Yang Chuntao, Tsedan Guru, Liu Yang, Hou Fujiang
State Key Laboratory of Grassland Agro-ecosystems, Key Laboratory of Grassland Livestock Industry Innovation, Ministry of Agriculture, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou 730020, China.
Animal Husbandry Science and Technology Demonstration Park of Maqu County, Gannan 743000, China.
J Anim Sci Technol. 2020 Jul;62(4):504-520. doi: 10.5187/jast.2020.62.4.504. Epub 2020 Jul 31.
Proliferation of shrubs at the expense of native forage in pastures has been associated with large changes in dry-matter intake and dietary components for grazing ruminants. These changes can also affect the animals' physiology and metabolism. However, little information is available concerning the effect of pastoral-shrub grazing on the rumen bacterial community. To explore rumen bacteria composition in grazing yaks and the response of rumen bacteria to increasing shrub coverage in alpine meadows, 48 yak steers were randomly assigned to four pastures with shrub coverage of 0%, 5.4%, 11.3%, and 20.1% (referred as control, low, middle, and high, respectively), and ruminal fluid was collected from four yaks from each pasture group after 85 days. Rumen fermentation products were measured and microbiota composition determined using Ion S5 XL sequencing of the 16S rRNA gene. Principal coordinates analysis (PCoA) and similarity analysis indicated that the degree of shrub coverage correlated with altered rumen bacterial composition of yaks grazing in alpine shrub meadows. At the phyla level, the relative abundance of in rumen increased with increasing shrub coverage, whereas the proportions of , and decreased. Yaks grazing in the high shrub-coverage pasture had decreased species of the genus UCG-001, XPB1014 group, AC2044 group, FCS020 group and , but increased species of R-7 group, NK4A214 group, 1, UCG-002, UCG-005 and UCG-008. These variations can enhance the animals' utilization efficiencies of cellulose and hemicellulose from native forage. Meanwhile, yaks grazed in the high shrub-coverage pasture had increased concentrations of ammonia nitrogen (NH-N) and branched-chain volatile fatty acids (isobutyrate and isovalerate) in rumen compared with yaks grazing in the pasture without shrubs. These results indicate that yaks grazing in a high shrub-coverage pasture may have improved dietary energy utilization and enhanced resistance to cold stress during the winter. Our findings provide evidence for the influence of shrub coverage on the rumen bacterial community of yaks grazing in alpine meadows as well as insights into the sustainable production of grazing yaks on lands with increasing shrub coverage on the Qinghai-Tibet Plateau.
牧场中灌木大量繁殖，以本地牧草为代价，这与放牧反刍动物的干物质摄入量和饮食成分的巨大变化有关。这些变化也会影响动物的生理和新陈代谢。然而，关于草原灌木放牧对瘤胃细菌群落的影响，目前可用信息很少。为了探究放牧牦牛的瘤胃细菌组成以及瘤胃细菌对高寒草甸灌木覆盖率增加的反应，48头牦牛被随机分配到四个灌木覆盖率分别为0%、5.4%、11.3%和20.1%的牧场（分别称为对照、低、中、高），85天后从每个牧场组的四头牦牛中采集瘤胃液。测量瘤胃发酵产物，并使用16S rRNA基因的Ion S5 XL测序确定微生物群组成。主坐标分析（PCoA）和相似性分析表明，灌木覆盖率与高寒灌丛草甸放牧牦牛瘤胃细菌组成的改变相关。在门水平上，瘤胃中 的相对丰度随灌木覆盖率的增加而增加，而 、 和 的比例则下降。在高灌木覆盖率牧场放牧的牦牛，UCG - 001属、XPB1014组、AC2044组、FCS020组和 的物种减少，但R - 7组、NK4A214组、1、UCG - 002、UCG - 005和UCG - 008的物种增加。这些变化可以提高动物对本地牧草中纤维素和半纤维素的利用效率。同时，与在无灌木牧场放牧的牦牛相比，在高灌木覆盖率牧场放牧的牦牛瘤胃中氨氮（NH - N）和支链挥发性脂肪酸（异丁酸和异戊酸）的浓度增加。这些结果表明，在高灌木覆盖率牧场放牧的牦牛可能在冬季提高了饮食能量利用率，并增强了对冷应激的抵抗力。我们的研究结果为灌木覆盖率对高寒草甸放牧牦牛瘤胃细菌群落的影响提供了证据，也为青藏高原灌木覆盖率增加地区放牧牦牛的可持续生产提供了见解。
