The objective of this study was to analyze the dynamics of nutrient balance, physiological biomarkers and comprehensive indexes associated with metabolism and function of organs in transition cows. Fourteen transition cows were used for this research. Dietary intake was recorded daily, and samples of the diet, venous blood and milk were collected for measurements. The balance values of net energy for lactation (NE_L ), metabolizable protein (MP), and metabolizable glucose (MG) were calculated, and regression analysis and calculation of comprehensive indexes were performed. Accordingly, the prepartum cows presented positive balances of NEL , MP, and MG, while severe negative balances were found during the postpartum period. Dynamic changes of energy metabolism, nutrient mobilization, liver function, anti-oxidative status and immune response, as indicated by blood biomarkers and modified comprehensive indexes, were out of sync with the calculated balance values, but they were closely related to the day relative to calving. Compared with the 21 d prepartum, the plasma concentrations of non-esterified fatty acids (NEFA) and β-hydroxybutyric acid (BHBA) were significantly increased around and after calving (P<0.05), and similar variation tendency was observed for most of other parameters. The occurrence of parturition and the initiation of lactation were more responsible for the negative balances of nutrients in transition dairy cows. Although negative balances of NE_L , MP and MG were not observed using the assessment model, the nutritional strategies should be applied before calving, because metabolic adaptations had been validated during the prepartum period. In addition, it was plausible to conclude that the decline of hepatic metabolism, defense function and insulin sensitivity are critical causes of metabolic dysfunction.

Previous studies demonstrated climate change had reduced rice yield in China, but the magnitude of the reduction and the spatial variations of the impact have remained in controversy to date. Based on a gridded daily weather dataset, we found there were obvious changes in temperatures, diurnal temperature range, and radiation during the rice-growing season from 1961 to 2010 in China. These changes resulted in a significant decline of simulated national rice yield (simulated with CERES-Rice), with a magnitude of 11.5%. However, changes in growing-season radiation and diurnal temperature range, not growing-season temperatures, contributed most to the simulated yield reduction, which confirmed previous estimates by empirical studies. Yield responses to changes of the climatic variables varied across different rice production areas. In rice production areas with the mean growing-season temperature at 12-14°C and above 20°C, a 1°C growing-season warming decreased rice yield by roughly 4%. This decrease was partly attributed to increased heat stresses and shorter growth period under the warmer climate. In some rice areas of the southern China and the Yangtze River Basin where the rice growing-season temperature was greater than 20°C, decrease in the growing-season radiation partly interpreted the widespread yield decline of the simulation, suggesting the significant negative contribution of recent global dimming on rice production in China’s main rice areas. Whereas in the northern rice production areas with relatively low growing-season temperature, decrease of the diurnal temperature range was identified as the main climatic contributor for the decline of simulated rice yield, with larger decreasing magnitude under cooler areas.

Southern rice black-streaked dwarf disease is a new rice disease that severely affects rice production in South China. To understand transmission capacity of the vector Sogatella furcifera to Southern rice black-streaked dwarf virus (SRBSDV) among different host plant species, potential host plants of SRBSDV collected from the diseased rice field and/or adjacent to the field in Hunan Province, China, were determined by RT-PCR, and the transmission rates of SRBSDV by S. furcifera among different host plant species were investigated. The results showed that host plants of SRBSDV in the rice fields were five of family Gramineae (Oryza sativa, Echinochloa crusgalli, Zea mays, Paspalum distichum, Alopecurus aequali) and two of family Cyperaceae (Juncellus serotinus and Cyperus difformis). S. furcifera could not transmit SRBSDV between gramineous plants and cyperaceous plants, and could not transmit SRBSDV between the gramineous plants, J. serotinus and C. difformis as well. However, SRBSDV could be transmitted by S. furcifera within gramineous plants. S. furcifera could transmit SRBSDV between interspecies among three species plants (O. sativa, E. crusgalli and Z. mays), and between P. distichum and A. aequali. At 15, 20, 25, 30, and 35°C, both macropterous and brachypterous adult of S. furcifera could transmit SRBSDV from the plants (e.g., E. crusgalli, Z. mays and O. sativa) infected with SRBSDV to rice seedlings. The transmission rates were first increased and then decreased with the increase of temperature. Macropterous adults transmitted SRBSDV from the viruliferous E. crusgalli, Z. may and rice plants to the healthy rice seedlings, and the infected rates of rice seedlings were 26.2, 18.8 and 23.7% at 15°C, 56.6, 64.6 and 53.6% at 25°C, and was 11.2, 10.2 and 7.3% at 35°C, respectively. Transmission capacity of brachypterous adults was significantly higher than that of macropterous adults at 15, 20 and 25°C (P<0.05), while transmission capacity of brachypterous adults was relatively lower compared with that of macropterous ones at 35°C. These results offer evidence on the transmission of SRBSDV via the vector S. furcifer among different host plants, which can be helpful to control Southern rice black-streaked dwarf disease by the appropriate cultural measures in South China.