Division of Animal Sciences, University of Missouri, Columbia 65211, USA.
J Dairy Sci. 2010 Apr;93(4):1320-34. doi: 10.3168/jds.2009-2071.
The article reviews ruminant ecology and evolution and shows insights they offer into livestock research. The first ruminants evolved about 50 million years ago and were small (<5 kg) forest-dwelling omnivores. Today there are almost 200 living ruminant species in 6 families. Wild ruminants number about 75 million, range from about 2 to more than 800 kg, and generally prefer at least some browse in their diets. Nine species have been domesticated within the last 10,000 yr. Their combined population currently numbers 3.6 billion. In contrast to wild ruminants, domestic species naturally prefer at least some grass in their diets, are of large body weight (BW; roughly from 35 to 800 kg), and, excepting reindeer, belong to one family (Bovidae). Wild ruminants thus have a comparatively rich ecological diversity and long evolutionary history. Studying them gives a broad perspective that can augment and challenge the status quo of ruminant research and production. Allometric equations, often used in ecology, relate BW to physiological measurements from several species (typically both wild and domestic). They are chiefly used to predict or explain values of physiological parameters from BW alone. Results of one such equation suggest that artificial selection has increased peak milk energy yield by 250% over its natural level. Voluntary feed intake is proportional to BW(0.9) across wild and domestic ruminant species. This proportionality suggests that physical and metabolic factors regulate intake simultaneously, not mutually exclusively as often presumed. Studying the omasum in wild species suggests it functions primarily in particle separation and retention and only secondarily in absorption and other roles. Studies on the African Serengeti show that multiple species, when grazed together, feed such that they use grasslands more completely. They support the use of mixed-species grazing systems in production agriculture. When under metabolic stress, wild species will not rebreed, but rather will extend lactation (to nourish their current offspring). This bolsters the suggestion that lactation length be extended in dairy operations. Cooperation between animal scientists and ecologists could generate more valuable insight.
本文综述了反刍动物的生态和进化，并展示了它们为家畜研究提供的见解。第一批反刍动物大约在 5000 万年前进化而来，体型较小（<5 公斤），是杂食性的森林动物。如今，有 6 个科的近 200 种活体反刍动物。野生反刍动物数量约为 7500 万，体重从 2 公斤到 800 多公斤不等，通常在饮食中至少喜欢一些嫩叶。9 个物种在过去 10000 年中被驯化。它们的种群总数目前为 36 亿。与野生反刍动物不同，家养物种自然更喜欢在饮食中至少有一些草，体重较大（大致从 35 公斤到 800 公斤），除驯鹿外，它们都属于一个科（牛科）。因此，野生反刍动物具有相对丰富的生态多样性和悠久的进化历史。研究它们可以提供一个广泛的视角，从而丰富和挑战反刍动物研究和生产的现状。在生态学中常用的比例方程将 BW 与来自多个物种（通常是野生和家养）的生理测量值联系起来。它们主要用于根据 BW 预测或解释生理参数的值。其中一个方程的结果表明，人工选择使产奶高峰期的能量产量比其自然水平提高了 250%。野生和家养反刍动物的自愿采食量与 BW（0.9）成正比。这种比例关系表明，物理和代谢因素同时调节摄食，而不是像通常假设的那样相互排斥。对野生物种瘤胃的研究表明，它主要在颗粒分离和保留中起作用，其次在吸收和其他作用中起作用。对非洲塞伦盖蒂的研究表明，当多种物种一起放牧时，它们的进食方式使它们更充分地利用草原。这支持了在生产性农业中使用混合物种放牧系统的建议。当处于代谢压力下时，野生物种不会重新繁殖，而是延长哺乳期（以滋养其当前的后代）。这支持了在奶牛养殖中延长哺乳期的建议。动物科学家和生态学家之间的合作可以产生更有价值的见解。
