Effect of in ovo feeding of γ-aminobutyric acid combined with embryonic thermal manipulation on hatchability, growth, and hepatic gene expression in broilers

Abstract

Objective: This study investigated the effects of <i>in ovo</i> feeding of γ-aminobutyric acid (GABA) and embryonic thermal manipulation (ETM) on growth performance, organ indices, plasma biochemical parameters, hepatic antioxidant levels, and expression of lipid metabolism-related genes in broilers.Methods: Two hundred and fifty eggs were assigned to one of four treatments: control eggs incubated under standard conditions (CON); eggs that received an <i>in ovo</i> injection of 10% GABA on day 17.5 of incubation (G10); thermally manipulated eggs between days 10 and 18 of incubation at 39.6°C for 6 h daily (TM); and eggs that received both treatments during incubation (G10+TM). After 28 days of rearing, five birds per treatment were selected for blood and organ sampling.Results: No differences were found in hatchability or growth parameters among different treatment groups. Hepatic gene expression of catalase (<i>CAT</i>) and glutathione peroxidase 1 (<i>GPx1</i>) was upregulated (p = 0.046 and p = 0.006, respectively) in the G10+TM group, while that of nuclear factor erythroid 2–related factor 2 (<i>NRF2</i>) was upregulated (p = 0.039) in the G10 group. In addition, the relative gene expression of NADPH oxidase 1 (<i>NOX1</i>) was significantly lower (p = 0.007) in all treatment groups than that in the CON group. Hepatic fatty acid synthase (<i>FAS</i>) levels and average daily feed intake (ADFI) of last week showed a positive correlation (r = 0.50, p = 0.038). In contrast, the relative gene expression of the extracellular fatty acid-binding protein (<i>EXFAB</i>) and peroxisome proliferator-activated receptor-γ (<i>PPAR-γ</i>) were positively correlated (r = 0.48, p = 0.042 and r = 0.50, p = 0.031) with the overall ADFI of birds.Conclusion: Taken together, the results of this study suggest that the combination of <i>in ovo</i> feeding of GABA and ETM can enhance hepatic antioxidant function in broilers.