Improvements in the performance of commercial broilers in the USA: analysis for the years 1997 to 2001

The performance of commercial broilers reported by broiler production units in the USA from 1997 to 2001 has been evaluated. There was a linear decrease in calorie conversion (CC) and number of days to produce a 2.27 kg bird (DAYS) but no change in percentage mortality. By contrast, there was a linear increase in final bird weight (FBW) during this period. There was a linear increase in the percentage of production units rearing birds to more than 2.5 kg and a decrease in those rearing birds to less than 2.0 kg or 2.0 to 2.5 kg. There were no differences in CC or DAYS during the first half of the year (January to June), but these traits showed a significant increase in July followed by a steep decline during August, September, and October. FBW was similar from January to June but showed a significant decrease in July. No consistent variation in monthly mortality was noted. It is concluded that improvements in the productivity of broilers have been achieved from 1997 to 2001 but that more attention should be given to the problem of broiler management during the summer months.