Litter samples were collected once every week, excluding the day of water spray and litter turning, from 5 different sites per house and pooled before measurement. The litter moisture content was determined by the loss of weight on drying. In brief, the pooled litter was weighed, dried for 15 min in an Electric Drying Oven (Model: FS-405, Advantec Co., Ltd., Saijyo, Japan) and weighed again. The decrease in weight was recorded as moisture content (%).