Sustainable grazing systems and dairy production based on the efficient utilization of grassland ecosystems in Hokkaido, northern region of Japan

摘要

Hokkaido is a major area of dairy production in Japan. Recent heavy consumption of concentrates by dairy cattle has not only increased milk production but has also led to environmental pollution, indicating that the development of dairy production in Hokkaido has not been based on efficient utilization of the grassland ecosystem. Grazing is now being studied once again as a sustainable production system in harmony with the environment. Research under practical dairy farming conditions in Konsen-district and experiments at Hokkaido University, Sapporo, showed that milk production from pasture under rotational grazing was 3. 6 - 7. 1 t/ha on the dairy farms and 7. 2 - 12. 6 t/ha on the experimental farm. These large variations seemed to be due not only to fundamental differences in climate but also to differences in grazing management on each farm and differences in experimental treatments. Higher milk production from pasture than meadow could be achieved under a rotational grazing system when the intensity, frequency and timing of defoliation were appropriately manipulated. On the other hand, set stocking was shown to increase milk production per unit area of pasture compared with rotational grazing when cows were grazed at an adequate stocking rate and at the appropriate sward height of grazing initiation. For sustainability not only of pasture production but also the soil environment, a stocking rate of about 30 cow-hr/day/ha may be appropriate for both grazing systems in the central part of Hokkaido.