Stimulus Birds
Birds given an LPS immune challenge significantly reduced the total grams of food they consumed post-injection (Figure 5, day*treatment: χ2 = 7.22, P = 0.007). This reduction in overall food intake was also macronutrient specific. Specifically, LPS-challenged birds did not alter their consumption of the high lipid diet (Figure 5A, all P≥ 0.557), but significantly decreased consumption of the high protein diet (Figure 5B, day*treatment: χ2 = 5.43, P = 0.020). Body mass also differed over time in the two treatments (Figure S8, day*treatment: χ2 = 10.37, P = 0.001), where LPS-injected birds lost weight in the days following the immune challenge. Fat score generally increased over time in saline-injected birds but was more variable over time in LPS-injected individuals (Figure S9, day*treatment: χ2 = 4.09, P= 0.043). Body mass and fat score did not vary between male and female finches (sex: all P ≥ 0.263).
Birds given an LPS immune challenge had lower bacterial richness (Figure S10; treatment: χ2 = 10.048, P adj = 0.008) and bacterial diversity (Figure S10; treatment: χ2 = 11.446,P adj = 0.004) than saline-injected birds, however this difference was already apparent prior to experimental treatment (Table S4). Neither the amount of fat diet consumed or protein diet consumed influenced observed richness or Shannon diversity (all P≥ 0.218). There was no effect of treatment, sampling timepoint, or interaction between treatment and time on the Bray-Curtis dissimilarity index, community membership (unweighted UniFrac), or community composition (weighted UniFrac) (Table S5, Figure S11: PERMANOVA, allP adj ≥ 0.657). When examining how treatment affected the abundance of different bacterial taxa, birds in the control group (saline) did not have any significant changes in bacterial relative abundances at the phylum (Figure S12) or genus (Figure S13) level between day 0 and day 5 samples (Table S6: allP adj ≥ 0.381). Additionally, there were no significant effects of an immune challenge with LPS on bacterial abundances at the phylum (Figure S12) or genus (Figure S13) level when comparing pre-treatment (day 0) samples to post-treatment (day 5) samples (Table S6: all P adj ≥ 0.775).