Combinations of herbs and probiotics as an alternative growth promoter: An in vitro study

Antibiotic growth promoters (AGPs) are added to animal feed to stimulate growth and increase livestock productivity. However, the regular use of antibiotics in animal diets has a considerable contribution to the occurrence of antibiotic resistance in livestock and humans. This study aimed to investigate the feasibility of red ginger (Zingiber officinale var. Rubrum), turmeric (Curcuma domestica), and wild ginger (Curcuma xanthorrhiza), Lactobacillus acidophilus, and Lactobacillus brevis as an alternative to AGPs.

The antibacterial activities and probiotic stimulatory effects of herbs were screened through the disk diffusion method and optical densitometry. The inhibitory ability of probiotics against pathogens was also tested through the disk diffusion method. The adhesion ability of probiotics was tested by mixing the optimal herbal combinations with broiler intestinal epithelial cells (10⁵ cells/ml). The cells were then subjected to Gram staining, and the number of adherent bacteria was calculated.

The test results showed that 3.13% ethanolic wild ginger extract had the highest inhibitory activity against Salmonella Enteritidis, followed by ethanolic red ginger extract and aqueous wild ginger extract at the same concentration. The three extracts also supported the growth of L. acidophilus and L. brevis. Further tests showed that the combination of 3.13% ethanolic red ginger extract had the highest inhibitory activity against S. Enteritidis, followed by ethanolic and aqueous wild ginger extract at the same concentration. The three extracts also supported the growth of L. acidophilus and L. brevis. Further tests showed that the combination of 3.13% ethanolic red ginger extract and 3.13% aqueous wild ginger extract had the best inhibitory effect on the growth of S. Enteritidis. The stimulatory effect of the combinations of herbal extract on the growth of L. acidophilus (0.18±0.00) and L. brevis (0.21±0.01) was better than those of individual extract, positive controls, and the glucose control. L. acidophilus and L. brevis had a weak inhibitory effect on the growth of S. Enteritidis (<6 mm). The adhesion ability of L. acidophilus (420.00±28.21) and L. brevis (259.33±24.03) was stronger than that of S. Enteritidis (202.00±14.00) under treatment with combined extracts.

The tested combinations of herbs and probiotics can adhere to the intestinal tract. Given this characteristic, herb and probiotic combinations may be developed as an alternative to conventional AGPs.