (Leeson and Summers, 1980) or even
to increase (Hurwitz et al., 1983). Lilja (1983) and Hurwitz et al. (1991) suggested that this may be explained
by an early development of internal organs, such as the
liver and intestines, and a later development of other
organs, such as the testes and spleen.
The change in composition of FFB during growth observed in our study is in agreement with data in the literature. The relatively high protein and lipid contents
at 1 wk of age in FFB were also observed by Leeson
and Summers (1980) and Hurwitz et al. (1983). During
the first week posthatch, the lipid content appeared
to decrease because of the mobilization of fat reserves
from the yolk sac. During this period, the poult is in
a transition phase between using endogenous nutrients
from the yolk sac to using dietary nutrients (Sklan et
al., 1996; Noy and Sklan, 2001). Later on, the lipid content in FFB increased with age, as observed by Hurwitz
et al. (1983). The lipid content in FFB at 15 wk of age
was close to values observed by Crouch et al. (2002)
in female breeder turkeys and those reported by Sell
(1993) in male turkeys at a similar age. It is known
that, apart from age, the diet can also affect the partitioning of energy retention between protein and lipids
in broiler chickens and turkeys (Priyankarage et al.,
2008). Defining body composition as a function of the
fat-free FFB mass enables the body composition to be
described independently of the protein-to-lipid ratio in
the body. In our study, the water, ash, and protein contents represented a constant proportion of the fat-free
FFB mass, which also means that water and ash are
constant relative to protein (2.9 and 0.17 of the protein
mass in FFB, respectively). Similarly, Eits et al. (2002)
measured an ash-to-protein ratio of 0.15 in the FFB
of broilers. However, Emmans (1989) and Eits et al.
(2002) observed that the water-to-protein ratio in fatfree FFB decreased in turkeys and broiler chickens during growth. These differences may be due to changes in
the relative contribution of carcass and viscera in FFB
during growth. As observed by Eits et al. (2002), the
constant ash-to-protein ratio in FFB may be due to the
combination of an increasing ash-to-protein ratio in viscera and a decreasing water-to-protein ratio in carcass.
Similarly, the constant water-to-protein ratio observed
in our study may be due to a decreasing contribution
of viscera in the feather-free protein mass and to an in-
73
creasing contribution of carcass, which has a low water
content in comparison with viscera.
Apart from Cys and Ile, the amino acid content in
FFB was relatively constant during growth. Our values
were close to those reported by Fisher and Scougall
(1982) and Hurwitz et al. (1983), suggesting that genetic selection has not significantly affected the amino
acid composition in FFB. Apart from the rapid change
during the first week, the content of several amino acids
in feather protein changed during growth, with an increase in Cys and Val and a decrease in Lys, Met, Trp,
His, and Tyr. Similar changes in amino acid composition were observed by Fisher et al. (1981), specifically
for His, the aromatic amino acids, and the sulfur-containing amino acids. These changes may be explained
by a change in the nature of feathers, as suggested by
Fisher and Scougall (1982) and Stilborn et al. (1997).
Similar to the lipid and protein contents in FFB, the
amino acid content in feather protein also changed very
rapidly during the first wk of age. For example, there
was a 2-fold decrease in the His content in feather protein from 1 to 3 wk of age. A similar reduction in His
content was observed by Stilborn et al. (1997) in broilers. The origin of these changes is not entirely clear
but may be related to the fact that, after hatching, the
young poult can consume essential nutrients, some of
which may be limiting during the in ovo stage. In ovo
administration of amino acids in broiler breeder eggs
has been shown to change the amino acid content of the
embryo (Ohta et al., 2001).
The changing contribution of feathers and FFB to
whole-body protein during growth implies that the
amino acid retention is not constant during the growth
of turkeys. Although feather mass represents only a
small part of BW (3 to 4%), the contribution of feather
protein retention to total protein retention ranged from
Figure 1. Average amino acid composition of whole-body protein
gain and the contribution of feathers and feather-free body to the
composition of whole-body protein gain in male growing turkeys from
3 to 15 wk of age (0.8 to 14 kg of BW).
74
Rivera-Torres et al.
13% at 0.8 kg of BW to 9% at 14 kg of BW. This,
combined with the fact that feathers have a high Cys
content, resulted in a reduction in the contribution of
feathers to whole-body Cys retention (from 36% at 0.8
kg of BW to 31% at 14 kg of BW). The Cys-to-Lys
retention ratio concomitantly declined from 31% at 0.8
kg of BW to 26% at 14 kg of BW. It is therefore likely
that the Cys requirement (relative to Lys) decreases
with increasing BW. The current study does not provide direct information concerning the amino acid requirement of turkeys. The requirement is determined
by the amino acid composition of retained protein, the
efficiency with which a limiting amino acid can be used
for growth, and the maintenance amino acid requirement. The ideal amino acid profile is an aggregate representation of these components. Assuming that the
ideal amino acid profile is constant implies that the
relative contribution of these components (or of body
tissues) does not change during growth. The results of
the current study indicate that for certain amino acids,
such as Cys, the concept of a constant ideal amino acid
profile may be an oversimplification of reality. A modeling approach may be a useful alternative to account for
the change in amino acid requirements during growth
(Firman, 1994).
ACKNOWLEDGMENTS
The authors thank Ajinomoto Eurolysine S.A.S.
for amino acid analyses, Maurice Alix, Sophie Daré,
Serge Dubois, Yolande Jaguelin, Régis Janvier, Francis
Le Gouevec and Anne Pasquier (INRA, Saint-Gilles,
France) for their collaboration in this experiment, and
Euronutrition Research Center (Saint-Symphorien,
France) for feed manufacturing.
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