Table 2.

Antibiotic alternatives and their functions and effects in broiler production. FCR, feed conversion ratio and BW, body weight.

Antibiotic Alternatives	Active Ingredients		Basic Functions	Advantages	Disadvantages	Effects on Broiler	References
Probiotics	Bacillus subtilis, Enterococcus faecium, Lactobacillus acidophilus, Bacillus licheniformis, Bifidobacterium bifidum		Appetite and digestion, stimulant, antioxidant	Modulation of immunity Proliferation of beneficial bacteria Increased nutrient absorption No development of resistance Stable	No antibacterial properties	Increased body weight and FCR Improved absorptive surface of duodenum and ileum Increase nutrient retention	Ghasemi et al. [72]; Giannenas et al. [73]; Levkut et al. [76]; Latha et al. [77]; Zhang et al. [78]; Popova [79]; Liu et al. [80]
Prebiotics	Fructo-oligosaccharides (FOS), inulin, galacto-oligosaccharides (GOS), trans-galacto-oligosaccharides (TOS)		Digestion, stimulant	Modulation of immunity Proliferation of beneficial bacteria No development of resistance Stable	No antibacterial properties Unknown nutrient absorption	Increased growth performance Stimulation of metabolic activity in intestine	Jozefiak et al. [82]; Morales-Lopez et al. [83]; Zhang et al. [84]; Baurhoo et al. [86]; Baurhoo et al. [87]
Organic acids	Citric acid		Digestion, stimulant, increased feed efficiency	Antibacterial properties Modulation of immunity Increased nutrient absorption Stable	Development of resistance is rare	Increased body weight Improved ileal nutrient digestibility, cell proliferation, and epithelial and villi height	Kum et al. [88]; Hassan et al. [90]; Nava et al. [91]; Adil et al. [92]; Chaveerach et al. [93]; Izat et al. [94]; Mohammadagheri et al. [95]; Hu and Guo [97]; Qaisrani et al. [98]
	Ascorbic acid
	Propionic acid and sodium bentonite
	Butyrate
Amino acids and enzymes	Phytase, lysins		Digestion, stimulant	Antibacterial properties Modulation of immunity		Improved growth performance	Cowieson et al. [99]; Fenton et al. [100]; Rios et al. [101]; Volozhantsev et al. [102]
Phytogenic feed additives	Pepper	Piperine	Digestion, stimulant	Modulation of immunity Antibacterial properties Proliferation of beneficial bacteria Increased nutrient absorption No development of resistance Stable		No effect on live performance	Windisch et al. [103]; Frankic et al. [104]; Toghyani et al. [105]; Li et al. [106]; Mpofu et al. [107]; Kirubakaran et al. [108]; Khattak et al. [109]; Peng et al. [110]; Pirgozliev et al. [111]; Jerzsele et al. [112]
	Garlic	Allicin	Digestion, stimulant, antiseptic			Higher body weight
	Ginger	Zingerone	Gastric stimulant			No effects on performance
	Rosemary	Cineol	Digestion, stimulant, antiseptic, antioxidant			Improved live weight and feed efficiency
	Thyme	Thymol	Digestion, stimulant, antiseptic, antioxidant			No significant effect on BW/FCR
	Mint	Menthol	Appetite, digestion, stimulant, antiseptic			Decreased serum total cholesterol, triglycerides, and low-density lipoprotein concentration
Nanoparticles (NPs)	Silver NPs		Digestion, Stimulant	Modulation of immunity Antibacterial properties Proliferation of beneficial bacteria Increased nutrient absorption No development of resistance Stable	Some toxicity in broilers	Increased body weight and FCR	Gangadoo et al. [114]
	Selenium NPs						Fuxiang et al. [115]; Hu et al. [116]; Cai et al. [117]; Mohapatra et al. [118]; Bagheri et al. [119]; Selim et al. [120]
	Copper NPs						Gangadoo et al. [114]; Mroczek-Sosnowska et al. [121]
	Metal NPs such as zinc oxide, zirconium dioxide, and platinum						Akbar and Anal [122]; Ravikumar and Gokulakrishnan [123]; Prasek et al. [124]
	Zn-bearing zeolite clinoptilolite NPs						Tang et al. [125]
	Nanosuspensions of clay minerals						Elshuraydeh [126]