الفهرس 
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Abstract
This study was carried out at the Poultry Farm, Department of animal production, Faculty of agriculture, South Valley University from 1 October to 12 November 2004. It was designed to study the effect of addition some probiotics into diets from plant origin on the growth performance, carcass traits and some digestive tract measurements in broiler chicks.
Three hundred sixty unsexed one-day old Hubbard broiler chicks were randomly distributed into 12 groups with 3 replicates each (3 diets x 4 levels of probiotics x 3 replicates x 10 chicks = 360 chicks). Three diets from each of the starter and grower diets were formulated from plant origin to have low levels of either protein or metabolizable energy in addition to control diet.
The first starter and grower diets were formulated to meet the nutrient requirement of broiler chicks according to NRC (1994) and served as a control treatment (control).
The second and third starter and grower diets were formulated to have 2% less protein, but adequate level of metabolizable energy ( low CP). or less metabolizable energy by about 200 Kcal ME/kg diets, but adequate level of crude protein (low ME) compared to control treatment respectively. Both starter and grower diets were supplemented with or without 0.1% Bio-min (as microbial growth promoter) or 0.03% Ronozyme (as enzymatic growth promoter) or 0.1% Super-bio–action (as microbial and enzymatic growth promoter). Management was similar for all treatment groups. Birds in each replicate were weekly weighted and feed consumation was record. Feed conversion (gram feed/gram gain) was calculated for the different experimental periods. Mortality was recorded daily and calculated for the entire experimental period. At 6 weeks of age, 36 birds were slaughtered to determine carcass traits (12 Treatments x 3 birds = 36 birds) and some digestive tract parameters. Morever, a digestible trial was conducted at the end of experiment to evaluate nutrients digestibility for each treatments.
The results revealed the following:-
A-Body weight and body weight gain:-
1- Diet had highly significant effects (p<0.01) on body weight and body weight gain of broiler chicks at one week old and from 4 to 6 weeks of age.
2- During the period from 4 to 6 weeks of age, the highest (p<0.05) body weight and body weight gain were recorded by birds fed on the low- ME diet. However, those fed on the control or low CP diets achieved similar body weight during the previous mentioned periods.
3- The addition of probiotics into broiler chick diets improved (p<0.05) body weight and body weight gain during the experimental period (from 1 to 6 week old) compared to the control diet (without probiotic).
4- All types of probiotic had similar improving effects on body weight and body weight gain at the end of both starting and growing periods. This improvement effects on body weight and body weight gain represented about 14.92%, 12.04%, and 11.73% and 15.47%, 12.57% and 12.17% over the control (without probiotic) by supplementation of Ronozyme, Biomin or Super bio-action respectively at 6 weeks of age.
B-Feed intake and feed conversion ratio:-
1- During the period from 4 to 6 weeks of age, the highest (p<0.05) feed intake was recorded for broiler chicks fed on low ME diet, while those fed on the control or low CP diets consumed similar amount of feed.
2- The superiority in feed intak for broiler chicks fed on the low-ME diet represented about 33.46% and 31.53% over those fed on the control or low CP diets respectively at marketing age (at 6 weeks of age).
3- Addition of Ronozyme as enzymatic probiotics into broiler chicks diet enhanced (p<0.05 ) feed intake during the first 4 weeks of age compared to those fed on the control or the two other probiotics (Biomin or Super bio-action). This enhancement effect of Ronozyme on feed intake was gradually decreased with advancing age of birds and disappeared at 5 and 6 weeks of age.
4- Diet had insignificant effect on cumulative feed conversion ratio of broiler chicks during the period from 2 to 6 weeks of age. The values of feed conversion ratios fluctuated between 1.72 to1.80 at 6 weeks of age.
5- The addition of probiotics into broiler chick diets improved (p < 0.05) feed conversion ratios during the period from 1 to 6 weeks of age. This improvement effects represented about 14.62% 14.57% and 17.09% for Ronozyme, Biomin and Super bio-action respectively over those fed on the control diet at 6 weeks of age.
C- Efficiency of protein and energy utilization:
1- Diet had significant effect (p < 0.01 or p<0.05) on both protein and energy utilization only during the starting period (from 1 to 3 weeks of age) while the differences in either growing (from 4 to 6 weeks of age) or whole experimental periods (from 1 to 6 weeks of age) were insignificant.
2- Broiler chicks fed on the low ME diet recorded the lowest (p<0.05) efficiency of protein utilization, but the best (p<0.05) efficiency of energy utilization at starting period compared to those fed the control or low CP diets.
3- Probiotics supplementation improved (p<0.01) the efficiency of energy utilization during starting, growing and entire experimental period while, the efficiency of protein utilization was improved (p < 0.05) only during starting period by the addition of probiotics into broiler chick diets.
D- Nutrients digestibility:
1- Diet had little effect on nutrients digestibility and only the digestion coefficients DM in both starter and grower diets and EE in grower diet was significantly (p < 0.01 or p < 0.05) influenced by the type of diet. Lowering the ME in the diet decreased (p < 0.05) DM digestibility in starter and EE digestibility in grower diet compared to the control diet.
2- Supplementation the diets with probiotics improved (p<0.05) the overall nutrients digestibility in starter diet and DM, CF and EE digestibility in grower diet.
E- Viability:-
Neither diet nor probiotics had significant effect on viability of broiler chicks during the entire experimental period.
F – Cost of feed/kg gain and economic return :
1- Broiler chicks fed on the low ME diet a achieved the lower (p<0.05) cost of feed/kg gain compared to those fed on the low CP diet, while feed cost/bird was the highest (p < 0.05) for birds fed on the low ME diet.
2- The economic efficiency for birds fed the low ME diet at marketing was better (p<0.05) by about 34.4% and 40.56% than those fed on the control or low CP diets respectively. However, broiler ckicks fed on the low CP diet insignificant decreased the economic efficiency by about 4.4% compared to those fed on the control diet.
3- Probiotics supplemented into broiler chicks diets decreased the cost of feed/kg gain and improved economic efficiency by about 29.5%, 23.5% and 28.3% by Ronozyme, Biomin and Super bio-action supplementation compared to the nonsupplemented control diet.
G – Carcass traits:
1- Diet had insignificant effect on dressing% of broiler chicks at 6 weeks of age which fluctuated between 75.79% to 78.55%.
2- Broiler chicks fed on the low CP diets achieved the highest (p<0.05) abdominal fat % while, those fed on the low ME diet had the lowest (p< 0.05) gizzard% at markiting age.
3- Probiotics supplementation improved carcass weight, while, dressing, abdominal fat, and giblets percentage were not significantly influenced.
H- Some digestive tract measurments :
1- Broiler chicks fed on the low CP diet recorded the highest (p<0.05) relative weight and length of duodenum compared to those fed on the control or the low ME diets.
2- Broiler chicks fed the low ME diet achieved the lowest (p<0.05) relative length of small intestine and cecum and relative weight and length of large intestine compared to those fed on the control or low CP diets.
3- The low ME diet increased (p<0.05) the thickness of cecum.
4- Addition of probiotics into broiler chick diets had negligible effect on digestive tract measurements and their positive effects were not adequate to induce changes in carcass tratits