Clinic for Zoo Animals, Exotic Pets and Wildlife, Vetsuisse Faculty, University of Zurich, Winterthurerstr. 260, 8057 Zurich, Switzerland.
Department of Zoology and Entomology, University of the Free State, PO Box 339, Bloemfontein 9300, South Africa.
Comp Biochem Physiol A Mol Integr Physiol. 2024 Jun;292:111621. doi: 10.1016/j.cbpa.2024.111621. Epub 2024 Mar 6.
Particle passage from the reticulorumen (RR) depends on particle density and size. A classic way of assessing these effects is the use of plastic markers of varying density and size that are recovered in the faeces. Here, we report results of an experiment where four fistulated reindeer (Rangifer tarandus, 96 ± 12 kg) were fed two different diets (browse, voluntary dry matter intake [DMI] 70 ± 10 g/kg/d; or a pelleted diet, DMI 124 ± 52 g/kg/d) and dosed via fistula with 8 different particle types combining densities of 1.03, 1.22 and 1.44 g/ml and sizes of 1, 10 and 20 mm. Generally, particles that passed the digestive tract intact (not ruminated) did so relatively early after marker dosing, and therefore had shorter mean retention times (MRT) than ruminated particles. On the higher intake, the overall mean retention time (MRT) of particles was shorter, but this was not an effect of shorter MRT for either intact or ruminated particles, but due to a higher proportion of intact particles at the higher intake. This supports the concept that ruminants do not adjust chewing behaviour depending on intake, but that a lower proportion of digesta is submitted to rumination due to pressure-driven escape from the forestomach at higher gut fills. Compared to cattle (Bos primigenius taurus), muskoxen (Ovibos moschatus) and moose (Alces alces) that had received the same markers, reindeer had a lower proportion of 1 mm particles that passed intact. Our results support the concept that the critical size threshold for particles leaving the ruminant forestomach is dependent on body size. While the results likely do not represent findings peculiar for reindeer, they indicate fundamental mechanisms operating in the forestomach of ruminants.
颗粒从网胃（RR）中的通过取决于颗粒的密度和大小。评估这些影响的一种经典方法是使用不同密度和大小的塑料标记物，这些标记物在粪便中被回收。在这里，我们报告了一项实验的结果，该实验中，给四只瘘管化驯鹿（Rangifer tarandus，96±12kg）喂食两种不同的饮食（灌木，自愿干物质摄入量[DMI]为 70±10g/kg/d；或颗粒饲料，DMI 为 124±52g/kg/d），并通过瘘管给 8 种不同类型的颗粒给药，这些颗粒结合了密度为 1.03、1.22 和 1.44g/ml 以及 1、10 和 20mm 的大小。一般来说，未经过反刍而完整通过消化道的颗粒相对较早地通过标记物给药，因此比反刍颗粒具有更短的平均停留时间（MRT）。在较高的摄入量下，颗粒的整体平均停留时间（MRT）更短，但这不是由于完整或反刍颗粒的 MRT 更短，而是由于在较高的摄入量下，完整颗粒的比例更高。这支持了反刍动物不会根据摄入量调整咀嚼行为的概念，而是由于在较高的肠道填充下，压力驱动的消化物从瘤胃中逃脱，导致反刍的消化物比例降低。与已经接受相同标记物的牛（Bos primigenius taurus）、麝香牛（Ovibos moschatus）和驼鹿（Alces alces）相比，驯鹿的完整通过的 1mm 颗粒比例较低。我们的结果支持了这样一个概念，即离开反刍动物瘤胃的颗粒的临界尺寸阈值取决于体型。虽然这些结果可能不适用于驯鹿特有的发现，但它们表明了反刍动物瘤胃中起作用的基本机制。
