The objective of this study was to evaluate the effect of different levels of folic acid (FA) supplementation on productive and physiological performance and immune response of laying hens fed diets varying in methionine (M) and metabolizable energy (ME) levels. A total number of two hundred and sixteen of Silver Montazah laying hens (28 weeks old), were randomly divided into 12 treatment groups (18 hens / each). All birds were housed in individual cages. The experimental design was conducted in 2 x 2 x 3 factorial arrangement of treatments, 2 levels of ME (2800 and 2600 Kcal/Kg diet), two levels of DL-methionine (0.40% and 0.30%) and three levels of folic acid (0.0, 10, and 20 mg /kg feed). The results can be summarized as follows:-Increasing ME significantly increased final body weight (P≤0.01), shell thickness (P≤0.01), plasma total protein, globulin, glucose, cholesterol, triglycerides, egg folate content and hatchability of total fertile eggs while, daily feed intake and feed conversion ratio (FCR) were decreased. -Methionine at a level of 0.40% in the diet increased significantly egg number, albumin%, plasma total protein, globulin and HDL. On the other hand daily feed intake, FCR, shell%, egg shape index% and egg specific gravity were significantly decreased.-Significant increases were observed in egg number, shell thickness, plasma total protein, globulin and egg folate content due to increasing FA supplementation in the diet while, Haugh units, plasma albumin and plasma folate recorded significantly their lowest values.-Feeding hens diet with ME of 2800 kcal/kg and a level of 0.40% M without FA supplementation significantly increased albumen % and plasma triglycerides. In this respect, FA supplementation at a level of 10 mg/kg diet significantly increased plasma HDL. On the other side, FA supplementation at a level of 20 mg/kg diet significantly increased body weight change, daily egg mass, shell thickness, plasma total protein, albumin, globulin and significantly improved hatchability of fertile eggs. In addition, antibody titre against NDV recorded the highest value with insignificant difference as compared to other treatments.-Hens fed diet with 2600 kcal/kg ME and a level of 0.30% M without FA supplementation laid eggs with the highest mean of specific gravity while increasing FA to 10 mg/kg decreased plasma HDL. Increasing the supplementation level of FA in the diet significantly increased daily feed intake while, plasma triglycerides was significantly decreased.-A significant increase was observed in Haugh units attributed to feeding hens diet of ME at level of 2600 kcal/kg and 0.40% M without FA supplementation.

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This experiment aimed to study effects of metabolizable energy and protein levels on the productive and reproductive performance of Sinai laying hens from 24 to 40 wk. A total of 180 Sinai laying hens was randomly assigned to six experimental diets of 2,850 (H ME = high ME), or 2,700 = low ME) kcal of ME/kg, each containing CP levels of 18% (H CP = high CP), 16% (M CP = medium CP), or 14% (L CP = low CP) in a 2× 3 factorial arrangement of treatments. Each dietary treatment contained 30 single-caged birds. The results were obtained as follows: final body weight (FBW), change in body weight (CBW), daily protein intake, daily energy intake, protein efficiency ratio (PER), energy efficiency ratio (EER), feed conversion ratio (FCR), egg number (EN), egg weight (EW), daily egg mass (EM), hen-day egg production rate (HDEP), were significantly improved in birds fed the high-energy-diets (P<0.01) compared with those fed the low-energy-diets. However, birds fed the low-ME diets consumed more feed compared with fed on high-energy-diets. Birds fed the diets termed as (H CP or M CP ) displayed significantly higher (P≤0.01) final body weight (FBW) and change in body weight, egg number and hen-day egg production rate than those received the low-CP diet (P<0.01). Increasing dietary protein level led to a gradual improvement in FBW (g), CBW, daily protein intake, EER, FCR, egg number, egg weight, daily egg mass and hen-day egg production rate. Interactions between ME and CP levels in the previously mentioned criteria were significant (P<0.05). Plasma cholesterol was significantly increased as a result of feeding on the high-ME diets compared with those given the low-ME diets. The same trend was also observed in respect of protein levels where there were significant differences on plasma activity of ALT which significantly increased (P≤0.01) when hens were fed on the high-CP diets compared with those fed on the diets containing L CP and M CP . Plasma cholesterol was significantly increased (P≤0.01) by increasing ME level in the diet with any dietary protein level compared with other treatment groups.The present results revealed that the diets containing ME level of 2,850 kcal/kg with 18 or 16% protein can improve egg production characteristics of Sinai laying hens. From the economic view point it can be suggested that a diet containing 16% protein with 2850 kcal/kg is optimal for Sinai laying hens to achieve the highest profitability compared with other treatments during studied period from 28-40 weeks of age.