Effect of a probiotic supplement (Bacillus subtilis) on struggling behavior, immune response, and meat quality of shackled broiler chickens exposed to preslaughter stress

ABSTRACT: This study aimed to investigate the impact of a dietary probiotic supplement on struggling behavior, immune response, and meat quality of shackled broiler chickens exposed to preslaughter stress. Two hundred and ten 1-day-old male Ross 708 broiler chicks were divided among 21 floor pens (10 chicks per pen). The pens were randomly distributed to 1 of 3 dietary treatments containing a probiotic, Bacillus subtilis, at 0 (control), 0.25 (0.25×), and 0.5 (0.5×) g/kg (n = 7). At the end of the experiment (d 35), birds were transported for a journey of 80 km to the abattoir, each crate contained 5 pen mates, 2 birds of them (2 bird per crate, total 14 birds per treatment) were randomly selected for testing. Struggling behavior measurements began after the birds had arrived at the abattoir. Serum and muscle samples (right leg and breast) were collected for immune response and meat quality parameters. The results indicated that probiotic supplemented broilers had lower breast muscle protein carbonyls and serum levels of IgM but higher breast muscle total antioxidant capacity (TAC) compared to those of controls. In addition, probiotic supplemented broilers’ leg and breast muscle had higher color lightness and greater water holding capacity (WHC%) with lower cooking loss (CL) and lower pH values (P < 0.05). Probiotic supplemented broilers’ breast and leg meat was also tastier (P < 0.05) compared to controls. There were no treatment effects on other measured parameters including struggling behavior, serum IgA and IgG concentrations, and breast muscle malondialdehyde (MDA) (P > 0.05). These results suggest that the probiotic supplement could be an alternative management tool for promoting broiler health and welfare by modifying immune response and meat quality.