Greenhouse gas (GHG) and ammonia emissions are important environmental impacts from meat chicken houses. This study measured ammonia (NH3), nitrous oxide (N2O) and methane (CH4) in two trials from paired, commercial meat chicken houses using standard (control) and mitigation strategies. In Trial 1, emissions from houses with standard litter depth of 47 mm (LD47) or increased litter depth of 67 mm (LD67) were compared. When standardised to a 42-day-old bird, emissions were 11.9 g NH3/bird, 0.30 g N2O/bird and 0.16 g CH4/bird from the LD47 and 11.7 g NH3/bird, 0.69 g N2O/bird and 0.12 g CH4/bird from the LD67. Emissions per kilogram of manure N were 0.14 and 0.11 for NH3-N, 0.003 and 0.005 N2O-N and CH4 conversion factors were 0.08% and 0.05%. Total direct and indirect GHG emissions reported in carbon dioxide equivalents were found to be higher in LD67 in response to the elevated direct N2O emissions. Trial 2 compared the impact of reduced crude protein (CP19.8) and a standard diet (CP21.3) developed using least-cost ration formulation, on emissions. Emissions per bird for the CP19.8 diet were 7.7 g NH3/bird, 0.39 g N2O/bird and 0.14 g CH4/bird, while emissions from birds fed the CP21.3 diet were 10.6 g NH3/bird, 0.42 g N2O/bird and 0.19 g CH4/bird. Significant differences were observed only in the NH3 results, where emissions were reduced by 27% for the low-CP diet. Because of the low emission levels, total mitigation potential from indirect GHG emissions was relatively small in Trial 2, corresponding to 11 t carbon dioxide equivalents/year per million birds.