ヒマラヤにおける草地利用

抄録

In the Himalayas, domesticated yak is fed at an altitudinal range of 3,000 to 5,000m. Below this zone, the cow is more common. Hybrids are fed at an intermediate zone. In order to analyze the genetic basis of milk protein variation, milk samples were taken from the nak (female yak), cow and their hybrid. By principle component analysis, yak and a highland type of cow (kirmcome) were clearly distinguished from midland (shakzam) and lowland (palang) cows. Local Sherpa people may produce suitable animals for each zone by controlling animal reproduction systems.
Generally speaking, a sustainable stocking rate is two adult animals per hectare in the central Himalayas. However, most pastures were overgrazed 3 to 10 times more than this level. The feedstuff stored over winter was half composed of hay and half of agricultural by-products such as rice straw and wheat straw. Grazing by animals provided 53 to 60 % of food intake (fresh plant weight). Ten % of fodder was provided by trees. For the total number of animals in this study region, the fodder shortage was very acute. Overpopulation of animals was estimated to be 31 to 73 %.
Tree fodder is a typical feedstuff in this region. Popular fodder trees are Quercus, Symplocos and Castanopsis. Extention programmes are needed to increase tree fodder production and conserve soils. Ten years are needed to establish a system for continuous tree fodder production. One fodder tree can produce 14 kg fresh matter per year. The shortage can overcome by planting an additional 10 to 15 fodder trees per cow.