الفهرس 
REVIEW OF LITERATUREOnly 14 pages are availabe for public view
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Abstract
A total number of 360 Manadarah laying hens and 36 Mandarah coaks (28 weeks) of age were fed on six levels of available phosphorus (0.45, 0.35, 0.30. 30.0, 0.25, 0.20 and 0.15%). With or without two levels of microbial phytase 0 and 800 FTU/kg). Birds were randomly distributed into 12 treatments T1 to T2, T12 birds of T1 to T6 were fed diets with six levels of AP without phytase supplementation and birds of T7 to T12 fed on the same six levels of AP with phytase supplementation (800 FTU/kg) and the different measurements were calculated and recorded. The results obtained could be summarized as follows: There was no significant effect of phosphorus level and microbial phytase on body weight change, final and initial body weight broken egg increased with feeding laying hens on diets lowing in AP (0.20 and 0.15), while phytase addition to the diets tend to decreasing of broken egg. The average of egg number and egg mass for birds fed of 0.45% AP were higher than that obtained by those fed the 0.15 AP, while phytase addition markedly increased egg number and egg mass, the lowest values of nutrients digestibility were recorded by feeding on diets with 0.20, 0.15% AP. However, phytase supplementation tend to improve the digestibility of most nutrients. The highest values of phosphorus retention% were recorded in diet containing 0.25% AP with phytase, the highest values of calcium retention% were recorded in diet containing 0.45% AP with and without phytase enzyme. Decreasing of available phosphorus levels increased plasma Ca, while plasma P decreased with decreasing of AP levels, however, decreasing of AP caused a decrease in plasma AST activity, plasma ALT activity wasn’t affected by decreasing levels of AP, plasma ALP activity was increased with the low of AP, while phytase addition decreased plasma ALP activity, plasma total protein was reduced by decreasing of AP, while phytase addition had no effect of plasma total protein. So, from this study, it could be concluded that phytase addition has beneficial effects on the performance of laying hens that feed on 0.25 and 0.20% AP with phytase supplemented and there is a high risk in reducing levels of AP to 0.15% with or without phytase addition.