Enteric methane output from selected herds of beef cattle raised under extensive arid rangelands

Abstract

Extensively raised beef cattle contribute to the highest levels of enteric methane (CH 4 ) gas emissions among all livestock. Expensive techniques and logistics hinder monitoring of such gas. Therefore, the objective of this study was to use an inexpensive laser methane detector (LMD) apparatus to determine the enteric CH 4 levels from a herd of beef cows raised on semi-arid rangelands. A total of 24 cows were selected from Boran and Nguni cows (n = 12 per breed) from two different farms. The parities of the cows were as follows: parity 1 (n = 6), parity 2 (n = 6), parity 3 (n = 6) and parity 4 (n = 6). An observer used a hand-held LMD to measure enteric CH 4 emissions plumes during the late afternoon hours when the animals were resting (either standing or lying down). Point measurements (expressed in ppm/m) were taken for six consecutive days and repeated once after every three months. The ratio of CH 4 output per kilogramme DMI was not different in within-breed and between-breed in both seasons. Generally, the dry season recorded the highest CH 4 output per kilogramme of live weight of cow. For example, Boran cows in parity 2 produced the highest output of 1.0 ± 0.04 g CH 4 per kilogramme live weight of cow while Nguni cows in parities 1, 2 and 4 each produced 0.9 ± 0.04 g CH 4 per kilogramme live weight of cow in the dry season. All the animals maintained optimal body condition scores in both seasons (ranging between the lowest of 3.2 ± 0.01 and the highest of 3.4 ± 0.01). Based on the results of the study, it is concluded that cows from both herds produced higher CH 4 per kilogramme live weight of cow in the dry season while maintaining optimal body condition scores in both seasons.

Role of emission sources and atmospheric sink on the seasonal cycle of CH<sub>4</sub> and δ<sup>13</sup>-CH<sub>4</sub>: analysis based on the atmospheric chemistry transport model TM5

“…This is more in line with EDGAR v4.3.2 compared to v5.0 at 30°S-90°S. A study performed in South Africa, concluded that Nguni and Boran cows produce more CH 4 per kilogram live weight of cow during the dry season (mid-May to October) compared to the wet season (November to early May) (Mapfumo et al, 2018), which partly corresponds to EFMM emissions peaking in August-October in EDGARv4.3.2 at 30°S-90°S. In contrast, Arndt et al (2018) measured emissions from Jersey cattle (primary breed) in California and found that animal housing (enteric fermentation as major source) had no seasonality, which corresponds well to EDGAR v5.0.…”

Influence of graded levels of baobab oil seed cake on growth performance and enteric methane emissions in Savannah × Boer crossbreed yearling goats.

“…The LMD equipment measures the concentration of CH4 between the equipment and the target point. It is based on infrared absorption spectroscopy and measures CH4 values as a plume [24][25][26]. Thus the measurements are in parts per million-metre (ppm-m) [25].…”

“…The equipment operates normally in the temperature range between 0 and 40 °C, in the humidity range of 20-90%, with a reaction time of 0.1 seconds. The LMD can detect CH4 concentrations between 1 and 50,000 ppm within a distance of up to 150 m. Gas column density was measured by directing the auxiliary LMD targeting (visible HeNe) laser beam at the nostrils of goats at a distance of 1.5m from the goat [26]. Prior the commencement of the measurements for each day, the LMD was off-set to adjust it to the ambient CH4.…”

Measuring Livestock CH4 Emissions with the Laser Methane Detector: A Review

“…Reported numbers of measurements per animal range from 1 [14] to 72 per cow [32] and 63 per goat [26]. When deciding on the appropriate number of replicates per animal, there is a trade-off between workload and invasiveness on the one hand and the quality of the data on the other.…”