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 broiler plants, their frequency and duration, and whether there was any correlation with performance of the birds. Information was available for five feed types (prestarter, starter, grower, first withdrawal, and final withdrawal). 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 different ION in the starter and grower feeds. Seasonal differences were apparent in the type of program and in the frequency of program changes. There was no consistent pattern in the sequence with which different programs were employed. There were no significant differences in calorie conversion or the number of days to produce a 2.27 kg bird, whether a single ION or a chemical followed by an ION was used, but mortality was significantly higher for the latter. For 1999, calorie conversion and mortality were higher in plants 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 weights of 1.5 to 2.0 kg, 2.0 to 2.5 kg, or more than 2.5 kg. There were significant differences in the use of salinomycin and nicarbazin in different regions of the US.