Comparison of fecal analysis and rumen evacuation techniques for sampling diet botanical composition of grazing cattle.

Abstract

Fecal samples, evacuated rumen samples, and non-evacuated rumen samples were compared at different seasons as techniques for determining diet botanical composition of cattle. The study was conducted at the New Mexico State University College Ranch near Las Cruces. Six rumen-fistulated steers were used spring (28 May-7 June), summer (19 July-8 August). fall 1989 (1-17 October), winter (8-28 January) 1990; 4 rumen-fistulated steers were used during summer (24 July-4 August) 1990. Sampling techniques differed (P < 0.05) for the proportion of some plant species in steer diets at certain seasons. In most cases, these differences were observed only for minor forage species. Similarity (%) between fecal samples, evacuated rumen samples, and non-evacuated rumen samples varied with season and with the particular techniques being compared. Similarity (%)between fecal samples and evacuated rumen samples (74%), and highest in summer (1989) between fecal samples and non-evacuated rumen samples (93%). Differential digestion, sampling procedures, and observer errors may explain these differences. For practical purposes, fecal analysis appears to be one of the best techniques to evaluate diet composition of large herbivores.