Influence of amino acid-deficient diets with and without wheat middlings inclusion on the horizontal transmission of Histomonas meleagridis in turkey poults.

The objective was to evaluate the influence of 2 amino acid (AA)-deficient diets on Histomonas meleagridis horizontal transmission and disease progression in turkey poults reared in battery cages. On day-of-hatch (d0), turkey poults were weighed, randomized, and assigned to 2 treatment groups (10 cages/group). From d0-6, all turkeys were fed an unmedicated, nutrient-adequate, corn and soybean meal (SBM) turkey starter diet. From d6-33, turkeys were fed 1 of 2 unmedicated amino acid-deficient diets: 1) corn-SBM-based or 2) corn-SBM-wheat middlings (WM)-based. Diets were formulated to be isocaloric and contain the same concentrations of total Ca, non-phytate P, and digestible AA. A seeder challenge model was utilized to replicate transmission of H. meleagridis in battery cages. On d13, all poults were weighed and 12 poults/group were orally gavaged with 8.32mg/kg (1mL) fluorescein isothiocyanate dextran to assess intestinal permeability. Additionally, 2/8 poults/cage were randomly selected and challenged with 1 × 105H. meleagridis cells/0.5mL (seeders) and placed back into the cage with non-challenged counterparts (contacts). On d27, seeder poults were removed and liver and cecal lesion scores were recorded. On d33, all remaining contact poults were weighed, euthanized, and lesion scored. Differences in turkey performance, mortality, intestinal permeability, and infection rate were not observed between dietary treatments (P > 0.05). There was a diet × age interaction (P < 0.05), where there was a greater increase in AME and AMEn with age in diet 1 compared with diet 2. Seeder turkeys on diet 1 had higher (P < 0.05) cecal lesion scores compared with diet 2. Differences in lesion scores in contact turkeys were not observed (P > 0.05). Data from this study indicate that inclusion of WM in an amino-acid deficient diet did not increase horizontal transmission or disease severity compared to the amino-acid deficient corn-SBM diet. Since both diets were nutrient-restricted, these findings should be interpreted within the context of animo acid deficiency and do not determine the effects of restriction relevant to an adequate diet.