Department of Animal Science, Faculty of Natural Resources, Rajamangala University of Technology Isan, Sakon Nakhon, Thailand.
Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands.
J Anim Physiol Anim Nutr (Berl). 2020 Mar;104(2):453-461. doi: 10.1111/jpn.13304. Epub 2020 Jan 24.
The background of the current in vitro study involves the issue of methane (CH ) production inherent to rumen fermentation. One of the dietary strategies to reduce enteric CH production by ruminants involves the supplementation of medium-chain fatty acids in diets. As such, oils containing high amounts of MCFA, such as coconut, palm kernel and krabok oil, are of much interest to formulate energy efficient and environmentally friendly rations for ruminants. Krabok oil (KO) reduces methanogenesis, but the appropriate inclusion level of dietary KO is unclear. We therefore investigated the dose-response relationship between krabok oil and CH production. In practice, the use of whole krabok seed (WKS), instead of KO, is easier, but the efficacy of WKS to inhibit methanogenesis was hitherto unknown. Thus, we also investigated whether WKS provides an alternative tool to inhibit CH production. The experimental substrates contained either KO, WKS, the residue of WKS after fat extraction residue (FER) or FER + KO. Appropriate amounts of WKS or its derivatives were added to a basal substrate so as to attain either a low, medium or high content of KO, that is, 37-46, 90-94 and 146-153 g/kg dry matter respectively. The experimental substrates were formulated to keep the amounts of incubated fat-free OM, crude protein, neutral detergent fibre and acid detergent fibre constant in order to avoid biased results through potential differences in fermentability between WKS and its derivatives, and the basal substrate. The latter resembled the ingredient composition of a total mixed ration commonly used in Thai dairy cows. Fully automated gas production (GP) equipment was used to measure gas- and CH production. Irrespective of the type of substrate (p ≥ .115), both the absolute (ml/g fat-free OM) and relative (% of total GP) CH production was reduced at the highest inclusion level of WKS or its derivatives (p ≤ .019). Total GP (ml/g fat-free OM), however, was reduced after incubation of FER, FER + KO, and WKS, but not KO, at the highest inclusion level of the respective substrates (p = .019). Volatile fatty acids were likewise affected (p ≤ .001). Krabok oil can inhibit CH production but only when the dietary KO content is at least 9.4% (DM). Supplementation of KO in the form of WKS, however, is considered not opportune because the fat extracted residue of WKS is poorly degraded during fermentation.
本体外研究的背景涉及瘤胃发酵固有的甲烷（CH ）产生问题。减少反刍动物肠道 CH 产生的饮食策略之一是在饮食中补充中链脂肪酸。因此，含有大量 MCFA 的油，如椰子油、棕榈仁油和卡波克油，对于为反刍动物配制高能效和环保的日粮非常有吸引力。卡波克油（KO）可减少甲烷生成，但日粮中 KO 的适当添加水平尚不清楚。因此，我们研究了 KO 与 CH 生成之间的剂量反应关系。实际上，使用整个卡波克种子（WKS）而不是 KO 更容易，但迄今为止，WKS 抑制甲烷生成的效果尚不清楚。因此，我们还研究了 WKS 是否提供了抑制 CH 生成的替代工具。实验底物含有 KO、WKS、脂肪提取后残渣（FER）或 FER+KO。向基础底物中添加适量的 WKS 或其衍生物，以达到 KO 的低、中、高含量，即 37-46、90-94 和 146-153 g/kg 干物质。实验底物的配方保持了孵育无脂肪 OM、粗蛋白、中性洗涤剂纤维和酸性洗涤剂纤维的量不变，以避免 WKS 及其衍生物与基础底物之间的发酵性差异导致的结果偏差。后者类似于泰国奶牛常用的全混合日粮的成分组成。使用全自动气体产生（GP）设备测量气体和 CH 产生。无论底物类型如何（p≥.115），WKS 或其衍生物的最高添加水平下，绝对（每克无脂肪 OM 的 ml/g）和相对（总 GP 的%）CH 产生均降低（p≤.019）。然而，在最高添加水平的 FER、FER+KO 和 WKS 孵育后，总 GP（每克无脂肪 OM 的 ml/g）减少，但 KO 则不然（p=.019）。挥发性脂肪酸也受到影响（p≤.001）。KO 可以抑制 CH 生成，但仅当饮食 KO 含量至少为 9.4%（DM）时。然而，以 WKS 的形式补充 KO 被认为不合适，因为 WKS 的脂肪提取残渣在发酵过程中降解不良。
