Mammalian herbivores are major suppliers of the worlds' milk, meat, and fiber products to humans. Their existence on the various land types on Earth can be attributed to a behavioral mechanism geared toward maximizing fitness (i.e., proliferation of their genes via the production of progeny) and is commonly explained by the body of evolutionary theory known as Optimal Foraging Theory (OFT) . The acquisition and assimilation of nutrients from food is of paramount importance to the ruminant because it is the fundamental process that enables survival, growth, and reproduction. Energy is the driving currency, but grazing ruminants face complex decisions in searching for and harvesting adequate forage to meet their energy requirements for survival, growth, and reproduction. Vegetation heterogeneity adds
complexity to even the simplest of ecosystems and is itself a circular process shaped by the effects of herbivory on the environment. While food intake lies at the heart of the survival of animal species, the discrimination by animals between plant species and their morphological organs is central to the survival and regeneration of the plant population.
Despite the advances that have been made in understanding forage intake [2-4], mechanistic explanations for diet choice and observed behavior remain scarce. The application of materials science theory to understanding biological problems in herbivores has led to a revived interest in quantifying plant fracture mechanics, but parallel progress in understanding the mechanistic relationships between animal and plant mechanical properties and grazing strategies in ruminants, particularly of contrasting body size, has been much slower. The force that grazing animals exert in procuring a bite has received little attention despite the clear linkages with herbage intake. This probably reflects the difficulties associated with quantification of bite force. The objectives of this chapter are to: (1) discuss the ruminant species, their harvesting apparatus, and the process that these herbivores use to harvest food, (2) clarify the terminology used to describe fracture mechanics as they apply to ruminants, (3) demonstrate how bite force can be quantified and discuss the problems and opportunities facing the researcher, and (4) introduce the concept of biting effort.
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