Modeling heat loss from the udder of a dairy cow

• Mechanistic model that predicts heat loss from the udder of a cow was developed.
• Udder tissue temperature approached core temperature for an air temperature 37°C.
• The udder can be considered as a heat sink.
• Cow cooling could be done by cooling the udder only.

A mechanistic model that predicts sensible and latent heat fluxes from the udder of a dairy cow was developed. The prediction of the model was spot validated against measured data from the literature, and the result agreed within 7% of the measured value for the same ambient temperature. A dairy cow can lose a significant amount of heat (388 W/m2) from the udder. This suggests that the udder could be considered as a heat sink. The temperature profile through the udder tissue (core to skin) approached the core temperature for an air temperature ≥≥37 °C whereas the profile decreased linearly from the core to skin surface for an air temperature less than 37 °C. Sensible heat loss was dominant when ambient air temperature was less than 37.5 °C but latent heat loss was greater than sensible heat loss when air temperature was ≥≥37.5 °C. The udder could lose a total (sensible + latent) heat flux of 338 W/m2 at an ambient temperature of 35 °C and blood-flow rate of 3.2×10−3 m3/(s m3 tissue). The results of this study suggests that, in time of heat stress, a dairy cow could be cooled by cooling the udder only (e.g., using an evaporative cooling jacket).