Effects of Thymus vulgaris and Melissa officinalis on histomorphological changes of the bursa of Fabricius as well as blood titers obtained from Newcastle vaccine

This research follows previous studies with the difference that the present study has been designed to investigate the effects of Melissa officinalis and thyme on birds' immune system using histology method which was raised for the first time. For this purpose, 40 broiler chicks of Ross 308 (one day-old) were obtained. Five gram of thyme and lemon balm powder mixture was added to the diet of the treatment group. Blood samples were taken randomly in order to HI test on the 10, 24, and 42 days old to measure the rate of antibody titer against Newcastle disease. Following preparation of paraffin blocks, the samples were stained using periodic acid shift (H&E) method. Histological data were statistically analyzed using T-TEST. There was no significant difference between the two groups (control and treatment groups) in the early period according to the results of HI (P>0.05). Although the HI results were not different meaningfully ( P<0.05) between the two groups in the growth and final periods, there was a meaningful difference (P<0.05) between the two groups in Morphometric parameters in terms of epithelial thickness, the amount of one row cells in the follicle cortex and the amount of one row cells in the follicle medulla. Based on the results obtained from bursa of Fabricius tissue changes it appears that the combination of thyme and Melissa officinalis can increase the density of B lymphocyte cells in cortex and medulla follicles in the bursa of Fabricius in the treatment group compared with the control group.