Effects of feeding nitarsone-medicated ration on the establishment of nematode parasites in the chicken

Birds were acquired at 1 d of age and given standardized doses of Ascaridia galli, Heterakis gallinarum, and Capillaria obsignata eggs containing infective larvae at 14, 21, and 28 d of age, or were left as uninfected controls. Subgroups of infected birds were placed on one of several ad libitum rations: 1) unmedicated throughout the study, 2) medicated from 42 to 56 d of age, and 3) medicated from 7 to 56 d of age. The uninfected control birds were placed on the unmedicated ration throughout the study. Medication was with nitarsone (Histostat) at a dietary level of 0.01875% (170.3 g/ton). All experimental groups were managed and investigated evenly. Parasite egg counts were determined for feces collected during the study, and birds were killed at 42, 63 and 65 d of age for parasite collection and quantification. No A. galli eggs were observed in the feces. Capillaria obsignata egg counts for the feces revealed no effect of treatment. Heterakis gallinarum egg counts for feces displayed a negative treatment effect at the end of the study only (P ≤ 0.05). No nematocidal effect of nitarsone was demonstrated for Capillaria or Heterakis burdens, but a treatment effect was significant (P ≤ 0.05) for Ascaridia relative to the number of adult parasites per bird, adult female size, and quantity of developed eggs per adult female.