Title section: 1-"The effect of the timing of exposure to Campylobacter jejuni on the gut microbiome and inflammatory responses of broiler chickens" Comment: I suggest the title is better to be (the difference in immune response of broiler chickens at 6 days and 20 days old after exposure to Campylobacter jejuni).

Abstract section: 2- The methodology is not present in abstract so it is not clear how the researchers do this work. Comment: The methodology should be added to abstract. 3-" The objective of this study was to compare the microbiota, inflammatory responses, and zootechnical parameters of broiler chickens not exposed to Campylobacter jejuni with those exposed either early at 6 days old or at the age commercial broiler chicken flocks are frequently observed to become colonized at 20 days old" Comment: the sentence from "are frequently observed to become colonized at 20 days old" is not relevant, if researchers mean after 20 days old exposure to campylobacter jejuni or another think. So should be more oriented.

Background section: 4- "The answer to this question appears to depend on the genetics of the host and varies with infecting Campylobacter strain" Comment: there are also other lines of evidence suggesting that external factors are responsible for the Campylobacter colonization pattern in broilers. It has been found in artificially inoculated birds that different C. jejuni genotypes may compete for colonization leading to a C. jejuni succession in broilers (Konkel et al., 2007). 5-" However, since the occurrence of a “lag period” is frequent, flock level evidence for early infection and shedding is limited [11]. It has been speculated that maternal antibodies provide protection from colonization by Campylobacter during the first 2 weeks of life but decline thereafter" Comment: After the lag-phase, chickens show an increased susceptibility to colonization with C. jejuni which coincides with a loss of maternally derived, circulating anti-Campylobacter IgY antibodies, suggesting that adaptive immunity is not critical in protecting broilers from colonization (Cawthraw et al., 2010). 6-" gain a better understanding of how the timing of Campylobacter colonization affects the microbiome and the innate and adaptive immune response" Comment: the paper need more reference about innate and adaptive immune response of chicken and I suggest this, https://biblio.ugent.be/publication/1888799/file/1888983.

Methods section: 7-" Seven birds from each group were euthanized for sampling at days 8, 15, 22, 28, and 35" Comment: the researcher remember different think in the background which is "The objective of this study was to compare the microbiota of chickens that were not exposed to Campylobacter, with those exposed either at a young age (6 days of age) or at the age at which birds often become positive in commercial production (20 days of age)".

Result section: Effect of C. jejuni colonization on cytokine and chemokine gene expression 8-" There was no significant change in the cytokine and chemokine expression in ileum tissues." Comment: actually if there is any change in cytokine and chemokine will estimate in blood or serum.

Discussion section: 9-"The TLG trial showed FCRs of 1.52 and 1.56 respectively for TLG1 and TLG2, whereas the TEG trial had FCRs of 1.48 and 1.45 respectively for TEG1 and TEG2." Comment: this is result not discussion. 10- "The fact that similar responses were present in all the birds despite the majority being culture negative for C. jejuni suggests that following administration of the bacteria, the organism is able to persist, affect shifts in the microbial community, and affect physiological change, but not necessarily multiply to the extent that it can be detected by culture from cecal content." Comment: the fact that the campylobacter jejuni cannot able to persist, affect shifts in the microbial community, and affect physiological change unless multiply to significant number make it easy to detect by culture.

Conclusion section: 11-" It has been suggested that the complex relationship that permits persistent, high-level cecal colonization of C. jejuni in its avian host without obvious pathology is a result of inefficiency within the chicken immune system combined with mechanisms that redirect the response toward tolerance [16]." comment: the reference should be deleted from conclusion. 12-Aknolegment should be added to paper.

Reference section: 13- reference number 10, 11, 14, 15, 24, 26, 28, 30, 36, 39, 45, 47, 48, 52, 53, needed website. 14- reference number 41, 42, 43 needed page number.