الفهرس 
Productive PerformanceOnly 14 pages are availabe for public view
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Abstract
The objective of this study was to investigate the beneficial effects of
early age thermal conditioning and lighting regime in reducing the adverse
effects of hot weather conditions, and improving the productive
performance of ducks reared under hot ambient temperature. A total of
160, one day -old Muscovy ducklings were used in this study . The brooding
temperature was regulated to be kept at 33
o
C at the first week by using gas
heaters then reduced 2
o
C weekly till reached the room temperature. At the
first day post hatching all birds were weighted, wing banded and then divided
into two equal groups. The control group was maintained under normal
ambient temperature while the second group was exposed to early age
thermal conditioning (exposed to 39±1°C for 6 h at the 5th day of age and
then subjected to normal ambient temperature. The birds of all groups were
maintained under continuous lighting program (23h light, 1h dark).During
the first week until the fourth week of age. After that, the two groups were
divided into two subgroup was subjected to normal day light (16 h light, 8h
dark) and the second subgroup was subjected to intermittent light regime of
4h light and 2h dark (make 16h light, 8h dark).
The obtained results could be summarized as follows:
1. Early heat conditioning of ducklings increased significantly live
body weight and body weight gain compared to control group at 8
and 12 weeks of age. However, the intermittent lighting program lad
no effect on both body weight and body weight gain.
2. The overall mean feed intake of Muscovy ducklings was
significantly decreased in early heat exposed group compared to the
control group at all ages studied. Also, feed conversion ratio the was
better in early heat exposed group compared to the control one.3. The lowest value of feed intake was recorded for the intermittent
light groups compared to the control group. Also, the intermittent
light group had the best feed conversion ratio all ages.
4. The overall means of liver, gizzard, heart and inedible parts
weight were significantly increased in early heat exposed group
compared to the control group. Also, spleen and thymus had the same
trend in early heat exposed group compared to the control group.
5. Carcass and heart weight percentages were significantly increased
in intermittent light group compared to the control group.
6. Rectal temperature and respiration rate were significantly lower in
early heat conditioning ducks than control ones at 12 weeks of age.
7. Rectal temperature and respiration rate were slightly low, but
insignificantly in intermittent light groups compared to control group at
12 weeks of age.
8. Early heat conditioning caused a significant increase in plasma
total proteins and globulin levels as compared to control group. Also,
values of albumin were insignificantly increased in early heat
exposed group as compared to control group.
9. Plasma total protein level was insignificantly increased in
intermittent light group compared to continuous light group. While,
intermittent light group had significantly increased plasma globulin
level compared to continuous light group.
10. Plasma total lipids and triglyceride concentrations of Muscovy
ducks were significantly decreased in early heat exposed group
compared to the control group at ages studied.
11. Intermittent light program had significantly decreased plasma total
lipids and triglycerides concentrations compared to other light group
12. Early heat exposure caused significantly decreased in both AST
and ALT activity compared with un-exposed ducks.
13. Intermittent light group had significantly decreased the activity of
plasma ALT and AST compared to continuous light group.14. Early heat exposure resulted in an insignificantly increased
T3
level compared to control group at 12 weeks of age. Intermittent
light group had significantly decreased plasma levels of T
3
compared
to continuous light group. Early heat exposure reduced the
corticosterone concentration compared with heat-stressed birds.
Plasma corticosterone concentration was significantly lower in
intermittent light groups compared to control group at 12 weeks of age
during heat stress.
15. The blood pH of Muscovy ducks were significantly decreased in
early heat exposed group compared to the control group.
16. Intermittent lighting program had significantly decreased plasma
the values of blood pH compared to continuous light group.
17. Red blood cells count, hemoglobin content and hematocrit %
increased in early heat-conditioning ducks than control birds at 12
weeks of age. Similar results were also recorded for the intermittent
light groups.
18. The heterophils and H/L ratio of Muscovy ducks were significantly
decreased in early heat conditioning group compared to the control
group. While, overall mean lymphocytes count was significantly
increased.
19. Heterophils and H\L ratio were significantly decreased for in
intermittent light groups compared to control group under early heat
conditioning. Also, intermittent light treatment induced a significant
increase in total white blood cell count and lymphocyte percentage.
20. The plasma lysozyme concentration of Muscovy ducks were
insignificantly increased in early heat conditioning and intermittent
group compared to the control group at 12 wks of age.
21. The overall mean malondialdehyde (MDA) contents of Muscovy
ducks were significantly decreased in early heat conditioning group
compared to the control group. While, the overall mean of SOD and
CAT activities were insignificantly increased in early heat exposed group compared to the control group. Intermittent lighting program
had insignificantly decreased MDA compared to continuous light
group. Also, intermittent light treatment induced a significant
increase in superoxide dismutase and catalase enzymes compared to
control group.
It is concluded that early age heat conditioning of Muscovy
ducklings and using an intermittent lighting program could enhance
the productive performance and antioxidant status of ducks without
adverse effects on blood parameters of ducks during the whole
experimental period.