Influence of weather conditions on milk production and rectal temperature of Holsteins fed two levels of concentrate.

Twelve lactating Holstein cows in 2nd lactation were allocated randomly, six each, to two feeding treatments: high concentrate (1 kg dairy concentrate to 2 kg milk produced) and low concentrate (1 kg dairy concentrate to 4 kg milk produced) from 7 to 106 days postcalving. Forage and water were provided ad libitum. Milk and butter fat yields and rectal temperatures were examined in relation to 9 weather variables (minimum, maximum and mean temperatures, relative humidity, temperature-humidity index (THI), radiation, wind velocity and mean temperature of the previous day). Averages for milk yield, fat yield and rectal temperature were respectively 20.4 kg, 0.7 kg and 38.9 degrees C for the high concentrate treatment and 18.4 kg, 0.6 kg and 38.6 degrees C for the low concentrate treatment. Whether conditions accounted for 5.6%, 0.8% and 10.8% of the day to day variation in milk yield, fat yield and rectal temperature, respectively, for the high concentrate group and 29.4%, 9.7% and 0.6%, respectively, for the low concentrate group. Only measures of ambient temperature, especially mean temperature, were closely associated with these traits.