COMPARING TECHNIQUES FOR DETERMINING STEER DIETS IN NORTHERN CHIHUAHUAN DESERT

Diets determined by bite count and microhistological analysis of esoph ageal extrusa and feces were compared for steers grazing on grass-shru blands in the northern Chihuahuan Desert. The study was conducted on t he Chihuahuan Desert Rangeland Research Center near Las Cruces, New Me xico, The purpose was to determine the similarity of 3 dietary techniq ues on arid, heterogeneous rangeland, It was proposed that the number of bites of each species eaten was directly proportional to the weight eaten as determined by the 2 microhistological techniques, Samples of diets were collected in 4 seasons from 2 steers grazing in a continuo us yearlong pasture and in seasonlong rotation pastures, The 3 dietary techniques did not give similar (P<0.10) estimates of the diets eaten by the steers, Mean similarity indices were highest (77%) comparing d iets from analysis of esophageal and fecal material, Lowest mean simil arity indices (57%) were from comparing diets from bite count and feca l analysis, Much of the discrepancy between techniques was because of different size plants being eaten and heterogeneity of plant distribut ion, An importance ranking of dietary species using the 3 techniques s howed that the top 3 species comprised over 68% of the total diets, An y of the 3 techniques can be used to determine the common species in t he diets which may be all that is necessary for some management and an alysis needs.