Dietary Bacillus subtilis-based direct-fed microbials alleviate LPS-induced intestinal immunological stress and improve intestinal barrier gene expression in commercial broiler chickens

Authors: GADDE, U - US Department Of Agriculture (USDA); OH, S - US Department Of Agriculture (USDA); LEE, Y - US Department Of Agriculture (USDA); Lillehoj, Hyun

Submitted to: Research in Veterinary Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/5/2017
Publication Date: 5/6/2017
Publication URL: http://handle.nal.usda.gov/10113/5685388
Citation: Gadde, U., Oh, S.T., Lee, Y.S., Lillehoj, H.S. 2017. Dietary Bacillus subtilis-based direct-fed microbials alleviate LPS-induced intestinal immunological stress and improve intestinal barrier gene expression in commercial broiler chickens. Research in Veterinary Science. 114:236-243.

Interpretive Summary: With an increasing concerns regarding the development of antibiotic resistance and efforts to promote the judicious use of antimicrobials in food-producing animals, there is a timely need for the development of viable alternatives that can ensure and maintain optimal animal health and performance. Direct-fed microbials (DFMs), often referred to as probiotics, are one such potential non-antibiotic replacement that has been studied extensively and used in commercial applications. In particular, Bacillus sp. have been shown to improve performance, positively modulate intestinal microflora, inhibit pathogen colonization, improve nutrient digestibility, and enhance immune activities in the gut of broiler chickens. In the present report, ARS scientists report the beneficial effect of dietary Bacillus subtilis-based probiotics on the performance, modulation of host inflammatory responses and intestinal barrier integrity of commercial broilers subjected to a stressful challenge. The results demonstrated that chickens fed diets with B. subtilis-based probiotics show significantly higher body weight at d15 of age compared to chickens fed non-supplemented diets or those supplemented with antibiotics. Detailed studies revealed that dietary probiotics modulated the inflammatory activities that occur in response to LPS challenge and play a role in the restoration of cytokine balance to minimize inflammation-induced damage. This information will advance the field of developing antibiotic alternative strategies for poultry production.

Technical Abstract: The present study investigated the effects of B. subtilis-based probiotics on performance, modulation of host inflammatory responses and intestinal barrier integrity of broilers subjected to LPS challenge. Birds at day 0 of age were randomly allocated to one of the 3 dietary treatments - controls, antibiotic (BMD), or probiotic (B. subtilis strain 1781) groups. At 14 days of age, half of the birds in each dietary treatment were injected with LPS @ 1 mg/kg body weight and the other half with sterile PBS. Body weight was measured at d14 (0hr), d15 (24hr post-LPS injection). Blood and ileum samples collected at 24hr post-LPS injection were used for determination of serum alpha-1-acid glycoprotein levels by ELISA, lymphocyte subsets in blood by flow cytometric analysis, intestinal cytokine, tight junction proteins, and mucin gene expression analysis by qRT-PCR. Birds fed probiotics weighed significantly higher than controls at 15 days of age irrespective of immune challenge. LPS challenge significantly reduced body weight gain at 24hr post-injection and the birds fed probiotics did not alleviate LPS-induced weight gain reduction. Serum alpha-1-acid glycoprotein levels were significantly higher in LPS injected birds and probiotic supplementation significantly reduced their levels. CD4+ lymphocytes were significantly increased in probiotic groups in the absence of immunological challenge, but were reduced during LPS challenge compared to controls. CD8+ lymphocytes were significantly reduced in probiotic fed birds. The LPS induced increased expression of cytokines IL8, TNFSF15 was reduced by probiotic supplementation, and IL17F, iNOS expression was found to be significantly elevated in probiotic fed birds subjected to LPS challenge. The reduced expression of tight junction proteins (JAM2, occludin and ZO1) and MUC2 induced by LPS challenge was reversed by probiotic supplementation. The results indicate that B. subtilis based probiotics differentially regulate intestinal immune and tight junction protein expression during states of immunological challenge.