A comparison of three continuous and four shuttle anticoccidial programs.

Continuous programs of a combination of narasin (40 ppm) and nicarbazin (40 ppm) (NaNi), narasin at levels of 60 and 70 ppm, and a 2 by 2 factorial shuttle design (NaNi or nicarbazin at 125 ppm, each for 27 or 28 days, followed by narasin at 60 or 70 ppm to termination), were compared with unmedicated controls for their anticoccidial efficacy and growth performance in nine broiler trials conducted in seven countries outside the United States. Cecal coccidial lesions were reduced only by treatments that incorporated nicarbazin either at the 40-ppm level in NaNi or at 125 ppm, whereas total intestinal lesion scores were reduced by all the anticoccidial programs tested. At Day 28, the three treatments containing NaNi and the treatment containing narasin at 60 ppm significantly improved weight gain and feed efficiencies over the two treatments containing nicarbazin at 125 ppm and the unmedicated controls. At termination all the anticoccidial programs significantly decreased the mortality rate and improved bird weights and feed efficiencies. Birds on the treatments containing NaNi either in the two shuttle programs or in the continuous program were significantly heavier than those on the two treatments containing nicarbazin at 125 ppm in shuttle programs.