Quail development in in ovo and ex ovo conditions: Preincubation influences stress proteins and antioxidants

Extreme temperatures, whether excessively high or low, are critical environmental stressors for organisms, profoundly impacting cellular metabolism and homeostasis. The presented study addresses the effects of varying incubation conditions on the expression of key stress-related genes (HSP70, HSP90, and SOD1) during quail development. Quail eggs were incubated using three distinct methods: standard incubation at 38.2°C and preincubation at either 22°C or 30°C in both <i>in ovo</i> and <i>ex ovo</i> conditions. Results revealed a distinctive contrast in survival rates: embryos cultured <i>ex ovo</i> showed significantly lower viability (26.41 %) compared to the <i>in ovo</i> method (87.66 %). Among <i>ex ovo</i> groups, preincubation at 30°C yielded the highest survival rate (43.48 %), highlighting the critical role of optimal preincubation temperature. The preincubation period resulted in a notable increase in the total weight of embryos in the <i>in ovo</i> group when compared to the <i>ex ovo</i> group. Additionally, preincubation at 30°C resulted in increased weight of the heart and liver in the <i>in ovo</i> group. Gene expression analysis showed clear differences between incubation methods. While <i>in ovo</i> incubation led to uniformly increased gene expression across all examined organs (liver, heart, and breast muscle) at both preincubation temperatures, the <i>ex ovo</i> conditions exhibited mixed results: decreased gene expression in the liver (SOD1) and muscle (HSP70, SOD1) but notable increased in the liver (HSP70) and heart (SOD1). Our findings suggest that preincubating quail eggs at 30°C for 12 h is associated with improved survival under <i>ex ovo</i> conditions, providing insights into optimizing <i>ex ovo</i> incubation practices.