Intestinal oxidative injury, autophagy-related alterations, and apoptosis during early cage transfer in laying ducks

Cage rearing of laying ducks offers advantages for intensive production, but the early period after cage transfer can elicit marked stress responses. This study investigated intestinal morphology, antioxidant status, DNA oxidative damage, autophagy-related changes, and apoptosis during the first 10 days after cage transfer in Shaoxing laying ducks. A total of 120 100-day-old female Shaoxing ducks were assigned to floor-rearing (FR) or cage-rearing (CR) treatments. In vivo, CR produced time- and tissue-dependent intestinal changes. On day 5, villus height and crypt depth were reduced in the duodenum, villus height and the villus height-to-crypt depth ratio were reduced in the jejunum, and crypt depth was increased in the ileum (P < 0.05). Antioxidant enzyme activities were altered at selected time points, intestinal MDA was increased on day 5, and serum 8-OHdG was increased on day 5 (P < 0.05). Jejunal ROS accumulation, autophagosome formation, and an increased LC3-II/LC3-I ratio were observed in CR ducks. TUNEL staining showed increased apoptosis, and PARP-1 protein abundance was significantly increased on day 5 (P < 0.05), whereas Caspase-3 showed an upward trend without statistical significance. Transcriptomic analysis identified differential expression of genes including CAT, BNIP3, PPARA, TLR4, and NFKB1 and enrichment of pathways including AGE-RAGE and Toll-like receptor signaling. In vitro, H₂O₂ exposure reproduced selected oxidative-stress-, autophagy-related-, and apoptosis-associated changes. Together, these findings show that early cage transfer is associated with intestinal oxidative injury accompanied by autophagy-related and apoptosis-associated changes in laying ducks.