Megaherbivores have been of particular interest to scientists because of the physiological and ecological challenges associated with their extreme body size. Yet, one question that has seldom been explored is how browsing megaherbivores cope with plant secondary metabolites (PSMs), such as tannins, found in their food. It is possible that the sheer body size of these megaherbivores allows them to ingest tannins with no deleterious effects. However, it is plausible that megaherbivores must rely on other mechanisms to cope with PSMs, such as the production of salivary tannin-binding proteins. Thus, we aimed to determine whether megaherbivore browsers produce tannin-binding proteins to further reduce the consequences of ingesting a tannin-rich diet. Using a series of laboratory assays, we explored whether elephants, black rhinoceros, and giraffe had tannin-binding proteins in their saliva. We tested for the presence of proline-rich proteins in the saliva using two different approaches: (1) SDS-PAGE using Laemmli’s (Laemmli, Nature 227:680–685, 1970) destaining method, and (2) comparative SDS-PAGE gels using Beeley et al.’s (Beeley et al. Electrophoresis 12:493–499, 1991) method for staining and destaining to probe for proline-rich proteins. Then, to test for the tannin-binding affinity of their saliva, we performed an inhibition assay. We did not observe proline-rich proteins in any of the megaherbivore species, but they did have other protein(s) in their saliva that have a high tannin-binding affinity. Our results highlight that, despite their large body sizes, and their abilities to tolerate low-quality food, browsing megaherbivores have likely evolved tannin-binding proteins as a way of coping with the negative effects of tannins.

巨型草食动物由于其极端的体型与生理和生态方面的挑战而引起了科学家的特别兴趣。但是，很少探讨的一个问题是浏览巨型草食动物如何处理食物中发现的植物次生代谢物（例如单宁）。这些巨型草食动物的绝对体型可能使他们摄入单宁而没有有害作用。然而，似乎有理由认为，食草动物必须依靠其他机制来应对PSM，例如唾液单宁结合蛋白的产生。因此，我们旨在确定大型草食动物浏览器是否产生单宁结合蛋白，以进一步减少摄入富含单宁饮食的后果。通过一系列实验室分析，我们探讨了大象，黑犀牛，长颈鹿的唾液中含有单宁结合蛋白。我们使用两种不同的方法测试了唾液中富含脯氨酸的蛋白的存在：（1）使用Laemmli's（Laemmli，Nature 227：680-685，1970）脱色方法进行SDS-PAGE，以及（2）比较SDS-PAGE凝胶使用Beeley等。的方法（Beeley等人，Electrophoresis 12：493-499，1991），用于染色和脱色以探测富含脯氨酸的蛋白质。然后，为了测试其唾液的单宁结合亲和力，我们进行了抑制试验。我们没有在任何大型草食动物物种中观察到富含脯氨酸的蛋白质，但是它们的唾液中确实有其他蛋白质具有很高的单宁结合亲和力。我们的研究结果表明，尽管体型庞大，并且能够忍受劣质食品，但是浏览巨型草食动物仍可能进化出单宁结合蛋白，以应对单宁的负面影响。