Physical Factors That Influence Fecal Analysis Estimates of Herbivore Diets

Abstract

hlicrobistological analysis of epidermal fragments in feces is often used to estimate the diet of berbrvores but is not generally accepted as a consistently reliable method. Gross errors arise, especially when diets are composed of berbage components with widely different morphological and structural characteristics. The present study investigated the possibility of using such physical characteristics to improve the reliability of the method. Over a 7 day period, 4 rumen-fistulated beef cows were given a fixed diet composed of a shrub, a grass, and a forb component. On the last 2 days, samples of rumen content and feces were taken for analysis of epidermal fragment. Forbs were underestimated , grasses overestimated , and shrubs correctly estimated. Correction factors to estimate true diet composition were defined as the biomass represented by the specific epidermal fragments (epidermal weight index) and the degree of degradation to which the epidermis is subjected in the digestion process (epidermal erodibility factor). These factors account for characteristic physical features of the different dietary components and were measured directly or were derived from the calibration esperiment. The utility of such factors depends on accurate determination of the component variables and may be oversbadowed by sampling error and observer bias in the microbistological identification of epidermal fragments.

Food–niche relationships within a guild of alpine ungulates including an introduced species

“…Another source of inaccuracy may be the adopted analytical technique. Grasses tend to be over-represented in faecal materials due to resistance of the epidermis to digestive processes (Neal, Pulkinen & Owen, 1973;Bartolome et al, 1995). However, faecal analysis is the only technique that can be used to compare diets all year round in a multispecies system.…”

Diet overlap between small ruminants and the European hare in a Mediterranean shrubland

“…Forbs and legumes are usually more nutritious and easily digestible than grasses and shrubs [1,41,42] and the different digestibilities of forage groups may bias potential estimates of herbivore diets [43,44]. Despite this bias, many studies consider microhistological analysis of faeces to be an accurate and precise method of qualifying herbaceous plant intake and species composition [41,45,46]. In this study, it was assumed that highly digestible or poorly identifiable forages would be underestimated in all diets, thus the comparison of the animals' diets would not be significantly influenced by differential digestion or identification [35].…”

Seasonality and edge effect determine herbivory risk according to different plant association models

“…Once collected in the field, faeces were kept at a temperature of )20°C until processed and analysed in the laboratory. The method of analysis (Bartolomé et al 1995) included a first stage in which samples were treated with nitric acid at 80°C and microscope slides were prepared. Epidermal plant fragments in faecal samples were then identified and recorded under a microscope.…”