The use of diclazuril in extended withdrawal anticoccidial programs: 1. Efficacy against Eimeria spp. in broiler chickens in floor pens.

A 49-d floor pen study was conducted with broiler chickens to compare the effects of different anticoccidial withdrawal times on the efficacy of 1 ppm diclazuril. The starter diet in three treatments contained 66 ppm salinomycin + 50 ppm roxarsone (3-nitro-4-hydroxyphenylarsonic acid), followed by 1 ppm diclazuril in the grower diet commencing on Day 17. Diclazuril was withdrawn from these treatments on Day 28, 35, or 42 (finisher diet), respectively. Two other treatments in the study were given 66 ppm salinomycin + 50 ppm roxarsone in the starter and grower diets to Day 28 or no anticoccidial (unmedicated). The starter (Days 0 to 16), grower (Days 17 to 35), and finisher (Days 36 to 49) diets in each treatment included 55 ppm bacitracin methylene disalicylate for growth promotion. Fifty 1-d-old chicks were randomly allotted to each of 10 pens per treatment using a randomized complete block design. Birds in each pen were raised on litter naturally contaminated with a mixture of Eimeria acervulina, Eimeria maxima, and Eimeria tenella. The results demonstrated that some performance loss occurred in the salinomycin Day 28 treatment. Means for weight gain and feed conversion on Day 49 were improved (P < 0.05) in each diclazuril treatment in comparison with the salinomycin and unmedicated treatments. Feed conversion means in the diclazuril Day 35 and Day 42 treatments were improved (P < 0.05) in comparison with the diclazuril Day 28 treatment, indicating that shorter withdrawal times provided further benefit.