Compensatory Growth in Broilers after Withdrawal of Ionophorous Anticoccidial Drugs

Three polyether, ionophorous anticoccidial drugs were fed to broiler chickens in floor pens for 5 or 6 weeks, then withdrawn for 2 weeks or 1 week, respectively. With monensin and salinomycin there was evidence of increased feed consumption and compensatory growth during the first week, but not the second week, after drug withdrawal. There was no evidence of compensatory growth in birds fed lasalocid. Final weights were best in birds fed lasalocid and salinomycin in comparison with unmedicated controls and birds fed monensin. There was evidence of increased feed consumption and compensatory growth in some treatments in which birds weighed more than controls prior to drug withdrawal.