Does early antibiotic administration to turkeys receiving a coccidiostat in the diet affect the yolk sac absorption rate, the maternal antibody levels, and the immune system efficiency?

Abstract The research aimed to determine whether the yolk sac resorption rate, the maternal antibody levels, as well as the efficiency of the immune system of growing turkeys may be affected by early administration of antibiotics and feeding a diet containing a coccidiostat. The experiment was conducted in a 3 × 2 factorial design, which included 3 groups of birds (CON, ENR, DOX), each of which was fed with or without monensin (+, −). The CON groups did not receive antibiotic supplementation (control groups), while those in the ENR groups received enrofloxacin at a dose of 10 mg/kg body weight (BW) for the first 5 days of life, and those in the DOX groups received doxycycline at a dose of 50 mg/kg BW for the first 5 days of life. The CON−, ENR−, DOX− groups did not receive monensin in their diet, while those in the CON+, ENR+, DOX+ groups received monensin at a dose of 90 mg/kg of feed. Adding monensin to the diet significantly decreased the feed conversion ratio (FCR) (P < 0.01) and body weight in 3-day-old and 7-day-old turkey hens (P < 0.05). Early enrofloxacin administration increased anti-ORT antibody titers in 1-day-old turkeys (P < 0.05), while monensin supplementation decreased several antibody titers such as anti-MPV, anti-NDV, and anti-ORT (P < 0.05). Immunoglobulin levels (IgY and IgM) and T cell percentages (CD4 + , CD8 + ) were also significantly reduced in young turkeys fed monensin (P < 0.01 to P < 0.05). Monensin disturbs passive and specific immunity, especially in young turkeys. Early enrofloxacin or doxycycline administration to young turkeys may lead to undesirable changes in the developing immune system, including impaired humoral immunity in later life. Enrofloxacin administration to turkeys in the first five days of life and feeding them a diet containing the coccidiostat monensin strongly stimulated the immune system, which in consequence caused changes in the immune system, indicating immunosuppression in the period distant from the enrofloxacin administration. The early administration of the antibiotics enrofloxacin or doxycycline with a diet without coccidiostat or containing the coccidiostat monensin did not affect the turkeys’ growth performance.