Characterization of Gastrointestinal Microbiome of Full-Fed and Feed Withdrawal Broiler Chickens
Abstract: Feed withdrawal (FW) and water withdrawal (WW) are common practices within the poultry industry; however, the overall impact of FW and WW on the litter, carcass, and entire gastrointestinal tract (GIT) has not been widely established. The objective of this study was to compare the effect of a 12-hour FW and 6-hour WW on the litter, carcass, and GIT compartments to a non-feed withdrawal (NFW) group. Broilers (N = 14) were raised on the same litter until 42 days old, and then equally divided into FW (n = 7) and NFW (n = 7) groups. The NFW group remained on litter with continued access to food and water for 12 hours. The FW group remained on litter without food for 6 hours and was then transferred to transportation crates to remove water and simulate transport conditions for an additional 6 hours. At the end of 12 hours, all birds were humanely euthanized, with litter, carcass rinsates, and GIT samples being collected. Genomic DNA was extracted from all samples, with the V4 region of the 16S rRNA gene sequenced (2x250bp) using Illumina MiSeq. Bioinformatic analyses were performed using QIIME2-2025.7, establishing significance at P < 0.05 and Q < 0.05. FW carcasses exhibited greater microbial richness and evenness before scalding and plucking (P = 0.004, Q = 0.004 and P = 0.048, Q = 0.048, respectively), and Enterobacteriaceae was present in a greater abundance on the FW carcasses both before and after the processing steps (Log-fold change = 1.00 and 1.62). In the GIT, both the proventriculus and jejunum demonstrated significant differences in relative phylogeny between the two treatments (P < 0.05, Q < 0.05), while the ceca revealed a trending difference in relative microbial abundance (P = 0.1, Q = 0.1). The litter of the FW group exhibited a richer, more even community with distinct relative abundance and phylogenetic differences (P < 0.05, Q < 0.05). These findings indicate the extensive impact of FW not only on the GIT but on the litter and the carcass and may prove to be advantageous for pathogens. Further studies are necessary to determine the functional alterations that occur during FW, as well as the impact this process has on disease transmission.