The evaluation of risk and hazard map of hot environment for dairy cows on the effects of climate change

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We tried to estimate the decrease of milk volume used by the meteorological data in order to evaluate its actual condition with THI (Temperature-Humidity Index) at a cattle shed. We evaluated to use the values of 20 days moving average of THI index, because the heat stress doesn't affect immediately. A value of THI exceeds more than 71 means the decrease of the milk volume. In hot weather 1994, THI was shown more than 71 between the beginning of July and the end of September in western Japan region. This pattern was also shown in cool summer 1993. The account of the decrease of milk yield in 1994 period was 278 kg per cattle in the case of Kumamoto city, and it was shown high values in western Japan region, while low values in Hokkaido area. Therefore, the estimation of the cost for a step of the hot environment was about thirty thousand yen per cattle. On the other hand, we also investigated the actual wet condition at a cattle surface in the period that fine mist cooling was generally conducted in summer season in last year. The method was to take thermo tracer pictures of wet condition at a cattle surface and to measure the pixel number based on the difference of the surface temperature. In the case of fine mist cooling system at our cattle shed, the wet cattle surface area was small; the side that was easy to get wet was 40-50%, difficult to get wet was less than 10%, and wet cattle surface area altogether was about 30% of all cattle surface area.