Faculty of Tropical AgriSciences, Czech University of Life Sciences Prague, Kamýcká 129, 165 00 Prague 6 - Suchdol, Czech Republic.
Leibniz-Institute for Zoo and Wildlife Research (IZW) Berlin, Alfred-Kowalke-Str. 17, 10315 Berlin, Germany.
Comp Biochem Physiol A Mol Integr Physiol. 2020 Aug;246:110720. doi: 10.1016/j.cbpa.2020.110720. Epub 2020 May 5.
The way that fluids and particles move through the forestomach of a ruminant is species-specific, and can be used to classify ruminants according to their digestive physiology into 'moose-types' (with little difference in fluid and small particle passage) and 'cattle-types' (where fluids move through the forestomach much faster than small particles). So far, 'moose-types' appear limited to a dietary niche of browsing, whereas 'cattle-types' are particularly prominent in the intermediate and grazing diet niches. However, some species, including members of the spiral-horned antelopes (the Tragelaphini), have a 'cattle-type' physiology but a browse-dominated diet niche. Eland (Taurotragus oryx), the largest member of the Tragelaphini, are strict browsers in the wild but have been considered intermediate feeders in the past, and can seemingly be maintained on grass diets. We quantified food intake, mean retention time (MRT) in the gastrointestinal tract and the reticulorumen (RR) of a solute, a small and a large particle marker, and diet digestibility in six eland each fed a monocot (grass hay) and a dicot (lucerne silage) forage. Food intake and digestibility was lower on the diet with higher fibre content (grass hay), with corresponding longer MRT. At the higher intakes on lucerne, the difference in MRT between small and large particles was larger, indicating a greater reliance on particle sorting and clearance under this condition of potentially limiting gut capacity. Regardless of diet or intake, the ratio of small particle and solute MRT in the RR was constant and small, at a quotient of 1.54, classifying the eland as a typical 'moose-type' ruminant. This finding is consistent with previous literature reports on low faecal metabolic nitrogen and high apparent protein digestibility in eland. Given the relative ease at which eland can be maintained under farm husbandry conditions, they appear ideal model ruminants to study the effects of differences in rumen physiology compared to cattle.
反刍动物前胃中流体和颗粒的移动方式具有物种特异性，可以根据其消化生理学将反刍动物分为“驼鹿型”（流体和小颗粒通过的差异很小）和“牛型”（流体比小颗粒更快通过前胃）。到目前为止，“驼鹿型”似乎仅限于觅食的生态位，而“牛型”则特别突出于中间和放牧的饮食生态位。然而，一些物种，包括螺旋角羚羊（ Tragelaphini ）的成员，具有“牛型”生理学，但却以食草为主的饮食生态位。大羚羊（ Taurotragus oryx ）是 Tragelaphini 中最大的成员，在野外是严格的食草动物，但过去被认为是中间食草动物，似乎可以用草食维持。我们量化了六头大羚羊每头采食单一饲料（干草）和混合饲料（紫花苜蓿青贮）时的食物摄入量、胃肠道和网胃（RR）中溶质、小和大颗粒标记物的平均停留时间（MRT）以及饲料消化率。高纤维含量（干草）的饮食的食物摄入量和消化率较低，相应的 MRT 更长。在紫花苜蓿的较高摄入量下，小颗粒和大颗粒之间的 MRT 差异更大，表明在这种可能限制肠道容量的条件下，对颗粒分类和清除的依赖性更大。无论饮食或摄入量如何，RR 中小颗粒和溶质 MRT 的比值保持不变且较小，为 1.54，将大羚羊归类为典型的“驼鹿型”反刍动物。这一发现与大羚羊粪便代谢氮低和表观蛋白消化率高的先前文献报道一致。鉴于大羚羊在农场饲养条件下相对容易维持，它们似乎是研究与牛相比瘤胃生理学差异影响的理想反刍动物模型。
