Ruminant Nutrition, Department of Animal Sciences, University of Göttingen, Göttingen, Germany.
Institute of Agricultural Sciences, ETH Zurich, Lindau, Switzerland.
J Anim Physiol Anim Nutr (Berl). 2023 Sep;107(5):1176-1186. doi: 10.1111/jpn.13815. Epub 2023 Mar 9.
Sheep with a relatively low methane yield were observed to have shorter fluid and particle mean retention times (MRT). Because the application of pilocarpine, a saliva stimulant, was successful in reducing retention times in ruminants in previous studies, we applied this substance to sheep, expecting a reduction in MRT and methane yield. Three non-pregnant sheep (74 ± 10 kg) were fed a hay-only diet in a 3 × 3 Latin square design with oral doses of 0, 2.5 and 5 mg pilocarpine/kg body weight and day. Measurements included feed and water intake, MRT of liquid and particulate phases in the reticulorumen (RR) and total gastrointestinal tract (GIT), ruminal microbial yield (via urinary purine bases and metabolic faecal nitrogen), total tract methane emission, apparent nutrient digestibility and rumen fluid parameters. Data were investigated for linear and quadratic effects using orthogonal polynomial contrasts. The MRT of liquid and small particles in the RR and total GIT, and the short-chain fatty acid concentration in rumen fluid, linearly declined with increasing pilocarpine dosage, while no quadratic relationship was detected. Intake of feed DM and water, apparent nutrient digestibility, methane yield and microbial yield were not affected by pilocarpine. When combining the sheep data with that of a similar experiment in cattle, we found that the MRT of the liquid phase was positively associated with estimated NDF digestibility and with methane production per digested NDF, but was not associated with microbial yield or the ratio of acetate to propionate. The ratio between MRT of the particulate and the liquid phase was smaller for sheep than that for cattle, and was not affected by treatment. Differences in this ratio might explain why species reacted differently to the saliva-inducing agent, which might help to explain the discrepancy between species in the effect of induced saliva flow on digestive parameters.
研究发现，甲烷排放量相对较低的绵羊具有较短的液体和颗粒平均停留时间（MRT）。由于在以前的研究中，应用毛果芸香碱（一种唾液刺激剂）成功地减少了反刍动物的停留时间，我们将这种物质应用于绵羊，期望减少 MRT 和甲烷产量。三头非妊娠绵羊（74±10kg）以干草为主的饮食，采用 3×3 拉丁方设计，每天口服 0、2.5 和 5mg/kg 体重的毛果芸香碱。测量包括饲料和水的摄入量、网胃（RR）和整个胃肠道（GIT）中液体和颗粒相的 MRT、瘤胃微生物产量（通过尿嘌呤碱基和代谢粪便氮）、总肠道甲烷排放、表观养分消化率和瘤胃液参数。使用正交多项式对比分析数据的线性和二次效应。RR 和总 GIT 中液体和小颗粒的 MRT，以及瘤胃液中的短链脂肪酸浓度，随毛果芸香碱剂量的增加呈线性下降，而未检测到二次关系。毛果芸香碱不影响饲料 DM 和水的摄入量、表观养分消化率、甲烷产量和微生物产量。当将绵羊数据与类似的牛实验数据结合起来时，我们发现液体相的 MRT 与估计的 NDF 消化率和每消化 NDF 的甲烷产量呈正相关，但与微生物产量或乙酸与丙酸的比例无关。与牛相比，绵羊的颗粒相与液体相的 MRT 比值较小，且不受处理的影响。这种比值的差异可能解释了为什么不同物种对唾液诱导剂的反应不同，这可能有助于解释诱导唾液流对消化参数的影响在不同物种之间存在差异的原因。
