*2.5. Fecal Slurry*

Feces were collected from single combed white Leghorn chickens housed at the Texas A&M University Poultry Research Center. Five hundred grams of organic matter, 500 mL of *Salmonella* Typhimurium (ST) and 500 mL of tap water were mixed. The ST was cultured in tryptic soy broth (Becton Dickinson and Company, Franklin Lakes, NJ, USA) for 24 h at 37 ◦C and passed every 8 h to be used to spike the fecal slurry before being blended and homogenized.

The final study, at the poultry processing facility, did not use the homogeneous fecal slurry method since the transport coops were recently contaminated by commercial broiler chickens.

## *2.6. Paint Roller Application*

The homogenous fecal slurry was blended and placed in a paint roller tray and a clean paint roller was used to apply the slurry onto the entrance of each compartment at a width equivalent to the length of one roller (23 cm). The slurry applied onto the transportation coops was given a 30 min dry time to simulate industry conditions.
