A total number of 240 hens of Mandarah local strain aging 58 weeks of age was used in a factorial design (3 source of vegetable oil groups x 4 feed additives) up to 70 weeks of age. Hens were divided randomly into three treatment groups. The 1st group was fed basal diet, 2nd group was fed the basal diet containing 3% corn oil, 3rd group was fed the basal diet containing 3% sunflower oil. Each treatment group was divided randomly into four subgroups. The 1st subgroup was fed basal diet without any supplementation t, 2nd group was supplemented with vitamin C at 100 mg/kg diet, 3rd subgroup was supplemented with kemzyme preparation at a rate of 0.05% of the diet, and the 4th subgroup was supplemented with both of vitamin C (100 mg/kg diet) and kemzyme preparation at level 0.05% of the diet.
The results indicated that feeding laying hens on vegetable oil sources (corn or sunflower oil at 3% diet) produced the best value of egg number, egg production, egg weight, egg mass, feed conversion and hell thickness as compared to those fed control diet.
However, chicks weight at hatching, values of serum cholesterol and yolk cholesterol were significantly (P<0.05) effect due to corn oil treatment as compared to other treatment. The vegetable oil sources had a beneficial effect on the digestion coefficient values of DM, CP and EE% and also improved the retained amount of calcium and phosphorus content as compared to the control diet.
On the other hand, hens fed diets supplemented with kemzyme only gave the best values of egg number, egg production and feed conversion. Hens fed diet supplemented with vitamin C resulted in the best value of egg weight and egg mass, while the lowest value of feed intake was recorded by hens fed diet supplemented with the combination of vitamin C and kemzyme preparation. The addition of vitamin C and mixture of vitamin C and kemzyme preparation gave the best values of egg shell quality, in almost coefficients of digestibility, calcium and phosphorus retention, fertility and hatchability and also the chick weight at hatching, while it was lower both of serum cholesterol and yolk cholesterol and also increase serum calcium and phosphorus content when compared to the other treatments.
Interaction results indicated no significant for previous traits, except for feed intake, feed conversion and the values of serum cholesterol, yolk cholesterol and total lipid, which were significant (P<0.05) affected.
Economic evaluation indicated that the use of oil (sunflower oil following corn oil) in supplementing layer diets improved NR and EE% as compared to the non supplemented diet, while kemzyme preparation recorded the highest value of NR and EE% follow by the mixture of vitamin C with kemzyme preparation as compared to the other treatments.