Regulatory capacities of a broiler and layer strain exposed to high CO 2 levels during the second half of incubation

Abstract

It has been shown that during embryonic chicken ( Gallus gallus) development, the metabolism of broiler embryos differs from that of layers in terms of embryonic growth, pCO 2/pO 2 blood levels, heat production, and heart rate. Therefore, these strains might adapt differently on extreme environmental factors such as exposure to high CO 2. The aim of this study was to compare broiler and layer embryos in their adaptation to 4% CO 2 from embryonic days (ED) 12 to 18. Due to hypercapnia, blood pCO 2 increased in both strains. Blood bicarbonate concentration was ~ 10 mmol/L higher in embryos exposed to high CO 2 of both strains, while the bicarbonates of broilers had ~ 5 mmol/L higher values than layer embryos. In addition, the pH increased when embryos of both strains were exposed to CO 2. Moreover, under CO 2 conditions, the blood potassium concentration increased in both strains significantly, reaching a plateau at ED14. At ED12, the layer strain had a higher increase in CAII protein in red blood cells due to incubation under high CO 2 compared to the broiler strain, whereas at ED14, the broiler strain had the highest increase. In conclusion, the most striking observation was the similar mechanism of broiler and layer embryos to cope with high CO 2 levels.