Department of Animal and Veterinary Sciences, AU Viborg-Research Centre Foulum, Aarhus University, 8830 DK-Tjele, Denmark.
Department of Animal and Veterinary Sciences, AU Viborg-Research Centre Foulum, Aarhus University, 8830 DK-Tjele, Denmark.
J Dairy Sci. 2024 Aug;107(8):5681-5698. doi: 10.3168/jds.2023-24343. Epub 2024 Apr 11.
Dietary methane (CH) mitigation is in some cases associated with an increased hydrogen (H) emission. The objective of the present study was to investigate the acute and short-term effects of acceptors for H (fumaric acid, acrylic acid, or phloroglucinol) supplemented via pulse-dosing to dairy cows fed CH mitigating diets (using nitrate or 3-nitrooxypropanol), on gas exchange, rumen gas, and VFA composition. For this purpose, 2 individual 4 × 4 Latin square experiments were conducted with 4 periods of 3 d (nitrate supplementation) and 7 d (3-nitrooxypropanol supplementation), respectively. In each study, 4 rumen-cannulated Danish Holstein cows were used. Each additive for CH mitigation was included in the ad libitum-fed diet within the 2 experiments (exp. 1 and exp. 2), to which the cows were adapted for at least 14 d. Acceptors for H were administered twice daily in equal portions through the rumen fistula immediately after feeding of the individual cow. In exp. 1 (nitrate), the treatments were CON-1 (no H-acceptor), FUM-1 (fumaric acid), ACR-1 (acrylic acid), and FUM+ACR-1 (50% FUM-1 + 50% ACR-1). In exp. 2 (3-nitrooxypropanol), the 3 treatments, CON-2, FUM-2, and ACR-2, were similar to CON-1, FUM-1 and ACR-1 treatments, however the fourth treatment was PHL-2 (phloroglucinol). Gas exchanges were measured in respiration chambers, and samples of rumen liquid and headspace gas were taken in time series relative to feeding and dosing on specific days. Headspace gas was analyzed for gas composition, and rumen liquid was analyzed for VFA composition and dissolved gas concentrations. Headspace gas composition and dissolved gas concentration were only measured in exp. 2. Dry matter intake was reduced upon acrylic acid supplementation. There were no significant effects of any treatments in any experiments on H emission, except for a decrease in hourly H emission rate (g/h) at 1 h after feeding in both experiments. In exp. 2, H headspace proportions increased with ACR-2 supplementation, whereas dissolved concentrations were unaffected. In exp. 1, cows on ACR-1 increased propionate proportion at 1 h after feeding. In exp. 2, both FUM-2 and ACR-2 increased rumen propionate proportion in the hours after feeding and dosing. There was no effect on rumen acetate for cows on PHL-2. There was a strong positive correlation between rumen dissolved CH and headspace CH (r = 0.84), whereas the equivalent correlation was weaker for H (r = 0.41). For the relationship between dissolved concentrations and emissions of CH and H, there was a moderate positive correlation for CH (r = 0.54), whereas it was weak for H (r = 0.28) with zero slope. In conclusion, the results suggested that fumaric acid and acrylic acid to some extent was reduced to propionate without associative effects on measures for H redirection. Furthermore, phloroglucinol seemed not to be metabolized in the rumen in the present study, because no effects on rumen acetate or measures of H were observed. Changes in H headspace and emission may be a poor proxy for actual changes in the rumen fluid concentration of H.
日粮甲烷(CH)减排有时与氢气(H)排放量增加有关。本研究的目的是研究通过脉冲给奶牛补充 H 受体(延胡索酸、丙烯酸或间苯三酚)对饲喂 CH 减排日粮(使用硝酸盐或 3-硝基氧基丙醇)的奶牛的气体交换、瘤胃气体和 VFA 组成的急性和短期影响。为此,进行了 2 个单独的 4×4 拉丁方实验,分别有 3 天(硝酸盐补充)和 7 天(3-硝基氧基丙醇补充)的 4 个周期。在每个研究中,使用了 4 头瘤胃插管的丹麦荷斯坦奶牛。在 2 个实验中(实验 1 和实验 2),CH 减排的每种添加剂都包含在自由采食的日粮中,奶牛至少适应了 14 天。H 受体在饲喂奶牛后立即通过瘤胃瘘管每天两次等分给药。在实验 1(硝酸盐)中,处理为 CON-1(无 H 受体)、FUM-1(延胡索酸)、ACR-1(丙烯酸)和 FUM+ACR-1(50% FUM-1 + 50% ACR-1)。在实验 2(3-硝基氧基丙醇)中,3 种处理,CON-2、FUM-2 和 ACR-2,与 CON-1、FUM-1 和 ACR-1 处理相似,然而,第四种处理是 PHL-2(间苯三酚)。在呼吸室中测量气体交换,并在特定日期相对于饲喂和给药进行时间序列采样,以获取瘤胃液和顶空气体样本。顶空气体分析用于气体组成,瘤胃液分析用于 VFA 组成和溶解气体浓度。仅在实验 2 中测量顶空气体组成和溶解气体浓度。在补充丙烯酸时,干物质摄入量减少。除了两个实验中在饲喂后 1 小时 H 排放率(g/h)降低外,任何处理都没有对 H 排放产生显著影响。在实验 2 中,随着 ACR-2 的补充,H 顶空比例增加,而溶解浓度不受影响。在实验 1 中,饲喂 ACR-1 的奶牛在饲喂后 1 小时丙酸比例增加。在实验 2 中,饲喂 FUM-2 和 ACR-2 的奶牛在饲喂和给药后几小时内增加了瘤胃丙酸比例。饲喂 PHL-2 的奶牛对瘤胃乙酸没有影响。瘤胃溶解 CH 与顶空 CH 之间存在很强的正相关(r = 0.84),而等效相关性较弱(r = 0.41)。对于 CH 和 H 的溶解浓度与排放之间的关系,CH 有中度正相关(r = 0.54),而 H 有弱相关(r = 0.28),斜率为零。总之,结果表明,延胡索酸和丙烯酸在一定程度上还原为丙酸,而对 H 重定向的措施没有关联影响。此外,在本研究中,间苯三酚似乎没有在瘤胃中代谢,因为没有观察到对瘤胃乙酸或 H 措施的影响。H 顶空和排放的变化可能是瘤胃液中 H 浓度实际变化的一个很差的替代指标。