OBSERVATION - CATTLE DIETS ON EXCELLENT AND GOOD CONDITION CHIHUAHUANDESERT RANGELANDS

Information is limited on the influence of range condition on cattle d iets in the Chihuahuan desert. Botanical composition of cattle diets o n Chihuahuan desert ranges in excellent and good condition was studied by microhistological analysis. Cattle feces were analyzed seasonally from fall 1991 through fall 1992. Excellent condition and good conditi on ranges supported 86% and 72% of the climax vegetation, respectively . Key species in cattle diets on the excellent condition range were bl ack grama (Bouteloua eriopoda Torr.) and threeawns (Aristida spp.). On the good condition range the key species were dropseeds (Sporobolus s pp.), threeawns and black grama. Total grass and black grama content o f cattle diets were greater on the excellent condition range. Seasonal trends occurred in cattle diets on good condition but not on excellen t condition range. Low availability of forbs and shrubs explained the high diets similarities among seasons on the excellent condition range . Cattle on good condition range readily used forbs and shrubs when gr een grass was unavailable. Nitrogen and phosphorus analyses of fecal s amples indicated diets were nutritionally superior on the good compare d to the excellent condition range. Our research and other studies sho w consumption of forbs and shrubs permits cattle to maximize their nut ritional welfare when grasses are dormant. The excellent condition ran ge in our study had a different(P<0.05) mean grass standing crop (999 kg/ha) across periods compared to on the good condition range (659 kg/ ha). Based on our research and other studies excellent condition Chihu ahuan desert range maximizes forage quantity for cattle but good condi tion range appears better from a nutritional standpoint in the spring and early summer. Our research and other studies indicate Chihuahuan d esert ranges dominated by black grama are most effectively used in win ter while ranges with a high dropseed component are best suited for us e in summer and early fall.