Growth performance, heart characteristics and the incidence of ascites in broilers in response to carbon dioxide and oxygen concentrations

The effects of carbon dioxide (CO2) and oxygen (O2) concentrations on growth performance, heart characteristics and the incidence of ascites were studied in two similar experiments. In experiment 1, 600 male broilers were subjected to LOW CO2 treatment (600 ppm CO2 and 20.9% O2 at wk 0; increasing to 2500 ppm CO2 and decreasing to 20.65% O2 at wk 6) and 600 male broilers were subjected to HIGH CO2 treatment (6000 ppm CO2 and 19.7% O2 at wk 0; decreasing to 2500 ppm CO2 and increasing to 20.65% O2 at wk 6). In this experiment, final body mass and total feed consumption were not different between the two treatments. The birds in the LOW CO2 treatment pens did not have a reduced ascites score compared to the birds in the HIGH CO2 treatment, however, the right ventricle area (RVA) was significantly reduced at the lower level of CO2 exposure from 0.50 to 0.47 cm2 suggesting an increased stress on the heart as a result of ascites in the high CO2 treatment. In Experiment 2, 300 male broilers were subjected to the LOW CO2 treatment (600 ppm CO2 and 20.9% O2 at wk 0; increasing to 2500 ppm CO2 and decreasing to 20.65% O2 at wk 6) and 300 male broilers to HIGH CO2 treatment (6000 ppm CO2 and 19.65% O2 at wk 0; at 6000 ppm CO2 and increasing to 20.3% O2 at wk 5 and decreasing to 2500 ppm CO2 and increasing to 20.65% O2 at wk 6). In this experiment, body mass and rates of gain were the same for both treatments. With the more extreme exposure, there was no difference between the ascites score, RVA, and right ventricle mass between the LOW CO2 and HIGH CO2 treatments. Mortality did not differ between the LOW CO2 and HIGH CO2 treatments in either experiment. Under recommended management practices, CO2 levels should not be a contributing factor to the incidence of ascites.