| Contents of macro (Ca, K, Mg, Na and P) and micro minerals (Fe, Mn, Zn, Cu, Co, Se) were analyzed in soils, forage and yak tissues in summer (July) and winter (December) at Tianzhu County, Gansu (TC), Datong County, Qinhai (DC), Maqu County, Gansu (MC) and Ruoergai, County, Sichuan (RC) in northeastern Qinghai-Tibetan Plateau. The primary objective was to study the mineral dynamics and relationships in soil-plant-animal system, which would provide guidelines for fertilizer application in grassland management, and supply recommendations for mineral addition in animal feed and feeding systems.The concentrations of mineral elements in soils varied with region and soil types. Soil characteristics have significant effects on the status of minerals, especially for soil organic carbon (SOC), soil pH and soil total nitrogen (TN). The concentrations of all mineral elements analyzed were above the critical levels for animal nutritional requirements except for Mg, P, and Se. The deficiencies of these minerals in soils would have potential adverse effects, resulting in the deficiency and/or imbalance of mineral elements in plants and animals.Results from plant analysis showed that concentrations of mineral elements varied with seasons. Most minerals in forage were below their critical level in winter in one or more counties, particularly for Na and Se for all regions. The excess K in forage may aggravate the deficiency in Na in summer. Similarly, the Cu deficiency may be induced by high Fe in forage. However, only Ca, Mg, Fe, and Mn were sufficient in the forage to meet the yak requirements in both winter and summer.Yak had high concentrations of most mineral elements in blood serum and liver in summer. However, Se in yak blood serum and liver was below the critical level in all regions in both summer and spring. Sodium in blood serum was also below the critical level in all regions except for yak in TC in winter. There was evidence for widespread deficiency in P for most regions in winter. In addition, the Cu deficiency occurred in all regions during winter and marginal deficiency in summer. Minerals in blood serum were correlated to minerals in forage except for P in summer. In contrast, there were no significant correlation for minerals between soil and forage except for K (P<0.01) and Se (P<0.05). No relationship were found in minerals between soil and yak except for K (P<0.05). Deficiency of minerals from soils could explain the variation in forage and yak blood and tissues. However, there were no significant correlations between forage and yak blood in winter except for Se. Minerals in soils were highly correlated to those in yak blood for most minerals. It was suggested that soil analysis was not reliable to assess the status of mineral elements in forage and yak for most minerals in summer. However there was close relationship existed between forage and yak blood, indicating that the forage analysis was reliable to predict the mineral status in yak free-grazing on native pasture in the Qinghai-Tibetan Plateau in summer. In contrast, minerals analysis in soil could be used to predict the mineral status in yak in winter rather than mineral analysis in forage. The seasonal dynamics could have great effects on the correlation of minerals in the soil-plant-animal system.Results showed that the deficiency in minerals was very common in the Qinghai-Tibetan Plateau, especially in forage and animals. Therefore, supplementation of minerals would be necessary for yaks to increase essential mineral level in blood, hence improving productivity of yaks. However, further research is needed to ascertain whether mineral deprivations are limiting productivity of grazing yaks.
|
PDF Full Text Request