Ding Luming

Case study 7: Qinghai-Tibetan Plateau rangelands.

The rangelands of the Qinghai-Tibetan Plateau cover an extensive area on the roof of the world. Grazing animals, principally yaks and sheep, and grazing-based livestock production systems remain an important source of livelihood. The rangelands have developed under a continental climate that is one of the most severe in the world where pastoral livestock production continues to be practised. The traditional forage-based, extensively managed pastoral livestock production systems are showing a decline in overall productivity and about one-third of the rangelands exhibit severe degradation. Reasons for this situation are examined here.

Influence of grazing intensity on performance of perennial grass mixtures in the alpine region of the Tibetan Plateau

Abstract Effects of grazing intensity on leaf photosynthetic rate (Pn), specific leaf area (SLA), individual tiller density, sward leaf area index (LAI), harvested herbage DM, and species composition in grass mixtures (Clinelymus nutans + Bromus inermis, Elymus nutans + Bromus inermis + Agropyron cristatum and Elymus nutans + Clinelymus nutans + Bromus inermis + Agropyron cristatum) were studied in the alpine region of the Tibetan Plateau. Four grazing intensities (GI), expressed as feed utilisation rates (UR) by Tibetan lambs were imposed as follows: (1) no grazing; (2) 30% UR as light grazing; (3) 50% UR as medium grazing; and (4) 70% UR as high grazing. Leaf Pn rate and tiller density of grasses increased (P < 0.05), while sward LAI and harvested herbage DM declined (P < 0.05) with the increments of GI, although no effect of GI on SLA was observed. With increasing GI, Elymus nutans and Clinelymus nutans increased but Bromus inermis and Agropyron cristatum decreased in swards, LAI and DM contribution. Whether being grazed or not, Elymus nutans + Clinelymus nutans + Bromus inermis + Agropyron cristatum was the most productive sward among the grass mixtures. Thus, two well‐performed grass species (Elymus nutans and Clinelymus nutans) and the most productive mixture of four species should be investigated further as the new feed resources in the alpine grazing system of the Tibetan Plateau. Light grazing intensity of 30% UR was recommended for these grass mixtures when swards, LAI, herbage DM harvested, and species compatibility were taken into account.

低海拔异地育肥牦牛与本地杂交肉牛(秦川×西门塔尔)在不同非蛋白氮水平饲粮条件下血液生理生化指标及生长性能的差异

为探究异地育肥牦牛模式，本试验对比了低海拔异地育肥耗牛与本地杂交肉牛（秦川×西门塔尔）在同等条件下血液生理生化指标和生长性能的差异。将体重相近的8头1岁本地杂交肉牛（秦川×西门塔尔）和8头4岁青海牦牛各分为2组，每组4头，同一品种的2组试验牛分别饲喂低非蛋白氮饲粮[LNPN，饲粮中缓释尿素添加量为1.0%（干物质基础）]和高非蛋白氮饲粮[HNPN，饲粮中缓释尿素添加量为1.5%（干物质基础）]。预试期10 d，正试期50 d。结果发现：牦牛与肉牛均在LNPN条件下表现出最高的平均日采食量和最小的料重比。饲粮非蛋白氮水平未对牦牛与肉牛的血常规指标造成显著影响（P>0.05），但是牦牛在各饲粮条件下中性粒细胞数目（Gran#）、平均红细胞体积（MCV）、平均红细胞血红蛋白含量（MCH）、红细胞分布宽度标准差（RDW-SD）、平均血小板体积（MPV）和血小板分布宽度（PDW）显著高于肉牛（P 0.05）。牦牛在各饲粮条件下血清总蛋白（TP）、尿素氮（UN）、肌酐（GREA）、免疫球蛋白A（IgA）、免疫球蛋白M（IgM）和免疫球蛋白G（IgG）水平均显著高于肉牛（P < 0.05）。牦牛在HNPN条件下的血清白蛋白（ALB）水平显著低于LNPN条件下（P < 0.05）。本试验结果表明，在肉牛和牦牛育肥饲粮中添加1.0%的缓释尿素替代饲粮蛋白质是可行的；低海拔异地育肥牦牛不会对牦牛健康产生不利影响。