Use of anticoccidial drugs in broiler chickens in the USA: Analysis for the years 1995 to 1999

Data collected by Agri Stats Inc. in the US for the years 1995 to 1999 was evaluated to determine the types of anticoccidial drug programs used by bro iler plants, their frequency and duration, and whether there was any correl ation with performance of the birds. Information was available for five fee d types (prestarter, starter, grower, first withdrawal, and final withdrawa l). The most popular program was an ionophore (ION; principally salinomycin ) in starter and grower feeds. A chemical (principally nicarbazin) was also used in the starter feed followed by an ION in the grower feed, or two dif ferent ION in the starter and grower feeds. Seasonal differences were appar ent in the type of program and in the frequency of program changes. There w as no consistent pattern in the sequence with which different programs were employed. There were no significant differences in calorie conversion or t he number of days to produce a 2.27 kg bird, whether a single ION or a chem ical followed by an ION was used, but mortality was significantly higher fo r the latter. For 1999, calorie conversion and mortality were higher in pla nts where chemical-ION programs had been used for more than 40% of the time during the previous 4 yr. The duration and frequency with which different programs were employed were similar whether birds were raised to final weig hts of 1.5 to 2.0 kg, 2.0 to 2.5 kg, or more than 2.5 kg. There were signif icant differences in the use of salinomycin and nicarbazin in different reg ions of the US.