Guarnido-Lopez Pablo, Menendez Hector Manuel, Husmann Aletta, Parsons Ira, Antaya Andrew, Brennan Jameson, Tedeschi Luis Orlindo
Department of Animal Science, Texas A&M University, College Station, TX 77843.
Department of Animal Science, South Dakota State University, Rapid City, SD 57702.
J Anim Sci. 2025 Jan 4;103. doi: 10.1093/jas/skaf229.
Global concern about the environmental impact of livestock production has been increasing over the past decade; consequently, research has focused on mitigating these emissions. Among all devices deployed to access greenhouse gases (GHG), the GreenFeed (GF) system is the most used for grazing systems. Nonetheless, the primary issue about GF use is its higher variability and the low repeatability (R) of GHG measurements in grazing individuals compared to other methods. Thus, this work aimed to assess both environmental and animal factors, as well as the variability of the GF itself, to explain GHG variability in cattle. These evaluations are usually conducted under experimental conditions, but in this work, both the variability and R values of CH4 were analyzed under commercial settings. Three and two GF units were deployed simultaneously in a dry lot and then in a grazing pasture, respectively, on a commercial cattle ranch. To evaluate the variability and R values of GHG, the GF collected enteric emissions, wind speed, wind direction, temperature, and animal data from 175 and 169 Angus heifers in dry lot and pasture settings, respectively. Variance component analyses were used to evaluate the influence of these factors on the GHG measurements. Results showed a coefficient of variation (CV) of CH4 and CO2 measured through the GF of 32% and 20%, respectively. Of the total CH4 variation in grazing conditions, 2.73% was explained by environmental factors and 38.3% was explained by animal factors, including feeding behavior (4.58%), between-animal variation (16.4%), date of the visit (12.5%), hour of the visits (3.05%), visits' duration (1.78%), and number of visits/day (1.25%). In contrast, in the dry lot, environmental and animal factors explained 7.49% and 8.58% of the CH4 variation, respectively. Finally, the GF equipment itself explained 0.15% and 2.06% of the variation of the CH4 in the grazing and dry lot conditions, respectively. The R values, measured as the animal variance divided by the sum of animal and error variances, increased linearly (0.094 to 0.23) in the dry lot, while in the grazing settings, it decreased linearly (0.098 to 0.056) from days 1 to 21. This study identified the most influential factors contributing to the variability of GHG emissions and the low R values of CH4 in commercial grazing cattle production, paving the way for enhanced future use of GF devices for reporting GHG emissions in grazing systems.
在过去十年中，全球对畜牧生产环境影响的关注日益增加；因此，研究重点一直放在减少这些排放上。在所有用于测量温室气体（GHG）的设备中，GreenFeed（GF）系统是放牧系统中使用最多的。然而，使用GF的主要问题是其变异性较高，与其他方法相比，放牧个体的温室气体测量的重复性（R）较低。因此，这项工作旨在评估环境和动物因素以及GF本身的变异性，以解释牛群中温室气体的变异性。这些评估通常在实验条件下进行，但在这项工作中，甲烷（CH4）的变异性和R值是在商业环境中进行分析的。在一个商业养牛场中，分别在一个干栏式畜舍和一个放牧牧场中同时部署了3个和2个GF单元。为了评估温室气体的变异性和R值，则分别从干栏式畜舍和牧场环境中的175头和169头安格斯小母牛身上，通过GF收集肠道排放、风速、风向、温度和动物数据。方差成分分析用于评估这些因素对温室气体测量的影响。结果显示，通过GF测量的CH4和CO2的变异系数（CV）分别为32%和20%。在放牧条件下，CH4总变异的2.73%由环境因素解释，38.3%由动物因素解释，包括采食行为（4.58%）、动物间变异（16.4%）访问日期（12.5%）、访问时间（3.05%）、访问持续时间（1.78%）和每天访问次数（1.25%）。相比之下，在干栏式畜舍中，环境和动物因素分别解释了CH4变异的7.49%和8.58%。最后，GF设备本身在放牧和干栏式畜舍条件下分别解释了CH4变异的0.15%和2.06%。以动物方差除以动物和误差方差之和来衡量的R值，在干栏式畜舍中呈线性增加（从0.094到0.23），而在放牧环境中，从第1天到第21天呈线性下降（从0.098到0.056）。这项研究确定了在商业放牧牛生产中导致温室气体排放变异性和CH4低R值的最有影响的因素，为未来在放牧系统中更有效地使用GF设备报告温室气体排放铺平了道路。
