Submitted to: International Symposium on Animal Genomics for Animal Health
Publication Type: Abstract Only
Publication Acceptance Date: 6/29/2007
Publication Date: 10/23/2007
Citation: Eicher, S.D., Davidson, M.K., Applegate, T.J., Patterson, J.A. 2007. TLR4, IL-1, and inos expression in coconut meal-fed broilers after an oral challenge with salmonella. [abstract] In: Proceedings of the International Symposium on Animal Genomics for Animal Health. Paris, France, October 23-25, 2007. CDROM.
Technical Abstract: Coconut meal is a potential immunomodulator, partially because of its lauric acid content. Chickens are commonly raised in confinement buildings, but a growing trend is to house birds in pasture systems where they may encounter different immunological challenges. Whether feeding coconut meal would be beneficial for chickens in each of the two systems, pasture or confinement, to circumvent or to combat a Salmonella challenge was tested. Sixty one-day-old broiler chickens were assigned to either a coconut meal diet or a standard corn/soy diet containing antibiotics in each of two studies. The first study was conducted with pasture raised broilers and the second with broilers in typical confinement housing. After receiving the diets for 4 weeks, birds were challenged orally with Salmonella 1x10^9. Six chickens from each dietary group were euthanized at 0, 6, 24 and 72 h after challenge and one cecal tonsil and a 3 cm segment of ileum near the ileal cecal junction were harvested for determination of toll-like receptor (TLR) 4, interleukin (IL)-1, and inducible nitric oxide synthase (iNOS) RNA expression. Since there was no replication between housing systems, they were not compared. The ileal-cecal junction had greater TLR4 expression at 4 h post-innoculation than did the antibiotic group (P < 0.001), but the relative abundance of TLR4 was not different between the treatments at 24 and 72 h and was not different than time 0 in the confinement system. Inducible NOS expression was greater for the coconut meal birds at 4 h, but the antibiotic birds had greater iNOS expression at 24 h in ileal-cecal junction tissue. Expression of IL-1 was greater for the antibiotic birds at 24 h, resulting from an increase in expression in this treatment and a decrease in expression in the coconut meal treatment. The TLR4 expression in the cecal tonsils was greater for the coconut meal birds (treatment and time effects, P < 0.001). The expression iNOs in the cecal tonsils was greater for the coconut meal birds at 4 and 24 h, but greater for the antibiotic fed birds at 72 h (P < 0.01). A treatment by time interaction was detected for IL-1 expression, with coconut meal birds expressing less at 4 h, but more at 72 h than the antibiotic fed birds. Expression of IL-1, iNOS, and TLR4 was greater for the coconut meal birds at 4 h post-innoculation (P < 0.001) in ileol-cecal junction tissues of pasture birds. The cecal tonsils also had greater expression of IL-1, iNOS, and TLR4 at 4 h post-innoculation for the coconut meal fed birds (P < 0.001 for IL-1 and TLR4, and P < 0.01 for iNOS). Coconut meal birds from pasture also expressed more TLR4 in cecal tonsils at d 0 (P < 0.001) and 72 h after inoculation (P < 0.02). These data show that the antibiotics were preventing an immediate response to the Salmonella inoculation, while the coconut meal birds were very responsive. When birds were raised in confinement, the effect of coconut meal feeding was more consistent, perhaps indicating greater environmental control. The response associated with the coconut meal feeding was rapid, detectable by 4 h after the inoculation. These data indicate that the coconut meal had caused an up-regulation of TLR4 in the cecal tonsils prior to the infection, creating a benefit of IL-1 up-regulation and iNOS by 4 h and a resolution of the response by 24 h. If coconut meal feeding has benefit, it appears to be more predictable in confinement housing.