Evaluation of Interval between Measurements for Quantification of Enteric Methane Emissions Measured by Respiration Chamber
Respiration chamber is the frequently employed techniques for measuring enteric CH4 emission in ruminants. However, rate of CH4 emissions is not consistent throughout day, the interval time between measurements usually miss maximum and minimum values and may affect the estimation of total CH4 emissions, which need verification.
Researchers from China Agricultural University and the Institute of Subtropical Agriculture (ISA) of the Chinese Academy of Sciences investigated the evaluation of interval between measurements and calculation method for the quantification of enteric methane emissions measured by respiration chamber. Their findings were published in Journal of Dairy Science.Details can be found at https://www.sciencedirect.com/science/article/pii/S0022030219304084
Scientists found that the 23-h kinetics of CH4 emissions and rates of CH4 emissions varied widely among 10 cows, and the amount of 23-h CH4 emissions was positively correlated with body weight (r = 0.70; P = 0.02) and age (r = 0.85; P = 0.002) of cows.
The rates of CH4 emissions were not constant throughout the day and ranged between 4.6 to 11.4 g/h. The maximum rate of CH4 emissions occurred about 1 to 2 h after feeding, and then the rate of CH4 emissions gradually declined to the basal level.
When animals were fed twice per day, two distinct peaks were observed in the diurnal kinetics of CH4 emissions. However, when measurement frequency was decreased by increasing the interval between measurements, diurnal kinetics of CH4 emissions changed significantly.
Furthermore, increased interval significantly (P ≤ 0.05) decreased maximum rate of CH4 emission and increased minimum rate of CH4 emission. When interval was increased from 0.5 to 180 min, the calculated amount of 23-h CH4 emissions was not affected. Although measuring CH4 concentrations at different intervals missed the maximum and minimum values in the kinetics of CH4 emissions, the missed maximum and minimum values might offset each other, leading to the unchanged estimate of total CH4 emissions.
When interval was extended to 4 h, the calculated amount of 23-h CH4 emissions were significantly (P < 0.001) increased in comparison to the estimate made using measurements at 0.5 min intervals.
This study indicated that increasing the interval between measurements may lead to an underestimate of maxima and an overestimate of minima with respect to the pattern of daily enteric CH4 emissions, but does not affect the estimate of 23-h CH4 emission if the interval between measurements is less than or equal to 3 h.
The research was supported by National Key Research and Development Program of China, National Natural Science Foundation of China, State Key Laboratory of Animal Nutrition, Hunan province science and technology plan, China Agriculture Research System, Youth Innovation Promotion Association CAS, CAS President’s International Fellowship.
Contact: Wang Min
E-mail: mwang@isa.ac.cn
Institute of Subtropical Agriculture, Chinese Academy of Sciences
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