Effects of Water Cup Cleaning on Drinking Behaviour, Water Intake, and Milk Yield of Lactating Dairy Cows in Tie-Stall Barns

Water cups in tie-stall barns often remain uncleaned for long periods, allowing organic matter and biofilms to accumulate, which may reduce drinking efficiency, defined as water intake per drinking event rather than drinking frequency, and increase hygienic risks, including potential bacterial contamination, in dairy cows. This study examined the short-term effects of cleaning heavily fouled water cups on drinking behaviour, water intake, and milk yield in lactating Holstein cows. Twenty-four cows were observed on a baseline day and again after a one-day adaptation period following cup cleaning, using a within-animal comparison. Cleaning significantly increased total daily water intake by approximately 5 L (p < 0.05) and water intake per drinking bout by approximately 2 L (p < 0.01), while drinking frequency, milk yield, and maintenance behaviours remained unchanged. Temperature–humidity conditions were similar across observation days, indicating that increased intake was attributable to improved water hygiene rather than environmental variation. Although cleaning enhanced drinking efficiency, the magnitude of increased water intake was insufficient to affect short-term milk yield. These findings demonstrate that regular water cup cleaning is a practical management practice that improves drinking efficiency and water hygiene, with potential implications for cow health and welfare.