Paper-Lecture2 - Oecologia(2000 125:8284 Springer-Verlag...

Info icon This preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Abstract In his landmark 1989 paper, R.R. Hofmann classified ruminants into three categories based upon di- gestive anatomy and preferred forages, and proposed that divergence of feeding strategies among ruminants is a re- sult of morphological evolution of the digestive tract. Be- cause of the hypothetical nature of these views and the in- grained beliefs that they challenged, several papers were published that reported tests of Hofmann’s predictions. The consensus among these papers was that Hofmann’s predictions were inadequate. I describe the experimental evidence that has been put forth in opposition to the rumi- nant diversification hypothesis and contend that we have failed to adequately test Hofmann’s predictions. Key words Concentrate selectors · Intermediate feeders · Roughage eaters · Rumen bypass · Ruminant diversification Early attempts to explain variation found in feeding strate- gies of free-ranging ruminants classified individual species as “browsers” or “grazers” based upon types of forage con- sumed. Though an important step in understanding the complexities of ruminant nutrition, Hofmann and Stewart (1972) recognized that feeding strategies of ruminants could not simply be classified into two categories, and pro- posed three categories (i.e., bulk and roughage eaters, se- lectors of concentrate forages, and intermediate feeders) based upon stomach structure and feeding ecology. Hof- mann (1984) later documented variation in all portions of the digestive anatomy among the three categories of his system of ruminant classification. The dynamic interac- tions among body size, fermentation and passage rates, and energetic requirements, and their influence on dietary strat- egy formed the basis for these early classifications. In a landmark paper, Hofmann (1989) expanded upon the concepts proposed by Hofmann and Stewart (1972) and Hofmann (1984) by providing a working hypothesis of the functional and morphological basis for diversity in ruminant feeding strategies. Hofmann (1989) proposed that feeding strategies ranged from nonselective intake of bulk roughage and efficient fermentation in the fore- stomach, to selectivity for concentrate forages (high in plant cell content) with increased post-ruminal digestion. This hypothesis challenged many beliefs regarding di- gestion in free-ranging ruminants and proposed that we reexamine the manner in which ruminant herbivores ob- tain nutrients from the environment. Because of the magnitude of Hofmann’s hypothesis, several papers (Gordon and Illius 1994, 1996; Robbins et al. 1995) were published describing tests of his predic- tions. These researchers examined components of Hof- mann’s hypothesis and concluded that they did not find support for morpho-physiological adaptations to diet type within classes of ruminants. They attributed differ- ences in digestive function to body mass or food charac- teristics. As a result, the consensus has been that Hof- mann’s hypothesis regarding gut morphology and func- tion in classes of ruminants is inadequate (Robbins et al.
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern