Enteric methane and carbon dioxide emissions measured using respiration chambers, the sulfur hexafluoride tracer technique, and a GreenFeed head-chamber system from beef heifers fed alfalfa silage at three allowances and four feeding frequencies.

The objective of this study was to determine methane (CH) and carbon dioxide (CO) emissions from 8 beef heifers (approximately 20 mo of age and 382 ± 24.3 kg BW) measured by respiration chambers and the sulfur hexafluoride (SF) tracer technique and a mobile head-chamber, spot-sampling system (GreenFeed; C-Lock Inc., Rapid City, SD) when fed alfalfa silage at 3 feeding levels and 4 feeding frequencies. Feeding frequency may affect CH yield (g/kg DMI), and measurement systems (such as GreenFeed or SF) are needed to obtain accurate estimates of CH emissions from individual cattle under grazing where new pasture is provided once or twice daily. The Hereford × Friesian heifers were used in 5 consecutive periods (P1 to P5) of 14 d with CH and CO emissions measured with the SF technique in wk 1 (5-6 d), with chambers in wk 2 (2 d), and with the GreenFeed system when not in chambers (8 d) of each period. Alfalfa silage was restricted to 6, 8, 8, and 8 kg DM/d in P1, P2, P3, and P4, respectively, and provided ad libitum (10.9-12.2 kg DM/d) in P5. Silage was fed in 2, 2, 3, and 4 meals per day in P1, P2, P3, and P4, respectively, and was continuously available (refilled twice daily) in P5. Methane production increased from 141 to 265 g/d as DMI doubled ( < 0.001), but average CH yields measured in respiration chambers (24.5 g/kg DMI) and by the SF technique (22.8 g CH/kg DMI) and the GreenFeed system (26.2 g/kg DMI) were unaffected by feeding management ( = 0.6 for chambers and SF and = 0.06 for GreenFeed). The CH yields estimated by the GreenFeed system did not differ from CH yields estimated by the chambers in P1, P2, P3, and P5 but were greater ( < 0.02) than CH yields estimated by the SF technique in P2, P3, P4, and P5. Yields of CO (g/kg DMI) decreased with increasing DMI ( < 0.04) and CO production (g/d) increased from 5,293 to 9,167 g/d as DMI increased ( < 0.001). In general, the SF technique and the GreenFeed system provided means for CH yield that were not different from those of respiration chambers, and CH yields (g/kg DMI) were unaffected by DMI level or feeding frequency.

Development of methane emission factors for enteric fermentation in cattle from Benin using IPCC Tier 2 methodology.

The objective of this study was to develop emission factors (EF) for methane (CH4) emissions from enteric fermentation in cattle native to Benin. Information on livestock characteristics and diet practices specific to the Benin cattle population were gathered from a variety of sources and used to estimate EF according to Tier 2 methodology of the 2006 Intergovernmental Panel on Climate Change (IPCC) Guidelines for National Greenhouse Gas Inventories. Most cattle from Benin are Bos taurus represented by Borgou, Somba and Lagune breeds. They are mainly multi-purpose, being used for production of meat, milk, hides and draft power and grazed in open pastures and crop lands comprising tropical forages and crops. Estimated enteric CH4 EFs varied among cattle breeds and subcategory owing to differences in proportions of gross energy intake expended to meet maintenance, production and activity. EFs ranged from 15.0 to 43.6, 16.9 to 46.3 and 24.7 to 64.9 kg CH4/head per year for subcategories of Lagune, Somba and Borgou cattle, respectively. Average EFs for cattle breeds were 24.8, 29.5 and 40.2 kg CH4/head per year for Lagune, Somba and Borgou cattle, respectively. The national EF for cattle from Benin was 39.5 kg CH4/head per year. This estimated EF was 27.4% higher than the default EF suggested by IPCC for African cattle with the exception of dairy cattle. The outcome of the study underscores the importance of obtaining country-specific EF to estimate global enteric CH4 emissions.