Effects of multimodal early-life stress on transport-induced responses in Pekin and Muscovy ducks

This study investigated whether exposure to multimodal early-life stress modifies physiological stress responses, fear behaviour and selected caecal bacterial populations in Pekin and Muscovy ducks subjected to road transportation under tropical conditions. A total of 416 one-day-old male ducklings (Pekin, n = 208; Muscovy, n = 208) were assigned to early-stress (ES) or non- early-stress (NES) treatments from day 3 to day 14 of age. Early-stressed ducks were exposed daily for 3 h to a combination of crating, mild cold (24 ± 1 °C), noise (100 dB), and darkness. On day 42 of age, ducks were either transported for 3 h or remained in their home pens. We evaluated serum corticosterone (CORT) and heat shock protein 70 (HSP70) levels, tonic immobility (TI) responses, selected caecal bacterial populations, and growth performance. Early-life stress did not affect growth performance, feed efficiency or mortality. Muscovy ducks exhibited longer TI duration (P < 0.0001) and required fewer inductions (P < 0.0001) than Pekin ducks, suggesting breed-related differences in fear responses. However, neither early-life stress nor transportation affected TI duration (P = 0.3117) and the number of inductions (P = 0.6562). The CORT responses to transportation were strongly breed-dependent (P = 0.0004). Pekin ducks showed higher corticosterone concentrations than Muscovy ducks, and early stressed Pekin ducks exhibited lower CORT concentrations following transportation than non-early-stressed transported ducks. In contrast, early-life stress had little effect on CORT responses in Muscovy ducks. Serum heat shock protein 70 concentrations were not affected by early-life stress or transportation (P = 0.4027). Ducks not exposed to early-life stress and subsequently transported showed the lowest caecal Lactobacillus spp. counts (P = 0.0050). The results suggest that early-life stress across multiple modalities can reduce physiological stress responses triggered by transportation and promote gut microbial stability in Pekin ducks while maintaining their performance. In contrast, Muscovy ducks showed minimal additional advantages, underscoring the breed-specific responses to early-life conditioning strategies.