Department of Animal Sciences and Industry, Kansas State University, Manhattan, KS 66506, USA.
J Anim Sci. 2023 Jan 3;101. doi: 10.1093/jas/skad176.
Enteric fermentation from cattle results in greenhouse gas production that is an environmental concern and also an energetic loss. Several methods exist to quantify gas fluxes; however, an open circuit gas quantification system (OCGQS) allows for unencumbered quantification of methane (CH4), carbon dioxide (CO2), and oxygen (O2) from grazing cattle. While previous literature has proven the accuracy of an OCGQS, little work has been done to establish the minimum number of spot samples required to best evaluate an individual grazing animal's gas fluxes and metabolic heat production. A GreenFeed system (C-Lock Inc.) was used to collect at least 100 spot samples each from 17 grazing cows. The mean gas fluxes and metabolic heat production were computed starting from the first 10 visits (forward) and increasing by increments of 10 until an animal had 100 visits. Mean gas fluxes and metabolic heat production were also computed starting from visit 100 (reverse) in increments of 10 using the same approach. Pearson and Spearman correlations were computed between the full 100 visits and each shortened visit interval. A large increase in correlations were seen between 30 and 40 visits. Thus, mean forward and reverse gas fluxes and metabolic heat production were also computed starting at 30 visits and increasing by 2 until 40 visits. The minimum number of spot samples was determined when correlations with the full 100 visits were greater than 0.95. The results indicated that the minimum numbers of spot samples needed for accurate quantification of CH4, CO2, and O2 gas fluxes are 38, 40, and 40, respectively. Metabolic heat production can be calculated using gas fluxes collected by the OCGQS with 36 spot samples. Practically, calculation of metabolic heat production will require 40 spot samples because the component gases for metabolic heat calculation require up to 40 spot samples. Published literature from nongrazing (confined) environments recommended a similar number of total spot samples. Large variation existed around the average number of spot samples for an animal per day, therefore a wide range of test durations may be needed to meet the same number of spot samples in different populations. For this reason, protocols for the OCGQS should be based on the total number of spot samples, rather than a test duration.
牛的肠道发酵会产生温室气体，这不仅引起了环境方面的关注，也是能量的损失。有几种方法可以量化气体通量；然而，开路气体量化系统（OCGQS）可以无障碍地量化放牧牛的甲烷（CH4）、二氧化碳（CO2）和氧气（O2）。虽然之前的文献已经证明了 OCGQS 的准确性，但很少有人致力于确定获得单个放牧动物气体通量和代谢产热的最佳评价所需的最少点样数。GreenFeed 系统（C-Lock Inc.）用于从 17 头放牧奶牛中收集至少 100 个点样。从最初的 10 次访问（正向）开始计算平均气体通量和代谢产热，并以每次增加 10 次的方式增加，直到动物有 100 次访问。从第 100 次访问（反向）开始，以相同的方式每次增加 10 次，也计算平均气体通量和代谢产热。计算了 100 次完整访问和每个缩短访问间隔之间的 Pearson 和 Spearman 相关性。在 30 到 40 次访问之间观察到相关性的大幅增加。因此，从 30 次访问开始，每次增加 2 次，直到 40 次访问，计算正向和反向平均气体通量和代谢产热。当与完整的 100 次访问的相关性大于 0.95 时，确定了点样的最小数量。结果表明，准确量化 CH4、CO2 和 O2 气体通量所需的最小点样数量分别为 38、40 和 40。代谢产热可以使用 OCGQS 收集的气体通量进行计算，需要 36 个点样。实际上，由于代谢热计算所需的组分气体需要多达 40 个点样，因此计算代谢产热需要 40 个点样。来自非放牧（封闭）环境的已发表文献推荐了类似数量的总点样。动物每天的平均点样数量存在很大差异，因此，为了在不同群体中达到相同数量的点样，可能需要不同的测试持续时间。出于这个原因，OCGQS 的方案应该基于点样的总数，而不是测试持续时间。
