Effects of Shower-Based Environmental Enrichment During a 35-Day Grow-Out Period on Production Performance, Stress Physiology, Fear Responses and Gut Health in Pekin Ducks

Abstract

Background and Objective: Pekin ducks exhibit a strong behavioral motivation for access to open water; however, commercial production systems in the United States typically provide only nipple drinkers. Overhead shower enrichment (SE) represents a potential alternative to ground-level water sources, yet its effects on production performance, physiological stress, behavioral fear responses and gut health remain incompletely characterized. The present study aimed to evaluate the effects of automated overhead shower enrichment on growth performance, physiological stress indicators, behavioral fear responses and ileal histomorphology in commercial Pekin ducks reared under standard management conditions in the United States.

Materials and Methods: Two replicated trials were conducted using a total of 640 Pekin ducklings (day 0-35). Birds were allocated to 16 pens per treatment, with 20 ducks per pen and assigned to either a shower enrichment group (SE; automated overhead sprinkler provided from day 7 to 35 at 30 min intervals for 10 h/day) or a nipple-drinker control group (CON). At day 35, outcomes assessed included growth performance (body weight and feed conversion ratio), physiological stress indicators (plasma corticosterone concentration, heterophil-to-lymphocyte ratio and bilateral asymmetry), behavioral fear responses (inversion and tonic immobility tests) and ileal histomorphology (villus height, crypt depth and villus height to crypt depth ratio).

Results: Body weight (2.73 vs. 2.67 kg, p = 0.12) and feed conversion ratio (1.525 vs. 1.532, p = 0.71) did not differ between the SE and CON groups. Similarly, physiological stress indicators, including heterophil-to-lymphocyte ratio (0.52 vs. 0.56, p = 0.59), composite asymmetry (1.23 vs. 1.25, p = 0.78) and plasma corticosterone concentration (10,814 vs. 10,653 pg/mL, p = 0.93), were not significantly affected by treatment. Behavioral fear responses were also comparable between groups (P > 0.05). Ileal villus height and the villus height to crypt depth ratio did not differ between treatments; however, ducks in the SE group exhibited significantly greater crypt depth than those in the CON group (132 vs. 86 μm, p = 0.007).

Conclusion: Shower enrichment did not adversely affect growth performance, physiological stress responses, or behavioral fear indicators in commercial Pekin ducks. The observed increase in ileal crypt depth, in the absence of changes in other histomorphological parameters, warrants further investigation. Overall, these findings indicate that overhead shower enrichment represents a welfare-enhancing, production-neutral strategy that is compatible with voluntary open-water certification standards.