Dietary safflower seed oil supplementation modulates antiviral immunity in specific-pathogen-free chickens infected with fowl adenovirus serotype 8a.

Fowl adenovirus serotype 8a (FAdV-8a) is an important cause of inclusion body hepatitis in chickens, but nutritional strategies for enhancing host resistance remain poorly characterized. This study evaluated whether dietary supplementation with safflower seed oil affected growth performance, viral burden, and immune responses in specific-pathogen-free chickens infected with FAdV-8a. Chickens received a basal diet containing 1% corn oil or the same diet containing 1% safflower seed oil and were inoculated oculonasally with 10⁶ TCID₅₀ of the low-virulence FAdV-8a strain JL/170408 at 21 d of age. Safflower seed oil increased average daily gain during days 1-21 and average daily feed intake during days 1-21 and 21-45, without affecting feed conversion ratio. The safflower seed oil group developed an earlier antibody peak (12 vs. 16 dpi) and generally higher antibody levels. Hepatic viral DNA loads were lower in safflower seed oil-fed birds at 3 and 7 dpi, whereas differences in viral DNA loads in other tissues were limited. Safflower seed oil also produced tissue- and time-dependent changes in avian β-defensins, Toll-like receptors, cytokines, antioxidant-related genes, NF-κB signaling molecules, PPAR-γ, CD4, and CD8. Overall, safflower seed oil supplementation was associated with improved early growth, enhanced FAdV-specific antibody responses, lower hepatic viral DNA loads, and broad transcriptional changes in immune- and antioxidant-related pathways. These findings support a modulatory effect of safflower seed oil on antiviral immune responses, while the underlying mechanisms require direct functional validation.