Dietary manipulation can substantially lower ammonia emissions from laying-hen manure. However, such dietary changes would be of little value if the changes cause inferior egg production and hen performance. Therefore, the objective of this study was to evaluate the effect of a diet containing EcoCal ^TM (gypsum and zeolite, at 3.5% inclusion rate), which has been shown to lower ammonia emission in laboratory-scale testing, on hen production performance as well as on gaseous emissions, in commercial high-rise laying-hen houses in Iowa. A companion paper (A.S. Leaflet R2450) describes the effect of the EcoCal diet on ammonia (NH3), hydrogen sulfide (H2S), and carbon dioxide (CO2) emissions. Comparative data were collected from December 2006 to May 2007. The period was broken into 2-wk increments for data analyses. There were differences between the control and EcoCal regimens for some 2-wk periods but no responses were consistently different between the two treatments during the 16-week time interval evaluated. A new phase of the study is ongoing for 2 additional years and subsequent analyses will help determine if hen production performance differences exist between the dietary regimens.