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Abstract
This study was carried out at the poultry research unit, Faculty of Agriculture,
Damanhour University and the laboratory work was completed at Department of Livestock
and Fisheries Research, Arid Land Cultivating Research Institute, City of Scientific
Research and Technology Applications during the period from 23/11 to 21/12/2010. The
response of productive, inner body organs, physiological and immunological traits to HS
and VC, VE and/or organic Zn supplementation was studied during 26-54 days of the age
using 192, 26-day-old males Fayoumi chickens and the same number of the commercial
broilers Arbor Acres strain. Chickens within each strain were randomly distributed among
8 treatment groups in factorial agreement 2 (strains) × 8 (treatments). Each treatment was
represented by 4 replicates of 6 chicks per replicate per strain. The treatment groups were:
Group 1 which served as a positive control and reared on neutral temperature
(approximately 20.8±4.9ºC) and fed the basal experimental diet without supplementation
with VC, VE and/or Zn. Groups 2 to 8 were exposed to HS (37±3.2ºC) with relative
humidity 53±8% for 6 hours /day for three successive days per week. Group 2 was served
as a negative control (heat-stressed control fed the basal diet without supplementation).
While, group 3, was heat-stressed with adding 200 mg VC /kg feed. Group 4, was heatstressed
with adding 200mg VE /kg feed. Group 5, was heat-stressed with adding 200mg
VC+200 mg VE/kg feed. Group 6, was heat-stressed with adding 200mg VC+30 mg
organic Zn/kg feed. Group 7, was heat-stressed with adding 200 mg VE+30 mg organic
Zn/kg feed. Group 8, was heat-stressed with adding 200 mg VC+200 mg VE+30 mg
organic Zn. Growth performance, cloacae temperature, respiration rate, HSP-70, survival
rate, carcass characteristics, inner organs, plasma biochemical constituents, blood
hematology and immune indices were studied. The results can be summarized as
following:
The effect of HS on growth performance was age and strain specific as growth of only
the commercial broiler strain was significantly decreased by 11.7% during only 26-40 days
of age and diminished in the following period, although growth was still lower of only the
commercial broilers by 8.6% for the whole period.
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Heat stress did not affect growth of Fayoumi strain, revealing that the native strain had
greater tolerance to HS than the commercial broilers.
The effect of HS on growth of the commercial broilers was coincided with decreasing
feed intake during only 26-40 days of age and this effect was obvious within each strain
being 3.5 and 4.5% for the commercial broiler strain (insignificant) and the native strain
Fayoumi (significant), respectively.
Heat stress significantly impaired FCR during only days 26-40 and days 41-54 of age,
but the effect is strain and age specific, showing that native strain showed impaired FCR
by 9.7% during 26-40 days of age (the 1st experimental period), and quickly customized to
HS during the following period and the whole period, indicating improved tolerance of
native strain to HS with prolonged of exposure to HS.
5. The adverse influence of HS on FCR of the commercial broilers was observed during
the second experimental period (41-56 days of age), showing a 9.2% decrease in FCR that
comparable to the decrease in FCR observed during the 1st experimental period within the
native breed.
6-For the whole experimental period, the effects of HS on growth, feed intake and FCR
were not significant for the native strain, but only growth of the commercial strains was
behind the thermonatural group (positive control).
For native strain, supplementation with VC+VE resulted in the best growth and FCR.
While, supplementation with VE and VC+VE completely overcame the negative effect of
HS on feed intake and thus growth of the commercial strain during 26-40 days of age.
Supplementation with VC and VC+Zn and VC+VE during days 26-40 of age to the
native strain overcame the negative effect on FCR. In addition, VC+VE group surpassed
FCR of their respective thermo-natural group (positive control) during the same period.
During 41-54 days of age, VC, VE and VC+Zn supplementation resulted in complete
recovery of FCR of the commercial strain while VC+Zn resulted in greater effect than VC
(11.5%) and VE (16.2%), showing again additive effect of Zn supplementation over VC
alone.
Supplementation with VC+VE improved FCR of the commercial broilers and native
strain by 5.3 and 16.6%; respectively showing greater effect on native strain.
For the whole period, supplementation with Zn over VC and VE improved growth
(5.4%) and FCR (8.5%) of the broiler strains.
For the whole period, the commercial broilers supplemented with VC+Zn showed the
greatest growth, and supplementation with VC+Zn, VE+Zn and VC+VE resulted in the
best FCR of this strain.
Commercial broilers on VC+ZN supplemented diets exhibited the highest EPEI while
those on VC+VE+Zn showed the lowest EPEI. While native strain fed diet supplemented
with VC+VE exhibited the highest EPEI, however, the negative control showed the lowest
EPEI.
Heat stress increased cloacae temperature and respiration rate by 5.0 and 2.7% and 34.6
and 30.2%, respectively of the commercial broilers and the native strain.
Heat stress significantly increased RBCs characteristics (PCV, Hgb, MCV, MCH) of
only the native strain.
Heat stress significantly increased plasma total protein of the commercial broilers, and
AST, AST/ALT ratio, and glucose of both strains while increasing plasma calcium and
Ca/IP ratio of the native strain.
The impairments in liver function were completely recovered due to supplementation
with VC+Zn and VC+VE+Zn while plasma glucose partially relieved due to VC+Zn
supplementation. In addition, all micronutrients supplementation induced a complete
recovery in the CA/IP ratio.
Heat stress decreased significantly SOD enzyme, and supplementation with VE and
VE+Zn restored SOD to the positive control level. In addition, VE+Zn increased GRx over
the positive control, also VC+Zn significantly increased TAC and Cat.
The positive effect VC+VE on growth performance was reflected in increasing
carcasses weight particularly of the commercial broilers.
The increased growth performance of the commercial broilers on VC+Zn was
coincided with positive effect of VC+Zn on antioxidant enzymes such as TAC and Cat of
the commercial broilers and contrary to the decrease observed in the native strain.
Supplementation with VC without or with Zn to the commercial broilers and the native
strain induced complete recovery in the RBCs characteristics, although VC alone was
adequate to induce the desire effect in both strains.
The effect of HS on immune response of chickens was manifested by a significant
decrease in lymphocyte (cell mediated immunity) and heterophil (humeral immunity) of
the commercial broilers, but a contrary trend was observed within the native strain as
lymphocyte increased, but eosniophil and HLR decreased.
It was found that, VC+Zn decreased WBCs of the commercial broilers and native
strain. On the other hand, VC+Zn induced different responses in lymphocyte based on
strain of chickens as it was decreased of the commercial strain and increased of the native
strain, emphasizing the nutrient (environment) by strain interaction.
Supplementation with VC+Zn significantly increased monocyte (phagocytes) of the
commercial broilers, but decreased it of the native strain. Moreover, similar trend was
shown in heterophil, revealing that VC+Zn increased heterophil and HLR of the
commercial broilers, but decreased heterophil and HLR of the native strain.
The supplementation with Zn over VC and VE increased antibody titer to NDV of the
native strain, showing the positive effect of Zn on humeral immunity and its additive effect
over VE. Also, Zn supplementation over VC alone to the commercial broiler strain induced
an additive effect on TAC and Cat emphasizing nutrient (environment) by strain
interaction.
Addition of VC and VE significantly PA of only the native strain, showing the
interaction between strain and micronutrients.
Heat stress increased HSP-70 mRNA synthesis and consequently HSP-70
concentration in the liver and supplementation with VE and VC+Zn and to greater extent
VC+VE+Zn significantly increased the expression of HSP in the liver of the commercial
broilers. The expression of HSP-70 was different among strain of chickens showing greater
HSP-70 in kidney and liver of the commercial broilers.
Genotype differences was observed in most in productive traits showing that the
commercial broilers grow faster, consumed more feed and utilized feed more efficiently
than the native strain Fayoumi chickens.
29. A strain differences was shown on only respiration rate with greater respiration rate of
the commercial broilers, but cloacae temperature and survival rate were not different
between strains.
30. The commercial strains had greater weight and percentage of dressed carcass and liver,
percentage pancreas and weight of liver, but lower percentage kidney, pancreas and heart.
The commercial broilers strain had lower plasma total protein, albumin, glucose,
cholesterol, inorganic phosphorus and alkaline phosphatase, PCV, Hgb, MCV, and MCH,
but higher plasma AST, ALT, AST/ALT ratio, Ca, Ca/IP ratio and antioxidants enzymes
(TAC, Cat and GRx).
32. White blood cells were lower of the native strain than that of the commercial broilers,
but HLR was higher.
33. The commercial broilers had significantly greater antibody titer to AIV than that of the
native stain.
In conclusion, genotype difference was shown in most of productive, physiological
HSP-70 and immunological traits. In addition, there was significant interaction between
micronutrients (environment) and genotype. This indicated that productive, physiological,
immunological and HSP-70 traits differ according to micronutrients. Thus micronutrients
should be selected according to the genetic makeup/productive capacity of chickens. It
could be suggested that VC+VE or VC+Zn may be used an agents for eliminating the
negative effect of HS on the growth performance of the commercial broilers and native.