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).