Effect of dietary wheat on the progression of Histomonas meleagridis infection in turkey poults.

Blackhead disease (Histomoniasis), caused by Histomonas meleagridis (HM), remains a major constraint to turkey production, and dietary factors that may influence disease progression are poorly defined. This study evaluated whether moderate wheat inclusion alters HM outcomes in turkey poults. A total of 432 one-day-old male turkey poults (Nicholas) were allocated to a 2 × 3 factorial arrangement with HM challenge (HM+ or HM-) and dietary wheat inclusion (0, 15, or 30%), yielding 6 treatments with 6 replicates (12 birds/replicate) for a 22-d experimental period. Diets were formulated to be isocaloric and isonitrogenous. Growth performance (BW, feed intake, BWG, FCR, and mortality) was assessed during d 0-12, d 13-16, and d 17-22. Additional parameters included infection rate and lesion severity (ceca and liver), clinical presentation, ileal digesta viscosity, intestinal histomorphology, jejunal cytokine/tight junction mRNA abundance, bone formation by calcein labeling, bone mineral density/content by DEXA, and cecal microbiota. Wheat × HM interactions were not detected for growth performance, mortality, lesion distributions, infection rate, clinical scores, or jejunal gene expression (P > 0.05). Wheat inclusion improved early performance prior to challenge. Poults fed 15% or 30% wheat had greater BW at d 12 and 16, with increased BWG and improved FCR during the pre-challenge/early infection periods (P < 0.05), whereas BW at d 22 was not influenced by wheat. In contrast, HM challenge markedly reduced BW, feed intake, and BWG, worsened FCR during d 17-22, and increased mortality (P ≤ 0.001). Dietary wheat did not mitigate HM-induced cecal and liver lesions, infection rate, or clinical presentation. HM challenge profoundly disrupted cecal microbiota, reducing alpha diversity and shifting community structure, characterized by expansion of Enterobacteriaceae and reduction of Lachnospiraceae. In conclusion, 15% wheat inclusion supported improved early growth and bone apposition under non-challenged conditions, but HM challenge overwhelmingly dictated disease severity and associated physiological and microbiome outcomes regardless of wheat level.