Feeding behaviour of yaks on spring, transitional, summer and winter pasture in the alpine region of the Qinghai–Tibetan plateau
Introduction
On the Qinghai–Tibetan plateau, China, yaks (Bos grunniens) are essential for providing meat, milk, skins, transport and fuel (faeces), and fulfill various socio-cultural functions within the pastoral society. However, due to their relatively restricted worldwide distribution and population number of 14.2 million, yaks have been the subject of considerably less research than the ubiquitous and more numerous common domesticated cattle (Bos taurus; 1291 million).
Grazing systems represent approximately 20% of the total land area of the earth's surface (Hodgson and Illius, 1996). Herbivore utilization of grass swards is limited by the quality and quantity of forage ingested (Fryxell, 1991, Ungar, 1996), and the interaction between the grazing animal and sward has important implications for the development of both. Therefore, quantifying diet selection, herbage intake and modification of the forage resource by the grazing animal will help to define limits to sustainable grazing systems on the Qinghai–Tibetan plateau, rather than present practices which have led to serious degradation of the pastures. High stocking rates and the over-utilization of these alpine grasslands are the main cause of this grassland degradation.
Behaviour studies have played an important role in the improvement of grazing management throughout much of the world (Goldson, 1962). Grazing behaviour is important because of the immediate effect on the animal's productivity and because of its consequences for future grazing opportunities, composition of pasture and productivity (Coates and Penning, 2000).
The yak is a specialized species that has adapted to living in harsh and high altitude environments. The majority of the world population of yak occurs on the high plateau of western China in alpine and sub-alpine regions with a cold and semi-humid climate. The centre of the yak's distribution is the Qinghai–Tibetan plateau. The objectives of this work were to assess the feeding behaviour of yak grazing on Qinghai–Tibetan rangeland on spring, transitional, summer and winter pastures. In addition, the effect of providing a concentrate supplement during the spring season on yak foraging behaviour, when herbage was depleted, was examined.
Section snippets
Location
Qinghai Lake grassland is typical of the alpine grassland of the Qinghai–Tibetan plateau. It is an important pasturing area for yak and sheep production, with a seasonal migration between different grazing areas. Typically, four pasture types are utilized over the year: spring, transitional, summer, autumn and winter pasture, with spring and winter pastures belong to one type, but divided by fences as different seasonal pastures. Before moving from spring pasture to summer pasture, the yaks are
Herbage mass, sward height and chemical composition
The herbage mass in period 1 (March), period 2 (April) and period 3 (May) on spring pasture, transitional pasture, summer pasture and winter pasture are shown in Table 1. The herbage mass was significantly higher in the dry periods (periods 1 and 2 on spring season, winter season) than in green periods (period 3 on spring season, transitional and summer seasons) (P < 0.05). The height of the dominant species in the four pastures during the different periods is shown in Table 1. The height of A.
Grazing and ruminating behaviour
Grazing activity occurred mainly, though not exclusively, during the hours of daylight (range: 06:00–19:00 h, in spring and winter seasons, respectively). At night, yaks avoid grazing and tend to gather in groups in order to reduce body heat loss, because of the cold night temperatures, and as a defense mechanism against attack by predators. However, with the growth of new green herbage in May (period 3) on the spring pasture, and subsequently on the transitional and summer pastures, the yaks
Conclusion
The results show that yaks adapted their foraging behaviour in response to changes in sward conditions. In the dry periods or seasons, the yaks did not extend their grazing time because of the low quality of forage. In the germinating season (period 3 of spring pasture), the yaks increased their bite rate and TGT as a response to reduced bite mass. This research on yak foraging behaviour is a valuable aid to the improvement of the management of grazing livestock under alpine grassland on the
Acknowledgements
We thank the staff of San Jiao Cheng Sheep Breeding Farm for assistance with the fieldwork. We also wish to thank M.D. Qin for making this research possible. We express our gratitude to Malcolm Gibb (formerly of the Institute of Grassland and Environmental Research, North Wyke, EX20 2SB, UK, E-mail: [email protected]) for his assistance in revising this manuscript. This paper is a contribution to project Ministry of Education/China/20040733004: ‘Evaluation of Germplasm Source of
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