الفهرس 
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Abstract
The present study was carried out at Al-Nahda Poultry Farm Cairo, Regional Center for Food and Feed (RCFF) and all chemical analyses were performed at the laboratories of the Regional Center for Food and Feed (RCFF), Agriculture Research Center, Giza, Egypt.
The present study designed to evaluate;
1. The effects of dietary (Saccharomyces cerevisiae) live yeast.
2. The effects of dietary yeast cell wall supplementation.
3. The effects of dietary combination between live yeast + yeast cell wall.
on the growth performance (life body weight, body weight gain, feed intake, feed conversion ratio, mortality rate, and some carcass traits, intestine microbiology and histopathology on broilers.
Chicks were fed diets; starter diets up to 12 days of age, grower diets up to 24 days of age and then, finisher diets up to 34 days of age. The diets were formulated to cover the chick requirements as recommended by the management guide data (Ross). Water and feed were offered ad-libitum and free from any medication as growth promoters, antibiotics or anticaking according to experimental diets.
At the end of experimental period (5 weeks of age), birds were randomly chosen from each group, fasted overnight, individually weighed, then slaughtered by sharp knife to complete bleeding, and their feather were removed. At autopsy, the abdominal cavity was opened and the liver, heart, gizzard and abdominal fat were removed and weighted. Their weights were recorded in gram to the nearest 0.001g. The eviscerated carcass was individually weighted and the carcass percentage was recorded.
The results obtained from this study are summarized as follow:
1. The final body weight and weight gain for broiler fed on diet supplemented by 3.0 gm yeast were higher significantly (P>0.05) than those fed on control diet.
2. FCR was improved for those fed diet supplemented by 3.0 gm yeast.
3. There were significant differences between treatment groups in carcass %, where no significant differences where observed for intestine, liver, heart, gizzard, and intestine between treatments.
4. There was no significant difference for small intestine pH measurements between treatments.
5. Results recorded Increased yeasts and lactic acid bacteria levels showed in small intestine for the treatments fed 2.0 or 3.0 gm live yeast and interaction with all levels with yeast cell wall.
6. The 3.0 gm yeast/kg diet enhanced villi height and width, the number and size of the crypts.
Concerning the second experiments:
1. The obtained results showed that live body weight (LBW) and body weight gain (BWG) significantly (P<0.05) improved at 12, 24, and 34 days of age for chinch’s which supplemented with 0.75 or 1.0 gm yeast cell wall/Kg diet compared with the un-supplemented diet (control).
2. On the other hand, the average daily feed intake insignificantly declined, while feed conversion ratio (FCR) significantly (P<0.05) improved and showed the similar pattern which observed with the results of BWG and DBWG.
3. There were significant differences between treatment groups in carcass %, The higher value was recorded for birds fed 0.75 or 1.0 gm yeast cell wall.
4. where no significant differences where observed for intestine, liver, heart, gizzard, and intestine between treatments.
5. There was no significant difference for small intestine pH measurements between treatments.
6. Results recorded Increased yeasts and lactic acid bacteria levels showed in small intestine for the treatments fed 0.75 or 1.0 gm yeast cell wall.
7. The 0.75 or 1.0 gm yeast/kg diet enhanced villi height and width, the number and size of the crypts.
Concerning the third experiments:
1- Results obtained showed significant (P<0.05) variations in BWG of birds due to treatments applied during all experimental periods.
2- Chicks fed on the diet supplemented with combination of 0.75 gm YCW + 1.0 gm Y or 1.0 gm YCW + 1.0 gm Y /kg diet, recorded the highest average LBW and BWG followed by those fed on the control diet.
3- Birds fed on the control diet (T1) consumed the lowest (P<0.05) average daily FI, whereas, the average daily FI was nearly similar for quails of all other treatments without almost non-significant differences in FI between different treatments.
4- Feed conversion (FC) values were significantly (P<0.01) affected by dietary treatments at all periods of estimation.
5- The higher improvement in FC values were observed for birds fed diets supplied with 0.75 gm YCW + 1.0 gm Y / kg diet followed by those fed 1.0 gm YCW + 1.0 gm Y /kg / kg diet (T5), then those fed on control diet.
6- Dressing percentage were significantly (P<0.001) affected by dietary treatments except relative giblets weight (liver, heart and gizzard).
7- Highly significant (P<0.001) differences were found in total microbial count and the different individual microbial species due to treatments effect.
8- Dietary treatments had highly significant effect (P<0.001) on total microbial and pathogens count in small intestine of chicks at end of the experiment.
9- Birds fed diets supplemented with combination of yeast and yeast cell wall at levels of 0.75 + 1.0 gm/kg diet showed significant (P<0.05) decrease in total microbial and pathogens count in the different small intestine parts followed by those fed the diet supplemented with 1.0 + 1.0 gm/kg diet) then birds fed control.
10- The 0.75 or 1.0 gm yeast cell wall + 1.0 yeast gm/kg diet enhanced villi height and width, the number and size of the crypts.
Conclusion:
Diets supplemented with live yeast with or without yeast cell wall improved growth performance traits and health by increased the absorption area in the gut and balanced microbial population in the gastrointestinal tract which has played an important role in the health and performance of the broilers and dressing percentage.