Development and evaluation of a thermoregulatory model for predicting thermal responses of dairy cows

This study developed a three-node mechanistic model to simulate processes of Holstein dairy cows physiological regulation and heat dissipation under various environmental conditions based on bio-physical laws. This model calculated the heat flow through three main nodes at the body core, skin and coat of a cow. Heat production by the animal and heat flow between the animal and the environment, including convection, long-wave radiation, skin evaporation and respiration, were calculated. Sub models of physiological regulation, including tissue resistance, respiration and sweating rate, were developed using the training dataset from an experiment conducted recently in climate-controlled respiration chambers, providing an improved modelling of the thermo-physiological process of dairy cows. The model requires information of climate and animal characteristics as inputs, and outputs body core, skin and coat temperatures. This model was evaluated through the testing experimental dataset. The root mean squared errors of prediction for body core and skin temperatures were 0.3 and 1.2 °C, respectively. This model was able to calculate dynamic changes in body core heat storage and the body and skin temperature variations. A simulation study was conducted on a dairy cow with 600 kg of body weight and 30 kg of daily milk yield with increasing ambient temperature at different relative humidity and air velocity levels. The predicted effects of environmental factors on the thermal responses were generally in line with the experimental results. The model is reliable to predict the thermal status of dairy cows and to predict the benefits of cooling methods and their limitations.