Effects of warm climatic periods on dairy cow behaviour and welfare in a maritime European climate

used to indicate points at which cattle will likely experience thermal stress (e.g., a THI threshold of 75 predicts thermal stress). However, high-yielding dairy cows that reside in temperate maritime climates may experience some degree of thermal discomfort below this threshold particularly when they are housed. Housing often results in high levels of humidity. The use of technology such as activity monitors and automated intake measures allow us to monitor responses. The aim of this study was to use technological solutions to assess behavioural changes in response to moderate increases in THI levels. Data from dairy cattle on an experimental unit were used. Data on daily lying times, lying bout frequency, step count, feed and water intake were extracted for 10 pairs of warmer (THI<65) and ten matching cooler (THI=43 to 60) periods. Each period was 3 or more days each, and warm and cooler periods were no more than 5 weeks apart to ensure that the data from the same animals were being compared. Results showed that total daily lying time was shorter during warmer periods than cooler periods (P<0.05; means and SEMs (h): warm: 11.4±0.04; cool: 12.0±0.04) with a tendency for cows to have more daily lying bouts in warm periods (P=0.08; (counts) warm: 12.1±0.1; cool: 11.9±0.1). However, there was no effect of THI level on the no. of steps taken by cows (P>0.05 (counts) warm: 858±6; cool: 856±6). Water intake was higher during warm periods (P<0.05: (l) = warm: 79.4±0.6; cool: 71.5±0.5). Milk yield was lower during warm periods than cool periods (P<0.05; (l): warm: 30.3±0.2; cool: 30.7±0.2). This suggests that behaviour and milk yield are adversely affected even in conditions that are not traditionally regarded as exceeding cows’ ability to cope with thermal challenge. Technological solutions aid in detection on cow thermal distress and may be used as a routine monitoring system.