Supplemental illite or in combination with probiotics improves performance and gut health in broilers challenged with Salmonella typhimurium

This research aimed to investigate the impact of adding illite on its own or together with a <italic>Clostridium butyricum</italic> and <italic>Bacillus subtilis</italic> (CB) complex to the diets of broilers facing challenges from <italic>Salmonella enterica</italic> serotype <italic>typhimurium</italic> (ST). A total of 72 one-day-old Arbor Acres broilers with initial body weight (BW) of 35.28 ± 0.34 g were used in a 4-week experiment. They were assigned to four treatment groups (six replications, three birds each per cage): 1) NC, non-challenge control, birds fed with basal diet; 2) CC, ST challenge control, birds fed with basal diet; 3) IA, the CC with 1% illite alone (10 g/kg); 4) ICB, the IA with 0.1% CB (1 × 10⁸ CFU/kg). In the ST challenge treatments, all broilers were orally inoculated with a total of 1.5 mL and 2.1 mL ST (1×10⁷ CFU/mL) for 3 consecutive days on 8 and 15 d, respectively. Our results showed that the ST challenge reduced (<italic>p</italic> &lt; 0.05) broiler performance, dry matter digestibility, and villus height (VH) and increased the levels of heterophil, interleukin-6, and tumor necrosis factor-α in serum, and crypt depth (CD). However, additives counteracted ST-induced impairments (<italic>p</italic> &lt; 0.05) in broilers, the IA and ICB showed higher body weight gain (BWG) at 15 to 21 d, and lower feed conversion ratio (FCR) at 15 to 21 d and 1 to 28 d compared with the CC. Also, the IA and ICB showed lower (<italic>p</italic> &lt; 0.05) CD and higher (<italic>p</italic> &lt; 0.05) VH to CD ratio, and count of <italic>Lactobacillus</italic> in feces than the CC at 28 d. Additionally, unlikely IA, the ICB increased (<italic>p</italic> &lt; 0.05) the BW at 21 d and the dry matter digestibility at 28 d, while decreasing (<italic>p</italic> &lt; 0.05) the FCR at 8 to 14 d and count of <italic>Salmonella</italic> in feces at 14 and 28 d. In conclusion, illite alone and in combination with CB can be effective tools in alleviating ST infection. Our results suggest illite and probiotic can be used as feed additives for ST-challenged broilers, separately or in combination to improve performance and gut health.