Comparison of the thermoregulatory behaviours of low and high producing dairy cows in a hot environment

This study was carried out to compare the thermoregulatory behaviours of low and high producing dairy cows in a hot environment. Forty-one Holstein Friesian cows in their first lactation were allocated to two groups (n = 21 for group 1, n = 20 for group 2) on the basis of their milk production: low (<20 kg) and high (>25 kg). For a period of 4 weeks, and 2 days per week, the behaviour of each cow was registered every 10 min for 6 h (06:00–07:00 h, 10:00–11:00 h, 13:00–14:00 h, 16:00–17:00 h, 20:00–21:00 h and 23:00–00:00 h), recording the frequency of eating, drinking, ruminating, standing, resting and locomotion. When air temperature increased from 06:00 a.m. to 16:00 p.m., the frequencies of eating (31.7–17.4%) and ruminating (18.1–14.6%) decreased while standing (25.0–38.4%) and drinking (5.2–7.4%) increased in high producing dairy cow (P < 0.001). However, the changes the respective frequencies for low producing dairy cows were 21.5–15.7% for eating, 12.4–17.3% for ruminating, 23.1–33.8% for standing and 2.1–5.9% for drinking during the same times of day (P < 0.001).However, the changes the respective frequencies for low producing dairy cows were 21.5–15.7% for eating, 12.4–17.3% for ruminating, 23.1–33.8% for standing and 2.1–5.9% for drinking during the same times of day (P < 0.001). Overall, low and high producing dairy cows showed 14.3% versus 18.5% eating, 2.8% versus 4.5% drinking, 21.0% versus 19.4% ruminating, 28.4% versus 30.1% standing, 26.0% versus 24.1% resting, 5.5% versus 1.7% locomotor and 2.1% versus 1.7% other activities, respectively (P < 0.001).In conclusion, high producing dairy cows were more sensitive than low producing dairy cows as shown by the former cows spending more time in standing but less time resting and in locomotor activity.