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1. The aim of this study was to investigate if genetic predisposition to ascites interacts with changed incubation conditions, and how this might affect the post-hatch performance and ascites susceptibility. 2. An ascites sensitive (A) and resistant (E) broiler line were incubated under standard or high CO2 conditions (up to 4%) from embryonic d 10 onwards. After hatch, chicks were exposed to cold from the 15th day of the rearing period to increase the incidence of ascites. 3. The A line had a higher post-hatch body weight from week three, higher blood pCO2 from d 21, higher haematocrit at d 35 and d 42, and higher plasma corticosterone concentration from d 21 onwards, compared with the E line, regardless of incubation conditions, supporting the given selection criteria. Ascites mortality did not, however, differ between lines. 4. Incubation under high CO2 conditions during the second half of incubation increased the ascites mortality, decreased body weight from week 4 onwards, affected venous blood pCO2, decreased blood pO2 from d 31, increased haematocrit at d 35 and d 42, and lowered the thyroxine and triiodothyronine concentrations at most sampling days. These effects were observed in both lines. The results suggested a metabolic programming of CO2 incubated chickens which affected ascites susceptibility. [ABSTRACT FROM PUBLISHER]

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, pCO2/pO2 blood levels, heat production, and heart rate. Therefore, these strains might adapt differently on extreme environmental factors such as exposure to high CO2. The aim of this study was to compare broiler and layer embryos in their adaptation to 4% CO2 from embryonic days (ED) 12 to 18. Due to hypercapnia, blood pCO2 increased in both strains. Blood bicarbonate concentration was ~10 mmol/L higher in embryos exposed to high CO2 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 CO2. Moreover, under CO2 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 CO2 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 CO2 levels., (Copyright © 2010 Elsevier Inc. All rights reserved.)