Abstract
This study was carried out to assess the impact of global warming on heifer growth performance in Japan. The animal experiment was conducted in the environmental laboratory. The relation between ambient temperature and predicted daily body weight gain was investigated, and it was found that at 26.4 and 28.8°C, the predicted daily weight gain decreased by 5 and 15%, respectively, compared to at 20.0°C and 60% relative humidity. The summer (July, August and September) data were analyzed with a program that illustrates the temperature range and area on the map. The database of “Climate Change Mesh Data (Japan)” was used to calculate the annual mean temperature under the climate change scenario at all 10×10 km mesh. From the present year to 2020's, 2040's and 2060's, the areas where the body weight gain reduced will expand to northerneastern Hokkaido area, and the degree of reduction will be accelerated with the passage of time, especially in July and August. The assessment of heifer's weight gain in August was estimated in the southern Kyushu area and the northerneastern Hokkaido area by temperature-humidity index. The body weight gain in the 2060's will decrease by 21% in the southern Kyushu area, but, the body weight gain in the 2060's will not be reduced in the northern-eastern Hokkaido area. Global warming will greatly affect heifer growth, and moreover greatly influence by the change of humidity in Japan.
