الفهرس 
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Abstract
This study was carried out at the Poultry farm of Animal and Poultry Production Dept. Faculty of Agriculture, Minia uviversity from 20 December 2017 to 30 January 2018. It was designed to study the effect of supplementing boiler diet with two different phytase enzyme sources e.g. (bacterial phytase-6 and / or fungal phytase-3) at recommended level on the performance, carcass characteristics, digestibly of nutrients and some physiological aspects. The chemical analyses were carried out at laboratories of the Department of Animal Production, Faculty of Agriculture, Minia University. two hundred forty (240), unsexed, one day old Arbor Acer broiler chicks were randomly distributed into six (6) groups with four (4) replicates each with ten chicks . Chicks were housed in tow-tiers wire floor batteries located in an open house under similar managerial conditions. Two diets (starter and grower) diets based on corn- soybean meal were formulated as recommended or low levels of crude protein, metabolizable energy, phosphorus and calcium by 10% reduction each . The basal starter and grower diets were formulated to meet the nutrients requirements of broiler chicks according to NRC (1994) and were used as a control dietary treatment. The second of starter and grower diets were formulated to have 10% decreasing crude protein, metabolizable energy, phosphorus and calcium than the control diet. Both starter and grower diets were supplemented with or 2 types (bacterial phytase-6 and / or fungal phytase-3) of phytases which recommended by the manufacturer. All chicks had full access to feed and water allover the experimental period (from 0 to 6 wks of age). Chicks in each replicate were weighed at one day as age and at the end of starting (at 21 days old) and growing periods (at 42 day old) and devided by the number of survived chicks to obtain the average live body weight. Feed conversion ratio was calculated (gm feed/ gm gain) at starting, growing and whole experimental periods.
At the end of the sixth week of age, 3 birds were randomly taken from each treatment and slaughtered (3 bird × 6 treatment = 18 birds) to measure carcass traits. Samples of blood were collected in heparinized and non-heparinized tubes at slaughtering time to measure some blood constituents in both plasma and serum (3 bird × 2 samples × 6 treatments = 36 samples).
At the beginning of the 7 th week of age, three birds from each treatment (3 birds × 6 treatments = 18 birds) were individually housed in wire cages, and fed on the same diets used during the growing period and feces were collected for 3 days. Samples of the tested diets and collected feces were chemically analysed according to A.O.A.C. (1990). to evaluate nutrients digestibility for each dietary treatment.
The results revealed the following:
- Birds fed the control diet presented the best body weight and body weight gain compared with the low density diet.
- Adding different enzyme sources of did not affect (P≥0.05) on body weight and body gain of birds
- During the period from 3-6 weeks of age, adding either fungil or bacterial enzyme to broiler diet significant improved feed intake.
- Numerically increase (P≥0.05) was noticed in feed intake when birds fed the control diet supplemented with fungal phytase.
- A highl improvement in feed conversion was recorded for the birds fed the control diet compared with the low density diet during the period from 0-3.
- Adding different enzyme sources improved (P≤0.05) feed conversion for the birds fed diets with bacterial phytase compared with others fed diet contain fungal phytase during the period from 3-6 weeks of age.
- Birds fed the control without enzyme addition recorded the best feed conversion followed by those fed low diet contained bacterial enzyme compared with the other interactions, during the period from 3-6 weeks of age.
- The control treatment recorded the greatest proportions of heart, spleen and edible parts.
- Adding enzyme sources to broiler diet improved the proportions of liver and edible parts; respectively.
- The birds fed low diet without enzyme supplementation recorded the highest (P≤0.05) proportions of edible parts compared with the other groups.
- A highly significant (P≤0.01) values of digestibility of crude protein and ether extract were recorded for the birds fed the control diet compared with the low density diet.
-The birds fed the control diet without enzyme addition recorded the best CF digestibility compared with the other treatment.
- A highly significant improvement (P≤0.01) was evaluated in total seram protein and globulins for the control group than the low density diet group.
-The birds fed the control diet with bacterial enzyme addition recorded the best serum albumen, however, the birds fed the control diet without enzyme addition recorded the highest value of serum cholesterol compared with the others treatments.
- Numerically increase (P≥0.05) was noticed in GOT in the birds fed the control diet followed by the birds fed low density diet supplemented with bacterial phytase compered with other treatments.
- Adding phtyase enzyme of bacterial source was economically only for birds fed low density diet.