Reducing Stress Susceptibility of Broiler Chickens by Supplementing a Yeast Fermentation Product in the Feed or Drinking Water

: Reducing stress is an important goal in animal production. Previous research has demonstrated the ability of Original XPCTM to reduce the stress response of broilers during heat stress. Three trials were conducted to evaluate the effects of adding Original XPCTM to the feed or AviCareTM to the water on stress susceptibility of broiler chickens. Treatments included: control nonstressed (CNS), control stressed (CS), stressed with Original XPCTM (1.25 kg/metric ton feed, 0⁻42 days; XPC), and stressed with AviCareTM (160 mL/100 L drinking water, 0⁻42 days; AVI). All stressed treatments received the following stressors: live coccidiosis vaccination (day 1), reared on reused litter (days 0⁻42), and heat stress with feed/water withdrawal (12 h on day 18). Plasma corticosterone and heterophil/lymphocyte (H/L) ratio were determined from 60 birds/T on day 19, and 24 birds/T on day 41. Physical asymmetry was determined using bilateral bone measurements from 60 birds/T on day 41. Birds provided XPC or AVI had lower corticosterone and H/L ratios than CS (p < 0.05) on day 19 and lower corticosterone, H/L ratios, and asymmetry scores than both CNS and CS on day 41 (p < 0.05) in all three trials. Supplementing XPC or AVI improved broiler welfare measured by reduced stress indicators after acute heat stress or normal rearing stress in all trials.