Effects of grazing systems on herbage mass and liveweight gain of Tibetan sheep in Eastern Qinghai-Tibetan Plateau, China

Abstract

Grazing strategies, consisting of grazing systems and stocking rate adjustments, have evolved from the need to sustain efficient use of the forage resources by livestock, increase animal performance and sustain forage production. A 3-year study was conducted with Tibetan sheep on the Eastern Qinghai-Tibetan Plateau, China to compare: (1) two grazing systems [season-long continuous (SLC; July to December) versus short duration with seasonal rotation (SDSR; July to September in growing-season pasture and October to December in cold-season pasture) with a stocking rate of 24 sheep months ha–1(SM ha–1)]; (2) SDSR system with 24, 36 and 48 SM ha–1; and (3) seasonal aspects of stocking rate under the SDSR system by comparing strategies of heavy stocking rate in the growing season and light stocking rate in the cold season (SDSR-HL) versus light stocking rate in the growing season and heavy stocking rate in the cold season (SDSR-LH). No differences were found between grazing systems in liveweight gain per head or per ha and in residual herbage mass. Liveweight gain per head for treatment SDSR24 was greater than for treatments SDSR36 and SDRS48, whereas liveweight gain per ha showed the opposite tendency. No differences were found between the SDSR-HL and SDSR-LH treatments in liveweight gain per head or per ha, whereas the ratio of residual herbage mass at the end of grazing the growing-season pasture to the cold pasture of treatment SDSR-LH was more than twice that of treatment SDSR-HL. Daily liveweight gain of Tibetan sheep decreased linearly with increasing grazing pressure in both growing and cold seasons. It was estimated that, at a grazing pressure index of 310 sheep days t–1 DM peak herbage mass, liveweight gain per head and ha appears to be optimised over the whole grazing period. Liveweight loss by Tibetan sheep during the cold season was apparent regardless of grazing pressure indicating that temperature had a stronger influence on sheep performance in the cold season than herbage availability.

Effect of Dietary Types on Feed Intakes, Growth Performance and Economic Benefit in Tibetan sheep and Yaks on the Qinghai-Tibet Plateau during Cold Season

“…However, under traditional grazing management, production efficiency of alpine pastoral husbandry and feed efficiency was quiet low due to irrational grazing-management regime and environmental factors [9,10]. In addition, natural grassland degradation became increasingly serious due to over-stocking and irrational utilization of nature pasture, which hampered the sustainable development of alpine pastoral grass-livestock husbandry on the QTP [9,16].…”

“…With cold-season extension, standing herbage biomass and nutrient content decreased dramatically, leading to herbage shortage for grazing animals (November to May). As a result, grazing animals suffered inadequate DMI and inferior nutrients which could not meet their daily requirement [10,35]. …”

“…It is estimated with a population of about 13 million domestic yaks and 50 million Tibetan sheep are living on the QTP [8,9], providing local herdsmen with daily necessities like meat, milk, wool, skins, fuel and economic benefit [4,8,10]. Tibetan sheep and yaks breeding have laid a solid foundation of alpine pastoral economy and pastoralists’ livelihood on the QTP.…”

“…Animals always suffered seasonal live-weight variations and viciously cycled in “alive in summer, strong in autumn, thin in winter, tired in spring”, due to seasonal fluctuations in herbage supply (biomass and nutrient content) and the contradiction between herbage supply and livestock’s requirement on the alpine rangeland [4,12,13]. When cold season came, grazing animals survived from inadequate herbage, low temperature and cold environment, which usually causing poor nutrition, health-related problem, low growth performance and even death of grazing livestock [10,13,14]. As a result, pastoralists suffered huge economic loss due to serious live-weight loss in grazing animals during cold season.…”

“…As a result, pastoralists suffered huge economic loss due to serious live-weight loss in grazing animals during cold season. Feed efficiency (total herbage intakes/total live-weight gain) and the off-take rate of livestock were quiet low under traditional grazing management [4,9,10,15]. More seriously, the vicious cycle was aggravated yearly due to over-stocking rate of livestock and irrational utilization of natural pasture on the QTP [16–18].…”