Diet composition and feed additives modulates redox status and mucosal immunity in newly-hatched broilers chicks

The plasticity of the digestive tract in the first days of life offers a unique window to early orientate digestive functions. Different feeding strategies can be considered to early modulate and improve chicken health and welfare while ensuring feed efficiency. In this trial, the effects of five additives, targeting specific biological functions namely vitamin E, butyrate, capsaicin, carvacrol, and xylo-oligosaccharides on digestive homeostasis were studied in diets based on maize and soybean meal (MS) or on wheat, distillery by-products and horse bean (WB). A total of 432 one-day-old chickens were distributed across 72 pens and reared until 10 days. Data were analysed using ANOVA to assess the effects of additives, diet, and their interaction on growth performance, intestinal enzymatic activities, redox balance indicators, gut morphology and gene expression in both the gut and plasma. Chickens fed the MS-based diet showed a lower feed conversion ratio (FCR) (-4.8%; P < 0.001) over the entire period compared to those fed the WB-based diet, independently of the feed additive supplementation. However, the effect of the additives in the digestive tract were partly dependent of the diet. Vitamin E and carvacrol reduced the activity of the jejunal alkaline phosphatase, only in animals fed the WB-based diet (-50.3% and − 58.6%, respectively; P = 0.001). In the jejunum, the expression of key oxidative stress and inflammation associated genes ( NOS2 , MYD88 , and SOCS1 ) was significantly increased in chickens subjected to the MS diet compared to those receiving the WB diet (respectively: +90.3%, + 78.3%, + 323.5%, all P < 0.001). Independently of the diet, vitamin E significantly decreased jejunal lipid peroxidation (-39.8%, P < 0.001) confirming its antioxidant properties. Capsaicin supplementation decreased plasma haptoglobin activity (-19.5%, P = 0.004). Only in the WB diet, vitamin E enhanced plasma total antioxidant status (+ 40.3%; P = 0.014). These findings demonstrate that digestive functionalities in young broilers chicks can be modulated early in life through specific feed additives, with effects partly influenced by the diet composition. These early effects on digestive functionality suggest the potential to modulate phenotypic trajectories from the earliest stages, with long-term consequences for performance, health, and welfare.