| The objectives of the current study were to evaluate the effectiveness of feeding a reduced emission diet (R) containing 6.9% of a gypsum-zeolite mixture and slightly reduced crude protein (CP) to 21-, 38-, and 59-wk old Hy-line W36 hens (trial 1, 2, and 3, respectively) on hen performance, emissions of NH3, H2S, NO, NO2, CO2 , CH4, non-methane total hydrocarbon, and apparent digestibility compared to feeding a commercial diet (C), and to compare different methods of estimating nutrient excretion from laying hens in environmental chambers. At each age, 640 hens were allocated randomly to one of eight environmental chambers for a 3-wk period. The C diet contained 18.0, 17.0, and 16.2% CP and 0.25, 0.20, and 0.20% Sulfur and the R diet contained 17.0, 15.5, and 15.6% CP and 0.99, 1.20, and 1.10% Sulfur in trials 1, 2, and 3, respectively. Average daily egg weight (56.3 g), average daily egg production (81%), average daily feed intake (92.4 g) and BW change (23.5 g), across ages, were unaffected by diet (P > 0.05). In trials 1, 2, and 3, daily NH3 emissions from hens fed the R diet (185.5, 312.2, and 333.5 mg/bird) were less than emissions from hens fed the C diet (255.0, 560.5, and 616.3 mg/bird; P < 0.01). Daily H2S emissions across trials from hens fed the R diet (4.08 mg/bird) were greater (P < 0.01) than from hens fed the C diet (1.32 mg/bird). Diet (P < 0.05) and age (P < 0.05) affected emissions of CO 2 and CH4. Averaged across diets the apparent digestibility of N was 53.4%. Apparent digestibility of S and P were lower (P < 0.05) in the R diet (18.7 and -11.41%, respectively) than in the C diet (40.71 and 0.30%, respectively). Across all ages and diets recovery of N, S, and P were 69, 63, and 102 %, respectively, using the environmental chambers method. These results demonstrate that diet and layer age influence air emissions from poultry feeding operations and the chamber method could be used as an effective method to estimate nutrient excretion for comparing different measurements and feeding strategies. |
