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Through the process of enteric fermentation, cattle produce methane (CH4), a potent greenhouse gas (GHG). Growing public concern about climate change has increased the need for accurate methods of measuring CH4 emissions from cattle directly to improve emission inventories and evaluate emissions mitigation techniques. The present study evaluated a ventilated head box system capable of measuring CH4 and carbon dioxide (CO2) emissions, and oxygen (O2) consumption from cattle. Six Holstein heifers were used to measure CH4 and CO2 emissions and O2 consumption from 2 ad libitum intake measurement periods (ADAPT and ADLIB) and 1 measurement period (RESTRICT) with intake restricted to 2% of BW on a DM basis. Methane emissions during RESTRICT were significantly lower (P < 0.0001) than both ad libitum periods. Daily CH4 emission rates per animal were 235.0 ± 6.19 L/d, 228.3 ± 6.18 L/d, and 193.2 ± 8.88 L/d for the periods ADAPT, ADLIB, and RESTRICT, respectively. Carbon dioxide emission rates were 3627 ± 90.72 L/d, 3632 ± 90.47, and 3184 ± 104.79 L/d for the ADAPT, ADLIB, and RESTRICT periods, respectively. Oxygen consumption rates were 3391 ± 99.77 L/d, 3454 ± 99.57 L/d, and 3002 ± 111.36 L/d for the periods ADAPT, ADLIB, and RESTRICT, respectively. The head box system evaluated provides an accurate method of measuring emissions from cattle and can provide information about daily variations and peaks in emissions. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine the effect of energy/monensin supplementation on CH4 emissions and performance of stocker calves grazing winter wheat (Triticum aestivum). Eight steers (BW = 261 ± 33 kg) and 8 heifers (BW = 240 ± 21 kg) were grazed in a 9-ha pasture with a GreenFeed CH4 measurement system (GEM; C-Lock Inc., Rapid City, SD) after initial adaptation in a dry lot. For 2 wk prior to treatments, baseline CH4 was measured for each animal. Calves were randomly assigned within sex to receive 0, 0.21, 0.43, 0.64, 0.86, or 1.07 kg/d of a supplement (primarily ground corn and wheat midds with mineral supplements and 150 mg/kg monensin.) The GEM bait feed was pelleted wheat midds. Calves were fed 3 d per wk in individual stalls and orts were weighed, so that actual supplement intake was used for analysis. It was assumed that some calves may not consume all available supplement, therefore two calves were assigned to the first 5 supplement levels and 6 assigned to the 1.07 kg/d treatment. This resulted in a relatively uniform distribution of actual supplement intakes in the range of 0.53 to 1.46 kg/d, when GEM bait intake was included. Forage intake was estimated by bolusing TiO2 for 14 days then collecting feces for 5 d, at the end of the experiment, using TiO2 and iADF as external and internal markers. Because several predictor variables were available, dependent variables of interest were subjected to backwards stepwise regression (PROC GLMSELECT in SAS) with baseline CH4, total supplement intake, forage intake, initial BW, sex, and monensin dose in the model. Animal performance increased linearly with total supplement intake and forage intake (P ≤ 0.02; R2 = 0.45). Supplement intake quadratically reduced forage intake (P = 0.01; R2 = 0.47). Methane production increased with increasing forage intake and initial BW, but the heifers produced less CH4 than steers (P = 0.01; R2= 0.74). Methane yield (g CH4/ kg of intake) decreased with increasing DMI and decreasing BW, and heifers yielded less CH4 than steers (P ≤ 0.01; R2 = 0.84). Supplement intake reduced CH4 emission intensity (g CH4/kg BW gain; P = 0.03). These results suggest that supplementing cattle grazing wheat pasture with an energy/monensin supplement improves sustainability. [ABSTRACT FROM AUTHOR]

The objective of this experiment was to determine the effect of whole cottonseed (WCS) supplementation on average daily gain (ADG) and enteric methane (CH4) production of steers grazing native range during spring. Steers (n = 18; body weight = 317 ± 5.5 kg) were adapted to an in-pasture CH4 measurement device (GreenFeed (GF); C-Lock Inc., Rapid City, South Dakota) for one week. Steers were stratified by adaptation-period use of GF and randomly assigned to treatments within stratifications. Treatments were either 0, 0.9, 1.8, 2.7, 3.6, or 4.5 kg of WCS (as-fed) per day offered in individual feeding stanchions. Orts were measured and actual WCS intake was used in the analysis. Unshrunk body weight was measured weekly before feeding for the duration of the experiment. Mean supplement intake per animal ranged from 0.89 to 2.86 kg per day. Total fat content of the diet (WCS + forage) at the greatest WCS intake was estimated to be 6.4%. Animal performance increased linearly as WCS intake increased (P = 0.02). Two of the three steers assigned to the 0 WCS treatment refused to use GF, and therefore CH4 emissions were unavailable. Because only one observation was available at 0 WCS, and the Cook's Distance of this point was greater than one (Di ≥ 7.48), the 0 WCS observation was excluded from further analysis. There tended to be a quadratic relationship between daily methane production (g of CH4 per animal per day) and WCS intake (P = 0.057), and there was a significant quadratic relationship between emission intensity (g of CH4 per kg of ADG) and WCS intake (P = 0.011) indicating minimum CFP at 2.0 kg WCS intake. The increased animal performance associated with WCS supplementation decreased emission intensity at moderate levels of supplementation. If ranchers choose to feed WCS to minimize emission intensity of steers grazing spring native range, they should feed approximately 2.0 kg per day of WCS. [ABSTRACT FROM AUTHOR]

The objective of this experiment was to determine the effect of whole cottonseed (WCS) supplementation on average daily gain (ADG) and enteric methane (CH4) production of steers grazing native range during spring. Steers (n = 18; body weight = 317 ± 5.5 kg) were adapted to an in-pasture CH4 measurement device (GreenFeed (GF); C-Lock Inc., Rapid City, South Dakota) for one week. Steers were stratified by adaptation-period use of GF and randomly assigned to treatments within stratifications. Treatments were either 0, 0.9, 1.8, 2.7, 3.6, or 4.5 kg of WCS (as-fed) per day offered in individual feeding stanchions. Orts were measured and actual WCS intake was used in the analysis. Unshrunk body weight was measured weekly before feeding for the duration of the experiment. Mean supplement intake per animal ranged from 0.89 to 2.86 kg per day. Total fat content of the diet (WCS + forage) at the greatest WCS intake was estimated to be 6.4%. Animal performance increased linearly as WCS intake increased (P = 0.02). Two of the three steers assigned to the 0 WCS treatment refused to use GF, and therefore CH4 emissions were unavailable. Because only one observation was available at 0 WCS, and the Cook's Distance of this point was greater than one (Di ≥ 7.48), the 0 WCS observation was excluded from further analysis. There tended to be a quadratic relationship between daily methane production (g of CH4 per animal per day) and WCS intake (P = 0.057), and there was a significant quadratic relationship between emission intensity (g of CH4 per kg of ADG) and WCS intake (P = 0.011) indicating minimum CFP at 2.0 kg WCS intake. The increased animal performance associated with WCS supplementation decreased emission intensity at moderate levels of supplementation. If ranchers choose to feed WCS to minimize emission intensity of steers grazing spring native range, they should feed approximately 2.0 kg per day of WCS. [ABSTRACT FROM AUTHOR]