Morphological characteristics of leaves from some legume forages: relation to digestion and mechanical strength

Publisher Website
Google Scholar
Abstract
Leaflets of bloat-causing and bloat-safe forage legumes were examined to identify morphological characteristics which might relate to mechanical strength, rate of digestion and bloat-causing potential. The bloat-causing legumes were alfalfa (Medicago sativa L.), white clover (Trifolium repens L.) and red clover (T. pratense L.). The bloat-safe legumes were cicer milk-vetch (Astragalus cicer L.), birdfoot-trefoil (Lotus corniculatus L.) and sainfoin (Onobrychis viciifolia Scop.). Only cicer milk-vetch had reticulate secondary and tertiary vein patterns and collenchyma or bundle sheath cells extending from the vascular tissue to both epidermal layers in the primary, secondary and tertiary veins. Sainfoin and birdsfoot-trefoil leaflets contained tannin sacs beneath the adaxial epidermis and extending into the mesophyll. Sainfoin also had an intermittent subepidermal layer of cells adjacent to the abaxial epidermis. Sainfoin and cicer milk-vetch leaflets were the least disrupted by shaking with glass beads. Digestion of whole leaflets by rumen microorganisms or a purified leaf-macerating enzyme was less extensive in the bloat-safe species. These digestion results and recent findings on the mechanical strength of leaflets from the same species may be related to secondary and tertiary vein patterns and structure.