Effects of crude protein and lysine contents of the diet on growth and body composition of slow-growing commercial broilers from 42 to 77 days of age
Effects of crude protein and lysine contents of the diet on growth and body composition of slow-growing commercial broilers from 42 to 77 days of age
Maxime QUENTIN 0 1
Isabelle BOUVAREL 0
Michel PICARD 1
0 Institut Technique de l'Aviculture , 28 rue du rocher, 75008 Paris , France
1 Institut National de la Recherche Agronomique-Station de Recherches Avicoles , 37380 Nouzilly , France
- The effects of two dietary crude protein levels (H = 22.5 and L = 17% on average) and four lysine levels (0.56, 0.66, 0.76 and 0.86%) were compared in a 2 × 4 factorial design, on growth and carcass composition of slow growing broilers (Label) during the finishing period (42-77 days). There were six pens of 28 male chickens per treatment. In each pen, 14 chicks received a stimulating starter diet (13 MJ·kg-1, 1.4% lysine) and the other 14 chicks a poor starter diet (12.1 MJ·kg-1, 1.1% lysine) from 0 to 6 days of age. The starter regime had no significant effect on subsequent performances and no interaction with the other traits. During the finishing period, lysine deficiency at 0.56% induced feather pecking and cannibalism resulting in more severe mortality with the H (33.9%) than the L diet (5.4%). Growth, feed conversion and breast meat yield were significantly improved by lysine supplementation up to 0.76% in the diet whatever the protein level. However, the deterioration of growth and feed conversion for lower lysine levels was more severe for the H diet compared to the L diet (interaction P < 0.001). The H fed chickens had less abdominal fat (3.3%) than the L fed chickens (4.3%) without a significant effect of the lysine level. The lysine requirement measured by regression (exponential and ascending line with a plateau) was close to 0.68%. High dietary protein levels associated with subdeficiency in lysine might favour cannibalism in label chickens during the finishing stage.
Pendant la période de finition, le taux le plus bas de lysine (0,56 %) a induit du picage et du
cannibalisme conduisant à une mortalité plus sévère pour le régime H (33,9 %) que pour le régime
L (5,4 %). La croissance, l’indice de consommation et le rendement en filets étaient significativement
améliorés par la supplémentation en lysine jusqu’au niveau de 0,76 % quel que soit le taux protéique.
Cependant, la détérioration de la croissance et de l’indice de consommation pour des teneurs de lysine
inférieures, était plus marquée pour le régime H que pour le régime L (Interaction P < 0,001). Les
poulets consommant les régimes H avaient en moyenne moins de gras abdominal (3,3 %) que ceux
consommant les aliments L (4,3 %) sans effet ou interaction avec le taux de lysine. Le besoin en
lysine mesuré par régression (exponentielle et linéaire à plateau) était proche de 0,68 %. Un taux
protéique élevé associé avec une subcarence en lysine peut favoriser le cannibalisme chez les poulets
label en finition.
poulet de chair / croissance / protéine / lysine / composition corporelle / cannibalisme
The development of new types of broiler
meat production in France requires updates
of the nutritional requirements of these
chickens. In 2003, half of the chicken meat
consumed came from genotypes with
relatively slow growth and a third of the
consumption from label chickens, whose life
span is at least twice longer compared to a
regular broiler for the same final body
weight. A comparison of the dietary regimes
offered to the different genotypes has been
]. Several differences between
fast and slow growing chickens suggest a
more precise decomposition of the
nutritional factors that might be involved.
Do slower growing birds require less
protein and amino acids than fast growing
broilers? The answer to this question varies
from one author to another. Even though
most publications report significant
genotype × diet interactions on growth [
] and body composition [1, 4], some note
that if expressed in dietary concentration
the requirement in lysine for example, does
not vary between slow and fast growing
chickens . The efficiency of protein
deposition in the body might remain relatively
constant even when a layer type bird is
compared to a broiler [
Recent research results suggest that the
starter diet might have long-term effects on
broiler growth and body composition [5, 9,
10] but these effects might be due to the
increased rate of growth in the young
modern broiler from hatching on and might be
less prevalent for slower growing birds.
The present research studied the responses
of slow growing male chickens to diets
differing in crude protein and essential amino
acid contents at two critical periods of their
life from biological (the first week) and
economical (the finishing period: 42 to 77 days)
points of view. Finally, increasing lysine
levels in the diet were compared at two
different crude protein dietary concentrations.
2. MATERIALS AND METHODS
2.1. Experimental design and housing
One thousand three-hundred and
fortyfour one day-old commercial male chicks of
a label genotype were obtained from a
commercial hatchery. Upon arrival, the chicks
were weighed and separated into groups of
50 individuals and randomly distributed
into 12 wood shaving floor pens (112 chicks
per pen) in an environmentally-controlled
poultry shed. From 1 to 6 days of age, 6 pens
(odd numbers) received starter diet S – and
the other 6 pens (pair numbers) starter diet
S+ ad libitum. All chicks were vaccinated
against coccidiosis (Paracox8,
Scheringplough ©) at 5 days of age. At 6 days of age
the chicks were weighed, wing banded and
randomly redistributed into 48 floor pens of
3 m2. However, in each pen there were
14 chicks having eaten the starter feed S– and
14 chicks having eaten the starter feed S+.
Temperature was 32 °C from Day 0 to
Day 7 and progressively reduced to reach
21 °C after Day 28. Lighting was 24 h a day
during the first 3 days and then reduced to
14 h until Day 14. An increase of 2 h light
a week was applied after Day 21 to reach 16 h
per day from Day 21 until the end of the
experiment. Light intensity was 50 lux for
the first 3 days, 20 lux until Day 15 and then
reduced to reach 10 lux at Day 21 and 5 lux
after 42 days of age.
From 7 to 42 days of age, the chickens
received the same grower feed and the final
stage of the experiment lasted from 42 to
77 days of age. During that period there
were 8 different experimental feeds
distributed each to 6 different pens of birds. The
8 treatments were arranged as a factorial
design: 2 crude protein levels × 4 lysine
contents. Each group of 8 neighbouring pens
was considered as a block and in each block,
the 8 experimental feeds were tested.
Feeds were prepared by the INRA Poultry
Research Station (Nouzilly, France) a week
before their use and analysed for dry matter,
nitrogen and total amino acid contents using
ion-exchange chromatography by Ajinomoto
(Amiens, France). For clarity, the analysed
values are used in the rest of the text. The
starter feeds (first week of age) were
presented as crumbs and the other feeds were
steam pelleted (diameter 2.5 mm). The two
starter diets were designed to be as different
as possible while remaining close to the
limits of practical uses (Tab. I). The S+ diet
contained 13 MJ·kg–1 (calculated), 22.1
crude protein (CP) and 1.34% lysine,
although the S– feed diet was less
concentrated, 12.1 MJ·kg–1, 20.6% CP and 1.03%
lysine. When tested on fast growing
broilers, the S– diet compared to S+ induced a
14% retardation at 6 days of age with long
lasting effects on growth and body
]. The grower feed was
intermediate between the two starters (Tab. I). The
two finisher basal diets (42–77 days of age)
combined cereals with sources of protein
from corn gluten meal, peas, a limited amount
of soybean and synthetic amino acids, in
order to differ in CP levels by 5.5% with a
similar low level of total lysine (0.56%).
Graded supplementation in lysine HCl led
to a range of four lysine levels (A = 0.56;
B = 0.66; C = 0.76 and D = 0.86%). Special
care was observed to balance the other
essential amino acids and also the
electrolyte levels in these feeds (Tab. I).
Mortality was recorded daily for each
pen. All chickens were individually
weighed and food intake was measured per
pen at 6, 21, 35, 42, 49, 56, 70 and 77 days
of age. Before slaughter at 77 days of age,
12 chickens per treatment (4 per pen, 2 S+
and 2 S–) were identified to match the
70 days average (and standard deviation)
bodyweight of each treatment (2 Starter
diets × 2 Protein levels × 4 Lysine levels).
On day 77, all chickens were fasted 8 hours
before slaughter and the 192 selected
chickens were transported to the slaughterhouse.
After scalding, automatic plucking and
manual gut removal, the carcasses were
chilled in a cold room for 24 h at 2 °C. The
right and left Pectoralis major and minor,
and abdominal fat were dissected and
weighed . Carcass composition data
were expressed as % of live body weight.
2.4. Statistical analysis
Mortality (% per pen) data were
subjected to Arc sin square root transformation
prior to analysis. The effect of the starter
diet during the first week was analysed by
a one way ANOVA of the two treatments
with 6 replicates (112 chicks per pen). The
starter diet effect and its interactions with
CP and lysine levels during the finishing
period, on body weight, mortality and body
composition were analysed by a three way
ANOVA by considering each pen as two
sub-pens composed by the average
performances of the S+ and the S– chickens per
pen. The effects of CP and lysine levels on
* Measured values. **Digestible protein and amino acid were calculated with the Rhône Poulenc Animal
Nutrition feedstuff digestible coefficient and corrected for the difference between measured and calculated values.
A Premix composition (as mg per kg of diet): Ca, 1600; Co, 0.6; Cu, 25; Fe, 50; I, 1; Mn, 85; Se, 0.25; Zn, 60.
Vitamin supplies: vitamin A (all-trans-retinol), 10000 IU; cholecalciferol, 2000 IU; vitamin E
(DL-alpha-tocopheryl acetate), 30 mg; thiamine, 1.5 mg; riboflavin, 4 mg; calcium pantothenate, 10 mg; vitamin B12, 0.015 mg;
menadione, 2 mg; pyridoxine hydrochloride, 2.5 mg; folic acid, 0.4 mg; biotin, 0.2 mg; choline, 500 mg; niacin,
30 mg; butylated hydroxyl toluene, 125 mg. B Danisco Animal Nutrition, UK. C Dietary Electrolyte Balance
(Na+ + K+ – Cl–).
performances, feed intake and feed
conversion ratio and body composition were
analysed by a two way ANOVA.
When significant, the differences between
the treatment means were tested using the
comparison test (P < 0.05).
Non linear regressions between body
weight gain or feed conversion and lysine
dietary level were performed on pen data, by
fitting the data to an exponential model: i.e.,
Body Weight Gain = A – B*exp(–C*Lysine
level) with A = plateau; B and C = coefficient
of the exponential curve; Lysine level =
level of lysine in the diet in %  and by
an ascending line with a plateau model .
3.1. Effects of the starter diet
The two-tested starter did not induce any
measurable effect on chicken growth,
mortality, or body composition in any of the
controls. Their average (± SE) body weight
at 6 days of age was 104.3 ± 0.4 and 104.4 ±
0.4 g per chick for S+ and S– respectively.
Similarly at 21 days of age their body
weight showed no detectable treatment
effect (S+ = 421.2 ± 1.5 and S– = 422.6 ±
1.5 g per chicken). Since no interaction with
the other treatments reached significance
(Tab. II), the protein nutrition factors during
the finishing period were analysed
independently from the starter diet.
3.2. Feather pecking, mortality and growth performances
Starting at 48 days of age (6 days after
feeding the experimental diets), feather
pecking was observed in some pens. The
problem developed up to the end of the
experimental period. Mortality was most
pronounced in the group fed the lowest
levels of lysine (A = 0.56%) and with the basal
diet rich in protein (Tab. III).
From 42 to 77 days of age, the interaction
between CP and lysine was highly
significant for feed intake and growth. The
interaction was mainly attributable to the strong
effect of lysine deficiency measured with
the protein basal-diet. Parallel to its effect
on mortality and feather pecking, low lysine
levels (A and B) depressed growth rate and
increased feed to gain ratio (Feed
conversion). Higher levels of lysine (C and D) or
of CP did not significantly affect growth,
feed intake or feed conversion (Tab. III).
3.3. Carcass composition
No significant interaction was observed
for breast meat yield or abdominal fat
contents (Tab. III). The high dietary CP level
did not significantly change the breast meat
yield (12.75% for high vs. 12.67% for low
dietary CP Level) but a 23% reduction in
fatness (estimated by the relative weight of
abdominal adipose tissue) was measured.
The lysine effect on breast meat yield was
characterised by a steady improvement of
breast meat yield from 0.56 to 0.86% of
lysine in the diet although the two higher
levels (0.76 and 0.86%) did not differ
significantly (Fig. 1).
One of the major results of the present
experiment is the interaction between
dietary crude protein and lysine concentration.
Not only the growth and feed conversion
were strongly reduced by lysine deficiency
when the dietary level of protein was high,
but also the sensitivity of label type male
chickens to feather pecking seemed involved.
Although the dietary interaction was highly
significant already at the first week of the
experiment (at 49 days of age) on body
weight gain when feather pecking was only
starting, high mortality for treatments A and
B with the high CP concentration might
have accentuated the effect of the lysine
deficiency on the final results.
Feather pecking and cannibalism are
induced or aggravated by deficiencies in
essential amino acids as by most nutritional
imbalances in chickens [
there are limited recent publications on
broilers since the fast growing birds have
scarce problems of feather pecking in
production. Conversely, the problem exists in
label chickens and can be accentuated by
outdoor weather conditions such as bright
sunny days and stormy summers (field
observation). In laying birds, a strong protein
deficiency (involving concomitant
essential amino acid imbalance) increases the
occurrence of feather pecking and
cannibalism  although the protein source (i.e.,
fishmeal compared to vegetable protein)
does not seem to have a significant effect on
this phenomenon . The innovation of
our result is to stress the interaction between
high protein with low lysine levels as a
critical factor for cannibalism in label chickens
raised in confinement. Even though such a
result was confirmed under more standard
conditions of production, it might present
some relevant nutritional application for
this type of birds.
An interaction between CP and lysine
has been reported in various genotypes [
]. Sklan and Plavnik  showed that
diets providing relative excesses of protein
should be avoided since they decrease the
efficiency of utilisation and increase
essential AA requirements. It has been reported
that the requirement in essential AA is
increased when the CP level in the feed is
]. However, as suggested by the
authors, other limiting factors might limit
the lysine response in the lowest CP dietary
levels. In the present study, all essential AA
were provided above the chicken needs
even in the low CP basal diet and the
requirement for lysine was not increased
parallel to the CP level of the diet. Fitting
the regressions of the average weight gain
(in g per chicken per day) and of the feed
conversion ratio with the lysine
concentration in the feed, the estimation of the
requirement for lysine was close to 0.68% of total
lysine (0.60% digestible) with the linear
plateau model whatever the CP level for
both variables (Tab. IV). Using 95% of the
asymptote of an exponential regression, the
feed conversion gave close results although
the growth rate corresponded to a higher
estimation of the lysine requirement for the
high CP level (0.73% total lysine) than for
the low CP level (0.67% total lysine).
However, it seems that the negative effect of a
sub deficiency in lysine on growth
parameters is accentuated by a dietary excess of
the other amino acids.
In accord with previous studies [
1, 3, 15
we found that dietary CP level acts more on
body deposition by decreasing fatness than
by enhancing muscular growth. The
metabolic explanation for this phenomenon
remains to be elucidated . In the absence
of significant differences in feed intake
when the birds were fed diets balanced in
lysine (diet D), a possible explanation is a
different energy partition. Birds fed a high
CP diet should get rid of a higher amount
of heat. This metabolic adaptation might be
due to an excess of amino acids. A leaner
carcass is poorer in energy than a fat one
because protein deposition fixes more water
than fat deposition. At similar body weight
and feed intake, a leaner bird looses more heat.
Despite the relatively slow growth rate of
the tested genotype, breast meat deposition
responded highly significantly to lysine
supplementation. Although the difference
between diets C and D was not significant,
the breast meat yield still did not reach a
plateau at the level of 0.86% (Fig. 1). In fast
growing broilers, the optimal breast meat
yield is frequently observed for lysine
levels lower or equal to that needed for optimal
feed conversion [
]. Paradoxically, our
results suggest that the estimation of the
lysine requirement of slow growing
finishing label chickens should take body
composition into closer consideration.
At a younger age, a response to the starter
feed richer in protein, amino acid and energy
was not expressed by those slow growing
birds although the same diets had highly
significant and long lasting effects on
protein growth in fast growing broilers [
The low protein requirement of slow
growing chickens might be an explanation.
However, expressed as a percentage of the diet,
this kind of effect is not always found
experimentally when comparing fast and slow
growing chickens [i.e., 7]. Another possible
explanation might be found in the
imbalance induced by a too fast early muscular
growth for the non-mature development of
digestive organs and metabolism in fast
growing broilers . Conversely, the early
development of the label type chicken is
slower and more balanced with the early
development of chicks that, at the beginning
of their life, are not really different in size
compared to their fast growing counterparts.
The balance between the degree of
maturity and growth rate might be a useful
direction of research to explain the variability of
reaction of different genotypes to the same
nutritional challenges . A label or a
broiler breeder have the same body weight
at hatching and are sexually mature at the
same age. Both age and live weight might
jointly characterise a nutritional state.
The requirement in lysine of male label
type chickens raised in confinement from
42 to 77 days of age, was close to 0.68%
(0.60% digestible lysine) in a 13 MJ·kg–1
diet. It did not seem to vary with the crude
protein content of the diet, but a more
detailed evaluation of the effects of higher
lysine levels on body composition (mainly
breast meat yield) should be pursued.
A high level of crude protein in the diet
accentuated the negative effects of a sub
deficiency in lysine on growth and feed
conversion and aggravated the consequences of
feather pecking. A low CP diet with
balanced levels of essential amino acids seems
worthwhile for slow growing chickens in
the finishing period. However, a low
protein level even balanced in essential amino
acids, induces fat deposition especially
when slow growing label chickens are kept
in confinement. The effects of exercise on a
free-range area might change this conclusion.
The tested compositions of the starter
diet did not affect performances of the slow
growing chicks under our conditions.
Further research taking into account both the
maturity (age) and the growth (weight) of
genotypes of different growth rate
potentials might help to better characterise their
The authors wish to thank Ajinomoto for the
analyses of the experimental feeds, the technical
staff of the experimental unit of the Poultry
Research Station, particularly C. Bouchot and S.
Nevoit for rearing the animals, and the staff of
the genetics and meat quality teams for their help
at the slaughterhouse and for carcass dissections.
established requirement between six and 8
weeks of age, Poultry Sci. 70 (1991) 2315–
 Ambrosen T., Petersen V.E., The influence of
protein level in the diet on cannibalism and
quality of plumage of layers, Poultry Sci. 76
 Bartov I., Plavnik I., Moderate excess of
dietary protein increases breast meat yield of
broiler chicks, Poultry Sci. 77 (1998) 680–688.
 Bilgili S.F., Moran E.T., Acar N., Strain-cross
response of heavy male broilers to dietary
lysine in the finisher feed: live performance
and further- processing yields, Poultry Sci. 71
 Eits R.M., Kwakkel R.P., Verstegen M.W.A.,
Emmans G.C., Responses of broiler chickens
to dietary protein: effects of early life protein
nutrition on later responses, Brit. Poultry Sci.
44 (2003) 1–12.
 Emmans G.C., Fisher C., Problems in
nutritional theory, in: Fisher C., Boorman K.N.
(Eds.), Nutrient requirement of poultry and
nutritional research, Butterworth, London,
UK, 1986, pp. 9–39.
 Han Y., Baker D.H., Lysine requirements of
fast- and slow-growing broiler chicks, Poultry
Sci. 70 (1991) 2108–2114.
 Hurwitz S., Sklan D., Talpaz H., Plavnik I.,
The effect of dietary protein level on the lysine
and arginine requirements of growing
chickens, Poultry Sci. 77 (1998) 689–696.
 Kerr B.J., Kidd M.T., Halpin K.M., McWard
G.W., Quarles C.L., Lysine level increases
live performances and breast meat yield in
male broilers, J. Appl. Poultry Res. 8 (1999)
 Kidd M.T., Fancher B.I., Lysine needs of
starting chicks and subsequent effects during
the growing period, J. Appl. Poultry Res. 10
 Leclercq B., Specific effect of lysine on
broiler production: comparison with
threonine and valine, Poultry Sci. 77 (1998) 118–
 Leclercq B., Beaumont C., Effects of genetic
potential on the lysine requirement and
economic results of simulated broiler flocks,
Anim. Res. 50 (2001) 67–78.
 Marche G., La découpe anatomique et la
dissection des volailles : le poulet, le canard, la
dinde, SYSSAF-INRA, Nouzilly, France,
 McKeegan D.E.F., Savory C.J., MacLeod
M.G., Mitchell M.A., Development of
pecking damage in layer pullets in relation to
 Acar N. , Moran E.T. , Bilgili S.F. , Live performance and carcass yield of male broilers from two commercial strain crosses receiving rations containing lysine below and above the dietary protein source , Brit. Poultry Sci . 42 ( 2001 ) 33 - 42 .
 Morris T.R. , Njuru D.M. , Protein requirement of fast- and slow-growing chicks , Brit. Poultry Sci . 31 ( 1990 ) 803 - 809 .
 Quentin M. , Bouvarel I. , Berri C. , Le BihanDuval E., Baéza E. , Jégo Y. , Picard M. , Growth, carcass composition and meat quality response to dietary concentrations in fast-, medium- and slow-growing commercial broilers , Anim. Res . 52 ( 2002 ) 65 - 77 .
 Quentin M. , Bouvarel I. , Picard M., Effects of the starter diet, light intensity and essential amino acids level on growth and caracass composition of broilers , J. Appl. Poultry Res . 17 ( 2005 ) 69 - 76 .
 Savory C.J. , Feather pecking and cannibalism , World's Poultry Sci. J . 51 ( 1995 ) 215 - 219 .
 Si J. , Fritts C.A. , Burnham D.J. , Waldroup P.W. , Relationship of dietary lysine level to the concentration of all essential amino acids in broiler diets , Poultry Sci . 80 ( 2001 ) 1472 - 1479 .
 Sklan D. , Plavnik I. , Interactions between dietary crude protein and essential amino acid intake on performances of broilers, Brit . Poultry Sci . 43 ( 2002 ) 442 - 449 .
 Smith E.R. , Pesti G.M. , Influence of broiler strain cross and dietary protein on the performance of broilers , Poultry Sci . 77 ( 1998 ) 276 - 281 .
 Smith E.R. , Pesti G.M. , Bakalli R.I. , Ware G.O. , Menten J.F.M. , Further studies on the influence of genotype and dietary protein on the performances of broilers , Poultry Sci . 77 ( 1998 ) 1678 - 1687 .
 Surisdiarto A. , Farrell D. , The relationship between dietary crude protein and lysine requirement by broiler chicks on diets with and without the ìideal protein balanceî , Poultry Sci . 70 ( 1991 ) 830 - 836 .