Sulfur Hexafluoride Tracer Technique Research Articles

Methane emissions of beef cattle on forages: efficiency of grazing management systems.

Fermentation in the rumen of cattle produces methane (CH4). Methane may play a role in global warming scenarios. The linking of grazing management strategies to more efficient beef production while reducing the CH4 emitted by beef cattle is important. The sulfur hexafluoride (SF6) tracer technique was used to determine the effects of best management practices (BMP) grazing compared with continuous grazing on CH4 production in several Louisiana forages during 1996-1998. Cows and heifers (Bos taurus) grazed common bermudagrass [Cynodon dactylon (L.) Pers.], bahiagrass (Paspalum notatum Flugge), and ryegrass (Lolium multiflorum Lam.) pastures and were wintered on bahiagrass hay with supplements of protein molasses blocks (PMB), cottonseed meal and corn (CSMC), urea and corn (URC), or limited ryegrass grazing (LRG). Daily CH4 emissions were between 89 and 180 g d(-1) for young growing heifers and 165 to 294 g d(-1) for mature Simbrah cows. Heifers on "ad lib" ryegrass in March and April produced only one-tenth the CH4 per kg of gain as heifers on LRG of 1 h. Using BMP significantly reduced the emission of CH4 per unit of animal weight gain. Management-intensive grazing (MIG) is a BMP that offers the potential for more efficient utilization of grazed forage crops via controlled rotational grazing and more efficient conversion of forage into meat and milk. Projected CH4 annual emissions in cows reflect a 22% reduction from BMP when compared with continuous grazing in this study. With the BMP application of MIG, less methane was produced per kilogram of beef gain.

Methane Emissions of Beef Cattle Grazing Tall Fescue Pastures at Three Levels of Endophyte Infestation

AbstractMethane (CH4) is produced by fermentation in the rumen of cattle. Methane may play a part in global warming scenarios. Tall fescue (Festuca arundinacea Schreb.) is an important forage in the eastern United States. The toxic syndrome associated with the endophytic fungus Neotyphodium coenophialum (E+) can be mitigated with management strategies that improve forage quality of E+ tall fescue pastures and animal performance. The sulfur hexafluoride (SF6) tracer technique was used to determine the effects of tall rescue pasture management on CH4 production in 1997–1998. Two steers (Bos taurus) on two pastures each of E+ tall fescue, of endophyte free (E−) tall fescue, of E+/E−(1:1 ratio), and of E+/ladino white clover (Trifolium repens L.), and four steers and four lactating cows with nursing calves grazing either unimproved (UP) or best management practices (BMP) pastures were used to collect eructated CH4 samples. Daily CH4 emissions were about 95 to 200 g d−1 for steers and 150 to 240 g d−1 for cows. Steers grazing E+/clover pastures emitted 20% less CH4 kg−1 d−1 than steers grazing E+, E−, or E+/E− in summer. Season and animal size were the major factors affecting CH4 emissions. This first estimation of CH4 emissions from free‐roaming cattle grazing tall fescue pastures indicates that (i) improved forage management strategies have little effect on daily emissions per animal that are primarily a function of rumen size and intake, and (ii) the amount of emission per unit of animal product is reduced when improved practices are implemented.

Measurement of methane emissions from ruminant livestock using a sulfur hexafluoride tracer technique

The purpose of this paper is to describe a method for determining methane emission factors for cattle. The technique involves the direct measurement of methane emissions from livestock in their natural environment. A small permeation tube containing SF[sub 6] is placed in the cow's rumen, and SF[sub 6] and CH[sub 4] concentrations are measured near the mouth and nostrils of the cow. The SF[sub 6] release provides a way to account for the dilution of gases near the animal's mouth. The CH[sub 4] emission rate can be calculated from the known SF[sub 6] emission rate and the measured SF[sub 6] and CH[sub 4] concentrations. The tracer method described provides an easy means for acquiring a large methane emissions data base from domestic livestock. The low cost and simplicity should make it possible to monitor a large number of animals in countries throughout the world. An expanded data base of this type helps to reduce uncertainty in the ruminant contribution to the global methane budget. 18 refs., 3 figs., 3 tabs.