الفهرس 
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Abstract
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v. SU~RY AND CONCLUSION
This work was carried out at Gazerrit El-Sheer Poultry
Farm, Animal Production Research Institute, Agricultural
Research Center, Egypt. Two experiments were planned to
study the effect of season (environmental temperature),
dietary protein and energy levels on the performance of
broiler chicks. The first experiment was carried out in
summer during July and August 1987: while the second one
was conducted in winter during January and Fabruary, 1988.
Each experiment included two growth periods, a starting
period from hatch to 4 weeks of age and, a finishing Period
from 5 to 8 weeks of age. In each experiment, 270 one-day
old Lohman broiler chicks were assorted at random into 9
groups, each containing 30 chicks in 3 replicates. In summer
or winter, chicks in all groups were fed on a starter
diet containing 22. 24% CP and 3052 kcal ME/kg during the
starting period (0-4 weeks of age) while three levels of CP
and three levels of ME were used in a factorial design to
form nine finisher diets to be used during the finisher period
(5-8 weeks of age). The CP levels used were 17, 18 and
19%, while the ME values were 3100, 3200 and 3300 kcal ME/kg
diet. The most important results obtained could be summarized
as follows :
Starting period (0-4 weeks of age):
1 • Chicks reared in winter recorded heavier body weights
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and weight gains than those grown in swrrner. The differenees
in body weights and weight gains due to season
effects were highly significant (p < 0.01) •
2. Differences in feed intake due to season effects
were significant (p (0.01), in winter, chicks consumed more
feed than in summer.
3. Birds grown in summer recorded the poorest feed
conversion and protein efficiency ratio values, while those
reared in winter showed the best values. The differences
in either feed conversion or protein efficiency ratio values
due to effects of season were significant (p < 0.01).
4. Feed cost/kg gain in winter was LE 1.023, while it
was LE 1.205 in summer, the differences were highly significant
(P< 0.01) •
Finishing period (5-8 weeks of age):
Weight gain:
L
1. At the termination of the finishing period, chicks
reared in winter recorded the highest weight gains, while
those grown in summer showed the lowest ones, the differences
were highly significant (P < 0.01).
2. Weight gain increased as dietary protein level increased
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from 17 to 19%. The differences in weiqht qain between
the 19% dietary protein level and either 17% or 18% level
were significant (p < 0.01 ). Whereas, no significant differences
in weight gain were detected between the 18 and
17% dietary protein levels.
3. Chicks fed on diets containinq either 3300 or
3200 Kcal ME/kg gained significantly (p < 0.01) more body
weight than those receiving diets with 3100 Kcal HE/kg.
Whereas, no significant weight gain differences were obtained
between the 3300 and 3200 Kcal ME/kg energy levels.
Feed intake:
1. Chicks consumed more (P < 0.01) feed in winter than
in sunmer.
2. Dirterences in reed intake due to effects of dietary
protein level were very small and non-significant.
3. Increasing the dietary energy level from 3100 Kcal
ME/kg to either 3200 or 3300 Kcal ME/kg slightly increased
feed intake of chicks, the differences failed to Show any
significant effects.
Feed conversion:
1. In summer, birds converted feed more efficiently
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than in winter (2.277 vs 2.546). Differences in feed conversion
values due to season effects were highly significant
(P < 0.01) •
2. Increasing the dietary protein level from 17% to
19% improved feed conversion values. Chicks fed on the
diet containing 19% CP showed the best values, while those
fed on the diet having 17% CP recorded the poorest ones.
The differences in feed conversion values between the 17%
dietary protein level and each of the 18% and 19% level or
between the 18% and 19% level were highly significant
(P < 0.01) •
3. Chicks given the diet with 3300 Kcal ME/kg energy
level recorded the best feed converaion values, while those
received the 3100 Kcal ME/kg energy level showed the poorest
values. The differences in feed conversion values among the
energy levels used were significant (p 0.01 or P 0.05).
Protein efficiency ratio:
1. Chicks reared in sunrner season had better protein
efficiency ratios than those grown in winter months (2.445
va 2.185). The differences due to season effects on efficieney
of protein utilization were significant (p < 0.01) •
2. Birds received the low dietary protein level (17”)
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recorded the best protein efficiency ratio (2.353) while
those consumed the medium level (18%) showed the poorest
ratio (2.274). The differences in protein efficiency ratio
between the 17% dietary protein level and either 18% or 19%
level were significant (P< 0.01), while no significant differences
were found between the 18% and 19% dietary protein
levels.
3. Protein efficiency ratio improved with increasing
of the dietary energy level. Increasing the energy level
from 3100 to either 3200 or 3300 Kcal ME/kg significantly
(p < 0.01) improved protein efficiency ratio, while increasing
the energy level from 3200 to 3300 Kcal ME/kg diet significantly
improved the efficiency of protein utilization at the
0.05 level of probability.
Feed cost:
1. The feed cost/kg gain for chicks reared in winter
was significantly (P < 0.01) higher than that for birds grown
in 8unmer.
2. Peed cost/kg gain decreased as dietary protein level
increased. The differences in feed cost/kg gain between the
17% and 19% and between the 18% and 19% dietary protein levels
were significant (P< 0.01), while no signitic:antdifferences
were detected between the 17% and 18% levels.
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3. Feed cost/kg gain differed slightly with increasing
the dietary energy level. The differences in feed cost/
kg gain due to energy level effects were very limited and
statistical not siqnificant.
Whole period (0-8 weeks of age):
Body weight:
1. The average final body weight at 8 weeks of age for
chicks reared in winter was significantly (p < 0.01) higher
than that for birds grown in summer.
2. The average body weight significantly (p< 0.01) increased
as dietary protein level increased from 17 to 19% and
from 18 to 19%, while no significant differences in body
weight were observed between 17 and 18% dietary protein levels.
3. No significant differencea in final body weight were
observed due to energy level.
Weight gain:
1. At 8 weeks of age, the average weight gain for chicks
reared in winter (1870 g) was significantly (P <”0.01) higher
than that for chicks grown in sWlllDer.
2. Weight gain increased as dietary protein level inereased.
Chicks fed the 19% dietary protein level had
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141
significantly (P < 0.01) heavier weight gains than those
on either 17 or 18% dietary protein level, while no significant
differences in weight gain were detected between
17 and 18~ dietary protein levels.
3. The energy level had no significant effect on
weight gain during the whole experimental period.
Feed intake:
1. The amounts of feed intake/chick at 8 weeks of age
were 4168 g in winter and 3338 g in summer. The differences
in feed intake due to season effect were highly significant
(P < 0.01).
2. Increasing the CP lev~l from 17 to 19% had no significant
effect on feed intake.
3. Feed intake differed slightly with increasing the
dietary energy level from 3100, to 3300 Kcal ME/kg, the differences
were very small and statistically non-significant.
Feed conversion:
1. Birds reared in s\UID8r were more (p<.0.01) efficient
in feed utilization than birds qrown in winter.
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2. Feed conversion values improved with the increase
of dietary protein level from 17 to 19%. The differences
due to dietary protein level in feed conversion values were
highly significant (P < 0.01).
3. The differences between the 3100 Kcal ME/kg dietary
energy level and 3200 or 3300 Real ME/kg energy level in.feed
conversion values were highly significant (p < 0.01) and those
between the 3200 and 3300 Rcal ME/kg levels were significant
(P < 0.05)
Protein efficiency ratio:
1. Protein efficiency ratio was significantly (p <0.01)
affected by season. Chicks reared in swnmer recorded the
best protein efficiency ratios (2.521.) whereas those grown
in winter showed the poorest ones (2.492).
2. Increasing the dietary protein level had an adverse
effect on protein efficiency ratios. Chicks fed on the 17%
dietary protein level recorded the best values (2.579) whereas
those fed on the 19% level showed the least ones (2.458).
Differences in protein efficiency ratios due to protein level
effects were significant (P < 0.01 or P <0.05) •
3. Increasing the energy level from 3100 to 3300 Rcal
ME/kg improved the protein efficiency ratios. The 3300 and
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3200 Kcal ME/kg dietary energy levels had significantly
higher (p < 0.01) protein efficiency ratios than the 3100
Kcal ME/kg energy level. Whereas, no significant differences
in protein efficiency ratios were detected between
the 3300 and 3200 Kcal ME/kg energy levels.
Peed cost:
1. Differences in feed cost!kg gain due to season
effects were highly significant (P < 0.01), chicks reared
in winter recorded the highest values, while those grown
in summer showed the lowest ones.
2. The highest cost!kg gain was recorded by chicks
fed the 17% dietary protein level, while the lowest cost
was recorded by those on the 19% l@vel. The dift’erences
in feed cost/kg gain due to dietary protein level et’fect
were in all cases highly significant (p < 0.01) •
3. The dietary energy level did not exert any significant
effect on feed cost/kg gain at 8 week. of age.
Carcass traits:
1. Drawn weight, liver and heart, either in grams or
relative to live body weight, for chicks reared in winter
were higher than for those grown in summer, the differences
in percentages of these traits due to season effects were
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144
highly significant (p < 0.01).
2. The differences in percentages of drawn weight
between the 17% and 19% dietary protein levels were significant
(p <.0.05), whereas no significant differences
were detected between either 17 and 18% or 18 and 19% dietary
protein levels. In addition, dietary protein level
had no significant effect on percentages of liver and
heart.
3. Dietary energy level did not exert any significant
effect on the percentages of drawn weight, liver and heart.
Results of this study indicate that feed intake was
inversely related to environmental temperature, thus broilers
in ~inter consumed more feed than in summer. The depression
in groweh rate observed during the finishing period in s~
mer season was mainly due to decrease in feed intake. Increasing
dietary protein and energy levels was suggested to
overcome the depression in both feed intake and growth rate
occurred during the season.
In general, on che basis of performance and economic
data, finishing broiler diets containing 19~ CP 3200 and 3300
Kcal ME/kg diet are recommended to be used in summer saason.
145
while those having 17% CP and 3100 Kcal ME/kg diet may
be used successfully in winter season. The present results
with finishing broiler chicks also indicate that
within the range of protein and energy tested, it is
difficult to alter the dressing percentages of the ~arcass,
liver and heart by dietary alteration of protein
and energy.