Table 2.

Example of different types of probiotics and their application in poultry to ameliorate intestinal morphology under heat-stressed conditions.

Probiotic Strains	Biological Performance under Heat Stress Conditions	Reference
Bacillus subtilis PB6	Increased the population of Bifidobacterium and Lactobacilli in the gut 3 × 107 CFU/kg (broiler chicken) Increased villus height, crypt depth, and promoted surface area for absorption in duodenum and ileum (broiler chicken)	[64]
Bacillus licheniformis	Restored the impaired villus-crypt structure and maintained normal surface area in the small intestine (laying hens) Avoided the impairment and regulated the stability of the epithelial intestine (layer chickens)	[45]
Probiotic mixture (B. licheniformis, B. subtilis, L. plantarum	Reversed the reduced villus height, crypt depth, and surface area structure (broiler chicken) Increased beneficial bacterial population Lactobacillus and Bifidobacterium and decreased injurious bacterial population Coliforms in small intestine (broiler chicken)	[74]
Probiotic mixture (L. pentosus ITA23 and L. acidophilus ITA44)	Increased the population of beneficial bacteria Lactobacillus, Bifidobacterium, Enterococcus (broiler chicken) Decreased the population of E. coli, respectively, in the gut (broiler chicken)	[141]