Exogenous Enzyme Improves Immunocompetence in Laying Hens Fed Diets Containing Safflower Meal

An experiment was conducted to study the effects of different levels of exogenous enzymes on egg quality characteristics and immunological responses of laying hens fed diets containing different levels of safflower meal. The 47-week old layers (Hy-Line W-36) were fed 10 experimental diets consisting five levels of safflower meal (0.0, 2.5, 5.0, 7.5 and 10.0%) and two levels of dietary exogenous enzyme (0.0 and 0.1% Bergazym P) during the experimentation. The trial period lasted for a total of 10 weeks, and egg quality indices were measured as two 35 day experimental periods. After 48 and 55 days of experiment, birds were injected with 1 mL of 7% Sheep Red Blood Cells (SRBC) intramuscularly. At the end of experiment, the antibody titer against SRBC and differential circulating leukocyte count were measured for investigating immune status. Least squares mean analysis showed that although the inner egg quality characteristics (yolk index and Haugh unit) were not influenced by dietary treatments, using the highest level of safflower meal caused remarkable decrease in eggshell weight and strength during the first 35-day experimental period. Nonetheless, these parameters showed tendency to decrease during the second trial period. The heterophils to lymphocytes ratio were significantly increased after feeding different levels of safflower meal and reach to the highest level in hens fed diet containing 10% of this meal. This response was due to the increase in heterophils population and contemporaneous decrease in lymphocytes percentage. Inclusion of 0.1% dietary enzyme had remarkable modulatory effect on heterophils count and the heterophils to lymphocytes ratio. Following the administration of dietary enzymes, the number of lymphocytes and thereby, the primary humoral immunity response increased significantly, however, this alteration had tendency to increase during the secondary immunity response against SRBS. Therefore, our results indicated that using high level of safflower meal (10%) in laying hens diet could have aversive effects on eggshell quality. Also, administration of dietary exogenous enzyme to the diets of laying hens would have beneficial effects on immunological responses, especially in terms of heterophil to lymphocyte ratio depression or improvement of humoral immunological functions