Poultry farmers in tropical, subtropical, and temperate climates have challenges due to heat stress caused by heat waves. Egypt's already dry climate will become even more severe due to climate change. The aim of the experiment was to examine the impact of N-acetyl cysteine (NAC) as antioxidant on growth performance, biochemical indicators, heat shock protein related genes and hepatic morphology for broiler chicks under heat stress. Two hundred and forty one-week-old male broiler chicks (Cobb 500) with an average initial body weight of 158.81±8.03 g were used in a completely randomized design with four treatments and ten replicates for 35 days. The basal diet was fed to the first group. The second (NAC1), third (NAC3), and fourth (NAC5) ones were dietary supplemented with 1, 3, and 5 g/kg NAC, respectively until 35 days old. Body weight (BW) and body weight gain (BWG) were improved ( p ˂ 0.05) in N-acetyl cysteine supplemented groups with at 3 g/ kg while feed conversion ratio (FCR) was improved in NAC3 and NAC5 respectively. Biochemical indices were improved by NAC supplementation compared to control group without negative effects on hematological parameters. Upregulation ( p < 0.001) of growth hormone related genes (growth hormone (GH), growth hormone receptors (GHR), and insulin-like growth factor 1 (IGF1)) was recorded in NAC3 group in comparison with other groups. Also, upregulation ( p < 0.05) of antioxidant-related genes (catalase (CAT), glutathione peroxidase 1 (GPX1), and superoxide dismutase 1 (SOD1)) of NAC3 group was shown. Meanwhile, the genes associated with heat shock proteins (heat shock transcription factor 1 (HSF1), heat shock protein 70 (HSP70), and heat shock protein 90 (HSP90) showed downregulations ( p < 0.05) in the NAC3 group compared to others. A notable reduction in congestion and erythrocytic extravasation was shown in the NAC3 group. Also, the morphology of the hepatocytes was more similar to normal. Collectively, dietary N-acetyl cysteine supplementation at a level of 3 g/kg ameliorates the adverse impacts of heat stress in broilers regarding growth performance, biochemical indicators, antioxidants and heat shock protein related genes and hepatic morphology.
EL-Barbary et al. (Sun,) studied this question.