• It was revealed that the intravaginal injection of Lactobacillus johnsonii, a type of lactic acid bacteria, into the oviductal vagina of laying hens led to an increase in beneficial bacteria in the oviductal mucosa and a decrease in pathogenic microorganisms.
• This treatment enhanced the gene expression of claudin 1 and 3, which are involved in mucosal barrier function in the magnum and vagina of the oviduct.
• Conversely, the gene expression of avian β-defensin (AvBD) 10, 11, and 12, which are antimicrobial peptides, decreased in the mucosa of the magnum, uterus, and vagina.

The oviduct of birds opens into the cloaca along with the digestive tract, making the oviductal mucosa susceptible to pathogenic microorganisms present in the intestinal contents. Therefore, enhancement of the oviductal mucosal barrier function is crucial for the safe production of chicken eggs and meat. While lactic acid bacteria were known to enhance the mucosal barrier function of the chicken's intestinal tract, their effects on the oviductal mucosal barrier function was unclear. Hence, this study aimed to investigate the effects of directly intravaginally administering Lactobacillus johnsonii, a type of lactic acid bacteria, on oviductal mucosal barrier function.

White Leghorn laying hens (500 days old) were intravaginally administered L. johnsonii suspension (experimental group) or no bacteria (control group) into the oviductal vagina for 7 days (n=6). As a result, intravaginal administration of L. johnsonii led to ⓵ an increase in the proportion of beneficial bacteria and a decrease in pathogenic microorganisms in the vaginal mucosa, ⓶ an increase in the gene expression of claudin-1 and claudin-3 in the magnum and vaginal mucosa, and ③ a decrease in the gene expression of avian β-defensins (AvBD) 10, 11, and 12 in the mucosa of the magnum, uterus, and vagina.

These results suggest that the intravaginal administration of L. johnsonii to laying hens can improve the microbial composition of the oviduct, enhance mechanical barrier function through claudins, and contribute to defense against pathogenic microbial infections in the oviduct. On the other hand, it was also revealed that intravaginal administration of lactic acid bacteria does not contribute to the enhancement of barrier function via AvBD in the oviduct.
 

• Journal: Poultry Science
• Title: Intravaginal injection of Lactobacillus johnsonii may modulates oviductal microbiota and mucosal barrier function of laying hens
• Authors: T. Nii, T. Shinkoda, N. Isobe and Y. Yoshimura
• DOI: org/10.1016/j.psj.2023.102699