Digestibility of Three Grass Hays by the Horse and Scanning Electron Microscopy of Undigested Leaf Remnants2

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Abstract
Digestibilities of three grass hays (smooth brome, tall fescue, native prairie) were determined in horses. Leaf structures recovered from fecal remnants were observed by scanning electron microscopy. Digestibilities of dry matter, cell-wall constituents and acid detergent fiber were similar for prairie and brome hays but lower (P<.01) for fescue. Hemicellulose digestibility was highest for brome hay (P<.05), while crude protein digestibility was lowest (P<.005) for prairie hay. Microscopy of residues showed that mesophyll and phloem were digested. Epidermal tissue remnants varied among hays and within leaf fragments. Other tissues schlerenchyma, lignified vascular bundles, cuticle) remained virtually intact. Adaxial cuticle was ruptured in leaves, and some phytoliths in fescue and prairie (bluestem) samples were missing. Digestion of leaves followed the same pattern as in ruminants, except that the horses did not digest structures, which ruminants degrade slowly. Copyright © 1982. American Society of Animal Science . Copyright 1982 by American Society of Animal Science