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Submitted to: International Conference on Greenhouse Gasses and Animal Agriculture
Publication Type: Proceedings Publication Acceptance Date: 7/1/2015 Publication Date: N/A Citation: N/A Interpretive Summary: Respiration chambers have been the preferred method to measure methane emission by cattle, but cattle must be housed in chambers and grazing interrupted. Automated head chambers (Greenfeed, C-Lock, Inc.; Rapid City, South Dakota, USA) are now available as a research tool to measure the methane emission by grazing cattle. Cattle are enticed to the chamber with feed and as they consume the bait the chamber collects a breath sample and analyzes it for methane. A criticism of this system is it only measures methane while the animal is feeding, possibly only 3 to 12 minutes/day. Because the system supplies discrete increments of feed (31 grams each drop), changing the time between the drops will change the length of the sampling period, but lengthening the drop interval discourages feeding. Two experiments were conducted to evaluate the effects that the interval between drops have on the methane estimates. In experiment 1, 16 heifers grazing native mixed grass prairie in Oklahoma had access to the head chamber with it programmed to provide meals with drop intervals of 18, 21, 24, or 27 seconds of 8 drops each and up to 4 meals a day for 57 days. In experiment 2, 16 heifers grazing the same pasture had access to the head chamber with it programmed to provide meals with drop intervals of 19, 27, 35, and 43 seconds of 8 drops each and up to 4 meals a day for 53 days. In each experiment, data were analyzed for the effects of drop interval on methane estimate and number of meals daily. As a result of this analysis, researchers will be able to estimate the optimal drop interval to obtain the best quality estimates of methane emission for cattle grazing extensive pasture landscapes. Technical Abstract: Respiration chambers have been the preferred method to measure methane emission by cattle, but cattle must be housed in chambers and grazing interrupted. Automated head chambers (Greenfeed, C-Lock, Inc.; Rapid City, South Dakota, USA) are now available as a research tool to measure the methane emission by grazing cattle. Cattle are enticed to the chamber with feed and as they consume the bait the chamber collects a breath sample and analyzes it for methane. A criticism of this system is it only measures methane while the animal is feeding, possibly only 3 to 12 minutes/day. Because the system supplies discrete increments of feed (31 grams each drop), changing the time between the drops will change the length of the sampling period, but lengthening the drop interval discourages feeding. Two experiments were conducted to evaluate the effects that the interval between drops have on the methane estimates. In experiment 1, 16 heifers grazing native mixed grass prairie in Oklahoma had access to the head chamber with it programmed to provide meals with drop intervals of 18, 21, 24, or 27 seconds of 8 drops each and up to 4 meals a day for 57 days. In experiment 2, 16 heifers grazing the same pasture had access to the head chamber with it programmed to provide meals with drop intervals of 19, 27, 35, and 43 seconds of 8 drops each and up to 4 meals a day for 53 days. In each experiment, data were analyzed for the effects of drop interval on methane estimate and number of meals daily. As a result of this analysis, researchers will be able to estimate the optimal drop interval to obtain the best quality estimates of methane emission for cattle grazing extensive pasture landscapes. |
