Alemu A W, Vyas D, Manafiazar G, Basarab J A, Beauchemin K A
J Anim Sci. 2017 Aug;95(8):3727-3737. doi: 10.2527/jas.2017.1501.
The objectives of this study were to evaluate the relationship between residual feed intake (RFI; g/d) and enteric methane (CH) production (g/kg DM) and to compare CH and carbon dioxide (CO) emissions measured using respiration chambers (RC) and the GreenFeed emission monitoring (GEM) system (C-Lock Inc., Rapid City, SD). A total of 98 crossbred replacement heifers were group housed in 2 pens and fed barley silage ad libitum and their individual feed intakes were recorded by 16 automated feeding bunks (GrowSafe, Airdrie, AB, Canada) for a period of 72 d to determine their phenotypic RFI. Heifers were ranked on the basis of phenotypic RFI, and 16 heifers (8 with low RFI and 8 with high RFI) were randomly selected for enteric CH and CO emissions measurement. Enteric CH and CO emissions of individual animals were measured over two 25-d periods using RC (2 d/period) and GEM systems (all days when not in chambers). During gas measurements metabolic BW tended to be greater ( ≤ 0.09) for high-RFI heifers but ADG tended ( = 0.09) to be greater for low-RFI heifers. As expected, high-RFI heifers consumed 6.9% more feed ( = 0.03) compared to their more efficient counterparts (7.1 vs. 6.6 kg DM/d). Average CH emissions were 202 and 222 g/d ( = 0.02) with the GEM system and 156 and 164 g/d ( = 0.40) with RC for the low- and high-RFI heifers, respectively. When adjusted for feed intake, CH yield (g/kg DMI) was similar for high- and low-RFI heifers (GEM: 27.7 and 28.5, = 0.25; RC: 26.5 and 26.5, = 0.99). However, CH yield differed between the 2 measurement techniques only for the high-RFI group ( = 0.01). Estimates of CO yield (g/kg DMI) also differed between the 2 techniques ( ≤ 0.03). Our study found that high- and low-efficiency cattle produce similar CH yield but different daily CH emissions. The 2 measurement techniques differ in estimating CH and CO emissions, partially because of differences in conditions (lower feed intakes of cattle while in chambers, fewer days measured in chambers) during measurement. We conclude that when intake of animals is known, the GEM system offers a robust and accurate means of estimating CH emissions from animals under field conditions.
本研究的目的是评估剩余采食量（RFI；克/天）与肠道甲烷（CH）产量（克/千克干物质）之间的关系，并比较使用呼吸室（RC）和GreenFeed排放监测（GEM）系统（C-Lock公司，南达科他州拉皮德城）测量的CH和二氧化碳（CO）排放量。总共98头杂交后备小母牛被分组饲养在2个牛栏中，自由采食大麦青贮饲料，其个体采食量由16个自动饲喂槽（GrowSafe，加拿大艾伯塔省艾尔德里）记录72天，以确定它们的表型RFI。根据表型RFI对小母牛进行排名，随机选择16头小母牛（8头RFI低的和8头RFI高的）进行肠道CH和CO排放量测量。在两个25天的时间段内，使用RC（每个时间段2天）和GEM系统（不在呼吸室的所有日子）测量个体动物的肠道CH和CO排放量。在气体测量期间，高RFI小母牛的代谢体重往往更大（P≤0.09），但低RFI小母牛的平均日增重往往更大（P = 0.09）。正如预期的那样，高RFI小母牛比效率更高的小母牛多消耗6.9%的饲料（P = 0.03）（分别为7.1和6.6千克干物质/天）。低RFI和高RFI小母牛使用GEM系统时的平均CH排放量分别为202和222克/天（P = 0.02），使用RC时分别为156和164克/天（P = 0.40）。在对采食量进行校正后，高RFI和低RFI小母牛的CH产量（克/千克干物质采食量）相似（GEM：27.7和28.5，P = 0.25；RC：26.5和26.5，P = 0.99）。然而，仅在高RFI组中，两种测量技术的CH产量存在差异（P = 0.01）。两种技术的CO产量（克/千克干物质采食量）估计值也存在差异（P≤0.03）。我们的研究发现，高效和低效的牛产生相似的CH产量，但每日CH排放量不同。两种测量技术在估计CH和CO排放量方面存在差异，部分原因是测量期间条件不同（牛在呼吸室内时采食量较低，在呼吸室内测量的天数较少）。我们得出结论，当动物的采食量已知时，GEM系统提供了一种在田间条件下估计动物CH排放量的可靠且准确的方法。
