NUTRITIONAL PROFILE AND LEAF SURFACE-STRUCTURE OF SOME MONOCOTYLEDONOUS AND DICOTYLEDONOUS SPECIES FOR GRAZING RUMINANTS IN SEMIARID REGIONS OF NORTHEASTERN MEXICO

This, study describes some aspects of nutritional and leaf ultrastruct ural characteristics of 8 monocotyledonous and 7 dicotyledonous specie s, showing large variations in these characters. High crude protein (C P) content was observed for monocotyledonous species such as Cyanodon dactylon (11%) and Bouteloua trifida (10.5%) as well as for dicotyledo ns Ruelia corzoi (19%) Lantana macropoda (19%), Palafoxia texana (18.6 %) and Sida filicaulis (18%). In general, dicotyledonous species showe d greater in situ digestibility of dry matter (ISDDM) crude protein (I SDCP) and neutral detergent fiber (ISDNDF). Linear regression equation s between in situ digestibilities and nutrient content showed that dig estibility of all plant species was negatively influenced by their fib er content and positively by their CP content. Both mono and dicotyled onous species showed large variations in the presence, abondance and s ize of trichomes, crystals and type of epicuticular wax Low trichome n umber, less pubescence, silica contents and smooth epicuticular wax an d high CP, low NDF and high in situ digestibility of DM and CP are des irable characteristics for grazing animals preference. The presence of smooth epicuticular wax and trichomes are characters related to droug ht resistance of some of the species prevalent in semiarid Mexico. The refore, ultrastructural characteristics of Leaf surface might be relat ed to the preference or non preference by the grazing animals.