Effects of Bacillus subtilis and Lactobacillus on growth performance, serum biochemistry, nutrient apparent digestibility, and cecum flora in heat-stressed broilers.

This study investigates the effect of dietary Bacillus subtilis and Lactobacillus on the growth performance, serum biochemistry, nutrient apparent digestibility, and cecum flora of broilers under heat stress (HS) and provides a theoretical basis for the application of probiotic additives to alleviate the stress of poultry under HS. A total of 200 Cobb broilers were randomly assigned to four replicates of 10 broilers in each of the five groups. The growth performance, serum biochemistry, nutrient apparent digestibility, and cecum flora of broilers were detected on the 28th, 35th, and 42nd days, respectively. Results revealed that HS can affect the growth performance and serum biochemical indexes of broilers, lowered the number of intestinal bifidobacteria and Lactobacillus, and increase the number of Escherichia coli in comparsion to the CON group. Compared with the HS group, the ADFI of HS broilers in the BS group and the combined group significantly increased (P < 0.05) at 22-28 days of age, and the serum calcium and phosphorus increased (P < 0.05) significantly at 42 days of age. Meanwhile, the number of Lactobacillus in the BS group and LAB group increased significantly at 42 days of age (P < 0.05). The number of Escherichia coli in the LAB group and combination group decreased significantly at 35 days of age (P < 0.01). The present study revealed that the addition of Bacillus subtilis or Lactobacillus to diets increased ADFI, increased probiotic counts, and lowered Escherichia coli counts in HS broilers, while probiotics alone work well.