Group Animal Husbandry in the Tropics and Subtropics, University of Kassel and Georg-August-Universitaet Goettingen, Steinstr. 19, 37213 Witzenhausen, Germany.
Group Animal Husbandry in the Tropics and Subtropics, University of Kassel and Georg-August-Universitaet Goettingen, Steinstr. 19, 37213 Witzenhausen, Germany.
Animal. 2021 Jan;15(1):100070. doi: 10.1016/j.animal.2020.100070. Epub 2020 Dec 10.
The laser methane detector (LMD) has been increasingly used in the last decade to assess the methane (CH) concentration in the exhaled air of ruminants. The CH concentration was mostly measured indoors, where animals were either retained in a feed fence or manually by a person to facilitate the LMD measurements. By contrast, the use of the LMD for measurements under outdoor conditions has been limited to very few studies. The present study applied the LMD to assess the CH concentration in air exhaled by four pasture-fed female Thuringian Forest goats when they were either expressing their natural grazing behaviour or when they were manually restrained at three times of the day during five consecutive days. We compared the activities, including rumination, and the CH concentration between restrained and free-roaming goats, and between goats, days, times of the day and goats' activities. We hypothesised that the restraint influences the goats' behaviour, particularly rumination, which could lead to a change in CH concentration. The overall CH concentration (median) was not affected by goats' restraint (6.5 ppm-m for restrained vs. 6.6 ppm-m for free-roaming). However, restraint influenced goats' rumination activity, with differences between individual goats and days. A lower rumination activity was recorded on the first and the last two days as compared to Day 2-3. Despite the greater rumination activity, the CH concentration was smaller on Day 2 (5.8 ppm-m) as compared to Day 5 (7.4 ppm-m). Similar observations were made with respect to behaviour and CH concentrations in free-roaming goats. By contrast, no differences in the proportion of time of activities were found between the times of day for restrained goats, while free-roaming goats preferred to stand idle but were less frequently lying idle in late afternoon. Still, the greatest CH concentration in restrained goats was obtained for the midday measurements (7.0 ppm-m), while it further increased until late afternoon for free-roaming goats (6.8 ppm-m). It is concluded that the restraint of animals during outdoor measurements can facilitate LMD measurements in grazing animals without changing the results for CH concentration in air exhaled by the animal. An adaptation period of one day followed by two to three measurement days with sufficient measurement periods to account for different activities is recommended to limit the impact on animals' stress level.
激光甲烷探测器 (LMD) 在过去十年中越来越多地用于评估反刍动物呼出空气中的甲烷 (CH) 浓度。CH 浓度主要在室内测量，动物要么被关在饲料围栏里，要么由人手动操作，以便进行 LMD 测量。相比之下，在户外条件下使用 LMD 进行测量的应用非常有限。本研究应用 LMD 评估了 4 只户外放牧的图林根森林母羊在表达其自然放牧行为时或在 5 天内每天 3 次被手动限制时呼出空气中的 CH 浓度。我们比较了在限制和自由放牧的羊之间以及在羊之间、天之间、一天中的时间和羊的活动之间的活动，包括反刍和 CH 浓度。我们假设限制会影响羊的行为，特别是反刍，这可能会导致 CH 浓度的变化。总的 CH 浓度（中位数）不受羊的限制（限制为 6.5ppm-m，自由放牧为 6.6ppm-m）的影响。然而，限制会影响羊的反刍活动，个体羊和天数之间存在差异。与第 2-3 天相比，第 1 天和最后两天的反刍活动较少。尽管反刍活动较多，但第 2 天（5.8ppm-m）的 CH 浓度比第 5 天（7.4ppm-m）小。在自由放牧的羊中也观察到了类似的行为和 CH 浓度观察结果。相比之下，限制羊一天中不同时间的活动时间比例没有差异，而自由放牧的羊更喜欢站着，但下午较晚时躺着的时间较少。尽管如此，限制羊的最大 CH 浓度是在中午测量时获得的（7.0ppm-m），而对于自由放牧的羊，直到下午晚些时候才会进一步增加（6.8ppm-m）。因此，在户外测量期间对动物进行限制可以在不改变动物呼出空气中 CH 浓度的情况下，方便 LMD 测量放牧动物。建议适应期为一天，然后进行两到三天的测量，测量时间要足够长，以考虑不同的活动，以限制对动物应激水平的影响。
