| dc.description.abstract | Because the expected changes in the climate for the next decades assume an increase in temperature, dealing with the heat load in highly productive dairy cattle is an important challenge for the dairy industry. Dairy cows can adapt to temperatures above 25 to 26 degrees Celsius by using coping strategies. These coping strategies can be classified as physiological or behavioral modifications. Physiological coping strategies include increased respiration rate, panting, sweating, reduced feed intake and milk yield, increased drinking and deteriorated reproductive performances. The behavioral coping strategies, as well the central spearheads in this research, include increased (inactive) standing time, decreased lying time and decreased activity and movement overall. The aim of this study is to provide insight into the influence of environmental temperature on lying time, inactive time, number of steps, eating time and ruminating time in a moderate climate. Air temperature is classified into three groups; 5-15 degrees Celsius (T5-15), 15-25 degrees Celsius (T15-25) and >25 degrees Celsius (T>25). 6 Dutch dairy farms participated in this study. A total of 1170 Holstein cows were enrolled in this study. Results of this study showed that lying time decreased in T15-25 and T>25 with 30 minutes and 48 minutes per day respectively relative to T5-15. Inactive time decreased with 3,5 minutes per day in T15-25 but increased with 19 minutes per day in T>25, relative to T5-15. Cows started to walk more when temperatures increased with 1400 steps more per day in T15-25 and 1373 steps more in T>25 relative to T5-15. Eating time increased with 7,8 minutes per day in T15-25 but decreased with 11,8 minutes per day in T>25 relative to T5-15 and ruminating time decreased with 13 minutes per day in T15-25 and 10 minutes per day in T>25 relative to T5-15. The study results show the expected pattern, but not to the extent that was expected, based on previous reports. An explanation may be that the study assumes that cows have heat stress when the temperatures rises above 25 degrees Celsius, but the intensity and duration of the heat period have not been taken into account. This leads to, in this study many situations have been referred to as heat stress, which are not actually experienced as heat stress by dairy cows. Much more research needs to be done, for example into delayed effects of a high heat load and individual cow factors like milk production, lactation status and lactation number, to fully understand the behavior of cows in heat stress and to predict the behavior of dairy cattle in heat stress. | |
