The effect of early administration of antibiotics or feeding a diet containing a coccidiostat on inflammatory responses and the morphological structure of selected organs of the immune system in young meat-type turkeys

It was assumed that early administration of enrofloxacin or doxycycline may impair immune func-tion and alter the morphology of organs of the immune system in turkeys, and that diets containing the cocci-diostat monensin, an ionophore antibiotic, can exert similar effects. The aim of this study was to determine whether early antibiotic administration or feeding a diet containing a coccidiostat affect immune function in young turkeys. The experiment had a completely ran-domized design, with 8 groups (a total of 3,080 one-day-old turkeys), 7 replicate pens per group and 55 birds per pen. The experiment had a 2-factorial design, with 4 treatments (C-control, M-monensin, E-enrofloxa-cin, and D-doxycycline) and 2 groups of birds (vacci-nated and unvaccinated) per treatment. Control group birds did not receive the coccidiostat or antibiotics. Group M was administered monensin at 90 mg/kg feed for the first 5 d of life, group E received enrofloxacin at 10 mg/kg BW, added to drinking water, for the first 5 d of life, and group D received doxycycline at 50 mg/kg BW, added to drinking water, for the first 5 d of life. One-day old turkeys from groups C+, M+, E+, and D+ were administered live-attenuated vaccines against tur-key rhinotracheitis (TRT) (Poulvac TRT; Zoetis, Par-sippany, NJ) and Newcastle disease (ND) (Nobilis ND clone 30; Merck, Rahway, NJ) by coarse spray; 28-day -old birds were administered a subcutaneously injected inactivated vaccine against Ornithobacterium rhinotra-cheale (ORT) (Ornitin, Phibro, Poland). Turkeys from groups C-, M-, E-, and D-were not vaccinated. It was found that early administration of enrofloxacin or doxycycline, or feeding a diet containing monensin, did not weaken the immune system of turkeys. The adminis-tration of monensin, in particular when combined with vaccination, was least effective in inhibiting inflamma-tory responses. Histological changes in immunocompe-tent organs (fatty degeneration) were also most severe in birds receiving monensin, followed by those adminis-tered doxycycline and enrofloxacin. The observed changes were exacerbated by vaccination.