Enhancing pig growth and gut health with fermented Jatropha curcas cake: Impacts on microbiota, metabolites, and neurotransmitters

AbstractGiven the escalating global crisis in feed protein availability, Jatropha curcas L. cake has attracted significant interest as a viable alternative protein source in animal feed. This experiment was conducted to investigate the effects of fermented Jatropha curcas L. cake (FJCC) as a protein feed in the diet of pigs. A total of 96 growing pigs with an average weight of 27.60 ± 1.59 kg were divided into three dietary groups with varying FJCC inclusion levels (0, 2.5, and 5%) for a 28 d trial. Results showed that the diet with 5% FJCC (FJCC5) demonstrated significant improvements in average daily gain (p = 0.009), feed‐to‐gain ratio (p = 0.036), nutrient digestibility, and intestinal morphology. Furthermore, the FJCC5 diet resulted in a decrease in pH values in different gut sections (jejunum p = 0.045, cecum p = 0.001, colon p = 0.012), and favorably altered the profile of short‐chain fatty acids (SCFAs) with increased butyric acid content (p = 0.005) and total SCFAs (p = 0.019). Additionally, this diet notably decreased IL‐6 levels in the jejunum (p = 0.008) and colon (=0.047), significantly reduced IL‐1 levels in the hypothalamus (p < 0.001), and lowered IL‐1, IL‐6, and IL‐10 levels in plasma (p < 0.05). Microbiota and metabolite profile analysis revealed an elevated abundance of beneficial microbes (p < 0.05) and key metabolites such as 4‐aminobutyric acid (GABA) (p = 0.003) and serotonin (5‐HT) (p = 0.022), linked to neuroactive ligand‐receptor interaction. Moreover, FJCC5 significantly boosted circulating neurotransmitter levels of 5‐HT (p = 0.006) and GABA (p = 0.002) in plasma and hypothalamus, with corresponding increases in precursor amino acids (p < 0.05). These findings suggest that FJCC, particularly at a 5% inclusion rate, can be an effective substitute for traditional protein sources like soybean meal, offering benefits beyond growth enhancement to gut health and potentially impacting the gut‐brain axis. This research underscores FJCC's potential as a valuable component in sustainable animal nutrition strategies.