ASABE Technical Library - Abstract

Abstract. Conductive cooling for dairy cattle holds promise as a way to relieve heat stress in dairy cattle. Proposed conductive cooling systems vary in their design for types and thicknesses of bedding and surface temperature of the conductive cooling surface. Our conductive cooling system circulates 4.5°C water through modified DCC waterbeds, and this system performed favorably when tested with lactating, heat-stressed dairy cows using 0.5 cm of sawdust bedding. For this experiment, heat flux and moisture content of bedding were measured for our conductive cooling system using dry sand and dry sawdust bedding with thicknesses of 0.5 cm, 2.5 cm, 7.5 cm, and 20 cm. For each treatment, heat flux was measured in three locations each on two of the beds with flux meters underneath thermostatically controlled heating pads set to 37.8°C. Sandbags weighing 20 kg were placed on top of the heating pads to simulate a cow lying down. Heat flux was also measured for no bedding. Bedding moisture content was measured after equilibrium was achieved and again 2 hrs later for both 60% and 80% relative humidity with an air temperature of 21°C and windspeed of 0.04 m/s. Duplicate bedding surface samples were taken from three locations on each of four waterbeds and dried to determine moisture content. Two of the four beds were cooled with 4.5°C water, and the other beds were control beds with water at ambient temperature. Control and cooled beds were switched after one set of data was collected, and the experiment was repeated with control and cooled beds opposite.Heat flux for no bedding averaged 1635 Watts/m^2. Sand that was 0.5 cm thick did not statistically significantly reduce the flux, but 2.5 cm, 7.5 cm, and 20 cm of sand reduced the flux by 47%, 77%, and 90%, respectively. Sawdust bedding reduced flux by 37% for 0.5 cm, 74% for 2.5 cm, 96% for 7.5 cm, and 97% for 20 cm. Condensation was observed for the 0.5 cm thick bedding for both bedding types and humidity levels. For 2.5 cm sand at 80% humidity, condensation occurred at the bed surface and at the top of the bedding, but for 2.5 cm sawdust condensation only occurred at the bed surface. Other treatments did not yield measureable amounts of condensation..