Time-course analysis of the effect of paraprobiotics ABG0050 on the intestinal immune system of broilers

Abstract

With tightening regulations on antibiotic use in broiler production, paraprobiotics (inactivated probiotics) may be a promising alternative to antibiotics. The aim of this study was to analyze the effects of continuous intake of the paraprobiotic Lactiplantibacillus plantarum ABG0050 on growth-associated changes in the immune system of broilers at homeostasis and on the response to immune stimulation. Eighteen three-day-old broiler chicks were divided into two groups: 1: basal diet (Ctrl), 2: basal diet with 0.01 % paraprobiotic ABG0050 (LB). They were reared until 21 days of age, and feces, containing immune-related components secreted in the digestive tract, were collected over time to measure changes in immune markers. On the last day, five birds per group were immunologically stimulated using LPS. Five hours after LPS administration, the birds were dissected, and proventricular tissue was collected to evaluate the expression levels of immune factors at their primary production sites. Analysis of immune markers from fecal samples over time revealed that the expression of antimicrobial peptides AvBD (avian β-defensin) 7 and 12 significantly changed in the LB group, suggesting a modification of innate immunity. Correlation analysis between immune markers and body weight gain (BWG) showed both positive and negative correlations. The expression levels of AvBDs and cytokines in the proventricular tissue after LPS stimulation were measured, and a two-way ANOVA was conducted to analyze the effects of LPS and LB. The results showed no significant effects of either factor on AvBDs, but the expression of Th1-type cytokines, including IFN-γ, IL-6, and IL-12, was significantly increased by the LB factor without interaction with LPS, suggesting that the Th1/Th2 balance was shifted towards Th1 dominance regardless of LPS stimulation. In conclusion, the paraprobiotic ABG0050 modifies both the innate and acquired immune systems of broilers, and the changes in immune markers were also associated with BWG. Furthermore, the modulation of the adaptive immune system by ABG0050 was observed regardless of antigen stimulation.

Keywords: Broiler; Intestinal immunity; Paraprobiotics; Probiotics.

Fig. 1

Correlation network analysis between body weight gain and immune markers at 3, 6, 10, 14, 21 days of age. Yellow circles represent measured elements. Elements with a positive correlation are connected by red lines, while those with a negative correlation are connected by blue lines. The thickness of each line indicates the strength of the correlation coefficient. Data from all animals (n = 18) were entered. Asterisks show significant statistical correlation between the elements (*p < 0.05). Abbreviations: “bwg” denotes body weight gain, and “fec” denotes fecal.

Fig. 2

Concentration of Avian β-defensin 1, 2, 6, 7, 10 and Cathelicidin1 in proventricular tissue analyzed by LC/MS. On the last day of the study, four animals from each group were administered PBS intraperitoneally (Ctrl (LPS-), LB (LPS+)), while the remaining five animals had LPS administered intraperitoneally (Ctrl (LPS+), LB (LPS+)). Data are presented as the mean ± SD; n = 4-5. Asterisks (*) indicate significant differences in the two-way ANOVA (*p = 0.05).

Fig. 3

Concentration of cytokines in proventricular tissue analyzed by LC/MS. On the last day of the study, four animals from each group were administered PBS intraperitoneally (Ctrl (LPS-), LB (LPS-)), while the remaining five animals had LPS administered intraperitoneally (Ctrl (LPS+), LB (LPS+)). Data are presented as the mean ± SD; n = 4-5. Asterisks (*) indicate significant differences in the two-way ANOVA (*p = 0.05).