Zhang Xiaoyu, Li Yang, Terranova Melissa, Ortmann Sylvia, Kreuzer Michael, Hummel Jürgen, Clauss Marcus
Department of Animal Sciences, Ruminant Nutrition, University of Göttingen, Göttingen, Germany.
Institute of Agricultural Sciences, ETH Zurich, Lindau, Switzerland.
J Anim Physiol Anim Nutr (Berl). 2023 Mar;107(2):394-406. doi: 10.1111/jpn.13733. Epub 2022 May 12.
While information on individual differences in digesta mean retention time (MRT) might be interesting when selecting phenotypes for digestive efficiency, MRT measurements are prohibitively labour-intensive for large-scale application. Therefore, more easily measured proxies of MRT might be helpful. We used the opportunity of an experiment applying saliva stimulant in cattle to investigate the effect of different individual chewing behaviour on fluid and particle MRT with a consistent diet. Four non-lactating cattle (670-850 kg body mass [BM]) were used in a 4 × 4 Latin square design, treated with the saliva stimulant pilocarpine in dosages of 0, 1, 2.5 and 5 mg/kg BM per day. The cattle were fed hay with dry matter intake (DMI) assigned according to their metabolic body weight. MRT in the whole gastrointestinal tract (GIT), the reticulorumen (RR) and the distal tract were measured using Co-EDTA, Cr-mordanted fibre and La-mordanted fibre as markers representing fluid, small particles (2 mm) and large particles (1 cm), respectively. The chewing behaviour was measured via noseband pressure sensor and expressed as chewing frequency (chews per time) and chewing intensity (chews per DMI), both for total chewing (ingestion plus rumination) and rumination chewing alone. The animals differed considerably in chewing behaviour and MRT measures. BM did not show a significant effect on chewing behaviour and MRT measures, though it tended to negatively correlated to total chewing intensity. Chewing intensity exerted a significant negative influence on MRT of fluid and particles in the RR, which was not the case for chewing frequency. Chewing frequency showed a significant relationship with MRT of large particles in the GIT. We suggest that chewing behaviour could influence MRT in two ways: (i) by affecting saliva production via the masticatory-salivary reflex and subsequently, the fluid inflow to the RR; (ii) by contributing to particle size reduction. Should the link between chewing behaviour and MRT be corroborated in larger studies, chewing measures, with their large interindividual variation, could emerge as an easy-to-measure proxy for MRT characteristics.
在选择消化效率的表型时，关于消化物平均停留时间（MRT）个体差异的信息可能会很有趣，但MRT测量对于大规模应用来说劳动强度过高。因此，更容易测量的MRT替代指标可能会有所帮助。我们利用在牛身上应用唾液刺激剂的实验机会，研究了在一致的日粮条件下，不同个体咀嚼行为对液体和颗粒MRT的影响。四头非泌乳牛（体重[BM]为670 - 850千克）采用4×4拉丁方设计，每天分别用剂量为0、1、2.5和5毫克/千克BM的唾液刺激剂毛果芸香碱进行处理。根据牛的代谢体重分配干草采食量（DMI）来喂养这些牛。使用Co - EDTA、铬媒染纤维和镧媒染纤维作为标记物，分别代表液体、小颗粒（2毫米）和大颗粒（1厘米），测量整个胃肠道（GIT）、瘤网胃（RR）和远端肠道的MRT。通过鼻带压力传感器测量咀嚼行为，并表示为咀嚼频率（每次的咀嚼次数）和咀嚼强度（每DMI的咀嚼次数），包括总咀嚼（摄入加反刍）和单独的反刍咀嚼。动物在咀嚼行为和MRT测量方面差异很大。BM对咀嚼行为和MRT测量没有显著影响，尽管它与总咀嚼强度呈负相关趋势。咀嚼强度对RR中液体和颗粒的MRT有显著的负面影响，而咀嚼频率则没有这种情况。咀嚼频率与GIT中大颗粒的MRT有显著关系。我们认为咀嚼行为可能通过两种方式影响MRT：（i）通过咀嚼 - 唾液反射影响唾液分泌，进而影响液体流入RR；（ii）通过促进颗粒尺寸减小。如果在更大规模的研究中证实咀嚼行为与MRT之间的联系，那么具有较大个体差异的咀嚼测量指标可能会成为一种易于测量的MRT特征替代指标。
