Bite-Count vs Fecal Analysis for Range Animal Diets

Abstract

This study indicated that the and fecal analysis methods give similar results for estimating major components of cattle diets in Texas. The method could not be used on large, brush-infested pastures with rough terrain; however, the fecal analysis metnod was easily used under such conditions. Other advantages of fecal analyses were: samples were collected with a minimum of field work, diets of wild and domestic animals could be obtained, and bad weather and poor field conditions were not problems. Major disadvantages of the fecal analysis technique were: forages with dense stellate trichomes were overestimated; mesquite beans were retained in the digestive tract for abnormally long periods; the laboratory phase required a trained technician; and the work was tedious. Knowledge of the species consumed by grazing-animals, season by season, is fundamental to proper grazing management. Commonly used methods for obtaining diet composition have included: direct animal observation, forage utilization, and identification of plant material collected by esophageal fistula from stomach contents, or from fecal material. Many researchers consider the esophageal fistula technique the most accurate (Harris et al. 1959; Rice 1970), and Cook (1964) found it less time consuming than other methods. However, identification of individual grasses or individual forbs is often impossible with fistula collections. Because of the obvious disadvantages of working with fistulated animals in large pastures; areas with rough, rocky, terrain; or areas heavily infested with brush, other methods that offer reasonably accurate data are often needed. Ideally, a method for determining grazing-animal diets will: (1) allow free animal movement and completely natural selection of all available plants and plant parts regardless of pasture size; (2) allow for diet determination regardless of Authors are graduate research assistant, professor, and technician, Department of Range and Wildlife Management, Texas Tech University, Lubbock 79409. At present, Sanders is assistant professor, College of Forestry, Wildlife and Range Sciences, University of Idaho, Moscow. This study is a contribution of the College of Agricultural Sciences, Texas Tech University No. T-9-161. The authors wish to thank R.A. Brown for his support during conduct of this study. Manuscript received January 29, 1979. terrain; (3) be equally useful for wild and domesticated animals; (4) not require slaughter of test animals; (5) require a minimum of animal care; (6) be relatively objective; and (7) allow identification of each individual plant species consumed. Microscopic examination of fecal material fits the criteria outlined. Baumgartner and Martin (1939) identified food items in squirrel diets more than 40 years ago by microscopic examination. More recently plant species consumed by sheep (Hercus 1960), cattle (Malechek 1966; Free et al. 1971), and horses (Regal 1960) were identified by examination of feces and/ or rumen contents through a microscope. Unequal digestibility among plants (Regal 1960) appears the most serious source of error in determining diet composition from fecal examination. Also, the laboratory analysis method is tedious (Ward 1970). A technique commonly used and that also meets the criteria outlined is a variation of the feeding-minutes method termed the bite-count method used by Reppert (1960) and McMahan (1964). Free et al. (1971) working with steers obtained diet information comparable to the esophageal fistula method using the technique. Because of brush infestation and the rough topography of most Texas ranges, obtaining usable diet information for management or research purposes is a major problem. Despite its limitations, microscopic evaluation of diets from fecal material seems to offer a viable choice. Therefore, the objective of this study was to find out if the fecal examination by microscope technique could provide diet compositions similar to those obtained from the method.