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| 1 | The adaptive strategies of yaks to live in the Asian highlands显示文摘The yak(Bos grunniens),an indigenous herbivore raised at altitudes between 3,000 and 5,000 m above sea level,is closely linked to more than 40 ethnic communities and plays a vital role in the ecological stability,livelihood security,socio-economic development,and ethnic cultural traditions in the Asian highlands.They provide the highlanders with meat,milk,fibres,leather and dung(fuel).They are also used as pack animals to transport goods,for travel and ploughing,and are important in many religious and traditional ceremonies.The Asian highlands are known for an extremely,harsh environment,namely low air temperature and oxygen content and high ultraviolet light and winds.Pasture availability fluctuates greatly,with sparse pasture of poor quality over the long seven-month cold winter.After longterm natural and artificial selections,yaks have adapted excellently to the harsh conditions:1)by genomics,with positively selected genes involved in hypoxia response and energy metabolism;2)anatomically,including a short tongue with a weak sense of taste,and large lung and heart;3)physiologically,by insensitivity to hypoxic pulmonary vasoconstriction,maintaining foetal haemoglobin throughout life,and low heart rate and heat production in the cold season;4)behaviourlly,by efficient grazing and selecting forbs with high nutritional contents;5)by low nitrogen and energy requirements for maintenance and low methane emission and nitrogen excretion,namely,‘Low-Carbon’and‘Nitrogen-Saving’traits;6)by harboring unique rumen microbiota with a distinct maturation pattern,that has coevolved with host metabolism.This review aims to provide an overview of the comprehensive adaptive strategies of the yak to the severe conditions of the highlands.A better understanding of these strategies that yaks employ to adapt to the harsh environment could be used in improving their production,breeding and management,and gaining benefits in ecosystem service and a more resilient livelihood to climate change in the Asian highlands. | Xiaoping Jing Luming Ding Jianwei Zhou Xiaodan Huang Allan Degen Ruijun Long | 2022 | Animal Nutrition2022，，2： | 2 |
| 2 | Plasma level of LH and sterdiol hormones in male and female domestic ostrich(struthio camelus)显示文摘 | Allan Degen A | 1994 | Gen Comp Endocr1994，93，： | 1 |
| 3 | A comparison of average daily gain,apparent digestibilities,energy balance,rumen fermentation parameters,and serum metabolites between yaks(Bos grunniens)and Qaidam cattle(Bos taurus)consuming diets differing in energy level显示文摘Yaks(Bos grunniens),indigenous to the harsh Qinghai-Tibetan Plateau,are well adapted to the severe conditions,and graze natural pasture without supplements all year round.Qaidam cattle(Bos taurus),introduced to the Qinghai-Tibetan Plateau 1,700 years ago,are raised at a lower altitude than yaks,provided with shelter at night and offered supplements in winter.Based on their different backgrounds,we hypothesized that yaks have lower energy requirements for maintenance than cattle.To test this hypothesis,we measured average daily gain(ADG),apparent digestibilities,energy balance,rumen fermentation parameters,and serum metabolites in growing yaks and cattle offered diets differing in metabolizable energy(ME)levels(6.62,8.02,9.42 and 10.80 MJ/kg),but with the same crude protein concentration.Six castrated yaks(155±5.8 kg)and 6 castrated Qaidam cattle(154±8.0 kg),all 2.5 years old,were used in 2 concurrent 4×4 Latin square designs.Neutral and acid detergent fiber digestibilities were greater(P<0.05)in yaks than in cattle,and decreased linearly(P<0.05)with increasing dietary energy level;whereas,digestibilities of dry matter,organic matter,crude protein and ether extract increased(P<0.05)linearly with increasing energy level.The ADG was greater(P<0.001)in yaks than in cattle,and increased(P<0.05)linearly with increasing energy levels.From the regressions of ADG on ME intake,the estimated ME requirement for maintenance was lower(P<0.05)in yaks than in cattle(0.43 vs.0.57 MJ/kg BW0.75).The ratios of digestible energy(DE):gross energy and ME:DE were higher(P<0.05)in yaks than in cattle,and increased(P<0.05)linearly with increasing dietary energy level.Ruminal pH decreased(P<0.05),whereas concentrations of total volatile fatty acids(VFAs)and ammonia increased(P<0.01)with increasing dietary energy level,and all were greater(P<0.05)in yaks than in cattle.Concentrations of ruminal acetate and iso-VFAs were greater(P<0.05),whereas propionate was lower(P<0.05)in yaks than in cattle;acetate decreased(P<0.001),whereas butyrate and propionate increased(P<0.001)linearly with increasing dietary energy level.Serum concentrations ofβ-hydroxybutyrate were lower(interaction,P<0.001)in yaks than in cattle fed diets of 9.42 and 10.80 MJ/kg,whereas non-esterified fatty acids were greater(interaction,P<0.01)in yaks than in cattle fed diets of 6.62 and 8.02 MJ/kg.Concentrations of serum leptin and growth hormone were greater in yaks than in cattle and serum insulin and growth hormone increased(P<0.01)linearly with increasing dietary energy level.Our hypothesis that yaks have lower energy requirements for maintenance than cattle was supported.This lower requirement confers an advantage to yaks over Qaidam cattle in consuming low energy diets during the long winter on the Qinghai-Tibetan Plateau. | Hu Liu Jianwei Zhou Allan Degen Hongshan Liu Xuliang Cao Lizhuang Hao Zhanhuan Shang Tao Ran Ruijun Long | 2023 | Animal Nutrition2023，，1： | 0 |
| 4 | Effects of degradation and species composition on soil seed density in the alpine grasslands, China显示文摘Grassland degradation can alter the structure and function of ecosystem and soil seed bank.Therefore,estimating the role of soil seed bank in vegetation regeneration of degraded grasslands is crucial.We selected grasslands with three levels of degradation,namely non-degraded(ND),mildly degraded(MD),and heavily degraded(HD)to analyze the effect of grassland degradation on soil seed bank,as well as the role of soil seed bank on vegetation regeneration of the alpine grasslands,China.Soil samples from each level were collected in May,before seedling emergence,in August,after completion of transient seed bank germination,and in December,after seed dispersal,to determine the seed density and species composition through germination experiment.Result showed that a total of 35 plant species was identified,including 15 species observed in both soil seed bank and above-ground vegetation.A total of 19,15,and 14 species of soil seed bank were identified in December,May,and August,respectively.The most abundant species in soil seed bank were Compositae(5 species),followed by Poaceae(4 species),and Cyperaceae(3 species).Degradation level has no significant impact on species richness and Shannon-Wiener index of soil seed bank.In addition,sampling month and grassland degradation affected soil seed bank density,in which December>May>August,and ND>MD>HD,indicating that density of transient seed bank was greater than persistent seed bank.Soil seed bank density of surface layer(0–5 cm)accounting for 42%–72%of the total density,which was significantly higher than that of deep layer(5–10 cm).Similarity of species composition between vegetation and soil seed bank was low,and it increased with degradation level(ranged from 0.14 to 0.69).We concluded that grassland degradation affects soil seed bank density more than species diversity,and soil seed bank contributed slightly to vegetation regeneration of degraded alpine grassland.Therefore,it is unlikely that degraded alpine meadow can be restored solely through soil seed bank. | LI Chunming MA Jiahui LI Liangyu HUANG Junlin LU Jinhua HUANG Mei Allan DEGEN SHANG Zhanhuan | 2023 | Journal of Arid Land2023，15，12： | 0 |
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