Tests were carried out on thirty, 42 days old Rock x Cornish chickens, divided into three experimental groups: I - control injected with saline, II - injected with a Calendula officinalis extraction supplemented with Bayol and III - treated with Bayol. The effects of the in vivo treatments and simultaneous antigen priming (0.5 ml of
a 5 % suspension of SRBC) on their humoral (lysozyme, anti-SRBC antibodies) and cell-mediated (leucocyte blast transformation) responses were investigated. Lysozyme (51.50 ± 32.30, 56.80 ± 41.27, 29.50 ± 22.73 μg/ml)(p<0.05), and anti-SRBC antibody titers (2.35 ± 0.86, 2.05 ± 0.65 and 1.90 ± 0.55) were the lowest in
Bayol treated group. Spontaneous stimulation index was positively influenced by the in vivo Bayol therapy (57.20 ± 8.88 per cent), when compared to that recorded for the other groups (31.06 ± 18.93 group I, 33.37 ±
19.26 group II).
