Assessment of phytobiotic supplementation to modulate pen-level infection dynamics of Swine Dysentery using a challenge model

Abstract Gut health is a key determinant of profitability and sustainability in swine production. Swine Dysentery, caused by Brachyspira hyodysenteriae , is a severe enteric disease affecting animal health and performance. Restrictions on antimicrobial use have increased the need for alternative strategies, including plant-derived phytobiotics, which may support intestinal health and host responses. This study evaluated the efficacy of a novel phytobiotic feed additive in an experimental Swine Dysentery challenge model. Thirty weaned piglets were assigned to a challenged positive control group, a challenged phytobiotic-supplemented group, or a non-challenged phytobiotic-supplemented negative control group. Faecal shedding, clinical signs, growth performance, and colonic histopathology were assessed over 28 days post inoculation. All challenged pigs shed B. hyodysenteriae at least once. However, phytobiotic-supplemented pigs showed fewer qPCR-positive faecal samples than positive controls, shorter shedding, and reduced proportions of diarrhoeic and dysentery-like faeces. Fewer pigs were classified as Swine Dysentery positive in the phytobiotic group, although not significantly. Histopathology showed reduced intraluminal crypt infiltrate, reaching values comparable to the negative control. Growth performance differed moderately among groups. Overall, the additive did not prevent infection but reduced bacterial shedding and clinical outcomes, supporting its use as a complementary strategy for Swine Dysentery control under experimental challenge conditions.