Effects of γ-aminobutyric acid on aggressive behaviour, jejunum villus morphology, serum biochemical indicators and hippocampal neuropeptide mRNA levels in piglets at weaning with mixing

The effects of γ-aminobutyric acid (GABA) on weanling piglets after mixing stress were investigated and the underlying molecular mechanism was analyzed. Sixty weaning piglets were randomly assigned to either the control group (weaning and mixing with a 3 : 3 sex ratio) or the GABA supplement group (30 mg GABA/kg body weight/day + weaning and mixing with a 3 : 3 sex ratio). Aggressive behaviours have been recorded for 2 days and the number of lesions for 3 days. The diarrhea rate on day 6 post-weaning and mixing was analyzed. Serum biochemical indicators, antioxidant variables, jejunum villus morphology and mRNA levels of stress-related neuropeptide genes of the hippocampus were investigated. The GABA addition decreased serum adrenocorticotropic hormone concentrations (P < 0.05), aggressive behaviours of weaned piglets 5 h after mixing (P < 0.05), lesion scores over the entire 3-day period (P < 0.01) and diarrhea rate (P < 0.01) and improved jejunum villus integrity. Serum neuropeptide Y (NPY) concentration (P < 0.05) and total superoxide dismutase activity (P < 0.01) were increased in the GABA supplement group, whereas serum malondialdehyde concentration had a decreasing tendency (0.05 < P < 0.1), and glutathione peroxidase activity had an increasing tendency (0.05 < P < 0.1). The GABA treatment group had increased mRNA levels of NPY (P < 0.05) and peptide YY (PYY) (P < 0.05) in the hippocampus, which may contribute to insights into the regulatory mechanism of GABA in weaning and mixing stress. The addition of GABA is beneficial to reduce weaning and mixing stress in piglets, and NPY and PYY may mediate the process.