The effect of dietary supplementation of a Bacillus-based direct fed-microbial on Pekin duck subjected to heat stress challenge

Limited research investigating the use of direct-fed microbials (DFM) to mitigate the effects of heat stress in Pekin ducks exists. This study evaluated the use of a DFM at different inclusion rates. Treatments included commercial-type basal diet (CON), or CON supplemented with 125, 250, 500, or 750 ppm DFM. On d 21–35, ducks were subjected to a cyclic heat stress challenge for 12 h/d. Performance, gait scores, footpad lesions, complete cell blood counts, total plasma corticosterone concentrations, fear testing, bone health, litter quality, and gut health were measured. Body weight on d 35 was lower for CON (p < 0.05) than all other treatments. Feed conversion (d 15–35) was higher (p > 0.05) in CON than all other treatments. Total plasma corticosterone concentrations and heterophil to lymphocyte ratios were greater for CON (p < 0.05) compared to all other treatments, indicating lower stress susceptibility in DFM treatments. The CON had lower villus height (p < 0.05) than the 125 and 250 ppm DFM treatments. There was a quadratic response observed with 500 ppm as the peak in performance and stress measures indicating it may be the optimum. These results indicate that DFM supplementation during heat stress can improve duck performance and welfare.