Butyrate is a short-chain fatty acid with considerable benefits to gut health, and in recent years has been commonly used as an alternative to antimicrobials in agricultural animal production. In this thesis, we assessed the protective effects of sodium butyrate (NaB) on larval zebrafish during a lethal Pseudomonas aeruginosa polysaccharide (LPS) challenge and elucidated potential protective mechanisms of action. Larval zebrafish were pre-treated with 3 concen-trations of NaB for 24 hours at 72 hours post fertilization (hpf), and then immune challenged with 60 μg/mL of LPS at 96 hpf. Our results demonstrate that larval zebrafish exposed to 6000 μM NaB prior to a lethal LPS challenge experi-enced significantly increased survival, and exposure to 6000 μM NaB significantly down-regulated the pro-inflammatory cytokine tumor necrosis factor α (TNF-α). Findings from this thesis are consistent with the beneficial effects of NaB in other vertebrate species and support potential use of NaB in aquaculture.