Luming Ding

The yak grazing system on the Qinghai-Tibetan plateau and its status

Yaks are a multifunctional and dominant livestock species on the Qinghai-Tibetan plateau. The yak grazing system is a traditional transhumance system. Research is focussed on both understanding and improving the system. Development of local economies and the use of new knowledge from yak research and modern technology are improving the system. However, the Qinghai-Tibetan plateau ecosystem is becoming dysfunctional through adverse climate sequences, over-population and over-grazing. The Chinese Government has implemented regional projects to address these degradation problems. Several policies have recently been introduced to improve yak grazing management. This paper reviews current knowledge on the system and the options for improving and optimising the system.

The sustainable development of grassland-livestock systems on the Tibetan plateau: problems, strategies and prospects

The Tibetan plateau is the source of most of the major rivers of Asia and has a huge impact on the livelihoods of the population, who have for centuries engaged in traditional herding practices. Sustainable management of the plateau is of critical importance not only for maintaining livelihoods but also because of its vital ecological function. The major problem of sustainable development in these grassland-livestock systems is the conflict between forage and livestock production. Despite considerable investment of manpower, material resources and capital over many years, attempts to resolve the problem have not been successful. The magnitude of conflict between forage and livestock is addressed by presenting 19 resolution strategies based on numerous research data. Each of these strategies is evaluated in terms of how it can be implemented, its potential benefits for livestock production, current progress and the requirement for further research. The 19 strategies have been divided into four topic categories, namely; grassland-forage, livestock, economy and market, society-culture, which cover the basic elements of sustainable development in this pastoral region. It is argued that improved planning and implementation of the proposed strategies must be based on the background investigation of natural and social status of the pastoral region. Particular attention needs to be given to genetic resources and technology in order to ensure the successful implementation of these proposals. In addition to expanding the use of 18 currently practiced strategies, the authors propose a further novel strategy of replacing the current intensive form of ecological migration with a model incorporating two semi-permanent settlements. The objective of this novel strategy is to retain the nomadic element of pastoral husbandry while increasing the temporal and spatial scale of rotational stocking to reduce pasture degradation on the Tibetan plateau. It is argued that these proposals should be urgently incorporated into two national plans for the pastoral livestock industry, and the construction of an ecologically safe shelter zone on the Tibetan plateau, while ensuring a sustainable livelihood of its pastoral residents. Ensuring a successful implementation of these strategies in resolving the conflict between grassland and livestock, and promoting sustainable development on the Tibetan plateau, requires willing support at the level of national investment and policy commitment and from the herdsmen.

Importance of Functional Ingredients in Yak Milk-Derived Food on Health of Tibetan Nomads Living Under High-Altitude Stress: A Review

Tibetan nomads have lived since ancient times in the unique and harsh environment of the Qinghai-Tibetan Plateau with average altitudes over 4000 m. These people have been able to live and multiply healthily over numerous generations under the extreme stress of high-altitude environment, including cold, hypoxia, and strong ultraviolet radiation, and with a simple diet devoid of vegetables and fruits for most of the year. Their survival depends heavily on yak milk, and its products comprise the main portion of their daily diet. In this review, yak milk and its derived products are examined in detail and compared with milk from other ruminant species. Yak milk products seem to be particularly rich in functional and bioactive components, which may play a role in maintaining the health status of Tibetan nomads. This includes particular profiles of amino acids and fatty acids, and high levels of antioxidant vitamins, specific enzymes, and bacteria with probiotic activity (yoghurt is the main food). Based on that, it is proposed that the Tibetan nomads have developed a nutritional mechanism adapted to cope with the specific challenges posed by the environment of the worlds highest plateau. Systematic studies are required to demonstrate this in a more mechanistic way.

Nitrogen metabolism and recycling in yaks (Bos grunniens) offered a forage-concentrate diet differing in N concentration

An experiment was conducted to characterise N use efficiency and quantify urea fluxes in yaks offered four levels of dietary N (1.43%, 1.97%, 2.45% and 2.90% of diet DM) in a 4 × 4 Latin square design. The incremental increase in N intake linearly increased N retention (P = 0.003) and the excretion of urinary N (P 0.05) in faecal N excretion was observed in growing yaks fed any of the four diets. Microbial N production had quadratic (P < 0.001) responses to dietary N, characterised by the highest microbial N production occurring in the 1.97% N diet (P < 0.05). As the N content of the diet increased, the urinary excretion of urea increased from 13% to 27% of urea entry rate (quadratic, P < 0.001), whereas gastrointestinal entry urea returned to ornithine cycling decreased from 46% to 40% (linear, P < 0.001), and the gastrointestinal entry urea used for anabolism increased from 50% to 56% (linear, P < 0.001). Gastrointestinal entry urea incorporated into bacterial N decreased linearly (P < 0.001) with incremental increase in N intake, and the greatest concentration (23.5%) of bacterial N originating from plasma urea N was in yaks fed the 1.43% N diet. As much as 87% of the urea synthesised in the liver was returned to the gastrointestinal tract when the yaks were fed a diet with 1.43% N (1.1 times the maintenance N level). Moreover, constantly greater urea production than the intake of digestible N, and the gastrointestinal-urea clearance than the kidney-urea clearance were observed, respectively, in the growing yaks, regardless of the level of N intake. These results suggest that yaks might be more efficient at utilising N under harsh environment than are cattle.

Apparent digestibility, rumen fermentation and nitrogen balance in Tibetan and fine-wool sheep offered forage-concentrate diets differing in nitrogen concentration

A comparative study of the effect of dietary nitrogen (N) content [Low: 11·0; Medium-Low (MLow): 16·7; Medium-High (Mhigh): 23·1; High: 29·2 N g/kg dry matter (DM)] on apparent digestibilities, rumen fermentation and N balance was conducted in coarse wool Tibetan sheep and Gansu Alpine fine-wool sheep at Wushaoling in the northeast of the Qinghai-Tibetan Plateau. It was hypothesized that responses would differ between breeds and that responses would favour Tibetan over fine-wool sheep at low N intakes. Eight wethers [four Tibetan sheep and four fine-wool sheep, 20–24 months old; body weight ± standard deviation was 52 ± 3·2 kg] were used in two concurrent 4 × 4 Latin square designs. Dry matter, organic matter, neutral detergent fibre and acid detergent fibre digestibilities were higher in Tibetan than fine-wool sheep when fed the Low, MLow and High N diets while N retention was higher when the animals were fed the Low and MLow N diets. Tibetan sheep had a higher rumen pH than fine-wool sheep; however, total volatile fatty acids were similar between breeds. Molar proportions of acetate were higher but propionate and butyrate lower in Tibetan than fine-wool sheep. In addition, Tibetan sheep had higher concentrations of ruminal free amino acid-N and soluble protein-N than fine-wool sheep. Plasma and saliva urea-N concentrations were higher in Tibetan than fine-wool sheep when supplied with the Low N diet. It was concluded that Tibetan sheep were better able to cope with low N feed than fine-wool sheep because of the higher N retention and higher DM and fibre digestibilities with Low and MLow diets.

Effect of weaning strategy on performance, behaviour and blood parameters of yak calves (Poephagus grunniens)

Early weaning can improve the body condition and reproductive performance of cows, but can be very stressful to both the calf and cow. The objectives of this study were to examine and compare the performance, behaviour and blood parameters of yak calves that were weaned using different methods. Twenty-six calves (94.3 ± 2.4 days old) were assigned to four weaning treatments: (1) weaned naturally following ad libitum sucking (NW, n = 13); (2) weaned abruptly and separated permanently from their mothers (AW, n = 5); (3) separated temporarily from their mothers for 15 days and then reunited (TW, n = 5); and (4) fitted with nose plates to prevent sucking for 15 days but allowed free access to their mothers (NP, n = 3). Girth size, as a measure of calf performance, was largest in NW and AW calves, intermediate in NP calves and smallest in TW calves. This indicated that the AW calves were able to consume adequate energy to compensate for the absence of milk. The weaned calves (TW and NP) spent more time grazing and, in general, played less than NW calves. In addition, TW calves stood more but walked less, whereas NP calves lay more but grazed and stood less than NW calves. Blood insulin was lower on Day 19 in the TW calves than in the other three treatments. We concluded that abrupt and permanent weaning was an appropriate strategy for yak calves on the Qinghai-Tibetan plateau.

Comparison of nitrogen utilization and urea kinetics between yaks ( Bos grunniens ) and indigenous cattle ( Bos taurus ) 1

Under traditional management on the Qinghai-Tibetan Plateau, yaks () graze only on natural pasture without supplements and are forced to cope with sparse forage of low N content, especially in winter. In contrast, indigenous Tibetan yellow cattle () require supplements during the cold season. We hypothesized that, in response to harsh conditions, yaks cope with low N intakes better than cattle. To test this hypothesis, a study of whole-body N retention and urea kinetics was conducted in 2 concurrent 4 × 4 Latin squares, with 1 square using yaks and 1 square using cattle. Four isocaloric forage-concentrate diets differing in N concentrations (10.3, 19.5, 28.5, and 37.6 g N/kg DM) were formulated, and by design, DMI were similar between species and across diets. Urea kinetics were determined with continuous intravenous infusion of NN urea for 104 h, and total urine and feces were concomitantly collected. Urea production, urea recycling to the gut, and ruminal microbial protein synthesis all linearly increased ( < 0.001) with increasing dietary N in both yaks and cattle. Urinary N excretion was less ( = 0.04) and N retention was greater ( = 0.01) in yaks than in cattle. Urea production was greater in yaks than in cattle at the 3 lowest N diets but greater in cattle than in yaks at the highest N diet (species × diet, < 0.02). Urea N recycled to the gut ( < 0.001), recycled urea N captured by ruminal bacteria ( < 0.001), and ruminal microbial protein production ( = 0.05) were greater in yaks than in cattle. No more than 12% of urea recycling was through saliva, with no difference between species ( = 0.61). Glomerular filtration rate was lower ( = 0.05) in yaks than in cattle. The higher urea recycling and greater capture of recycled urea by ruminal microbes in yaks than in cattle suggest that yaks use mechanisms to utilize dietary N more efficiently than cattle, which may partially explain the better survival of yaks than cattle when fed low-N diets.

Trolox equivalent antioxidant capacities and fatty acids profile of 18 alpine plants available as forage for yaks on the Qinghai-Tibetan Plateau

Traditionally, yaks (Poephagus grunniens) raised on the Qinghai-Tibetan plateau graze only natural pasture and much of their diet consists of sedges, in particular Kobresia spp. These ruminants are subjected to an extremely harsh environment of strong UV radiation, hypoxia and severe cold, which can lead to high oxidative stress. Consequently, it was predicted that sedges would contain high concentrations of functional antioxidants when compared with other alpine plants, and that this would help them survive the harsh conditions. To test the prediction, 18 alpine plants on the Qinghai-Tibetan plateau, which are available to yaks as forage, were examined. These plants, including four sedges, five grasses, five forbs and four shrubs, were analysed for gross constituents, Trolox equivalent antioxidant capacity, phenol content, and fatty acids composition. Based on their Trolox equivalent antioxidant capacity, the 18 plants were divided into three groups: low, medium and high. Three of the four sedges were ranked in the medium group and one in the low group, whereas three of four shrubs were ranked in the high group. The total phenol content of the plants ranged between 1.1 and 12.4 g gallic acid equivalents per 100 g DM, with the shrubs containing the highest concentrations. The prediction that sedges would contain higher antioxidant capacity than other alpine plants was not supported. It was concluded that other factors such as anti-nutritional contents and biomass availability are also important in determining dietary selection in yaks.

Recruitment of seedlings versus ramets as affected by pasture degradation in alpine meadows and the implications for ecological restoration

Background: The degradation of alpine meadows on the Qinghai-Tibetan Plateau (QTP) has an impact on vegetation recruitment from seedlings and ramets. Aims: Understanding the relative contribution of recruitment by seedling and ramet in alpine meadows is for the ecological restoration of degraded grasslands on the QTP. Methods: An experiment was conducted to investigate seedling and ramet densities, species composition and their relationships with standing vegetation in plots representative of non-degraded (ND), lightly (LD), moderately (MD) and severely degraded (SD) alpine meadows. Results: With increasing degradation and the reduction in vegetation cover, the number of seedlings and ramets declined. The proportion of young plants arising from seedlings was low, with the majority of species reproducing clonally. The establishment of seedlings of forbs in SD meadows led to species-rich, forb-dominant vegetation in these areas. Conclusions: LD and MD meadows appear to be able to be managed by reduced grazing for the restoration of grass- and sedge-dominated pastures. In contrast, restoration of SD meadows will require additional intervention, such as of seeding and weed eradication.

Inhibitory action of allelochemicals from Artemisia nanschanica to control Pedicularis kansuensis, an annual weed of alpine grasslands

The inhibitory action of allelochemicals can be used effectively for biological weed management and can minimise environmental impacts related to herbicides. The aim of the present study was to identify allelochemicals of Artemisia nanschanica Krasch, a typical weed with strong allelopathic effects, that could potentially control Pedicularis kansuensis Maxim, the key pioneer weed that causes rapid degradation of alpine pastures. Gas chromatography and mass spectrometry were used to identify the compounds of six extracts from A. nanschanica. Two ethyl acetate extracts were the most effective in reducing the seed germination rate and in inhibiting seedling shoot and root growth of P. kansuensis. Three chemical compounds from the ethyl acetate extracts were identified for their allelopathic inhibitory effects, a sesquiterpene and two aromadendrene oxides, with the sesquiterpene being the most effective. The three compounds showed the best inhibitory effect through synergistic action. We concluded that the three allelochemicals of A. nanschanica, either alone or in combination, can be used to biologically control P. kansuensis in alpine pastures on the Tibetan plateau.