Case Study: Water budget of a dairy farm with a tie-stall barn for milk cows and summer pasturing of heifers and dry cows

Water use (i.e., pumped water) was measured over a full year on a small dairy farm consisting of ~34 lactating and ~39 nonlactating animals (calves, heifers, and dry cows). Crop production was rain fed and was not included in the analysis. Animals were housed in a tie-stall barn during the winter and cool season (mid-October to mid-May) and outdoors in a yard or pasture during the warm season. Annual average water use was 5,180 L/d, with 82% being drinking water and 18% for milking system cleaning. Distinct diurnal patterns of drinking water intake were observed for each animal group, which differed when cows were located indoors or outdoors. Seasonal changes in water intake were significant. Nonlactating animals accounted for 27% of whole-farm water intake in the summer (July-September). In the warm season, herd-scale milk production declined while water consumption increased. As a result, the whole-farm water used per liter of milk had a strong positive correlation with monthly average temperature humidity index (THI) and could have been additionally influenced by other factors such as herd composition, precipitation, feed intake, forage quality and availability, and day length. When THI was below 50, water use ranged from 4.3 to 4.8 L/kg of milk, and it increased to a maximum of 6.7 L/kg at a THI of 68. The annual average water use was 5.35 L/kg of milk. This study demonstrates that the water used per kilogram of milk produced was affected not only by changes in water use but also by changes in herd-scale milk production.