الفهرس 
REVIEW OF LITERATUREOnly 14 pages are availabe for public view
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Abstract
The present study was carried out in poultry physiology research lab, Faculty of Agriculture, Ain Shams University, during the period from Augustus to October 2020 under the Egyptian environmental conditions.
The study aimed to investigate the effect of androgen and anti-estrogen levels on hatchability, embryonic mortality percentages, post-hatch performance, some blood parameters, testosterone and estrogen plasma levels and histocytological measurements of lymphoid organs were estimated under Egyptian environmental conditions.
750 broiler breeder eggs with an average weight of 62 ± 0.46 g were obtained from a commercial broiler breeder flock (Cobb-500) at 52 weeks of age. All eggs were normally incubated at 37.6 ± 0.1○C, 65 % relative humidity (RH) and turned through 45ₒevery 2 hours (h) for 18 days and then transferred to hatcher basket with 37○C, 75-80 % relative humidity in a locally manufacture automatic incubator obtained from PTO incubation system company, Alexandria, Egypt.
At the 4th embryonic day, eggs were candled, so infertile eggs and early dead embryos were excluded. Then, the remaining eggs (700) were randomly divided into ten equal groups, each of 70 eggs.
• The 1st group (C) of eggs was set as control.
• The 2nd group (S) was sham.
• The 3ed group (T0) was injected with 100µ of sterilized sesame oil.
• The 4th group (T1) was injected with75µg of testosterone propionate dissolved in 100µl of sterilized sesame oil.
• The 5th group (T2) was injected with 25µg of testosterone propionate dissolved in 100µl of sterilized sesame oil.
• The 6th group (T3) was injected with 10µg of testosterone propionate dissolved in 100µl of sterilized sesame oil.
• The 7th group (A0) was injected with 100µ of distal water.
• The 8th group (A1) was injected with 0.1 mg letrozole dissolved in 100µl of distilled water.
• The 9th group (A2) was injected with 0.075 mg letrozole dissolved in 100µl of distilled water.
• The 10th group (A3) was injected with 0.05 mg letrozole dissolved in 100µl of distilled water.
Hatchability, embryonic mortality percentages, post-hatch performance, some blood parameters, testosterone, and estrogen plasma levels and histocytological measurements of lymphoid organs were estimated were estimated.
The results obtained can be summarized as follows:
1. Hatchability % was significantly decreased, while embryonic mortality rate was significantly increased by testosterone in Ovo injection.
2. Live body weights were significantly badly affected by testosterone and letrozole levels at hatch, but this effect improved laterally at 35 days of age by the letrozole treatments but still with lower values for testosterone treatments.
3. Mortality rate was elevated at the testosterone treatments and hand androgen inhibitor’s treatment had the lower values of mortalities compared to the rest groups.
4. Dressing % was significantly affected by androgen and estrogen inhibitor as LBW the estrogen inhibitor had the highest value.
5. Heart and gizzard relative weights weren’t significantly affected by the treatments neither androgen nor anti estrogen treatments.
6. There were no clear significant differences between the androgen and the anti-estrogen treatments on the relative weights of pancreas, proventriculus and small intestine percentages.
7. Androgen and anti estrogen treatments cause a significant increase in the relative percentages of head and legs compared to control.
8. Protein profile was significantly improved by antiestrogen levels, while the androgen groups had the lowest values of total protein at hatch and at 35 days of age.
9. Estrogen plasma levels were significantly decreased by both androgen and antiestrogen in Ovo injection as the higher levels of in Ovo injection with androgen or with anti estrogen achieved the lowest estrogen plasma levels at hatch.
10. Testosterone plasma levels were significantly increased by both treatments compared to control groups at hatch.
11. Bursa of Fabricius relative weight were significantly increased by antiestrogen in Ovo injection and significantly decreased by androgen in Ovo injection compared to control groups.
12. The same as were the spleen relative weights, they were significantly increased by antiestrogen in Ovo injection and significantly decreased by androgen in Ovo injection compared to control groups.
13. androgen in Ovo injection had a significant negative effect on immune performance at hatch.
14. On contrast anti-estrogen in Ovo injection significantly increased the immune performance plasma values compared to control.
15. The effect of androgen and antiestrogen treatment on immune performance decreased over time as there was no significante effect on α2, β2 plasma level at 35 days of age.
16. Androgen treatments significantly decreased IgM, α1, β1 and γ compared with control groups at 35 days of age.
17. In Ovo injection with letrozole significantly increased IgM, α1, β1 and γ plasma levels at 35 days of age compared with control groups and didn’t significantly affect α2, β2 plasma level at 35 days of age.
18. In Ovo injection with letrozole significantly improved the histological characteristics of bursa of Fabricius gland at hatch.
19. In Ovo injection with 100 µg letrozole significantly increased follicles number per section, follicle length and width, follicle cross section area and percentage of cortex area compared with control.
20. There were no significant differences between control groups and androgen treatments on histological measurements of bursa of Fabricius at hatch.
21. The number of follicles per section was significantly increased by in Ovo injection with letrozole on the other hand in Ovo injection with testosterone propionate significantly decreased follicle number per section.
from the results reported herein, it could be concluded that:
We concluded that estrogen inhibitor (letrozole) significantly enhance hatchability and later chick performance on contrast with testosterone treatments badly affected hatchability and growth performance later studies should be conducted to investigate the reason of such contrast.