الفهرس 
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Abstract
This study was carried out at the Poultry Nutrition Farm, Poultry
Production Department, Faculty of Agriculture, Ain Shams University.
An experiment was conducted to study the genetic differences in
productive performance, some plasma constituents, carcass
characteristics, microbial population and histological examination of
small intestine of two broilers strains fed natural feed additives.
One hundred and twenty six unsexed 1 day – old of Hubbard were
obtained from a commercial hatchery, randomly distributed into 7
treatments and one hundred and twenty six unsexed 1 day – old of Ross
broiler chicks were obtained from a commercial hatchery, randomly
distributed into 7 treatments. Each treatment comprised of 18 chicks
which divided into 3 replicates of 6 chicks each.
The results obtained from this experiment could be summarized as
follows:
1- No significant differences among strains in live body weight during the
experimental period
2- No significant differences among strains in live body weight gain
during the experimental period
3- Feed additive enhance live body weight and body weight gain compared
with control diet with significant differences.
4- There was a significant difference between strains in feed consumption
at overall period
5- No significant differences among strains in Feed conversion ratio.
6- There was a significant difference between feed additives and control
diet in FCR.
7- There was a significant difference between strains in dressing
percentage, while the dressing percentage of Ross was greater than
Hubbard.
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SUMMARY AND CONCLUSION
Tamer M. B. Mostafa, (2017), M.Sc., Fac. Agric., Ain Shams Univ.
8- There was a significant positive effect of adding feed additive in
dressing percentage, while the dressing improved from 71.32% for
control to 72.95% for 2kg/ton probiotic,
9- The most important differences occur due to probiotic and prebiotic in
carcass traits was the reduction in pad fat percentage.
10- There were no significant differences between Hubbard and Ross
broiler in percentage of pectoralis minor, drumstick and thigh.
11- There are no significant differences among additives in percentage of
pectoralis minor and major. On the other hand, there were significant
differences in percentage of drumstick and thigh.
12- The strain wasn’t significantly affected on Glucose, T. protein,
Albumin, Globulin and A/G ratio.
13- There were a significant reduction in triglycerides, cholesterol and
Aspartate transaminase due to inclusion of probiotic or peobiotic.
14- Hubbard broiler was better than Ross broiler in villus height, Hubbard
was 559.81 compared with Ross was 394.40 μm with significant
differences.
15- prebiotic or probiotic enhance villi morphology conditions by
increasing villus height which cause an increase in absorption surface
area and lead to increase nutrients digestibility.
16- Prebiotic or probiotic additions decreased crypt depth significantly.
17- There was a significant differences in (TLAB) total lactic acid bacteria
count due to inclusion of Probiotic or prebiotic
18- Inclusions of probiotic or prebiotic led to decrease the count number of
total coliforms bacteria.
19- Inclusions of probiotic or prebiotic led to decrease the count number of
total E. Coli bacteria.
In conclusion, the effect of feed additive on tested traits is clearer
than strain effect; it could be due to the genetics background of strains
tested are the same