The impact of dietary fortification of an exogenous mono component protease enzyme with or without its matrix values (ME 31.5 Kcal, CP 0.84%, methionine 0.018%, lysine 0.05%, threonine 0.034%) on growth performance traits, feed digestibility, serum parameters, selected immune parameters, total counts of ileal clostridia species, carcass traits as well as duodenal histomorphological picture was studied. A total of 300-day old chicks (Cobb500) were randomly assigned to five separate floor pens equal experimental groups with three replicates (20 birds /replicate). Birds were fed either on corn-soybean meal basal diets (starter-grower and finisher) without any supplementation (G1) and served as control group, or basal diets to which protease enzyme was added on top at a rate of 200 ppm (G2). Birds in (G3) were fed on the basal diets to which protease was added at the same inclusion level but subtracting the whole matrix value of the enzyme. Birds in (G4) were fed on the fortified basal diets after subtracting only the metabolizable energy matrix value of the enzyme. Birds in (G5) were reared on the fortified basal diets after subtracting only the crude protein as well as amino acids matrix value of the enzyme. The experimental period extended for five weeks. Birds in groups 2 and 4 significantly ( P 0.05) surpassed all groups in weight gain, feed consumption and FCR, also these groups were significantly ( P 0.05) better in dressing %. Also G2 (protease on the top) and G4 (Low ME values) showed a significant elevation of CP digestibility and showed a significant (P 0.05) reduction of total ileal clostridia species counts. In addition G2 showed an increase in villus height and villus to crypt ratios compared to other experimental groups. In conclusion, broiler chickens respond positively to supplementation of protease enzyme and it can be used safely on the top of their diets.

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