Energy and economic values of greenhouse sheds to replace winter grazing in northwestern China

To demonstrate that winter grazing in northwestern China is counterproductive to animal production, 40 ewes from two farms were kept throughout a winter inside makeshift greenhouse sheds while another 40 ewes were left grazing in the traditional manner. Results show that the average temperature inside the greenhouse was 10, 14 and 4°C higher than outside at 9 am, 12 noon and 9 pm, respectively (all P  < 0.001), and that ewes inside the greenhouse lost 3 kg less bodyweight than those outside ( P  < 0.001). An analysis using the authors' bioeconomic model suggests that the proposed method can save 2.4 MJ day −1 head −1 of metabolizable energy and, at the gross economic benefit of 1191 yuan or $189 year −1 , the initial cost of 3000 yuan or $477 can be paid off within three seasons.