The effect of increased atmospheric temperature and CO2 concentration during crop growth on the chemical composition and in vitro rumen fermentation characteristics of wheat straw

Xiangyu He, Yanping Wu, Min Cai, Chunlong Mu, Weihong Luo, Yanfen Cheng, Weiyun Zhu

This experiment was conducted to investigate the effects of increased atmospheric temperature and CO2 concentration during crop growth on the chemical composition and in vitro rumen fermentation characteristics of wheat straw. The field experiment was carried out from November 2012 to June 2013 at Changshu (31°32'93″N, 120°41'88″E) agro-ecological experimental station. A total of three treatments were set. The concentration of CO2 was increased to 500 μmol/mol in the first treatment (CO2 group). The temperature was increased by 2 °C in the second treatment (TEM group) and the concentration of CO2 and temperature were both increased in the third treatment (CO2 + TEM group). The mean temperature and concentration of CO2 in control group were 10.5 °C and 413 μmol/mol. At harvesting, the wheat straws were collected and analyzed for chemical composition and in vitro digestibility. Results showed that dry matter was significantly increased in all three treatments. Ether extracts and neutral detergent fiber were significantly increased in TEM and CO2 + TEM groups. Crude protein was significantly decreased in CO2 + TEM group. In vitro digestibility analysis of wheat straw revealed that gas production was significantly decreased in CO2 and CO2 + TEM groups. Methane production was significantly decreased in TEM and CO2 + TEM groups. Ammonia nitrogen and microbial crude protein were significantly decreased in all three treatments. Total volatile fatty acids were significantly decreased in CO2 and CO2 + TEM groups. In conclusion, the chemical composition of the wheat straw was affected by temperature and CO2 and the in vitro digestibility of wheat straw was reduced, especially in the combined treatment of temperature and CO2.