Gastrointestinal Tract and Neuroendocrine System Responses of Young Turkeys to the Early Administration of Antibiotics or Feeding a Diet Containing a Coccidiostat

This study investigated the effects of early and short-term administration of an antibiotic or feeding a diet containing a coccidiostat on gastrointestinal function and the blood levels of selected hormones in young turkeys. A total of 1540 Hybrid Converter turkeys were allocated to 4 groups on the day of hatch. Each group consisted of 7 pens with 55 birds per pen. Group ENR was treated with enrofloxacin for the first 5 d of life, group DOX received doxycycline for 5 d and group MON was administered monensin for 84 d. CON birds served as a control group without any antibiotic treatment or MON administration. An analysis of the activity of bacterial enzymes revealed that the cecal microbiota of turkeys were less sensitive to MON than to the other 2 antibiotics. Turkeys subjected to ENR and DOX treatments were characterized by lower (P < 0.05) extracellular activity of cecal bacterial β-glucosidase, compared with groups CON and MON. The extracellular activity of cecal bacterial α-galactosidase and β-galactosidase decreased significantly in response to the experimental treatment with DOX (P < 0.05 vs. CON). Turkeys treated with ENR had higher total activity of bacterial β-galactosidase than those administered DOX or MON. Despite the differences in the enzymatic activity of microbiota, the use of antibiotics did not affect the concentrations of total short-chain fatty acids or ammonia in the cecal digesta of turkeys. A diet containing MON and the early administration of ENR or DOX induced an increase in blood noradrenaline levels (P = 0.004) in 56-day-old turkeys. Early DOX use increased plasma cortisol concentrations (P < 0.001) and decreased plasma serotonin levels (P = 0.006) in 56-day-old turkeys. Over the entire experiment (up to 12 wk of age), the use of MON improved the BW gain of turkeys (P = 0.055) and feed conversion (P = 0.016), compared with the DOX treatment.