Meat Quality of Slow- and Fast-Growing Chicken Genotypes Fed Low-Nutrient or Standard Diets and Raised Indoors or with Outdoor Access

Abstract

Consumer interest in free-range and organic poultry is growing. Two concurrent experiments were conducted to assess 1) the impact of alternative genotype and production system and 2) the impact of genotype and diet on meat quality of chickens for specialty markets. Specifically, a slow-growing genotype (slow) and a fast-growing genotype (fast) were raised for 91 and 63 d (females), respectively, or 84 and 56 d in the case of the second trial (males). In each trial, the slow birds were placed before the fast birds to achieve a similar final BW at processing. Each genotype was assigned to 4 pens of 20 birds each and raised in indoor floor pens in a conventional poultry research facility; each genotype was also assigned to 4 floor pens in a small facility with outdoor access. A low-nutrient diet was used, formulated for a slower rate of production. Birds were commercially processed and deboned at 4 h postmortem. In the second trial, the diets compared were a conventional diet that met NRC requirements or the low-nutrient diet, and all birds were raised indoors. There was an interaction between genotype and production system for the color (b*; P < 0.05). The meat and skin of the slow birds became more yellow when the birds had outdoor access; however, this did not occur when the fast birds had outdoor access. The breast meat of the slow birds had more protein and alpha-tocopherol (P < 0.05) than the fast birds and half the amount of fat (P < 0.05). In addition, the meat of the outdoor birds had more protein than the indoor birds (P < 0.05). The slow birds had poorer water-holding capacity but were more tender than the fast birds (P < 0.05). The type of diet had little impact on meat quality. These data indicate that meat quality differences exist between genotypes with different growth rates and raised in alternative production systems.

Full text

Meat Quality of Slow- and Fast-Growing Chicken Genotypes Fed Low-
Nutrient or Standard Diets and Raised Indoors or with Outdoor Access
A. C. Fanatico, P. B. Pillai, J. L. Emmert, and C. M. Owens
1
Center for Excellence in Poultry Science, University of Arkansas, Fayetteville 72701
ABSTRACT Consumer interest in free-range and or-
ganic poultry is growing. Two concurrent experiments
were conducted to assess 1) the impact of alternative
genotype and production system and 2) the impact of
genotype and diet on meat quality of chickens for spe-
cialty markets. Specifically, a slow-growing genotype
(slow) and a fast-growing genotype (fast) were raised for
91 and 63 d (females), respectively, or 84 and 56 d in the
case of the second trial (males). In each trial, the slow
birds were placed before the fast birds to achieve a similar
final BW at processing. Each genotype was assigned to
4 pens of 20 birds each and raised in indoor floor pens
in a conventional poultry research facility; each genotype
was also assigned to 4 floor pens in a small facility with
outdoor access. A low-nutrient diet was used, formulated
for a slower rate of production. Birds were commercially
processed and deboned at 4 h postmortem. In the second
Key words: chicken, genotype, meat, alternative production system
2007 Poultry Science 86:2245–2255
INTRODUCTION
A growing awareness of human health and nutritional
concerns has led to specialty markets for poultry pro-
duced in alternative systems such as free-range or or-
ganic. This trend, like the shift to further processing, can
add value to poultry products.
Modern birds grow very fast due to genetic selection,
efficient production systems, improved nutrition, and
regular veterinary attention. Meat chickens reach a mar-
ket weight as early as 6 wk and have high breast meat
yields due to the high demand for breast meat in the
United States. However, selection for fast growth and
high yield may have negatively impacted the sensory and
functional qualities of the meat (Dransfield and Sosnicki,
1999; Le Bihan-Duval, 2003), pushing muscle fibers to
their maximum functional size constraints (Macrae et al.,
2006). Parts and further processing represents 91% of US
poultry markets (National Chicken Council, 2006). The
©2007 Poultry Science Association Inc.
Received January 8, 2007.
Accepted June 9, 2007.
1
Corresponding author: cmowens@uark.edu
2245
trial, the diets compared were a conventional diet that
met NRC requirements or the low-nutrient diet, and all
birds were raised indoors. There was an interaction be-
tween genotype and production system for the color (b*;
P < 0.05). The meat and skin of the slow birds became
more yellow when the birds had outdoor access; however,
this did not occur when the fast birds had outdoor access.
The breast meat of the slow birds had more protein and
α-tocopherol (P < 0.05) than the fast birds and half the
amount of fat (P < 0.05). In addition, the meat of the
outdoor birds had more protein than the indoor birds (P
< 0.05). The slow birds had poorer water-holding capacity
but were more tender than the fast birds (P < 0.05). The
type of diet had little impact on meat quality. These data
indicate that meat quality differences exist between geno-
types with different growth rates and raised in alternative
production systems.
amount of further processing in the US poultry industry
underscores the need for good meat quality.
Although US consumers are accustomed to paying low
prices for poultry meat, they are increasingly interested
in products that they perceive as naturally produced or
environmentally friendly, provide a high level of nutri-
tion with no contaminants, good flavor, provide good
welfare for the birds, and provide more information about
the products they eat. The organic market in many coun-
tries has strong growth due to environmental concerns,
personal health concerns, highly publicized food scares,
and debates over genetically modified food (Chang and
Zepeda, 2005). Interest is growing in quality aspects
rather than quantity of meat and provide opportunities
for market segmentation in the United States.
Whereas some countries have very specific definitions
for free-range and or other specialty production, the
USDA does not. The term free-range is permitted on la-
bels after a review process in which producers simply
submit written descriptions of their production system
to ensure it provides outdoor access (USDA, 2006). As a
result, production systems vary widely from large sta-
tionary houses with yards to small portable houses that
are moved frequently to new pasture. In contrast, EU

FANATICO ET AL.2246
legislation for free-range poultry meat specifies maxi-
mum stocking densities for indoor and outdoor areas,
age at slaughter, as well as a diet that is at least 70%
cereals at finishing, ensuring a low-protein diet for slow
growth (European Union, 1991). For organic production,
the USDA’s National Organic Program (USDA, 2005) re-
quires outdoor access, organic feeds produced without
synthetic chemicals, and prohibits the use of antibiotics,
but again it does not specify stocking densities or slow-
growing genotypes as the EU organic program does (EEC,
1991). Another well-known program, the French Label
Rouge program, requires slow-growing genotypes, a low-
nutrient diet at finishing, and an 81-d growing period
(Ministere de L’Agriculture, 1996), and the products sell
for a premium.
In the US slow-growing genotypes are not required
in any specialty programs and, in fact, are not widely
available. The conventional Cornish × White Plymouth
Rock cross is typically used in specialty and conventional
production. However, these fast-growing birds were de-
veloped for production in indoor, climate-controlled con-
ditions. These birds grow quickly with high yield but they
may not be appropriate for alternative systems where
conditions are not well controlled. Meat quality is a com-
plex trait that is influenced by genetic and environmental
factors, and the variation in meat quality within and be-
tween animals can be large (Rehfeldt et al., 2004).
Conventional diets typically meet NRC requirements
for commercial broilers; however, these requirements
were developed for fast-growing broilers in indoor pro-
duction. In specialty programs in Europe, a low-protein
diet is used to support a slower rate of growth and im-
prove meat quality (Komprda et al., 2000; Dreisigacker,
2005; Sundrum, 2006). Moreover, diets typically do not
include routine medications or animal by-products.
Because US producers have the option to use any geno-
type in specialty production and various production prac-
tices, it is important to provide information to help them
make decisions. The objectives of this study were to assess
the impact of genotype, production system, and diet on
meat quality. Specifically, slow- and fast-growing geno-
types were compared, as well as a conventional indoor
production system and alternative system with outdoor
access. In addition, low-nutrient and conventional diets
were compared. Alternative poultry production systems
and genotypes need to be evaluated in a US setting where
few studies of this type have been conducted. In addition,
a domestic slow-growing genotype was used.
MATERIALS AND METHODS
Two experiments were conducted at the University of
Arkansas Poultry Research Farm from August to Novem-
ber 2004; all procedures were approved by the University
of Arkansas Institutional Animal Care and Use Commit-
tee. In both experiments a slow-growing genotype (slow;
S & G Poultry, Clanton, AL) and a fast-growing genotype
(fast; Cobb-Vantress Inc., Siloam Spring, AR) were com-
pared. Because of the difference in growth rate, chick
placement dates in both experiments were staggered in
an attempt to reach a similar final BW at the time of
processing (Fanatico et al., 2005b). For each treatment, 4
replicated pens per treatment were used, containing 20
birds per pen in both experiments. Feed and water were
freely available in both trials.
Experiment 1: Production System
The objective of experiment 1 was to evaluate the im-
pact of production system (indoor vs. outdoor access)
on the meat quality of female slow- and fast-growing
genotypes, which were raised for 91 or 63 d, respectively.
Birds were randomly assigned to pens in a conventional
indoor facility or a portable facility with outdoor access.
The 4 treatments consisted of slow-growing birds given
outdoor access (slow-out), slow-growing birds that were
confined indoors (slow-in), fast-growing birds given out-
door access (fast-out), and fast-growing birds that were
confined indoors (fast-in).
The indoor treatments were raised in floor pens in a
conventional poultry research facility that contained a
concrete floor, side curtains, and fans for ventilation and
cooling. A thermostatically controlled heater and gas
brooders along the length of the house were used to
provide additional heat during brooding. Indoor pens
measured 1.8 m × 1.8 m (6.2 birds/m
2
) and contained 1
bell waterer and hanging tube feeder. Pens contained
new wood shavings, and a constant photoperiod of 24 h
was provided.
The treatments with outdoor access were grown in a
small portable facility (that was not moved during the
course of this trial) measuring 3.7 m × 5.5 m. The facility
was insulated and naturally ventilated but had no access
to power. Propane space heaters were used to keep night-
time temperatures above 15.5°C inside the house. No arti-
ficial lighting was used; photoperiod was limited to natu-
ral daylight. The house was subdivided into 8 indoor
pens that opened to 8 separate yards, which was sur-
rounded by electric net fencing. The indoor areas of each
pen measured 1.2 m × 1.5 m (11.1 birds/m
2
), and all pens
allowed outdoor access through bird exits (0.6 m × 0.5
m). Birds were allowed access to grassy yards during
daytime hours unless the outdoor temperature was less
than 4.4°C. The outdoor yards were at 9.3 m
2
in dimension
and completely covered with vegetation (a combination
of cool-season fescue and warm-season Bermudagrass).
The indoor portion of each pen contained 1 fount-style
waterer and hanging tube feeder, and the floor was cov-
ered with fresh wood shavings. The outdoor portion of
each pen contained 1 waterer and a range-type tube feeder
with a rain shield. Temperature and photoperiod/inten-
sity in this facility obviously differed from the conven-
tional facility and was considered to be part of the alterna-
tive production system.
All birds were provided with multiphase diets that
were formulated to be low in protein and energy as used
by the French Label Rouge program for slow-growing
birds (Table 1). Although the study was not conducted

ALTERNATIVE PRODUCTION SYSTEM AND GENOTYPE MEAT QUALITY 2247
Table 1. Composition of experimental diets
1
Conventional Low nutrient
Ingredient Starter Grower I Grower II Finisher Starter Grower I Grower II Finisher
%
Corn 55.06 66.12 72.17 77.48 61.45 64.75 69.85 72.05
Soybean meal 37.18 27.94 22.61 18.08 29.00 21.00 15.00 10.50
Wheat middlings — — — — 6.00 11.00 12.00 14.30
Corn oil 3.96 2.31 2.05 1.29 — — — —
Dicalcium phosphate 1.20 1.30 1.10 1.10 1.40 1.20 1.00 1.00
Limestone 1.60 1.40 1.30 1.30 1.30 1.30 1.40 1.40
NaCl 0.40 0.40 0.30 0.30 0.40 0.30 0.30 0.30
Vitamin mix
2
0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20
Mineral mix
2
0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10
CholineⴢCl (60%) 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10
DL
-Met 0.1563 0.0815 0.0174 — — — — —
Sacox salinomycin
3
0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05
Calculated composition
ME, kcal/kg 3,100 3,100 3,150 3,150 2,886 2,902 2,946 2,956
CP, % 22.9 19.4 17.4 15.7 20.5 17.7 15.5 13.9
Digestible Lys, % 1.10 0.89 0.76 0.65 0.94 0.76 0.62 0.52
Digestible Met, % 0.41 0.33 0.28 0.26 0.31 0.27 0.25 0.23
Digestible Cys, % 0.41 0.34 0.29 0.26 0.31 0.28 0.25 0.24
Digestible Thr, % 0.75 0.63 0.53 0.50 0.65 0.55 0.47 0.41
Ca, % 1.00 0.90 0.80 0.80 0.90 0.85 0.80 0.80
Nonphytate P, % 0.45 0.35 0.30 0.30 0.45 0.35 0.30 0.30
Protein:energy ratio
4
7.39 6.26 5.52 4.98 7.10 6.10 5.26 4.70
1
Conventional diets were fed in experiment 2, whereas low-nutrient diets were fed in experiments 1 and 2.
2
Provided (per kilogram of diet): vitamin A, 7,715 IU (retinyl acetate); cholecalciferol, 2,204 IU; vitamin E, 16.5 IU (
DL
-α-tocopheryl acetate);
thiamin, 1.54 mg; niacin, 38.6 mg; riboflavin, 6.6 mg;
D
-calcium pantothenate, 9.9 mg; vitamin B
12
, 0.013 mg; vitamin B
6
, 2.8 mg;
D
-biotin, 0.07 mg;
folic acid, 0.88 mg; menadione dimethylpyrimidinol bisulfite, 3.30 mg; choline, 400 mg; ethoxyquin, 125 mg; Se, 0.1 mg; MnSO
4
ⴢH
2
O, 308 mg;
FeSO
4
ⴢ7H
2
O, 250 mg; ZnSO
4
ⴢ7H
2
O, 440 mg; CuSO
4
ⴢ5H
2
0, 39.3 mg; MgO, 43.9 mg; and Ca(IO3)2ⴢH
2
O, 3.2 mg.
3
Sacox 60, Hoechst-Roussel Agri-Vet. Co., Somerville, NJ. Provided 66 mg of salinomycin activity/kg.
4
Calculated as protein (%) divided by energy (kcal/kg) multiplied by 1,000.
under specific organic guidelines, the diets were devoid
of animal by-products and synthetic methionine. Anticoc-
cidial medication was included. All chicks were brooded
in the indoor facility; chicks in the treatments with out-
door access were moved to the portable facility at 3 wk
of age.
Experiment 2: Dietary Nutrient Level
The objective of experiment 2 was to evaluate the im-
pact of dietary nutrient level (conventional vs. low-nutri-
ent) on the meat quality of male slow- and fast-growing
genotypes, which were raised for 84 or 56 d, respectively.
Birds in this trial were raised for a shorter period of
time than birds in experiment 1 (conducted concurrently)
because processing capacity dictated that the 2 experi-
ments be terminated on different days. Moreover, because
of gender and diet differences, males in experiment 2
were expected to grow at a faster rate than the females in
experiment 1. All birds were housed in the conventional
indoor facility described above. The experimental diets
consisted of a low-nutrient diet (as used in experiment
1) or a conventional diet that was formulated according
to NRC (1994) recommendations (Table 1). Diets were
provided in multiple phases, and the 4 treatments con-
sisted of slow-growing birds fed the low-nutrient diets
(slow-low), slow-growing birds fed the conventional diets
(slow-conventional), fast-growing birds fed the low-nu-
trient diets (fast-low), and fast-growing birds fed the con-
ventional diets (fast-conventional).
Experiments 1 and 2: Processing and
Sample Analysis
At trial termination all birds were commercially pro-
cessed at the University of Arkansas Pilot Processing
Plant. Feed was withheld for 10 h before slaughter, and
broilers were weighed individually at the plant. Auto-
mated equipment was used for stunning, scalding, pick-
ing, vent opening, and evisceration. Birds were electri-
cally stunned (11 V, 11 mA, 10 s) and soft-scalded at 53°C
for 120 s. Carcasses were prechilled at 12°C for 15 min
and chilled (immersion) at 1°C for 1 h. After chilling, the
carcasses were aged on ice for an additional 2.5 h before
hand deboning at 4 h postmortem. Pectoralis major sam-
ples were then collected for evaluation of meat quality.
Due to logistical reasons, birds in experiment 2 were aged
on ice for 3.75 h and then deboned at 5.25 h postmortem.
At 24 h postmortem, the breasts were weighed to deter-
mine drip loss, which was expressed as a percentage of
the initial muscle weight. Inadvertently, drip loss was not
determined for experiment 2. Color was measured by the
CIELAB method using a Minolta colorimeter (Minolta
CR-300, Minolta Corp., Ramsey, NJ). In this method,
higher L* values are light, higher a* values are red, and
higher b* values are yellow. Three color measurements

FANATICO ET AL.2248
were taken on the medial surface of each right breast
and then averaged. The color of the skin (thigh) was
also measured.
Breast fillets were cooked on racks in aluminum-lined,
covered pans in a preheated convection oven to an inter-
nal temperature of 76°C. After cooking, the breasts were
weighed to determine cook loss. Cook loss was deter-
mined by calculating the weight loss during cooking as
a percentage of the weight before cooking. Total moisture
loss was calculated from the cooked weight as a percent-
age of the raw weight at the time of deboning.
Tenderness was assessed on the breast fillets with the
Meullenet-Owens razor shear (MORS) method (Cavitt et
al., 2004). Razor blade shear energy (Nⴢmm) was deter-
mined on intact fillets. Energy was determined using a
Texture Analyzer (model TA-XT2i; Texture Technologies,
Scarsdale, NY) with a 5-kg load cell using a razor blade
with a height of 24 mm and a width of 8.9 mm set to a
penetration depth of 20 mm. Crosshead speed was set at
5 mm/s and was triggered by a 10 g of contact force.
Data points were collected with an acquisition rate of 200
points per second. Breasts were punctured across muscle
fibers, and shear energy was calculated as the area under
the force deformation curve from the beginning to the end
of the test. The fillets from the fast-growing treatments
averaged 34 mm in height, and those from the slow-
growing treatments averaged only 20 mm. Data from
fillets less than 20 mm in height were calculated to base
shear energy on the smaller height.
Muscle pH of Pectoralis major was determined using
the iodoacetate method as described by Sams and Janky
(1986) and Jeacocke (1977). Five samples were taken from
each replication of each treatment (n = 20 samples per
treatment) at 24 h and frozen at −80°C for 3 mo.
Proximate analysis was performed on the raw breast
(fat was trimmed) at the University of Arkansas Central
Analytical Laboratory. In experiment 1, DM content, ash,
protein, fat, vitamin A, α-tocopherol, and δ-tocopherol
were determined by AOAC approved methods (AOAC,
1990). Fat was reported as a percent of DM. Five samples
were taken from each replication in each treatment (n =
20 samples from each treatment). However, for vitamin
analysis, only 2 samples from each replication of each
treatment (n = 8 from each treatment) were analyzed. The
nutrient analysis was more limited in experiment 2; there
was no analysis of treatments with the fast-growing geno-
type (only slow-growing birds raised indoors and slow-
growing birds raised with outdoor access), and then only
DM, ash, protein, and fat content were analyzed (no vita-
min analysis).
Statistical Analysis
The data were subjected to ANOVA using the GLM
procedure (SAS, 2004) appropriate for a completely ran-
domized design; a factorial arrangement of treatments
was used. Treatment means were separated using the
LSD multiple comparison procedure.
RESULTS AND DISCUSSION
There are many aspects to overall meat quality of poul-
try products, which may be affected by genotype, age,
gender, type of production system, stocking density, tem-
perature, diet, and other factors. The number of factors
evaluated in these experiments was necessarily limited
and focused on factors (genotype, age as a function of
genotype, production system, and diet) likely to cause
an impact or variation in meat quality. Outdoor poultry
production, in particular, is inherently variable due to
changes in temperature, photoperiod, level of activity, etc.
Growth data is reported separately (Fanatico et al.,
2005b), but a brief summary is given here to provide an
indication of the differences in weight gain and body
composition. In experiment 1, the weight gain of the fast-
growing birds exceeded that of the slow-growing birds
even though the slow birds were started earlier in an
attempt to reach a similar weight. In experiment 2, the
low-nutrient diet reduced the weight gain of the slow,
but not the fast; whereas on the conventional diet, weight
gains were similar between the genotypes. The carcass
weights reflected the differences in weight gain. The fast
genotype exhibited superior breast yield in both experi-
ments. Breast yield were reduced by the low-nutrient diet
in the case of the fast birds. Although birds differed in
both age and body composition, it is important to evaluate
meat quality under conditions that are representative of
alternative production systems.
Nutrient Composition
In experiment 1, which evaluated genotype and pro-
duction system, there were no significant differences
among treatments for dry matter or ash in breast meat
(P > 0.05), indicating little difference in mineral contents
(Table 2). This agrees with previous work (Latter-Dubois,
2000; Fanatico et al., 2005a), although Baeza et al. (2002)
found that fast-growing ducks had increased protein and
mineral contents and decreased moisture in breast muscle
compared with slow-growing ducks, explained by a dif-
ference in the stage of muscle development.
There was a genotype effect for the protein content of
the breast meat. The slow birds had higher protein than
fast (P < 0.05; Table 2), which may be related to age.
Typically, as an animal ages, the composition of body and
muscle changes; protein and fat increase and moisture
decreases (Aberle et al., 2001), although lower moisture
was not evident in breast meat in experiment 1. In the
present trial, the slow birds were 4 wk older than the fast
at harvesting. Production system also affected protein
content. The outdoor birds had higher protein than indoor
(P < 0.05; Table 2), possibly related to exercise in an out-
door system contributing to muscle development and
higher protein.
In experiment 2, which evaluated genotype and diet,
the conventional diet led to a higher dry matter, lower
ash content, and higher protein than the low diet (P <
0.05; Table 3), which may be related to the fact that the

ALTERNATIVE PRODUCTION SYSTEM AND GENOTYPE MEAT QUALITY 2249
Table 2. Impact of genotype and production system on nutrients in breast meat (experiment 1)
α-Tocopherol,
3
Item DM,
1
% Ash,
1
% Protein,
1
% Fat,
1,2
% Vitamin A,
3
␮g/g of fat ␮g/g of fat
Slow-outdoor access 26.37 4.00 13.90
a
4.47
b
14.61 274.07
a
Slow-indoor 25.99 4.10 13.56
b
5.25
b
9.90 224.93
ab
Fast-outdoor access 25.56 4.10 13.45
b
7.90
a
7.11 152.43
b
Fast-indoor 26.5 4.00 13.00
c
8.86
a
11.34 212.40
ab
Pooled SEM 0.26 0.05 0.09 0.33 4.20 65.76
ANOVA P-value
Genotype 0.2280 0.9132 0.0001 0.0001 0.1933 0.0758
Production system 0.6818 0.5980 0.0010 0.0214 0.9152 0.8771
Genotype × production system 0.0799 0.1470 0.5465 0.7812 0.0654 0.1392
a–c
Means within a column lacking a common superscript differ (P < 0.05).
1
n = 20.
2
Based on a percentage of DM.
3
n=8.
conventional diet resulted in higher fat in breast meat.
As the amount of fat increases in the body, the moisture
decreases (Aberle et al., 2001).
There were also genotype and production system ef-
fects in terms of intramuscular fat content (IMF; experi-
ment 1). The breast meat of the slow birds had half the
amount of fat than fast (P < 0.05; Table 2). Poultry meat
is known for being low in fat because unlike other meat
animals, fat is mainly deposited subcutaneously or in the
abdomen rather than in the meat (IMF). Domestic poultry
selected for rapid growth show excessive body fat deposi-
tion (Leclercq, 1988), although a certain amount of intra-
muscular fat is associated with sensory and meat quality
traits (Gerbens, 2004). Like the present study, Wattana-
chant et al. (2004) also reported higher protein and lower
fat in the slow-growing genotype compared with fast-,
and Havenstein et al. (2003) reported that 2001 broilers
had more whole carcass fat than 1957 broilers at 4 differ-
ent ages.
The outdoor birds had lower fat than the Indoor birds
(P < 0.05; Table 2; experiment 1). This is consistent with
other studies that have shown that the additional space
provided in free-range and organic production increases
leanness in poultry, most likely due to activity (Robertson
et al., 1966; Lei and van Beek, 1997; Castellini et al., 2002a).
Low density and outdoor access favor myogenesis instead
of lipogenesis (Castellini et al., 2002b).
In experiment 2, the conventional diet led to a higher
fat content than the low diet, which is not surprising
because the conventional diet is higher in energy. Ha-
Table 3. Impact of diet on nutrients in breast meat (experiment 2)
Item DM,
1
% Ash,
1
% Protein,
1
% Fat,
1
%
Conventional diet 26.41
a
3.97
b
13.29
b
7.23
a
Low-nutrient diet 25.84
b
4.11
a
13.51
a
5.08
b
Pooled SEM 0.12 0.03 0.06 0.43
P-value
ANOVA 0.0120 0.0136 0.0303 0.0123
a,b
Means within a column lacking a common superscript differ (P <
0.05).
1
n = 20.
venstein et al. (2003) found that modern diets resulted in
better growth rates but also produced considerably higher
fat levels than 1957 diets. Peter et al. (1997) studied the
impact of protein level and energy level on carcass and
meat quality of slow-growing meat chickens grown to 12
wk and found that breast meat quality (chemical composi-
tion, grill loss, shear force) was only slightly influenced
by feeding. Peter et al. (1997) found that increasing protein
level lowered IMF in breast meat, whereas increasing
dietary energy increased IMF. Crude protein content of
the carcass increases with increasing dietary protein,
whereas increasing dietary energy leads to decreased pro-
tein contents in the carcass (Peter et al., 1998).
There were no significant differences in terms of vita-
minA(P > 0.05), but a genotype effect existed for α-
tocopherol (Table 2; experiment 1). Vitamin E is a fat
soluble vitamin, and although the fast birds had higher
α-tocopherol content than slow, when expressed on a unit
of fat basis, the content of α-tocopherol was higher in
slow birds than the fast (P < 0.05). Surprisingly, there
was no impact on vitamins from outdoor access. It was
expected that there would be more vitamins in the meat of
outdoor birds because forage plants are high in vitamins.
Karsten et al. (2003) found eggs from chickens raised on
legume pasture have more vitamin A and E and more
omega-3 fatty acids than eggs from chickens raised in-
doors. Robertson et al. (1966) found the meat of free-
range birds to contain more thiamine than the indoor
birds. It may be necessary to move housing frequently,
especially in seasons when there is little regrowth of
plants, to see a greater impact from production system.
Color
Color is one of the first characteristics noticed by con-
sumers when buying meat products. In natural and or-
ganic markets, where carcasses are often marketed whole,
the color of the skin plays a particularly important role.
Skin color is dependent on the genetic ability of the bird
to produce melanin pigments in the dermis and epider-
mis, as well as to absorb and deposit carotenoid pigments
in the epidermis (Fletcher, 1999). Scalding can also impact

FANATICO ET AL.2250
Table 4. Impact of genotype and production system on breast meat
1
and thigh
1
skin color (experiment 1)
Skin Meat
Item L* a* b* L* a* b*
Slow-outdoor access 72.19
b
0.44
c
14.58
a
51.04
a
2.55
b
7.55
a
Slow-indoors 73.68
a
−0.17
d
13.17
b
51.91
b
2.54
b
6.32
b
Fast-outdoor access 69.86
c
4.01
a
9.98
c
51.77
ab
4.12
a
4.84
c
Fast-indoors 70.05
c
3.32
b
10.27
c
52.16
b
3.83
a
5.29
c
Pooled SEM 0.49 0.27 0.39 0.25 0.18 0.20
ANOVA
P-value
Genotype 0.0001 0.0001 0.0001 0.0750 0.0001 0.0001
Production system 0.0049 0.0004 0.1768 0.0289 0.4244 0.0765
Genotype × production system 0.0211 0.7523 0.0489 0.3552 0.4618 0.0013
a–d
Means within a column lacking a common superscript differ (P < 0.05).
1
n = 80; measured at 24 h postmortem.
skin color. The use of a soft scald allows retention of the
cuticle and associated pigments, whereas a hard scald,
which is common during processing in the United States,
will remove portions of the cuticle and the epidermis and
pigments as well.
In experiment 1, there was an interaction between geno-
type and production system for the yellowness of the
skin (P < 0.05). The slow birds had significantly higher
b* values than fast both indoors and outdoors, indicating
more yellow skin, and when the slow had access to the
outdoors, their skin became even more yellow than when
indoors (P < 0.05; Table 4). Production system had no
effect on skin color of the fast birds (P > 0.05). This interac-
tion was attributed to the fact that the slow birds spent
more time outdoors and were more active than the fast
and foraged more. Use of the outdoor area and foraging
behavior are reported separately (C. Falcone and J.
Mench, University of California, Davis, CA, unpublished
data). Apparently, the fast birds did not forage sufficiently
to ingest pigments from the plants. This interaction is in
agreement with previous findings (Fanatico et al., 2005a).
In selling cut-up parts, uniformity of meat color in
packages is important. Myoglobin content is a major fac-
tor contributing to meat color and is dependent on spe-
cies, muscle, and age of bird. Other intrinsic factors, such
as muscle and pH, can also influence meat color (Fletcher,
2002). Color is also an indicator of meat quality (Owens
et al., 2000; Woelfel et al., 2002). The L* value indicates
the degree of paleness and is associated with poor meat
quality; pale, soft, and exudative meat is an increasing
problem in the poultry industry (Baeza et al., 2002). In
the present trials, there was no genotype effect on L*
value. In contrast, Berri et al. (2001) found that the breast
meat of breeds selected for fast-growth was more pale
and less red than that of nonselected birds, which was
explained by a lower level of heme. Because heme pig-
ments normally increase with age (Baeza et al., 2002),
slow-growing birds normally have a redder meat than
fast- because the slow-growing are typically older (Gor-
don and Charles, 2002). However, in the present study,
the slow birds were less red (lower a*) than the fast (P <
0.05). Nielsen et al. (2003) also found the breast meat of
slow-growing birds to be less red than fast-growing. The
meat of the slow birds was more yellow than that of the
fast birds (P < 0.05), which agrees with other findings
(Quentin et al., 2003; Fanatico et al., 2005a; Santos et
al., 2005a).
A production system effect was evident in the meat as
in the skin. The meat of the indoor birds had higher L*
values (paler meat) than outdoor birds (P < 0.05; Table
4), but all the values were within normal ranges as charac-
terized by Woelfel et al. (2002). In contrast, Castellini et
al. (2002a) found that organic production system with
outdoor access resulted in higher paleness values com-
pared with indoor system. These differences in trends
of meat paleness may be related to the differences in
environmental conditions in each study. Outdoor access
and associated exercise could impact muscle fibers and
color. In fact, Brackenbury and Williamson (1989) found
that the oxidative capacity of the chicken iliotibialis later-
alis caudalis muscle increased from 40 to 60% after 15
wk of treadmill training. Outdoor access resulted in the
same impact on the yellowness (b* value) of slow as was
discussed above for skin.
In experiment 2, the genotype effect on color was simi-
lar to results of experiment 1 (Table 5). On the conven-
tional diet, the meat of the slow birds was more pale than
the fast birds, but in the case of the low diet, there was
no difference between genotypes (P > 0.05). Lyon et al.
(2004) has found that breast meat is lighter in color when
birds are fed a wheat-based diet compared with corn. In
the present study, although the low diet included wheat
middlings and less corn than the conventional, the low
diet did not result in lighter meat.
pH
Postmortem pH decline is one of the most important
events in the conversion of muscle to meat due to its
impact on meat texture, color, and water-holding capacity
(WHC; Aberle et al., 2001). The rate of pH decline is
dependent on the activity of glycolytic enzymes just after
death; the ultimate pH is determined by the initial glyco-
gen reserves of the muscle (Bendall, 1973). A low pH is
associated with poor water-holding capacity and poor
functionality (Owens et al., 2000; Woelfel et al., 2002), and

ALTERNATIVE PRODUCTION SYSTEM AND GENOTYPE MEAT QUALITY 2251
Table 5. Impact of genotype and diet on breast meat
1
and thigh skin color
1
(experiment 2)
Skin Meat
Diet L* a* b* L* A* b*
Slow-low nutrient 73.28
a
0.69
d
10.94
a
52.19
a
2.83
b
3.92
a
Slow-conventional 72.31
b
1.04
c
10.49
a
52.89
b
2.93
b
4.38
a
Fast-low nutrient 70.60
c
2.98
b
7.81
b
52.43
ab
4.51
a
2.48
b
Fast-conventional 68.24
d
3.51
a
6.83
b
51.66
a
4.79
a
2.85
b
Pooled SEM 0.27 0.12 0.35 0.30 0.13 0.21
ANOVA
P-value
Genotype 0.0001 0.0001 0.0001 0.1221 0.0001 0.0001
Diet 0.0001 0.0025 0.0610 0.8989 0.1522 0.0661
Genotype × diet 0.0213 0.4710 0.4639 0.0289 0.5132 0.8475
a–d
Means within a column lacking a common superscript differ (P < 0.05).
1
n = 80; measured at 24 h postmortem.
a high pH is associated with poor shelf life because it is
a more favorable environment for bacteria (Aberle et al.,
2001). Although all pH values in this study were in normal
ranges and do not indicate problems, in experiment 1,
the slow birds had a lower ultimate pH compared with
the fast (P < 0.05; Table 6). Others have also found lower
pH in slow-growing genotypes compared with fast-grow-
ing (Wattanachant et al., 2004; Berri et al., 2005; Santos
et al., 2005b). Selection for fast growth and high yield has
reduced the rate and extent of pH decline (Berri et al.,
2001, 2005), possibly due to a decrease in the glycolytic
potential, which is essentially a measure of glycogen con-
tent (Monin and Sellier, 1985; Baeza et al., 2002). Fernan-
dez et al. (2001) found fast-growing turkeys had lower
glycogen content than slow-growing in the pectoralis su-
perficialis muscle, which normally leads to less decline
in pH.
Slow-growing birds may be more stress susceptible
than fast-growing birds. According to Debut et al. (2005),
active birds such as slow-growing birds are more prone
to shackling stress, which leads to rapid breast muscle
acidification. The fast-growing birds do not struggle as
much, and their pH decline is slower. Breast muscle is
more sensitive to wing flapping on the shackling line than
thigh muscle.
Exercise is likely to affect muscle metabolism (Farmer
et al., 1997). In the present study, outdoor access resulted
Table 6. Impact of genotype and production system on pH and instru-
mental tenderness of breast meat (experiment 1)
Item pH
1
TE,
2
Nⴢmm
Slow-outdoor access 5.53
c
111.16
b
Slow-indoors 5.60
b
102.57
b
Fast-outdoor access 5.72
a
140.11
a
Fast-indoors 5.69
a
149.88
a
Pooled SEM 0.02 5.10
ANOVA P-value
Genotype 0.0001 0.0001
Production system 0.2947 0.9096
Genotype × production system 0.0187 0.0941
a–c
Means within a column lacking a common superscript differ (P <
0.05).
1
n = 20.
2
Meullenet Owens razor shear, TE = total energy;n=40.
in lower pH in slow, and there was no impact in fast.
The impact of exercise is likely to differ due to the amount
of foraging and the environment. Like the present study,
Castellini et al. (2002a) and Culioli et al. (1990) also found
outdoor access resulted in lower pH, but in contrast, Alva-
rado et al. (2005) found that outdoor access resulted in
higher pH.
Water-Holding Capacity
Water-holding capacity is important in whole meat and
further processed meat products and can be measured
by drip or cook loss. Poor WHC affects functionality, as
well as sensory characteristics. The slow birds had higher
drip loss than the fast (P < 0.05; Table 7), which agrees
with earlier findings (Fanatico et al., 2005a). Because the
fillets from the slow birds are smaller and thinner in
dimension, they had relatively more surface area in rela-
tion to muscle mass exposed to the air, which may have
resulted in more drip loss. As breast weight increased,
the drip loss was less (r = −0.73 in experiment 1). Baeza
et al. (2002) found a decrease in drip loss with increasing
age at slaughter, partly explained by the decrease in mus-
cle water content of duck breast (Baeza et al., 2002). In
the present study, the fast birds had more thaw loss than
the slow (P < 0.05), possibly related to the freezing rate.
Because fillets from fast birds were heavier (P < 0.05) and
had large dimensions (i.e., thicker), the freezing rate was
likely slower, possibly resulting in larger ice crystal for-
mation, leading to more membrane damage. The fast
birds also lost more water than the slow during cooking
(P < 0.05), which may be related to higher fat in fast.
Chartrin et al. (2006) found that cooking loss was greater
in breast muscle containing high lipid levels. This also
may be due to larger fillet dimensions, which leads to
more cooking time and more moisture loss. As breast
weight increased, so did thaw and cook loss (r = 0.85
and 0.90, respectively, in experiment 1). Previous findings
showed a higher cook loss in slow-growing broilers com-
pared with fast-growing broilers (Lonergan et al., 2003;
Fanatico et al., 2005a), which may be related to the higher
fat content of the fast.
When total moisture loss is considered, the slow birds
had more moisture loss than the fast. This agrees with

FANATICO ET AL.2252
Table 7. Impact of genotype and production system on water-holding capacity of breast meat (experiment 1)
Item Breast weight,
1
g Drip loss,
1
% Thaw loss,
1
% Cook loss,
1
% Total loss,
1,2
%
Slow-outdoor access 311.8
b
1.26
a
0.63
b
13.37
d
32.19
bc
Slow-indoors 296.2
b
1.54
a
0.81
b
14.58
c
37.52
a
Fast-outdoor access 792.4
a
0.88
b
1.24
a
18.11
b
28.83
c
Fast-indoors 799.8
a
0.95
b
1.52
a
22.1
a
33.12
abc
Pooled SEM 0.03 0.11 0.11 0.38 1.55
ANOVA P-value
Genotype 0.0001 0.0007 0.0001 0.0001 0.0274
Production system 0.8776 0.1204 0.0538 0.0001 0.0090
Genotype × production system 0.6654 0.3603 0.6741 0.0030 0.7412
a–d
Means within a column lacking a common superscript differ (P < 0.05).
1
n = 80.
2
Calculated as [(fillet weight at deboning − cooked weight) / fillet weight at deboning] × 100.
Santos et al. (2005b) who found that the breast meat of
a slow-growing genotype had poorer WHC than fast-
growing ones. Castellini et al. (2002b) attributed poor
WHC in slow-growing birds to their tissue being less
mature metabolically at harvest than the fast-growing
birds. Interestingly, Berri et al. (2005) found when slow-
growing and fast-growing, heavy birds were slaughtered
under conditions which minimized struggle, the slow-
growing had better WHC, as measured by drip loss, than
birds from a heavy line. The authors concluded that breast
meat from heavy broilers was predisposed to poor pro-
cessing ability.
Production system impacted WHC. The indoor birds
had more total loss than the outdoor (P < 0.05) (Table 7;
experiment 1). This agrees with Latif et al. (1998) who
found under intensive management (indoor), a slow-
growing genotype had better WHC (leg quarters) than
fast-growing, and Castellini et al. (2002a) found that or-
ganic production with outdoor access system resulted in
poorer WHC.
There was an interaction between genotype and diet
for the thaw loss (experiment 2). The low diet led to more
thaw loss in the case of the fast birds (P < 0.05) but not
the slow (Table 8). For cook loss, there were both genotype
and diet main effects. The slow birds had a higher cook
loss than the fast, and the birds on the low diet had a
higher cook loss than the conventional (P < 0.05). Jensen
et al. (1984) also found birds on a low energy diet had
Table 8. Impact of genotype and diet on water-holding capacity of
breast meat (experiment 2)
Item Breast weight,
1
g Thaw,
1
% Cook,
1
%
Slow-low nutrient 352
c
2.17
b
25.07
a
Slow-conventional 408
b
2.18
b
23.92
ab
Fast-low nutrient 544
a
3.40
a
22.13
b
Fast-conventional 590
a
1.47
c
18.35
c
Pooled SEM 13 0.19 0.68
ANOVA P-value
Genotype 0.0001 0.2015 0.0001
Diet 0.0024 0.0003 0.0033
Genotype × diet 0.6988 0.0003 0.0763
a–c
Means within a column lacking a common superscript differ (P <
0.05).
1
n = 80.
lower cook loss. However, Quentin et al. (2003) found
diet concentration had little impact on pH and drip loss
in fast-, medium-, and slow-growing meat chickens that
were fed with 3 different levels of protein and energy.
Tenderness
Texture, particularly tenderness, is a crucial consumer
attribute. In the present study, the slow birds were more
tender than the fast birds in both experiments (P < 0.05)
as measured by the MORS method (lower total energy;
Table 6). The values for slow treatments were in the cate-
gory of extremely tender, and the fast treatments were
categorized as moderately to slightly tender as catego-
rized by Cavitt et al. (2004). It was expected that the slow
birds would be less tender than the fast because the slow
were older. According to Fletcher (2002), older birds are
more mature at the time of harvest and have more cross-
linking of collagen. In addition, the fast birds had more
IMF in breast meat, which is usually associated with
higher tenderness (Le Bihan-Duval, 2003). Other studies
have found the meat of slow-growing or older genotypes
to be less tender compared with fast-growing (Castellini
et al., 2002b; Wattanachant et al., 2004; Fanatico et al.,
2005a). However, like the present study, Farmer et al.
(1997) found that breast meat from slow-growing birds
was more tender than meat from fast-growing birds.
Although all treatments were deboned at 4 h postmor-
tem, it is possible that fast and slow genotypes have differ-
ent rates of rigor due to their different BW. Berri et al.
(2005) found that a heavy line of fast-growing broilers
had higher pH at 15 min postmortem than slow- and
fast-growing birds, although the ultimate pH of the fast-
growing (not heavy line) was higher than others.
The differences in tenderness may be related to endoge-
nous proteolytic activity during aging. Birds with large
muscle mass accrete protein through reduced protein ca-
tabolism (Dransfield and Sosnicki, 1999). Because they
have reduced proteolytic potential, there is less postmor-
tem proteolysis and, therefore, reduced tenderization in
the meat. Schreurs et al. (1995) compared birds with dif-
ferent grow rates and found that fast-growing birds show
little proteolytic activity, whereas slow-growing birds like
White Leghorns show high rates. There was a 12-fold

ALTERNATIVE PRODUCTION SYSTEM AND GENOTYPE MEAT QUALITY 2253
difference in the amount of ␮-calpain. Slow-growing
birds had higher ␮-calpain and m-calpain and lower cal-
pastatin than fast-growing birds (Schreurs et al., 1995).
Outdoor access has been shown to result in meat that
is more firm than indoor production (Castellini et al.,
2002a; Santos et al., 2005a). In this trial, there was no
impact of production system on tenderness. In previous
research, outdoor access actually resulted in more tender
meat in the case of the fast birds (Fanatico et al., 2005a).
According to Dingboom and Weijs (2004), the impact of
exercise on meat quality is minor and ambiguous.
Adequate nutrition is needed for normal muscle devel-
opment and weight gains, but low-nutrient diets are used
in Europe with extensive poultry production to slow
growth and improve meat quality. Feed restriction in
quantity or quality leads to decreased muscle fiber diame-
ter (Rehfeldt et al., 2004). However, in the present trial,
the low nutrient diet did not have a significant impact
on tenderness (data not shown). Chartrin et al. (2006)
found that feeding levels had no effect on tenderness, but
tenderness was negatively correlated with breast muscle
weight. Ristic (1988) compared a high-protein/high-en-
ergy diet and a high energy diet compared with a stan-
dard diet and found no significant differences in sensory
data, cooking losses, instrumental tenderness, or chemical
composition. Grashorn (2006) found that nutrient level
did not impact the texture of the breast. Moritz et al.
(2005) found few differences in cook loss and texture of
breast meat among broilers raised in conventional and
alternative production systems and without or without
synthetic methionine and feed restriction, although feed
restriction led to a firmer breast texture.
Conclusions
The study focused on factors important to alternative
poultry producers: genotype, production system, and
diet. A better understanding of meat quality of widely
divergent genotypes raised in different production sys-
tems and provided different diets will help producers
make informed decisions about their production systems.
There was little effect from a meat quality perspective
of raising birds with outdoor access, other than reduced
fat and increased yellow color, but some consumers prefer
this natural system (Neufield, 2002). There were advan-
tages from the use of an alternative genotype, including
more vitamins; however, WHC was worse. Slow-growing
birds are less efficient than fast-growing birds due to their
slower rate of growth; however, slow-growing genotypes
may bring premium prices. Although some producers
use a low energy diet to raise birds more slowly to im-
prove the meat quality (Dreisigacker, 2005), there were
no meat quality advantages from using a low nutrient
feed in this study. These data indicate that meat quality
differences exist among genotypes with different growth
rates and reared in alternative production systems and
may be ways to add value to poultry carcasses.
ACKNOWLEDGMENTS
We would like to thank the USDA Southern Region
Sustainable Agriculture Research and Education program
and the US Poultry and Egg Association for funding for
this research.
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