a comparison between the effects of a probiotic (bioplus 2b) and an antibiotic (virginiamycin) on the performance of broiler chickens under heat stress condition

an experiment was conducted on 400 broilers to evaluate the effects of dietary supplementation ofantibiotic and probiotic on performance of birds under heat stress condition. the first group of chickens, thecontrol group, received a diet without any antibiotic and probiotic. the second group received diet with0.02% virginiamycin antibiotic; the two other groups were fed diets with 0.05% and 0.1% bioplus 2bprobiotic, respectively. the addition of antibiotic to the diet significantly improved body weight gain during0–3 and 4–6 weeks (heat stress) periods as compared to the control and 0.05% probiotic-supplementedgroups (p0.05). addition of antibioticor various levels of probiotic to the diet significantly improved feed conversion ratio during 4–6 weeks (heatstress) period as compared to the control group (p0.05). supplementation of diet with various levels of probiotic had no significanteffect on antibody titer against srbc, ndv vaccine and haemoglobin content (p>0.05). however,supplementation of diet with 0.1% probiotic significantly increased wbc count and decreased h/l ascompared to the control group (p